Reconciling the Dawn-Dusk Asymmetry in Mercury's Exosphere with the Micrometeoroid Impact Directionality

NASA Technical Reports Server (NTRS)

Pokorny, Petr; Sarantos, Menelaos; Janches, Diego

2017-01-01

Combining dynamical models of dust from Jupiter-family comets and Halley-type comets, we demonstrate that the seasonal variation of the dust/meteoroid environment at Mercury is responsible for producing the dawn-dusk asymmetry in Mercury's exosphere observed by the MESSENGER spacecraft. Our latest models, calibrated recently from ground-based and space-borne measurements, provide unprecedented statistics that enable us to study the longitudinal and latitudinal distribution of meteoroids impacting Mercury's surface. We predict that the micrometeoroid impact vaporization source is expected to undergo significant motion on Mercury's surface toward the nightside during Mercury's approach to aphelion and toward the dayside when the planet is approaching the Sun.

Mineralogy of the Mercurian Surface

NASA Technical Reports Server (NTRS)

Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Nittler, Larry R.; Peplowski, Patrick N.; Weider, Shoshana Z.; Evans, Larry R.; Frank, Elizabeth A.; McCoy, Timothy

2016-01-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft orbited Mercury for four years until April 2015, revealing its structure, chemical makeup, and compositional diversity. Data from the mission have confirmed that Mercury is a compositional end-member among the terrestrial planets. The X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) on board MESSENGER provided the first detailed geochemical analyses of Mercury's surface. These instruments have been used in conjunction with the Neutron Spectrometer and the Mercury Dual Imaging System to classify numerous geological and geochemical features on the surface of Mercury that were previously unknown. Furthermore, the data have revealed several surprising characteristics about Mercury's surface, including elevated S abundances (up to 4 wt%) and low Fe abundances (less than 2.5 wt%). The S and Fe abundances were used to quantify Mercury's highly reduced state, i.e., between 2.6 and 7.3 log10 units below the Iron-Wustite (IW) buffer. This fO2 is lower than any of the other terrestrial planets in the inner Solar System and has important consequences for the thermal and magmatic evolution of Mercury, its surface mineralogy and geochemistry, and the petrogenesis of the planet's magmas. Although MESSENGER has revealed substantial geochemical diversity across the surface of Mercury, until now, there have been only limited efforts to understand the mineralogical and petrological diversity of the planet. Here we present a systematic and comprehensive study of the potential mineralogical and petrological diversity of Mercury.

Mapping the Topography of Mercury with MESSENGER Laser Altimetry

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Cavanaugh, John F.; Neumann, Gregory A.; Smith, David E..; Zubor, Maria T.

2012-01-01

The Mercury Laser Altimeter onboard MESSENGER involves unique design elements that deal with the challenges of being in orbit around Mercury. The Mercury Laser Altimeter (MLA) is one of seven instruments on NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. MESSENGER was launched on 3 August 2004, and entered into orbit about Mercury on 18 March 2011 after a journey through the inner solar system. This involved six planetary flybys, including three of Mercury. MLA is designed to map the topography and landforms of Mercury's surface. It also measures the planet's forced libration (motion about the spin axis), which helps constrain the state of the core. The first science measurements from orbit taken with MLA were made on 29 March 2011 and continue to date. MLA had accumulated about 8.3 million laser ranging measurements to Mercury's surface, as of 31 July 2012, i.e., over six Mercury years (528 Earth days). Although MLA is the third planetary lidar built at the NASA Goddard Space Flight Center (GSFC), MLA must endure a much harsher thermal environment near Mercury than the previous instruments on Mars and Earth satellites. The design of MLA was derived in part from that of the Mars Orbiter Laser Altimeter on Mars Global Surveyor. However, MLA must range over greater distances and often in off-nadir directions from a highly eccentric orbit. In MLA we use a single-mode diode-pumped Nd:YAG (neodymium-doped yttrium aluminum garnet) laser that is highly collimated to maintain a small footprint on the planet. The receiver has both a narrow field of view and a narrow spectral bandwidth to minimize the amount of background light detected from the sunlit hemisphere of Mercury. We achieve the highest possible receiver sensitivity by employing the minimum receiver detection threshold.

Space-Weathering on Mercury: Inferences Based on Comparison of MESSENGER Spectral Data and Experimental Space Weathering Data

NASA Astrophysics Data System (ADS)

Gillis-Davis, J. J.; Blewett, D. T.; Lawrence, D. J.; Izenberg, N. R.; McClintock, W. E.; Holsclaw, G. M.; Domingue, D. L.

2009-12-01

Production and accumulation of submicroscopic metallic iron (SMFe) is a principal mechanism by which surfaces of airless silicate bodies in the Solar System, exposed to the space weathering environment, experience spectral modification. Micrometeorite impact vaporization and solar-wind sputtering produce coatings of vapor-deposited SMFe. Both processes can be more intense on Mercury and, as a result, more efficient at creating melt and vapor. In addition, Ostwald ripening may cause SMFe particles to grow larger due to the high surface temperatures on Mercury (as great as 450°C). Spectral effects on the ultraviolet-visible-near-infrared continuum change with the amount and size of SMFe present. Thus, the physical properties and abundance of iron in Mercury’s regolith can be understood by comparing spectral data from controlled space-weathering experiments with spectra from MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer (MASCS). Knowledge of SMFe size and abundance may provide information on the space weathering conditions under which it was produced or subsequently modified. Reflectance spectra of laboratory-produced samples with varying SMFe grain sizes (average grain sizes of 8, 15, 35, and 40 nm) and iron compositions (from 0.005 to 3.8 wt% Fe as SMFe) are compared with MASCS disk-integrated reflectance from the first flyby of Mercury and will be compared with observations of spectral end members targeted for the third flyby. We compare spectra from 300 nm to 1400 nm wavelength, scaled to 1 at 700 nm, from the laboratory and MASCS. This comparison between laboratory and remote-sensing spectra reveals an excellent match with observations of Mercury for samples with an average iron metal grain size of 8 nm and 1.65 wt% FeO and 15 nm and 0.13 wt% Fe. These average grain sizes of the SMFe component are larger than the average grain size determined for lunar soil samples using transmission electron microscopy (3 nm in rims and 10-15 nm in agglutinates) but are smaller than values obtained from lunar spectra with the methods used here (15-25 nm). We can also infer that silicates in Mercury's high reflectance plains are potentially iron poor, precluding thick vapor deposits coating - both spectral data sets lack a 1-μm absorption and the experimental iron particles are suspended in an iron-free silica gel. Thus, our conclusion on the basis of spectral comparison is that SMFe on Mercury is potentially smaller than on the Moon and that Ostwald ripening is not a major influence on the surface of Mercury. The absence of pronounced darkening of the equatorial regions of Mercury in images from Mariner 10 and MESSENGER's Mercury Dual Imaging System supports also suggest an apparent lack of Ostwald ripening.

A Low O/Si Ratio on the Surface of Mercury: Evidence for Silicon Smelting?

NASA Astrophysics Data System (ADS)

McCubbin, Francis M.; Vander Kaaden, Kathleen E.; Peplowski, Patrick N.; Bell, Aaron S.; Nittler, Larry R.; Boyce, Jeremy W.; Evans, Larry G.; Keller, Lindsay P.; Elardo, Stephen M.; McCoy, Timothy J.

2017-10-01

Data from the Gamma-Ray Spectrometer (GRS) that flew on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft indicate that the O/Si weight ratio of Mercury's surface is 1.2 ± 0.1. This value is lower than any other celestial surface that has been measured by GRS and suggests that 12-20% of the surface materials on Mercury are composed of Si-rich, Si-Fe alloys. The origin of the metal is best explained by a combination of space weathering and graphite-induced smelting. The smelting process would have been facilitated by interaction of graphite with boninitic and komatiitic parental liquids. Graphite entrained at depth would have reacted with FeO components dissolved in silicate melt, resulting in the production of up to 0.4-0.9 wt % CO from the reduction of FeO to Fe0—CO production that could have facilitated explosive volcanic processes on Mercury. Once the graphite-entrained magmas erupted, the tenuous atmosphere on Mercury prevented the buildup of CO over the lavas. The partial pressure of CO would have been sufficiently low to facilitate reaction between graphite and SiO2 components in silicate melts to produce CO and metallic Si. Although exotic, Si-rich metal as a primary smelting product is hypothesized on Mercury for three primary reasons: (1) low FeO abundances of parental magmas, (2) elevated abundances of graphite in the crust and regolith, and (3) the presence of only a tenuous atmosphere at the surface of the planet within the 3.5-4.1 Ga timespan over which the planet was resurfaced through volcanic processes.

KSC-04PD-0676

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- At Astrotech Space Operations facilities near KSC, workers adjust wires on the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft during rotation on the turnover fixture. Workers will perform the propulsion system phasing test firing gas through the thrusters in order to verify that the right thrusters fire when expected as part of prelaunch testing at the site. Launch is scheduled for May 11 from Pad 17-B, Cape Canaveral Air Force Station. The spacecraft will fly past Venus three times and Mercury twice before starting a year-long orbital study of Mercury in July 2009.

KSC-04PD-0671

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- At Astrotech Space Operations facilities near KSC, workers make adjustments to the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft now resting on the turnover fixture. Workers will perform the propulsion system phasing test firing gas through the thrusters in order to verify that the right thrusters fire when expected as part of prelaunch testing at the site. Launch is scheduled for May 11 from Pad 17-B, Cape Canaveral Air Force Station. The spacecraft will fly past Venus three times and Mercury twice before starting a year-long orbital study of Mercury in July 2009.

KSC-04PD-0672

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- Astrotech Space Operations facilities near KSC, workers remove protective covers from the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft now resting on the turnover fixture. Workers will perform the propulsion system phasing test firing gas through the thrusters in order to verify that the right thrusters fire when expected as part of prelaunch testing at the site. Launch is scheduled for May 11 from Pad 17-B, Cape Canaveral Air Force Station. The spacecraft will fly past Venus three times and Mercury twice before starting a year-long orbital study of Mercury in July 2009.

KSC-04PD-0670

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. -- At Astrotech Space Operations facilities near KSC, workers help while an overhead crane lowers the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) spacecraft onto a turnover fixture. Workers will perform the propulsion system phasing test firing gas through the thrusters in order to verify that the right thrusters fire when expected as part of prelaunch testing at the site. Launch is scheduled for May 11 from Pad 17-B, Cape Canaveral Air Force Station. The spacecraft will fly past Venus three times and Mercury twice before starting a year-long orbital study of Mercury in July 2009.

Return to Mercury: a global perspective on MESSENGER's first Mercury flyby.

PubMed

Solomon, Sean C; McNutt, Ralph L; Watters, Thomas R; Lawrence, David J; Feldman, William C; Head, James W; Krimigis, Stamatios M; Murchie, Scott L; Phillips, Roger J; Slavin, James A; Zuber, Maria T

2008-07-04

In January 2008, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft became the first probe to fly past the planet Mercury in 33 years. The encounter revealed that Mercury is a dynamic system; its liquid iron-rich outer core is coupled through a dominantly dipolar magnetic field to the surface, exosphere, and magnetosphere, all of which interact with the solar wind. MESSENGER images confirm that lobate scarps are the dominant tectonic landform and record global contraction associated with cooling of the planet. The history of contraction can be related to the history of volcanism and cratering, and the total contractional strain is at least one-third greater than inferred from Mariner 10 images. On the basis of measurements of thermal neutrons made during the flyby, the average abundance of iron in Mercury's surface material is less than 6% by weight.

The planet Mercury (1971)

NASA Technical Reports Server (NTRS)

1972-01-01

The physical properties of the planet Mercury, its surface, and atmosphere are presented for space vehicle design criteria. The mass, dimensions, mean density, and orbital and rotational motions are described. The gravity field, magnetic field, electromagnetic radiation, and charged particles in the planet's orbit are discussed. Atmospheric pressure, temperature, and composition data are given along with the surface composition, soil mechanical properties, and topography, and the surface electromagnetic and temperature properties.

MESSENGER Searches for Less Abundant or Weakly Emitting Species in Mercury's Exosphere

NASA Technical Reports Server (NTRS)

Vervack, Ronald J., Jr.; McClintock, William E.; Killen, Rosemary M.; Sprague, Ann L.; Burger, Matthew H.; Merkel, Aimee W.; Sarantos, Menelaos

2011-01-01

Mercury's exosphere is composed of material that originates at the planet's surface, whether that material is native or delivered by the solar wind and micrometeoroids. Many exospheric species have been detected by remote sensing, including H and He by Mariner 10, Na, K, and Ca by ground-based observations, and H, Na, Ca, Mg, and Ca+ by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft. Other exospheric species, including Fe, AI, Si, 0, S, Mn, CI, Ti, OH, and their ions, are expected to be present on the basis of MESSENGER surface measurements and models of Mercury's surface chemistry. Here we report on searches for these species made with the Ultraviolet and Visible Spectrometer (UVVS) channel of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS). No obvious signatures of the listed species have yet been observed in Mercury's exosphere by the UVVS as of this writing. It is possible that detections are elusive because the optimum regions of the exosphere have not been sampled. The Sun-avoidance constraints on MESSENGER place tight limits on instrument boresight directions, and some regions are probed infrequently. If there are strong spatial gradients in the distribution of weakly emitting species, a high-resolution sampling of specific regions may be required to detect them. Summing spectra over time will also aid in the ability to detect weaker emission. Observations to date nonetheless permit strong upper limits to be placed on the abundances of many undetected species, in some cases as functions of time and space. As those limits are lowered with time, the absence of detections can provide insight into surface composition and the potential source mechanisms of exospheric material.

The Mercury Laser Altimeter Instrument for the MESSENGER Mission

NASA Technical Reports Server (NTRS)

Cavanaugh, John F.; Smith, James C.; Sun, Xiaoli; Bartels, Arlin E.; Ramos-Izquierdo, Luis; Krebs, Danny J.; Novo-Gradac, Anne marie; McGarry, Jan F.; Trunzo, Raymond; Britt, Jamie L.

2006-01-01

The Mercury Laser Altimeter (MLA) is one of the payload science instruments on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, which launched on 3 August 2004. The altimeter will measure the round trip time-of-flight of transmitted laser pulses reflected from the surface of the planet that, in combination with the spacecraft orbit position and pointing data, gives a high-precision measurement of surface topography referenced to Mercury's center of mass. The altimeter measurements will be used to determine the planet's forced librations by tracking the motion of large-scale topographic features as a function of time. MLA's laser pulse energy monitor and the echo pulse energy estimate will provide an active measurement of the surface reflectivity at 1064 nm. This paper describes the instrument design, prelaunch testing, calibration, and results of post-launch testing.

KSC-04pd1566

NASA Image and Video Library

2004-07-27

KENNEDY SPACE CENTER, FLA. - On Launch Pad 17-B at Cape Canaveral Air Force Station, the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft is ready for installation of the fairing, a molded structure that fits flush with the outside surface of the Delta II upper stage booster and forms an aerodynamically smooth joint, protecting the spacecraft during launch. Seen on the left is one of the solar panels on the spacecraft. On the right is part of the heat-resistant, ceramic-cloth sunshade that will protect the spacecraft’s instruments as MESSENGER orbits the Mercury where the surface reaches a high temperature near 840 degrees Fahrenheit and the solar intensity can be 11 times greater than on Earth. MESSENGER is scheduled to launch Aug. 2 aboard a Boeing Delta II rocket and is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

First In-Situ Observations of Exospheric Response to CME Impact at Mercury

NASA Astrophysics Data System (ADS)

Raines, J. M.; Wallace, K. L.; Sarantos, M.; Jasinksi, J. M.; Tracy, P. J.; Dewey, R. M.; Weberg, M. J.; Slavin, J. A.

2018-05-01

We present the first in-situ observations of enhancements to Mercury's He exosphere generated by CME impact. These results have implications for understanding exosphere generation and loss processes, as well space weathering of the planet's surface.

Mercury's Seasonal Sodium Exosphere: MESSENGER Orbital Observations

NASA Technical Reports Server (NTRS)

Cassidy, Timothy A.; Merkel, Aimee W.; Burger, Matthew H.; Sarantos, Menelaos; Killen, Rosemary M.; McClintock, William E.; Vervack, Ronald J., Jr.

2014-01-01

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Ultraviolet and Visible Spectrometer (UVVS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft now orbiting Mercury provides the first close-up look at the planet's sodium exosphere. UVVS has observed the exosphere from orbit almost daily for over 10 Mercury years. In this paper we describe and analyze a subset of these data: altitude profiles taken above the low-latitude dayside and south pole. The observations show spatial and temporal variation but there is little or no year-to-year variation; we do not see the episodic variability reported by ground-based observers. We used these altitude profiles to make estimates of sodium density and temperature. The bulk of the exosphere is about 1200 K, much warmer than Mercury's surface. This value is consistent with some ground-based measurements and suggests that photon-stimulated desorption is the primary ejection process. We also observe a tenuous energetic component but do not see evidence of the predicted thermalized (or partially thermalized) sodium near Mercury's surface temperature. Overall we do not see the variable mixture of temperatures predicted by most Monte Carlo models of the exosphere.

Mercury's Seasonal Sodium Exosphere: MESSENGER Orbital Observations

NASA Technical Reports Server (NTRS)

Cassidy, Timothy A.; Merkel, Aimee W.; Burger, Matthew H.; Killen, Rosemary M.; McClintock, William E.; Vervack, Ronald J., Jr.; Sarantos, Menelaos

2014-01-01

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) Ultraviolet and Visible Spectrometer (UVVS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft now orbiting Mercury provides the first close-up look at the planet's sodium exosphere. UVVS has observed the exosphere from orbit almost daily for over 10 Mercury years. In this paper we describe and analyze a subset of these data: altitude profiles taken above the low-latitude dayside and south pole. The observations show spatial and temporal variations, but there are no obvious year-to-year variations in most of the observations. We do not see the episodic variability reported by some ground-based observers. We used these altitude profiles to make estimates of sodium density and temperature. The bulk of the exosphere, at about 1200 K, is much warmer than Mercury's surface. This value is consistent with some ground-based measurements and suggests that photon-stimulated desorption is the primary ejection process. We also observe a tenuous energetic component but do not see evidence of the predicted thermalized (or partially thermalized) sodium near Mercury's surface temperature. Overall we do not see the variable mixture of temperatures predicted by most Monte Carlo models of the exosphere.

Small-scale turbulence detected in Mercury's magnetic field

NASA Astrophysics Data System (ADS)

Schultz, Colin

2011-11-01

With its closest approach a mere 46 million kilometers from the Sun, the blast of the solar wind was supposed to wash away any chance that Mercury could hold on to a magnetic field—an idea rejected by the observations of the Mariner 10 spacecraft in 1974. Though Mercury was shown to harbor a weak magnetic field (one-hundredth the strength of Earth's), its structure, behavior, and interactions with the solar wind remained heavily debated, yet untested, until the 14 January 2008 approach of NASA's MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) orbiter. Using a continuous scalogram analysis—a novel statistical technique in space research—Uritsky et al. analyzed the high-resolution magnetic field strength observations taken by MESSENGER as it flew within a few hundred kilometers of the planet's surface. The authors found turbulence in Mercury's magnetosphere, which they attributed to small-scale interactions between the solar wind plasma and the magnetic field. At large spatial and temporal scales the solar wind can be thought of as a fluid with some magnetic properties—a domain well explained by the theories of magnetohydrodynamics.

Exploring Mercury's Surface in UltraViolet from Orbit

NASA Astrophysics Data System (ADS)

Izenberg, N.

2017-12-01

The MESSENGER Mission's Ultraviolet and Visible Spectrometer (UVVS) component of its Mercury Atmosphere and Surface Composition Spectrometer (MASCS) instrument obtained approximately 4600 point observations of Mercury's surface in middle ultraviolet (MUV; 210 nm - 300 nm) and far ultraviolet (FUV; 119.1 - 122.5 nm and 129.2 - 131.5 nm) wavelengths over the course of its orbital mission, mostly in Mercury's southern hemisphere. Given the very low (<1 to 2 wt %) average abundance of iron in the silicates of Mercury observed by multiple MESSENGER instruments, the near- to middle-ultraviolet wavelengths encompassing the oxygen metal charge transfer band (<400 nm), which is more sensitive to the presence of iron than the classic 1 micron absorption band, provides potentially useful additional compositional insight into the top layer of Mercury's regolith. The presence of nano- and microphase carbon also has potentially significant expression in the ultraviolet, and the interplay and variation between carbon and iron in mercury surface materials is an active area of investigation. Analysis of middle-UV surface reflectance and parameters appear to support the presence of varying amounts of carbon in different spectral or geologic units on Mercury. Far-UV reflectance data is currently under-utilized, but analysis of lunar surface by the Lunar Reconnaissance Orbiter (LRO) Lyman Alpha Mapping Project (LAMP) indicate that the data are sensitive to both composition and space weathering. The far-UV reflectance from MASCS may provide similar information for the Mercury surface, complementing results from longer wavelengths. MESSENGER data products for surface reflectance include middle-UV reflectance spectra, ultraviolet far-UV reflectance values, combined middle-UV through near-infrared spectra (210 nm - 1450 nm), a global `spectral cube' of near-UV to near-IR, and an upcoming UV spectral cube.

KSC-04pd1433

NASA Image and Video Library

2004-07-02

KENNEDY SPACE CENTER, FLA. - A worker (left) at Astrotech Space Operations in Titusville, Fla., questions another worker about the oxygen connection in his protective suit before spacecraft propellant loading of the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft. Liftoff of MESSENGER aboard a Boeing Delta II Heavy rocket, bound for Mercury, is scheduled for Aug. 2. The spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

KSC-04PD-1575

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. On Launch Pad 17-B at Cape Canaveral Air Force Station, Boeing workers complete the installation of the fairing around the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft. The fairing is a molded structure that fits flush with the outside surface of the upper stage booster and forms an aerodynamically smooth joint, protecting the spacecraft during launch. MESSENGER is scheduled to launch Aug. 2 aboard a Boeing Delta II rocket and is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

Viewing Mercury's Surface-bound Exosphere from Orbit: Eighteen Months of Observations by the Mercury Atmospheric and Surface Composition Spectrometer aboard the MESSENGER Spacecraft

NASA Astrophysics Data System (ADS)

McClintock, W. E.; Benna, M.; Burger, M. H.; Cassidy, T.; Killen, R. M.; Merkel, A. W.; Sarantos, M.; Solomon, S. C.; Sprague, A. L.; Vervack, R. J.

2012-12-01

Prior to the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission, Mercury's surface-bounded exosphere was known to contain H and He, observed by Mariner 10, as well as Na, K, and Ca, observed from the ground. The exosphere is the interface between the planet's surface and the surrounding space environment. Its composition and structure are controlled by interactions among the surface, magnetosphere, solar wind, sunlight, and impacting meteoroids. When species are liberated from the surface with sufficient energy, they can be accelerated by solar radiation pressure to form an anti-sunward tail. During three flybys en route to orbit, the Ultraviolet and Visible Spectrometer (UVVS) channel of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) aboard MESSENGER discovered Mg in the tail and detected Ca+ in a narrow region centered ~ 2.5 Mercury radii anti-sunward of the planet's terminator. UVVS began routine orbital observations of both the dayside and nightside exosphere on March 29, 2011. It regularly measures altitude profiles for all previously detected neutral species with the exception of He and K. The former has no emission features within the UVVS wavelength range (115-600 nm), and the latter has only one relatively weak feature there. A single component of Ca is usually observed at lower altitudes (~2000 km) and exhibits the strong equatorial, dawn enhancement observed during the flybys. Mg distributions exhibit two components. The more energetic component has been detected at high altitudes, up to 4000 km above the surface on both the dayside and nightside, and shows a dawn enhancement similar to Ca. Dayside distributions of Na exhibit two components with e-folding heights comparable to profiles above the poles obtained during the third flyby. Concentrations of all three species exhibit seasonal variability. The best studied of these is Na, for which maximum dayside density occurs at a Mercury true anomaly angle of 180°. UVVS also observes H. It is less well studied than Ca, Mg, and Na because signal from the exospheric H is often contaminated by emission from interplanetary hydrogen and sunlight reflected from the surface. O has also been detected near the subsolar point, but its emission is too weak for routine study. UVVS observations also include wavelength scans for neutral species that are known or are predicted to be present in the surface materials (e.g., Si, Al, S, Mn, Fe, and OH), but emissions from these species are not sufficiently bright for detection with current operational scenarios. The UVVS team uses a variety of techniques to relate exosphere composition and structure to source processes, including tomographic inversion and Monte Carlo modeling. Correlations of Mercury's neutral exosphere composition and structure with direct measurements of the space environment from MESSENGER's Magnetometer (MAG) and Energetic Particle and Plasma Spectrometer (EPPS) provide further insight into source processes.

KSC-04PD-1539

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. Inside the environmental curtain suspended around the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft while in the mobile service tower at Launch Complex 17-B, Cape Canaveral Air Force Station, a worker removes the protective material wrapped around MESSENGER. Visible at right is the sunshade that will protect MESSENGERs instruments during exposure to the sun as it orbits Mercury. Scheduled to launch Aug. 2, MESSENGER will return to Earth for a gravity boost in July 2005, then fly past Venus twice, in October 2006 and June 2007. It is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. Processing is being done at Astrotech Space Operations in Titusville, Fla.

Seasonal variations of Mercury's magnesium dayside exosphere from MESSENGER observations

NASA Astrophysics Data System (ADS)

Merkel, Aimee W.; Cassidy, Timothy A.; Vervack, Ronald J.; McClintock, William E.; Sarantos, Menelaos; Burger, Matthew H.; Killen, Rosemary M.

2017-01-01

The Ultraviolet and Visible Spectrometer channel of the Mercury Atmospheric and Surface Composition Spectrometer instrument aboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft made near-daily observations of solar-scattered resonant emission from magnesium in Mercury's exosphere during the mission's orbital phase (March 2011-April 2015, ∼17 Mercury years). In this paper, a subset of these data (March 2013-April 2015) is described and analyzed to illustrate Mg's spatial and temporal variations. Dayside altitude profiles of emission are used to make estimates of the Mg density and temperature. The main characteristics of the Mg exosphere are (a) a predominant enhancement of emission in the morning (6 am-10 am) near perihelion, (b) a bulk temperature of ∼6000 K, consistent with impact vaporization as the predominant ejection process, (c) a near-surface density that varies from 5 cm-3 to 50 cm-3 and (d) a production rate that is strongest in the morning on the inbound leg of Mercury's orbit with rates ranging from 1 × 105 cm-2 s-1 to 8 × 105 cm-2 s-1.

Seasonal Variations of Mercury's Magnesium Dayside Exosphere from MESSENGER Observations

NASA Technical Reports Server (NTRS)

Merkel, Aimee W.; Cassidy, Timothy A.; Vervack, Ronald J., Jr.; McClintock, William E.; Sarantos, Menelaos; Burger, Matthew H.; Killen, Rosemary M.

2017-01-01

The Ultraviolet and Visible Spectrometer channel of the Mercury Atmospheric and Surface Composition Spectrometer instrument aboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft made near-daily observations of solar-scattered resonant emission from magnesium in Mercury's exosphere during the mission's orbital phase (March 2011-April 2015, approx.17 Mercury years). In this paper, a subset of these data (March 2013-April 2015) is described and analyzed to illustrate Mg's spatial and temporal variations. Dayside altitude profiles of emission are used to make estimates of the Mg density and temperature. The main characteristics of the Mg exosphere are (a) a predominant enhancement of emission in the morning (6 am-10 am) near perihelion, (b) a bulk temperature of approx. 6000 K, consistent with impact vaporization as the predominant ejection process, (c) a near-surface density that varies from 5/cu cm to 50/cu cm and (d) a production rate that is strongest in the morning on the inbound leg of Mercury's orbit with rates ranging from 1×10(exp 5)/sq cm/s to 8×10(exp 5)/sq cm/s.

KSC-04pd1485

NASA Image and Video Library

2004-07-19

KENNEDY SPACE CENTER, FLA. - Workers at Astrotech Space Operations in Titusville, Fla., place a protective cover around the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft at Astrotech Space Operations in Titusville, Fla. Bagging the Mercury-bound MESSENGER precedes its placement in a transportation canister for the journey to Launch Pad 17-B at Cape Canaveral Air Force Station, Fla. Liftoff of MESSENGER aboard a Boeing Delta II Heavy rocket is scheduled for Aug. 2. The spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

KSC-04pd1567

NASA Image and Video Library

2004-07-27

KENNEDY SPACE CENTER, FLA. - On Launch Pad 17-B at Cape Canaveral Air Force Station, the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft is seen atop the Delta II upper stage booster (middle) and the Delta II launch vehicle below. The spacecraft is ready for installation of the fairing, a molded structure that fits flush with the outside surface of the upper stage booster and forms an aerodynamically smooth joint, protecting the spacecraft during launch. Seen on the right is one of the solar panels on the spacecraft. On the left is the heat-resistant, ceramic-cloth sunshade that will protect the spacecraft’s instruments as MESSENGER orbits the Mercury where the surface reaches a high temperature near 840 degrees Fahrenheit and the solar intensity can be 11 times greater than on Earth. MESSENGER is scheduled to launch Aug. 2 and is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

KSC-04pd0600

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers secure NASA’s MESSENGER spacecraft on a test stand. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0601

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers secure NASA’s MESSENGER spacecraft on a test stand. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0602

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers secure NASA’s MESSENGER spacecraft on a test stand. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

Exploring Mercury's Surface-Bound Exosphere with the Mercury Atmospheric and Surface Composition Spectrometer: AN Overview of Observations during the First Messenger Flyby

NASA Astrophysics Data System (ADS)

McClintock, W. E.; Bradley, E. T.; Izenberg, N. R.; Killen, R. M.; Kochte, M. C.; Lankton, M. R.; Mouawad, N.; Sprague, A. L.; Vervack, R. J.

2008-12-01

Mercury's surface-bound exosphere is the interface between the planet's surface and the external stimuli that interact with it. Its composition and structure are controlled by surface, magnetosphere, and solar-wind processes. Prior to the MESSENGER mission the exosphere was known to contain H, He, and O from Mariner 10 observations, as well as Na, K, and Ca that were discovered during ground-based observations. Na has been extensively studied since its discovery in 1985, including observations of a neutral Na tail first reported in 2002. Undetected species, including Mg, Fe, Al, and S, are also expected to exist in the exosphere. MESSENGER's initial flyby of Mercury, which occurred on January 14, 2008, offered the first opportunity to measure the planet's neutral tail from space. As the spacecraft approached the planet from the nightside, the UltraViolet and Visible Spectrometer (UVVS) channel of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) scanned the tail beginning at altitudes of 24,500 km behind Mercury's nightside surface and covering a region of space approximately three planet diameters tall and centered on the Sun-Mercury line. The UVVS measured emissions from Na during the entire observation. It also observed neutral hydrogen beginning approximately 5,000 km above the nightside surface. The spatial distributions of both species were seen to be asymmetric, with enhanced densities occurring in the northern hemisphere. UVVS observations of Ca, which were made as the spacecraft traversed the nightside exosphere, exhibited enhanced emission toward the dawn terminator, with north-south behavior similar to that of Na and H. These observations suggest that the relatively high-energy source processes that give rise to species observed in the tail were localized near the northern and morning hemispheres during the flyby. This inference is supported by magnetic field observations made with the MESSENGER Magnetometer, which observed a strong radial component of the interplanetary magnetic field (Bx) directed antisunward after MESSENGER passed outside the magnetosphere. This magnetic field orientation is expected to result in a greater number of open field lines in the northern hemisphere, preferentially allowing solar wind plasma to impinge upon the surface in that region.

KENNEDY SPACE CENTER, FLA. - Shipped in an air-conditioned transportation van from NASA’s Goddard Space Flight Center in Greenbelt, Md., NASA’s MESSENGER spacecraft, the first Mercury orbiter, arrives at the Astrotech Space Operations processing facilities near KSC. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be offloaded and taken into a high bay clean room. After the spacecraft is removed from its shipping container, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - Shipped in an air-conditioned transportation van from NASA’s Goddard Space Flight Center in Greenbelt, Md., NASA’s MESSENGER spacecraft, the first Mercury orbiter, arrives at the Astrotech Space Operations processing facilities near KSC. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be offloaded and taken into a high bay clean room. After the spacecraft is removed from its shipping container, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

Observations of Mercury's Surface-Bounded Exosphere from Orbit: Results from the Mercury Atmospheric and Surface Composition Spectrometer aboard the MESSENGER Spacecraft

NASA Astrophysics Data System (ADS)

McClintock, W. E.; Burger, M. H.; Cassidy, T. A.; Killen, R. M.; Merkel, A. W.; Sarantos, M.; Solomon, S. C.; Vervack, R. J., Jr.

2015-12-01

The Mercury Atmospheric and Surface Composition Spectrometer (MASCS), on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, conducted orbital observations of Mercury's dayside and nightside exosphere from 29 March 2011 to the end of the mission on 30 April 2015. Over slightly more than four Earth-years, MASCS measured emission profiles versus altitude for calcium (Ca), sodium (Na), and magnesium (Mg) at a daily cadence. These species exhibit different spatial distributions, suggesting distinct source processes. MASCS observed seasonal variations in all three species that are remarkably repeatable from one Mercury year to the next, and did so consistently during the entire 17-Mercury-year duration of the orbital phase of the mission. Whereas MASCS has characterized the seasonal variation, it has provided, at best, only weak evidence for the episodic behavior observed in ground-based studies of Na. Joint analyses of MASCS observations and surface precipitation patterns for energetic particles inferred from observations by the Energetic Particle Spectrometer (EPS) and the Fast Imaging Plasma Spectrometer (FIPS) on MESSENGER have not yielded clear correlations. This lack of correlation may be due in part to the MASCS observational geometries. MASCS has conducted a number of searches for other, weakly emitting species. Hydrogen data from the orbital phase are consistent with profiles observed during MESSENGER's flybys of Mercury. Oxygen detections have proven elusive, and the previously reported observation with a brightness of 4 R may only be an upper limit. Ongoing analysis of weak species data suggests that additional species are present.

Oxygen Depletion on the Surface of Mercury: Evidence of Silicon Smelting?

NASA Technical Reports Server (NTRS)

McCubbin, F. M.; Vander Kaaden, K. E.; Peplowski, P. N.; Bell, A. S.; Evans, L. G.; Nittler, L. R.; Boyce, J. W.; Keller, L. P.; McCoy, T. J.

2017-01-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft collected data that provided important insights into the structure, chemical makeup, and compositional diversity of Mercury. The X-Ray Spectrometer (XRS) and Gamma-Ray Spectrometer (GRS) onboard MESSENGER provided the first detailed chemical analyses of Mercury's surface. Among the many discoveries included several surprising characteristics about the surface of Mercury, including elevated S abundances (up to 4 percent by weight), low Fe abundances (less than 4 percent by weight), and relatively low O abundances (O/Si ratio of 1.40 plus or minus 0.03). The surface chemistry as determined by MESSENGER has been used to identify up to nine distinct geochemical terranes on Mercury. Numerous modeling and experimental efforts have been undertaken to infer the mineralogy and petrology of mercurian lavas and surface materials. However, all of these efforts have presumed valence states for each of the elements according to the following: Si4+, Ti4+, Al3+, Cr2+, Fe2+, Mn2+, Mg2+, Ca2+, Na+, K+, S2-, Cl-. Based on these valence assignments, cations are charged balanced with the anions O2-, S2-, and Cl- and the compositions are recast in terms of oxides, sulfides, and chlorides. Based on these assumptions, the geochemical terranes that have been identified on Mercury yield O/Si wt. ratios ranging from 1.61 to 1.84, which is substantially higher than the preliminary O/Si ratio of 1.40 plus or minus 0.03 determined by the MESSENGER GRS]. We have re-evaluated the O/Si ratio using the entire MESSENGER dataset to reassess its implications for the geochemistry of Mercury.

Estimating Surface and Subsurface Ice Abundance on Mercury Using a Thermophysical Model

NASA Astrophysics Data System (ADS)

Rubanenko, L.; Mazarico, E.; Neumann, G. A.; Paige, D. A.

2016-12-01

The small obliquity of the Moon and Mercury causes some topographic features near their poles to cast permanent shadows for geologic time periods. In the past, these permanently shadowed regions (PSRs) were found to have low enough temperatures to trap surface and subsurface water ice. On Mercury, high normal albedo is correlated with maximum temperatures <100 m and high radar backscatter, possibly indicating the presence of surface ice. Areas with slightly higher maximum temperatures were measured to have a decreased albedo, postulated to contain of organic materials overlaying buried ice. We evaluate this theory by employing a thermophysical model that considers insolation, scattering, thermal emissions and subsurface conduction. We model the area fraction of surface and subsurface cold-traps on realistic topography at scales of ˜500 m , recorded by the Mercury Laster Altimeter (MLA) on board the MErcury Surface, Space ENviroment, GEochemistry and Ranging (MESSENGER) spacecraft. At smaller scales, below the instrument threshold, we consider a statistical description of the surface assuming a Gaussian slope distribution. Using the modeled cold-trap area fraction we calculate the expected surface albedo and compare it to MESSENGER's near-infrared surface reflectance data. Last, we apply our model to other airless small-obliquity planetary bodies such as the Moon and Ceres in order to explain other correlations between the maximum temperature and normal albedo.

Evidence from numerical experiments for a feedback dynamo generating Mercury's magnetic field.

PubMed

Heyner, Daniel; Wicht, Johannes; Gómez-Pérez, Natalia; Schmitt, Dieter; Auster, Hans-Ulrich; Glassmeier, Karl-Heinz

2011-12-23

The observed weakness of Mercury's magnetic field poses a long-standing puzzle to dynamo theory. Using numerical dynamo simulations, we show that it could be explained by a negative feedback between the magnetospheric and the internal magnetic fields. Without feedback, a small internal field was amplified by the dynamo process up to Earth-like values. With feedback, the field strength saturated at a much lower level, compatible with the observations at Mercury. The classical saturation mechanism via the Lorentz force was replaced by the external field impact. The resulting surface field was dominated by uneven harmonic components. This will allow the feedback model to be distinguished from other models once a more accurate field model is constructed from MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) and BepiColombo data.

Global Inventory and Characterization of Pyroclastic Deposits on Mercury: New Insights into Pyroclastic Activity from MESSENGER Orbital Data

NASA Technical Reports Server (NTRS)

Goudge, Timothy A.; Head, James W.; Kerber, Laura; Blewett, David T.; Denevi, Brett W.; Domingue, Deborah L.; Gillis-Davis, Jeffrey J.; Gwinner, Klaus; Helbert, Joern; Holsclaw, Gregory M.;

Performance Assessment of the Mercury Laser Altimeter on MESSENGER from Mercury Orbit

NASA Technical Reports Server (NTRS)

Sun, Xiaoli; Cavanaugh, John F.; Neumann, Gregory A.; Mazarico, Edward M.

2009-01-01

The Mercury Laser Altimeter (MLA) is one of seven instruments on the MErcury Surface, Space ENvironment GEochemistry, and Ranging (MESSENGER) spacecraft,a mission in NASA's Discovery Program. MESSENGER was launched on August 3, 2004, and entered into orbit about Mercury on March 29, 2011. As of June 30, 2011 MLA started to collect science Measurements on March 29, 2011. As of June 30, 2011 MLA had accumulated about 3 million laser ranging measurements to the Mercury surface through one Mercury year, i.e ., one complete cycle of the spacecraft thermal environment. The average MLA laser output-pulse energy remained steady despite the harsh thermal environment, in which the laser bench temperature changed by as much as 15 C over a 35 min operating period . The laser beam-collimating telescope experienced a 30 C temperature swing over the same period, and the thermal cycling repeated every 12 hours. Nonetheless, MLA receiver optics appeared to be aligned and in focus throughout these temperature excursions. The maximum ranging distance of MLA was 1500 km at near-zero laser-beam incidence angle (and emission angle) and 600 km at 60 deg incidence angle. The MLA instrument performance in Mercury orbit has been consistent with the performance demonstrated during MESSENGER's Mercury flybys in January and October 2008 and during pre-launch testing. In addition to range measurements, MLA data are being used to estimate the surface reflectance of Mercury at 1064 nm wavelength, including regions of permanent shadow on the floors of polar craters. MLA also provides a measurement of the surface reflectance of sunlight at 1064 nm wavelength by its noise counters, for which output is a monotonic function of the background light.

KSC-04PD-1601

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. On Launch Pad 17-B at Cape Canaveral Air Force Station, the Mobile Service Tower begins to roll back from the pad, revealing the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) spacecraft aboard a Delta II rocket, Model 7925-H with heavy lift capability. MESSENGER is ready for liftoff on Aug. 2 at 2:16 a.m. EDT and is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

KSC-04PD-1603

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. On Launch Pad 17-B at Cape Canaveral Air Force Station, the Mobile Service Tower rolls back revealing the MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) spacecraft aboard a Delta II rocket, model 7925-H with heavy lift capability. MESSENGER is ready for liftoff on Aug. 2 at 2:16 a.m. EDT and is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

National Medal of Science

NASA Image and Video Library

2014-11-20

President Barack Obama congratulates MESSENGER Principal Investigator, director of Columbia University's Lamont-Doherty Earth Observatory, Sean Solomon, after awarding him the National Medal of Science, the nation's top scientific honor,Thursday, Nov. 20, 2014 during a ceremony in the East Room of the White House in Washington. MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. Photo Credit: (NASA/Bill Ingalls)

KSC-04pd1447

NASA Image and Video Library

2004-07-06

KENNEDY SPACE CENTER, FLA. - The Boeing Delta II Heavy second-stage engine, the Aerojet AJ10-118K, is lifted up the mobile service tower at Pad 17-B, Cape Canaveral Air Force Station. The Delta II is the launch vehicle for the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft, scheduled to lift off Aug. 2. Bound for Mercury, the spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

KSC-04pd1630

NASA Image and Video Library

2004-08-03

KENNEDY SPACE CENTER, FLA. - Wrapped in clouds of smoke, the Boeing Delta II rocket with its MESSENGER spacecraft on top climbs free as it lifts off on time at 2:15:56 a.m. EDT from Launch Pad 17-B, Cape Canaveral Air Force Station. MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) is on a seven-year, 4.9-billion-mile journey to the planet Mercury. The spacecraft will fly by Earth, Venus and Mercury several times, as well as circling the sun 15 times, to burn off energy before making its final approach to the inner planet on March 18, 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

Characterization of the Morphometry of Impact Craters Hosting Polar Deposits in Mercury's North Polar Region

NASA Technical Reports Server (NTRS)

Talpe, Matthieu, J.; Zuber, Maria T.; Neumann, Gregory A.; Mazarico, Erwan; Solomon, Sean C.; Vilas, Faith

2012-01-01

Earth-based radar images dating back two decades show that the floors of some polar craters on Mercury host radar-bright deposits that have been proposed to consist of frozen volatiles. Several hypotheses have been put forth to explain their source, including volcanic outgassing, chemical sputtering, and deposition of exogenous water ice. Calculations show that volatiles are thermally stable in permanently shadowed areas. An earlier study of the depths of north polar craters determined with photoclinometric techniques applied to Mariner 10 images yielded the conclusion that the mean ratio of crater depth d to rim-crest diameter D for craters hosting polar deposits is two-thirds that of the mean ratio for a comparable population of neighboring craters lacking such deposits. This result could be explained by (though doesn't require) the presence of a thick layer of volatiles within the polar deposit-hosting craters. Here we use altimetric profiles and topographic maps obtained by the Mercury Laser Altimeter (MLA) to revisit this analysis. MLA is an instrument on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which has been orbiting Mercury since March 2011. MLA transmits a 1064-nm laser pulse at 8 Hz during MESSENGER's trajectory over Mercury s surface. The MLA illuminates surface areas averaging between 15 m and 100 m in diameter, spaced approx 400 m apart along the spacecraft ground track. The radial precision of individual measurements is <1 m, and the current accuracy with respect to Mercury s center of mass is better than 20 m. As of mid-December 2011, MLA coverage had reached to 15 S and has yielded a comprehensive map of the topography of Mercury s northern hemisphere. The MLA data are used here to quantify the shapes of craters in the north polar region and to avoid the shadowing bias of photoclinometric techniques.

Mercury: Photomosaic of the Shakespeare Quadrangle of Mercury (Southern Half) H-3

NASA Technical Reports Server (NTRS)

1974-01-01

This computer generated photomosaic from Mariner 10 is of the southern half of Mercury's Shakespeare Quadrangle, named for the ancient Shakespeare crater located on the upper edge to the left of center. This portion of the quadrangle covers the geographic region from 20 to 45 degrees north latitude and from 90 to 180 degrees longitude. The photomosaic was produced using computer techniques and software developed in the Image Processing Laboratory of NASA's Jet Propulsion Laboratory. The pictures have been high-pass filtered and contrast enhanced to accentuate surface detail, and geometrically transformed into a Lambert conformal projection.

Well defined bright streaks or ray systems radiating away from craters constitute another distinctive feature of the Mercurian surface, remarkably similar to the Moon. The rays cut across and are superimposed on all other surface features, indicating that the source craters are the youngest topographic features on the surface of Mercury.

The above material was taken from the following publication... Davies, M. E., S. E. Dwornik, D. E. Gault, and R. G. Strom, Atlas of Mercury,NASA SP-423 (1978).

The Mariner 10 mission was managed by the Jet Propulsion Laboratory for NASA's Office of Space Science.

KSC-04pd0597

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers prepare for contact of NASA’s MESSENGER spacecraft with a test stand. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0599

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers verify the correct placement of NASA’s MESSENGER spacecraft on a test stand. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0594

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers prepare to move NASA’s MESSENGER spacecraft onto a test stand using an overhead crane. There, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0598

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers check for the correct alignment of NASA’s MESSENGER spacecraft as it is lowered onto a test stand. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0595

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers lower NASA’s MESSENGER spacecraft onto a test stand using an overhead crane. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0603

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, the attachment of NASA’s MESSENGER spacecraft to a test stand is complete. The spacecraft is now ready for employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, to begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd0596

NASA Image and Video Library

2004-03-22

KENNEDY SPACE CENTER, FLA. -- At the Astrotech Space Operations processing facilities, workers monitor NASA’s MESSENGER spacecraft as it is lowered onto a test stand by an overhead crane. Once in place, employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will begin final processing for launch, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched aboard a Boeing Delta II rocket no earlier than July 30 on a six-year mission to study the planet Mercury.

KSC-04pd1483

NASA Image and Video Library

2004-07-19

KENNEDY SPACE CENTER, FLA. - Workers from the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. get ready to “bag” the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft in the background at Astrotech Space Operations in Titusville, Fla. Placing a protective cover around the Mercury-bound MESSENGER precedes its placement in a transportation canister for the journey to Launch Pad 17-B at Cape Canaveral Air Force Station, Fla. Liftoff of MESSENGER aboard a Boeing Delta II Heavy rocket is scheduled for Aug. 2. The spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by APL.

KSC-04pd1484

NASA Image and Video Library

2004-07-19

KENNEDY SPACE CENTER, FLA. - Workers from the Johns Hopkins University Applied Physics Laboratory in Laurel, Md., begin placing a protective cover around the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft at Astrotech Space Operations in Titusville, Fla. Bagging the Mercury-bound MESSENGER precedes its placement in a transportation canister for the journey to Launch Pad 17-B at Cape Canaveral Air Force Station, Fla. Liftoff of MESSENGER aboard a Boeing Delta II Heavy rocket is scheduled for Aug. 2. The spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by APL.

Tomographic Reconstruction of Mercury's Exosphere from MESSENGER Flyby Data

NASA Technical Reports Server (NTRS)

Killen, Rosemary M.; McClintock, William E.; Slavin, James A.; Solomon, Sean C.; Vervack, Ronald J., Jr.

2011-01-01

The exosphere of Mercury is among the best-studied examples of a common type of atmosphere, a surface-bounded exosphere. Mercury's exosphere was probed in 2008-2009 with Ultraviolet and Visible Spectrometer (UVVS) measurements obtained during three planetary flybys by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft [1-3]. The measurements detailed the distribution of two previously known metallic constituents of Mercury's exosphere, Na and Ca, and indicated the presence in the gas phase of yet another metallic species, Mg. Such measurements can answer fundamental scientific questions regarding the relative importance of possible source and loss processes for exospheric species ejected from a surface boundary [4]. The trajectory of MESSENGER during the last of its three flybys provided the best spatial coverage prior to orbit insertion. The measurements by MESSENGER of Na, Ca, and Mg during the third flyby have been analyzed with a novel tomographic method. This approach maximizes the amount of information that can be extracted from line-of-sight measurements because it yields three-dimensional distributions of neutrals consistent with the data.

Carbon on Mercury's Surface - Origin, Distribution, and Concentration

NASA Technical Reports Server (NTRS)

Klima, Rachel L.; Blewett, David T.; Denevi, Brett W.; Ernst, Carolyn M.; Murchie, Scott L.; Peplowski, Patrick N.; Perera, Virange; Vander Kaaden, Kathleen

2018-01-01

Distinctive low-reflectance material (LRM) was first observed on Mercury in Mariner 10 flyby images. Visible to near-infrared reflectance spectra of LRM are flatter than the average reflectance spectrum of Mercury, which is strongly red sloped (increasing in reflectance with wavelength). From Mariner 10 and early MErcury, Surface, Space, ENvironment, GEochemistry, and Ranging (MESSENGER) flyby observations, it was suggested that a higher content of ilmenite, ulvospinel, carbon, or iron metal could cause both the characteristic dark, flat spectrum of LRM and the globally low reflectance of Mercury. Once MESSENGER entered orbit, low Fe and Ti abundances measured by the X-Ray and Gamma-Ray Spectrometers ruled out ilmenite, and ulvospinel as important surface constituents and implied that LRM was darkened by a different phase, such as carbon or small amounts of micro- or nanophase iron or iron sulfide dispersed in a silicate matrix. Low-altitude thermal neutron measurements of three LRM-rich regions confirmed an enhancement of 1-3 weight-percent carbon over the global abundance, supporting the hypothesis that LRM is darkened by carbon.

Petrology and Geochemistry of Mercury

NASA Astrophysics Data System (ADS)

Weider, Shoshana Z.

2018-04-01

Although having knowledge of a terrestrial planet's chemistry is fundamental to understanding the origin and composition of its rocks, until recently, the geochemistry of Mercury—the Solar System's innermost planet—was largely unconstrained. Without the availability of geological specimens from Mercury, studying the planet's surface and bulk composition relies on remote sensing techniques. Moreover, Mercury's proximity to the Sun makes it difficult to study with Earth/space-based telescopes, or with planetary probes. Indeed, to date, only NASA's Mariner 10 and MESSENGER missions have been sent to Mercury. The former made three "flyby" encounters of Mercury between 1974 and 1975, but did not carry any instrument to make geochemical or mineralogical measurements of the surface. Until the MESSENGER flyby and orbital campaigns (2008–2015), therefore, knowledge of Mercury's chemical composition was severely limited and consisted of only a few facts. For example, it has long been known that Mercury has the highest uncompressed density of all the terrestrial planets (and thus a disproportionately large iron core). In addition, Earth-based spectral reflectance observations indicated a dark surface, largely devoid of iron within silicate minerals. To improve understanding of Mercury's geochemistry, the MESSENGER payload included a suite of geochemical sensing instruments: namely the X-Ray Spectrometer, Gamma-Ray Spectrometer, and Neutron Spectrometer. Indeed, the datasets obtained from these instruments (as well as from other complementary instruments) during MESSENGER's 3.5-year orbital mission allow a much more complete picture of Mercury's geochemistry to be drawn, and quantitative abundance estimates for several major rock-forming elements in Mercury's crust are now available. Overall, the MESSENGER data reveal a surface that is rich in Mg, but poor in Al and Ca, compared with typical terrestrial and lunar crustal materials. Mercury's surface also contains high concentrations of the volatile elements Na, S, K, and Cl. Furthermore, the total surface Fe abundance is now known to be <2 wt%, and the planet's low reflectance is thought to be primarily caused by the presence of C (in graphite) at a level of >1 wt%. Such data are key to constraining models for Mercury's formation and early evolution. Large-scale spatial variations in the MESSENGER geochemical datasets have also led to the designation of several geochemical "terrains" across Mercury's surface, which do not always align to otherwise mapped geological regions. Based on the MESSENGER geochemical results, several recent petrological experiments and calculations have been, and continue to be, performed to study Mercury's surface mineralogy. The results show that there are substantial differences in the precise mineral compositions and abundances among the different terrains, but Mercury's surface appears to be dominated by Mg-rich olivines and pyroxenes, as well as plagioclase and sulphide phases. Depending on the classification scheme used, Mercury's ultramafic surface rocks can thus be described as similar in nature to terrestrial boninites, andesites, norites, or gabbros.

MERTIS: the thermal infrared imaging spectrometer onboard of the Mercury Planetary Orbiter

NASA Astrophysics Data System (ADS)

Zeh, T.; Peter, G.; Walter, I.; Kopp, E.; Knollenberg, J.; Helbert, J.; Gebhardt, A.; Weber, I.; Hiesinger, Harry

2017-11-01

The MERTIS instrument is a thermal infrared imaging spectrometer onboard of ESA's cornerstone mission BepiColombo to Mercury. MERTIS has four goals: the study of Mercury's surface composition, identification of rock-forming minerals, mapping of the surface mineralogy, and the study of the surface temperature variations and thermal inertia. MERTIS will provide detailed information about the mineralogical composition of Mercury's surface layer by measuring the spectral emittance in the spectral range from 7-14 μm at high spatial and spectral resolution. Furthermore MERTIS will obtain radiometric measurements in the spectral range from 7-40 μm to study the thermo-physical properties of the surface material. The MERTIS detector is based on an uncooled micro-bolometer array providing spectral separation and spatial resolution according to its 2-dimensional shape. The operation principle is characterized by intermediate scanning of the planet surface and three different calibration targets - free space view and two on-board black body sources. In the current project phase, the MERTIS Qualification Model (QM) is under a rigorous testing program. Besides a general overview of the instrument principles, the papers addresses major aspects of the instrument design, manufacturing and verification.

A comprehensive study of Mercury and MESSENGER orbit determination

NASA Astrophysics Data System (ADS)

Genova, Antonio; Mazarico, Erwan; Goossens, Sander; Lemoine, Frank G.; Neumann, Gregory A.; Nicholas, Joseph B.; Rowlands, David D.; Smith, David E.; Zuber, Maria; Solomon, Sean C.

2016-10-01

The MErcury, Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft orbited the planet Mercury for more than 4 years. The probe started its science mission in orbit around Mercury on 18 March 2011. The Mercury Laser Altimeter (MLA) and radio science system were the instruments dedicated to geodetic observations of the topography, gravity field, orientation, and tides of Mercury. X-band radio-tracking range-rate data collected by the NASA Deep Space Network (DSN) allowed the determination of Mercury's gravity field to spherical harmonic degree and order 100, the planet's obliquity, and the Love number k2.The extensive range data acquired in orbit around Mercury during the science mission (from April 2011 to April 2015), and during the three flybys of the planet in 2008 and 2009, provide a powerful dataset for the investigation of Mercury's ephemeris. The proximity of Mercury's orbit to the Sun leads to a significant perihelion precession attributable to the gravitational flattening of the Sun (J2) and the Parameterized Post-Newtonian (PPN) coefficients γ and β, which describe the space curvature produced by a unit rest mass and the nonlinearity in superposition of gravity, respectively. Therefore, the estimation of Mercury's ephemeris can provide crucial information on the interior structure of the Sun and Einstein's general theory of relativity. However, the high correlation among J2, γ, and β complicates the combined recovery of these parameters, so additional assumptions are required, such as the Nordtvedt relationship η = 4β - γ - 3.We have modified our orbit determination software, GEODYN II, to enable the simultaneous integration of the spacecraft and central body trajectories. The combined estimation of the MESSENGER and Mercury orbits allowed us to determine a more accurate gravity field, orientation, and tides of Mercury, and the values of GM and J2 for the Sun, where G is the gravitational constant and M is the solar mass. Several test cases illuminate results on the estimation of PPN parameters.

A Test of General Relativity with MESSENGER Mission Data

NASA Astrophysics Data System (ADS)

Genova, A.; Mazarico, E.; Goossens, S. J.; Lemoine, F. G.; Neumann, G. A.; Nicholas, J. B.; Rowlands, D. D.; Smith, D. E.; Zuber, M. T.; Solomon, S. C.

2016-12-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft initiated collection of scientific data from the innermost planet during its first flyby of Mercury in January 2008. After two additional Mercury flybys, MESSENGER was inserted into orbit around Mercury on 18 March 2011 and operated for more than four Earth years through 30 April 2015. Data acquired during the flyby and orbital phases have provided crucial information on the formation and evolution of Mercury. The Mercury Laser Altimeter (MLA) and the radio science system, for example, obtained geodetic observations of the topography, gravity field, orientation, and tides of Mercury, which helped constrain its surface and deep interior structure. X-band radio tracking data collected by the NASA Deep Space Network (DSN) allowed the determination of Mercury's gravity field to spherical harmonic degree and order 100, as well as refinement of the planet's obliquity and estimation of the tidal Love number k2. These geophysical parameters are derived from the range-rate observables that measure precisely the motion of the spacecraft in orbit around the planet. However, the DSN stations acquired two other kinds of radio tracking data, range and delta-differential one-way ranging, which also provided precise measurements of Mercury's ephemeris. The proximity of Mercury's orbit to the Sun leads to a significant perihelion precession, which was used by Einstein as confirmation of general relativity (GR) because of its inconsistency with the effects predicted from classical Newtonian theory. MESSENGER data allow the estimation of the GR parameterized post-Newtonian (PPN) coefficients γ and β. Furthermore, determination of Mercury's orbit also allows estimation of the gravitational parameter (GM) and the flattening (J2) of the Sun. We modified our orbit determination software, NASA GSFC's GEODYN II, to enable simultaneous orbit integration of both MESSENGER and the planet Mercury. The combined estimation of both orbits leads to a more accurate estimation of Mercury's gravity field, orientation, and tides. Results for these geophysical parameters, GM and J2 for the Sun, and the PPN parameters constitute updates for all of these quantities.

The low-degree shape of Mercury

NASA Astrophysics Data System (ADS)

Perry, Mark E.; Neumann, Gregory A.; Phillips, Roger J.; Barnouin, Olivier S.; Ernst, Carolyn M.; Kahan, Daniel S.; Solomon, Sean C.; Zuber, Maria T.; Smith, David E.; Hauck, Steven A.; Peale, Stanton J.; Margot, Jean-Luc; Mazarico, Erwan; Johnson, Catherine L.; Gaskell, Robert W.; Roberts, James H.; McNutt, Ralph L.; Oberst, Juergen

2015-09-01

The shape of Mercury, particularly when combined with its geoid, provides clues to the planet's internal structure, thermal evolution, and rotational history. Elevation measurements of the northern hemisphere acquired by the Mercury Laser Altimeter on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft, combined with 378 occultations of radio signals from the spacecraft in the planet's southern hemisphere, reveal the low-degree shape of Mercury. Mercury's mean radius is 2439.36 ± 0.02 km, and there is a 0.14 km offset between the planet's centers of mass and figure. Mercury is oblate, with a polar radius 1.65 km less than the mean equatorial radius. The difference between the semimajor and semiminor equatorial axes is 1.25 km, with the long axis oriented 15° west of Mercury's dynamically defined principal axis. Mercury's geoid is also oblate and elongated, but it deviates from a sphere by a factor of 10 less than Mercury's shape, implying compensation of elevation variations on a global scale.

Modeling Mercury

NASA Astrophysics Data System (ADS)

Burger, M. H.; Killen, R. M.; M, N.; Sarantos, M.; Crider, D. H.; Vervak, R. J.

2009-04-01

Mercury has a tenuous exosphere created by the combined effects of solar radiation and micrometeoroid bombardment on the surface and the interaction of the solar wind with Mercury's magnetic field and surface. Observations of this exosphere provide essential data necessary for understanding the composition and evolution of Mercury's surface, as well as the interaction between Mercury's magnetosphere with the solar wind. The sodium component of the exosphere has been well observed from the ground (see review by Killen et al., 2007). These observations have revealed a highly variable and inhomogeneous exosphere with emission often peaking in the polar regions. Radiation acceleration drives exospheric escape producing a sodium tail pointing away from the sun which has been detected up to 1400 Mercury radii from the planet (Potter et al. 2002; Baumgardner et al. 2008). Calcium has also been observed in Mercury's exosphere showing a distribution distinct from sodium, although also variable (Killen et al. 2005). During the first two encounters with Mercury by MESSENGER, observations of the exosphere were made by the UltraViolet and Visible Spectrometer (UVVS) channel of the Mercury Atmospheric and Surface Composition Spectrometer (MASCS). Sodium and calcium emission were detected during both flybys, and magnesium was detected for the first time in Mercury's exosphere during the second flyby. The spatial distributions of these species showed significant, unexpected differences which suggest differences in the mechanisms responsible for releasing them from the surface. We present a Monte-Carlo model of sodium, magnesium, and calcium in Mercury's exosphere. The important source mechanisms for ejecting these species from the surface are sputtering by solar wind ions, photon-stimulated desorption, and micrometeoroid impact vaporization. Thermal desorption on the dayside does not supply enough energy to significantly populate the exosphere, although it does play a role in redistributing volatiles over the surface. In addition, atomic calcium can be produced from the dissociation of Ca-bearing molecules, such as CaO, which can be formed in impact vapors. The primary loss processes are the escape of neutrals ejected with sufficient energy and photoionization. The former process is supplemented by radiation pressure which accelerates neutrals anti-sunward such that escaping neutrals form a tail pointing away from the sun. Because Mercury's heliocentric distance and radial velocity vary during its orbit, both loss processes are functions of Mercury's true anomaly. We also consider the spatial distribution of the surface source. Impact vaporization is roughly isotropic over the surface, although there may be a leading/trailing asymmetry in the impact rate due to Mercury's orbital motion. Sputtering is confined to regions where the solar wind can impact the surface, which is shielded somewhat by the internal magnetic field. The surface regions vulnerable depend on the solar wind conditions. References: Baumgardner et al., GRL, 35, L03201, 2008. Killen, R.M. et al., Space Sci. Rev. 132, 433-509, 2007. Killen, R.M. et al., Icarus, 173, 300-311, 2005. Potter et al., Meteoritics & Planetary Sci., 37, 1165, 2002.

Future observations of and missions to Mercury

NASA Technical Reports Server (NTRS)

Stern, Alan S.; Vilas, Faith

1988-01-01

Key scientific objectives of Mercury explorations are discussed, and the methods by which remote observations of Mercury can be carried out from earth and from space are examined. Attention is also given to the scientific rationale and technical concepts for missions to Mercury. It is pointed out that multiple Venus-Mercury encounter trajectories exist which, through successive gravity assists, reduce mission performance requirements to levels deliverable by available systems, such as Titan-Centaur, Atlas-Centaur, and Shuttle/TOS. It is shown that a single launch in July of 1994, using a Titan-Centaur combination, could place a 1477-kg payload into orbit around Meercury. The components of a Mercury-orbiter payload designed to study surface geology and geochemistry, atmospheric composition and structure, the local particle and fields environment, and solid-body rotation dynamics are listed.

Evidence for Surface and Subsurface Ice Inside Micro Cold-Traps on Mercury's North Pole

NASA Technical Reports Server (NTRS)

Rubanenko, L.; Mazarico, E.; Neumann, G. A.; Paige, D. A.

2017-01-01

The small obliquity of Mercury causes topographic depressions located near its poles to cast persistent shadows. Many [1, 9, 15] have shown these permanently shadowed regions (PSRs) may trap water ice for geologic time periods inside cold-traps. More recently, direct evidence for the presence of water ice deposits inside craters was remotely sensed in RADAR [5] and visible imagery [3]. Albedo measurements (reflectence at 1064 nm) obtained by the MErcury Space ENviroment GEochemistry and Ranging Laser Altimeter (MLA) found unusually bright and dark areas next to Mercury's north pole [7]. Using a thermal illumination model, Paige et al. [8] found the bright deposits are correlated with surface cold-traps, and the dark deposits are correlated with subsurface cold-traps. They suggested these anomalous deposits were brought to the surface by comets and were processed by the magnetospheric radiation flux, removing hydrogen and mixing C-N-O-S atoms to form a variety of molecules which will darken with time. Here we use a thermal illumination model to find the link between the cold-trap area fraction of a rough surface and its albedo. Using this link and the measurements obtained by MESSENGER we derive a surface and a subsurface ice distribution map on Mercury's north pole below the MESSENGER spatial resolution, approximately 500 m. We find a large fraction of the polar ice on Mercury resides inside micro cold-traps (of scales 10 - 100 m) distributed along the inter-crater terrain.

Aubrite and Impact Melt Enstatite Chondrite Meteorites as Potential Analogs to Mercury

NASA Technical Reports Server (NTRS)

Wilbur, Z. E.; Udry, A.; Mccubbin, Francis M.; McCubbin, F. M.; Combs, L. M.; Rahib, R. R.; McCoy, C.; McCoy, T. J.

2018-01-01

The MESSENGER (MErcury Sur-face, Space ENvironment, GEochemistry and Ranging) orbiter measured the Mercurian surface abundances of key rock-forming elements to help us better understand the planet's surface and bulk geochemistry. A major discovery is that the Mercurian surface and interior are characterized by an extremely low oxygen fugacity (ƒO2; Iron-Wüstite (IW) -7.3 to IW-2.6. This is supported by low Fe and high S abundances on the surface. This low ƒO2 causes a different elemental partioning from what is observed on Earth. Using surface composition, it was shown that the Mercurian surface mainly consists of normative plagioclase, pyroxene, olivine, and exotic sulfides, such as niningerite ((Mg,Mn, Fe)S) and oldhamite (CaS).

National Medal of Science

NASA Image and Video Library

2014-11-20

President Barack Obama delivers remarks at the National Medals of Science and National Medals of Technology and Innovation Awards Ceremony, Thursday, Nov. 20, 2014 in the East Room of the White House in Washington. MESSENGER Principal Investigator, director of Columbia University's Lamont-Doherty Earth Observatory, Sean Solomon, was awarded the National Medal of Science, the nation's top scientific honor, at the ceremony. MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. Photo Credit: (NASA/Bill Ingalls)

National Medal of Science

NASA Image and Video Library

2014-11-20

President Barack Obama, right, and MESSENGER Principal Investigator, director of Columbia University's Lamont-Doherty Earth Observatory, Sean Solomon, listen as a citation is read prior to the President bestowing the National Medal of Science, the nation's top scientific honor to Solomon, Thursday, Nov. 20, 2014 during a ceremony in the East Room of the White House in Washington. MESSENGER (MErcury Surface, Space ENvironment, GEochemistry, and Ranging) is a NASA-sponsored scientific investigation of the planet Mercury and the first space mission designed to orbit the planet closest to the Sun. Photo Credit: (NASA/Bill Ingalls)

KSC-04pd1453

NASA Image and Video Library

2004-07-06

KENNEDY SPACE CENTER, FLA. - Workers in the mobile service tower on Pad 17-B, Cape Canaveral Air Force Station, check the progress of the Boeing Delta II Heavy second-stage engine as it descends toward the first stage. The Delta is the launch vehicle for the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft, scheduled to lift off Aug. 2. Bound for Mercury, the spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

KSC-04pd1446

NASA Image and Video Library

2004-07-06

KENNEDY SPACE CENTER, FLA. - The Boeing Delta II Heavy second-stage engine, the Aerojet AJ10-118K, is ready for lifting up the mobile service tower at Pad 17-B, Cape Canaveral Air Force Station. The Delta II is the launch vehicle for the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft, scheduled to lift off Aug. 2. Bound for Mercury, the spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

Mercury's Sodium Exosphere: Observations during the MESSENGER Orbital Phase

NASA Technical Reports Server (NTRS)

Killen, Rosemary M.; Cassidy, Timothy A.; Vervack, Ronald J., Jr.; Burger, Matthew H.; Merkel, Aimee W.; Sarantos, Menelaos; Sprague, Ann L.; McClintock, William E.; Benna, Mehdi; Solomon, Sean C.

2012-01-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft entered into orbit about Mercury on March 18,2011. We now have approximately five Mercury years of data from orbit. Prior to the MESSENGER mission, Mercury's surface-bounded exosphere was known to contain H, He, Na. K, and Ca. The Ultraviolet and Visible Spectrometer (UVVS) began routine orbital observations of both the dayside and nightside exosphere on March 29. 2011, measuring altitude profiles for all previously detected neutral species except for He and K. We focus here on what we have learned about the sodium exosphere: its spatial, seasonal, and sporadic variation. Observations to date permit delineation of the relative roles of photon-stimulated desorption (PSD) and impact vaporization (IV) from seasonal and spatial effects, as well as of the roles of ions both as sputtering agents and in their possible role to enhance the efficiency of PSD. Correlations of Mercury's neutral sodium exosphere with measurements from MESSENGER's Magnetometer (MAG) and Energetic Particle and Plasma Spectrometer (EPPS) provide insight into the roles of ions and electrons. Models incorporating MAG observations provide a basis for identifying the location and area of the surface exposed to solar wind plasma, and EPPS observations reveal episodic populations of energetic electrons in the magnetosphere and the presence of planetary He(+), 0(+), and Na(+),

Calcium in Mercury's Exosphere: Modeling MESSENGER Data

NASA Technical Reports Server (NTRS)

Burger, Matthew H.; Killen, Rosemary M.; McClintock, William E.; Merkel, Aimee; Vervack, Ronald J.; Sarantos, Menelaos; Sprague, Ann L.

2011-01-01

Mercury is surrounded by a surface-bounded exosphere comprised of atomic species including hydrogen, sodium, potassium, calcium, magnesium, and likely oxygen. Because it is collisionless. the exosphere's composition represents a balance of the active source and loss processes. The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface. Space ENvironment. GEochemistry. and Ranging (MESSENGER) spacecraft has made high spatial-resolution observations of sodium, calcium, and magnesium near Mercury's surface and in the extended, anti-sunward direction. The most striking feature of these data has been the substantial differences in the spatial distribution of each species, Our modeling demonstrates that these differences cannot be due to post-ejection dynamics such as differences in photo-ionization rate and radiation pressure. but instead point to differences in the source mechanisms and regions on the surface from which each is ejected. The observations of calcium have revealed a strong dawn/dusk asymmetry. with the abundance over the dawn hemisphere significantly greater than over the dusk. To understand this asymmetry, we use a Monte Carlo model of Mercury's exosphere that we developed to track the motions of exospheric neutrals under the influence of gravity and radiation pressure. Ca atoms can be ejected directly from the surface or produced in a molecular exosphere (e.g., one consisting of CaO). Particles are removed from the system if they stick to the surface or escape from the model region of interest (within 15 Mercury radii). Photoionization reduces the final weighting given to each particle when simulating the Ca radiance. Preliminary results suggest a high temperature ( I-2x 10(exp 4) K) source of atomic Ca concentrated over the dawn hemisphere. The high temperature is consistent with the dissociation of CaO in a near-surface exosphere with scale height <= 100 km, which imparts 2 eV to the freshly produced Ca atom. This source region and energy are consistent with data from the three MESSENGER flybys; whether this holds true for the data obtained in orbit is under investigation.

Crater Morphometry and Crater Degradation on Mercury: Mercury Laser Altimeter (MLA) Measurements and Comparison to Stereo-DTM Derived Results

NASA Technical Reports Server (NTRS)

Leight, C.; Fassett, C. I.; Crowley, M. C.; Dyar, M. D.

2017-01-01

Two types of measurements of Mercury's surface topography were obtained by the MESSENGER (MErcury Surface Space ENvironment, GEochemisty and Ranging) spacecraft: laser ranging data from Mercury Laser Altimeter (MLA) [1], and stereo imagery from the Mercury Dual Imaging System (MDIS) camera [e.g., 2, 3]. MLA data provide precise and accurate elevation meaurements, but with sparse spatial sampling except at the highest northern latitudes. Digital terrain models (DTMs) from MDIS have superior resolution but with less vertical accuracy, limited approximately to the pixel resolution of the original images (in the case of [3], 15-75 m). Last year [4], we reported topographic measurements of craters in the D=2.5 to 5 km diameter range from stereo images and suggested that craters on Mercury degrade more quickly than on the Moon (by a factor of up to approximately 10×). However, we listed several alternative explanations for this finding, including the hypothesis that the lower depth/diameter ratios we observe might be a result of the resolution and accuracy of the stereo DTMs. Thus, additional measurements were undertaken using MLA data to examine the morphometry of craters in this diameter range and assess whether the faster crater degradation rates proposed to occur on Mercury is robust.

Distribution, Statistics, and Resurfacing of Large Impact Basins on Mercury

NASA Technical Reports Server (NTRS)

Fassett, Caleb I.; Head, James W.; Baker, David M. H.; Chapman, Clark R.; Murchie, Scott L.; Neumann, Gregory A.; Oberst, Juergen; Prockter, Louise M.; Smith, David E.; Solomon, Sean C.;

People

NASA Astrophysics Data System (ADS)

2001-07-01

Exploring Mercury PhD student Mark Bentley explains how and why he got involved Mark Bentley is studying for a PhD in planetary science. He is helping to design and build instruments for a forthcoming ESA mission to explore the surface of Mercury. Mark Bentley Space has excited and inspired me for as long as I can remember; my earliest memory of this is being allowed to stay up 'really late' to watch the Space Shuttle Columbia land in 1981, at the age of five. Science in general has always interested me. Although I probably didn't recognize it as such at the time, my fascination with collecting all sorts of equipment (or as my parents called it, 'junk') and finding out what made them tick was an early demonstration of this. At school it seemed natural to take science subjects (Physics, Chemistry and Maths A-levels) and then to consider University though physics was not my first thought. I was all set for the respectable career of computer science, not realizing that my space interests could lead anywhere, until I flicked through the first prospectus I received. By luck it was from Leicester University, and while computer science was offered it also had something called 'Physics with Space Science and Technology'. The rest, as they say, is history... After graduating I spent the following two years working for a UK company developing satellite simulators. But then I started thinking about doing a PhD attracted by the flexibility of directing my own research. I knew that I wanted something that involved space science and the element of discovery, but also something that looked at the engineering and technology of a space mission. The timing was fortuitous shortly after I committed myself to a PhD, the European Space Agency announced the selection of BepiColombo, a mission to Mercury, as one of its 'Cornerstone' (large scale) missions. Here was a mission big on science (no spacecraft has ever orbited Mercury, let alone landed on it) and technology as well! So that takes me to where I am now in my first year at the Planetary and Space Sciences Research Institute of the Open University in Milton Keynes. If everything goes according to plan, three years later I will be Dr Bentley and know a whole lot more about Mercury! So what am I now? A physicist at heart, but I guess 'planetary scientist' is more accurate... The great thing about studying the planets is that the field can be stretched to encompass just about any aspect of science you care to choose from biology, through engineering, to physics and more. Planetary science fits well with the modern 'trend' for multidisciplinary research as well as being on the leading edge of modern science, and one of the most international areas of study. In studying our solar system we aim to learn more about the processes that formed the planets and ultimately life itself. For the foreseeable future the nine major bodies and their associated moons are our only glimpse back in time to the early life of our corner of the Universe. Over the past few decades, a relatively short period of time, we have expanded our understanding of the planets by orders of magnitude. Instruments like the Hubble Space Telescope have enabled more and more detailed images of both the near and far, whilst robotic space probes have extended scientists' senses to the far corners of the solar system. The two least studied planets lie at the two extreme ends of our system. Pluto sits at the outer edges of the solar system, a small icy ball that astronomers even argue about calling a planet. Mercury, messenger of the Gods, is a relative inferno, closer to the Sun than any other body. Mercury is not an easy target for spacecraft. Tucked deep in the Sun's gravitational well, any mission must lose about 60% of its orbital energy in order to match Mercury's orbit. The only spacecraft to visit Mercury to date was Mariner 10, a NASA mission flown in the mid-70s. It had far too much energy to enter orbit and could just make several quick passes, leaving an incomplete image of only half of the planet. This, and observations made from Earth, provide almost all of our knowledge of Mercury. Earth observations, however, are hampered by the planet's proximity to the Sun, making observations possible only at dawn and dusk. A mosaic of images of Mercury from the NASA Mariner 10 spacecraft. ©NASA In the mid-80s improved radar equipment allowed high resolution mapping of surface features from the Earth. Amongst the results were two tantalising mysteries: a large dome feature, similar in some ways to shield volcanoes seen on Mars, observed on the unimaged side of the planet and complex scattering of returned radar from distinct areas around the poles, suggesting that water ice may exist in craters there. Both NASA and the European Space Agency (ESA) are now planning missions to Mercury. The US team are using a newly discovered trajectory that will allow them to reach Mercury using traditional chemical propulsion, incorporating various planetary flybys so-called 'gravity assist' manoeuvres. The European team, on the other hand, has proposed a much more complex mission. In order to get to Mercury, ESA have adopted a novel technology knows as 'solar electric propulsion' (SEP). The basic principle is that electrical energy is produced using solar cells, and this is used to accelerate ions of gas, producing a continuous, if low thrust. The upshot is that the mission is much less constrained by the alignment of the planets and other trajectory concerns and can complete the journey in only two and a half years. BepiColombo, ESA's Mercury mission, will actually consist of three spacecraft! The planetary orbiter will stay close to Mercury and perform remote sensing and mapping of the surface environment. The magnetospheric orbiter, now going to be built by the Institute for Space and Astronautical Science (ISAS) in Japan, will fly in a highly eccentric orbit that takes it from within a few hundred kilometres of the surface to a distance of several planetary radii. This means it will fly in and out of the magnetosphere, the magnetic 'bubble' formed by interaction of the planetary magnetic field with the solar wind. The third and final element is termed the 'MSE' the Mercury Surface Element, or in plain terms a lander, and this is where my research comes in. There is only so much that remote observation can tell us about a planet. The only true way of verifying what we are seeing is to literally go and 'dig the dirt'. The lander on BepiColombo is designed to do just that, using inflated airbags to cushion its descent to the surface. This 'soft landing' will take place in the polar regions of Mercury, where the surface temperature is moderate—between -50 and +70 °C at the sub-solar point at Mercury's closest approach to the Sun the temperature can reach over 400 °C! It is the potential for making these surface measurements that forms my PhD research. There are a whole series of fundamental questions that scientists would like to answer about Mercury. For example: why is the planet much denser than the other 'terrestrial' bodies? And how has such a small planet got a magnetic field? The answers to these questions need data from several complementary sources. The first step is to identify the science goals, then look at what measurements could be made to resolve or constrain these questions, and finally consider the physics of obtaining this data. My project focuses on the surface and sub-surface material on the planet. The surface of Mercury, like the Moon, has been shaped by the impacts upon it and this is still very much in evidence from images of the planet. Craters of many different sizes are evident over most of the surface. These impacts also break up rocks on the surface and produce a finer distribution of particles, known as regolith. The stratigraphy of this material can therefore tell us something about the change in impact environment over time. A conceptual design of the BepiColombo Mercury Surface Element (lander) ©ESA. Conceptual image of the BepiColombo spacecraft at Mercury ©ESA. As well as being interesting in its own right, the regolith also interacts with almost all other aspects of the Mercurian environment. By analysing the regolith we will be able to find out about Mercury's thin atmosphere and also (because the magnetosphere affects the amount of solar wind hitting the planet's surface) changes in the magnetosphere. Planets like the Earth and Jupiter rely on an electrically conductive ionosphere to close the current systems generated by the magnetosphere. Some researchers believe that on Mercury these currents could flow through, or very close to, the surface itself! Designing and building instruments to work in an environment like the surface of Mercury is one of the major challenges I face. Not only must they be capable of surviving extremes of temperature and vibration they must also be small enough to fit into a total lander payload mass of just 7 kg and complete their investigations within the one week expected lifetime of the MSE. In order to take measurements in more than one place, the lander must be equipped with some limited form of mobility. A 'micro-rover' will be carried and deployed after landing, a miniature tracked vehicle that will carry instruments (probably an alpha x-ray spectrometer) to specific target rocks and areas around the lander. To keep things simple the rover will be physically and electronically connected to the lander by a flexible tether. The lander will also carry a 'mole', a slender cylinder (currently being developed for the Beagle-2 Mars lander) with an internal hammering mechanism. Once pushed into the top layer of soil the mole will be able to drive itself down, pushing aside or breaking small rocks, to a depth of several metres, taking measurements as it goes. Over the past few months we have been studying some of the instruments which could be carried by the mole. Concentrating on just one of these it is easy to see how quickly you run into problems! If the MSE lands near the poles, one of the most fascinating activities would be to look for evidence of water ice. In recent years researchers looking at life on the Earth have shown that if water is present, even in the most inhospitable of environments, life often finds a way to survive. The possibility of water on any planet is therefore an exciting prospect! One possible way to look for ice either at or near the surface is to extract a sample using the mole as it penetrates the regolith, heat it at a constant rate and record the amount of energy used to maintain that rate. This technique, differential scanning calorimetry, can observe phase changes in materials and so help to identify them. The technical challenges of performing even this simplistic analysis task are quite daunting. We have to design and build a sample acquisition mechanism that can withstand launch and landing and work at extreme temperatures, heat a sample down a borehole and reject excess heat and the electronics must fit into a 2 cm diameter by 50 cm long mole. So although BepiColombo will not launch until 2009 and will not arrive at Mercury until 2012, there's more than enough work to keep me busy until then!

Planetary science. Low-altitude magnetic field measurements by MESSENGER reveal Mercury's ancient crustal field.

PubMed

Johnson, Catherine L; Phillips, Roger J; Purucker, Michael E; Anderson, Brian J; Byrne, Paul K; Denevi, Brett W; Feinberg, Joshua M; Hauck, Steven A; Head, James W; Korth, Haje; James, Peter B; Mazarico, Erwan; Neumann, Gregory A; Philpott, Lydia C; Siegler, Matthew A; Tsyganenko, Nikolai A; Solomon, Sean C

2015-05-22

Magnetized rocks can record the history of the magnetic field of a planet, a key constraint for understanding its evolution. From orbital vector magnetic field measurements of Mercury taken by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft at altitudes below 150 kilometers, we have detected remanent magnetization in Mercury's crust. We infer a lower bound on the average age of magnetization of 3.7 to 3.9 billion years. Our findings indicate that a global magnetic field driven by dynamo processes in the fluid outer core operated early in Mercury's history. Ancient field strengths that range from those similar to Mercury's present dipole field to Earth-like values are consistent with the magnetic field observations and with the low iron content of Mercury's crust inferred from MESSENGER elemental composition data. Copyright © 2015, American Association for the Advancement of Science.

A whole new Mercury: MESSENGER reveals a dynamic planet at the last frontier of the inner solar system

NASA Astrophysics Data System (ADS)

Johnson, Catherine L.; Hauck, , Steven A.

2016-11-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission yielded a wealth of information about the innermost planet. For the first time, visible images of the entire planet, absolute altimetry measurements and a global gravity field, measurements of Mercury's surface composition, magnetic field, exosphere, and magnetosphere taken over more than four Earth years are available. From these data, two overarching themes emerge. First, multiple data sets and modeling efforts point toward a dynamic ancient history. Signatures of graphite in the crust suggest solidification of an early magma ocean, image data show extensive volcanism and tectonic features indicative of subsequent global contraction, and low-altitude measurements of magnetic fields reveal an ancient magnetic field. Second, the present-day Mercury environment is far from quiescent. Convective motions in the outer core support a modern magnetic field whose strength and geometry are unique among planets with global magnetic fields. Furthermore, periodic and aperiodic variations in the magnetosphere and exosphere have been observed, some of which couple to the surface and the planet's deep interior. Finally, signatures of geologically recent volatile activity at the surface have been detected. Mercury's early history and its present-day environment have common elements with the other inner solar system bodies. However, in each case there are also crucial differences and these likely hold the key to further understanding of Mercury and terrestrial planet evolution. MESSENGER's exploration of Mercury has enabled a new view of the innermost planet, and more importantly has set the stage for much-needed future exploration.

Global Distribution of Mercury's Neutrals from MESSENGER Measurements Combined with a Tomographic Method

NASA Technical Reports Server (NTRS)

Sarantos, Menelaos; McClintock, Bill; Vervack, Ron, Jr.; Killen, Rosemary; Merkel, Aimee; Slavin, James; Solomon, Sean C.

2011-01-01

The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft entered orbit about Mercury on March 18, 2011. Since then, the Ultraviolet and Visible Spectrometer (UVVS) onboard this spacecraft has been observing Mercury's collisionless exosphere. We present measurements by MESSENGER UVVS of the sodium, calcium, and magnesium distributions that were obtained during multiple passes through the tail over a period of one month. Global maps of the exosphere were constructed daily from such measurements using a recently developed tomographic technique. During this period, Mercury moved towards the Sun from being about 0.44 astronomical units (AU) to approximately 0.32 AU from the Sun. Hence, our reconstructions provide information about the three-dimensional structure of the exosphere, the source processes for these species, and their dependence with orbital distance during the entire in-leg of Mercury's orbit.

On the Edge of Mercury

NASA Image and Video Library

2015-02-04

In this image, Mercury's horizon cuts a striking edge against the stark blackness of space. On the right, sunlight harshly brings the landscape into relief while on the left, the surface is shrouded in the darkness of night. This image was acquired as part of MDIS's limb imaging campaign. Once per week, MDIS captures images of Mercury's limb, with an emphasis on imaging the southern hemisphere limb. These limb images provide information about Mercury's shape and complement measurements of topography made by the Mercury Laser Altimeter (MLA) of Mercury's northern hemisphere. The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft's seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System's innermost planet. In the mission's more than three years of orbital operations, MESSENGER has acquired over 250,000 images and extensive other data sets. MESSENGER is capable of continuing orbital operations until early 2015. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

MESSENGER: The Discovery Mission to Mercury

NASA Astrophysics Data System (ADS)

McNutt, R. L.; Solomon, S. C.; Gold, R. E.; Domingue, D. L.

2004-12-01

NASA's MErcury, Surface, Space ENvironment, GEochenistry, and Ranging (MESSENGER) spacecraft, launched on 3 August 2004, has begun its voyage to initiate a new era in our understanding of the terrestrial planets. The mission, spacecraft, and payload are designed to answer six fundamental questions regarding the innermost planet: What planetary formational processes led to Mercury's high metal/silicate ratio? What is the geological history of Mercury? What are the nature and origin of Mercury's magnetic field? What are the structure and state of Mercury's core? What are the radar-reflective materials at Mercury's poles? What are the important volatile species and their sources and sinks on and near Mercury? Planet formational hypotheses will be tested by measuring the surface abundances of major elements by X-ray and gamma-ray spectrometry. The geological history will be determined from high-resolution color imaging of the heavily cratered highlands, intercrater plains, and smooth plains. MESSENGER will provide detailed views of both the Caloris basin and its antipodal terrain. Topographic, mineralogical, and elemental abundance data will be used to seek evidence of volcanic features and units. Measurement of Mercury's magnetic field and its interaction with the solar wind will distinguish the intrinsic dipole and quadrupole components while separating these from the current systems driven by solar-wind-induced convection. The structure of the internal field will put constraints on dynamo models. Such models will also be constrained by measuring Mercury's libration to determine the extent of a fluid outer core. Both water ice and sulfur have been postulated as major constituents of the high-radar-backscatter polar deposits. MESSENGER will combine gamma-ray and neutron spectrometry of the surface with ultraviolet spectrometry and in situ particle measurements to detect both neutral and charged species originating from the surface. Such measurements will address the sources and sinks of volatiles and their couplings with the surface on a global basis as well as the nature of the polar deposits. To broaden scientific participation in the mission, the MESSENGER project is working with NASA to establish a Participating Scientist Program. The MESSENGER team is also continuing its informal interaction with members of the BepiColombo project to maximize the overall scientific return from both missions.

KSC-04PD-1535

NASA Technical Reports Server (NTRS)

2004-01-01

KENNEDY SPACE CENTER, FLA. In the mobile service tower at Launch Complex 17-B, Cape Canaveral Air Force Station, workers move a panel into place above the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft. The overhead panel will suspend an environmental curtain around the spacecraft while in the tower before encapsulation. Scheduled to launch Aug. 2, MESSENGER will return to Earth for a gravity boost in July 2005, then fly past Venus twice, in October 2006 and June 2007. It is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md. Processing is being done at Astrotech Space Operations in Titusville, Fla

KSC-04pd1451

NASA Image and Video Library

2004-07-06

KENNEDY SPACE CENTER, FLA. - On Pad 17-B, Cape Canaveral Air Force Station, workers move the Boeing Delta II Heavy second-stage engine, the Aerojet AJ10-118K, inside the mobile service tower. The engine will be mated with the first stage of the Delta II, which is the launch vehicle for the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft, scheduled to lift off Aug. 2. Bound for Mercury, the spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

KSC-04pd1449

NASA Image and Video Library

2004-07-06

KENNEDY SPACE CENTER, FLA. - - The Boeing Delta II Heavy second-stage engine, the Aerojet AJ10-118K, approaches the top of the mobile service tower on Pad 17-B, Cape Canaveral Air Force Station. The engine will be mated with the first stage of the Delta II, which is the launch vehicle for the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft, scheduled to lift off Aug. 2. Bound for Mercury, the spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

Spectroscopy of sulfides in the simulated environment of Mercury and their detection from the orbit

NASA Astrophysics Data System (ADS)

Varatharajan, I.; Maturilli, A.; Helbert, J.; Hiesinger, H.

2017-09-01

In order to detect the mineral diversity on the planet's surface, it is essential to study the spectral variations along broad wavelength range in their respective simulated laboratory conditions. MESSENGER (Mercury Surface, Space Environment, Geochemistry, and Ranging) mission to Mercury discovered that irrespective of its formation closest to the sun, Mercury in rich in volatiles than previously expected especially S (4 wt%). S in the Mercury interior can be brought to the surface through volcanic activity as slag deposits in Mercury hollows and pyroclasts. However, the complete spectral library of sulfide minerals in vacuum conditions at Mercury's daytime temperature in the wide spectral range (0.2-100 µm) is still missing. This affects our detectability and understanding of distribution, abundance, and type of sulfides on Mercury using spectral datasets in the past missions to Mercury. In the case of Mercury, the effect of thermal weathering in the spectral behavior of these sulfides must be studied carefully for their effective detection. In the study, we thermally processed the fresh synthetic sulfides by heating them slowly upto 500 ºC in vacuum and during the process, we measured the thermal radiance/emissivity of these sulfides in the thermal infrared spectral region (TIR: 7-14 µm) at the interval of every 100 ºC. After this, we collectively measured the spectral reflectance of fresh and heated synthetic sulfides at wide spectral range (0.2-100 µm) at four different phase angles, 26º, 40º, 60º, 80º. Therefore, this study facilitates the detection of sulfides by past and future missions to Mercury by any spectrometer of any spectral range. The synthetic sulfides used in the study includes MgS, FeS, CaS, CrS, TiS, NaS, and MnS. Thus, the emissivity measurements in the study will support the The Mercury Radiometer and Thermal Imaging Spectrometer (MERTIS) payload of ESA/JAXA BepiColombo mission to Mercury which will study the surface mineralogy at wavelength range of 7-14 μm at spatial resolution of 500 m/pixel. The measured reflectance of these sulfides in 0.2-100 µm at various phase angles will support the measurements from past (MDIS, MASCS on MESSENGER) and future missions (SIMBIO-SYS/VIHI on BepiColombo) to Mercury.

Dark Material at the Surface of Polar Crater Deposits on Mercury

NASA Technical Reports Server (NTRS)

Neumann, Gregory A.; Cavanaugh, John F.; Sun, Xiaoli; Mazarico, Erwan; Smith, David E.; Zuber, Maria T.; Solomon, Sean C.; Paige, Daid A.

2012-01-01

Earth-based radar measurements [1-3] have yielded images of radar-bright material at the poles of Mercury postulated to be near-surface water ice residing in cold traps on the permanently shadowed floors of polar impact craters. The Mercury Laser Altimeter (MLA) on board the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft has now mapped much of the north polar region of Mercury [4] (Fig. 1). Radar-bright zones lie within polar craters or along poleward-facing scarps lying mainly in shadow. Calculations of illumination with respect to solid-body motion [5] show that at least 0.5% of the surface area north of 75deg N lies in permanent shadow, and that most such permanently shadowed regions (PSRs) coincide with radar-bright regions. MLA transmits a 1064-nm-wavelength laser pulse at 8 Hz, timing the leading and trailing edges of the return pulse. MLA can in some cases infer energy and thereby surface reflectance at the laser wavelength from the returned pulses. Surficial exposures of water ice would be optically brighter than the surroundings, but persistent surface water ice would require temperatures over all seasons to remain extremely low (<110 K). Thermal models [6,7] incorporating direct and scattered radiation, Mercury s eccentric orbit, 3:2 spin-orbit resonance, and near-zero obliquity generally do not support such conditions in all permanently shadowed craters but suggest that water ice buried near the surface (<0.5 m depth) could survive for > 1 Gy. We describe measurements of reflectivity derived from MLA pulse returns. These reflectivity data show that surface materials in the shadowed regions are darker than their surroundings, enough to strongly attenuate or extinguish laser returns. Such measurements appear to rule out widespread surface exposures of water ice. We consider explanations for the apparent low reflectivity of these regions involving other types of volatile deposit.

Mercury: Photomosaic of the Michelangelo Quadrangle H-12

NASA Technical Reports Server (NTRS)

2000-01-01

The Michelangelo Quadrangle, which lies in Mercury's southern polar region, was named in memory of the famous Italian artist. The Mercurian surface is heavily marred by numerous impact craters. Ejecta deposits, seen as bright lines or rays, radiate outward from the point of impact, along the planet's surface indicating the source craters are young topographical features. The rays found on Mercury are similar to ones found on the surface of Earth's moon.

Several large lobate scarps, steep and long escarpments which usually show a largely lobate outline on a scale of a few to tens of kilometers, are clearly visible in the lower left side of the image slicing through a variety of terrains including several large impact craters.

The Image Processing Lab at NASA's Jet Propulsion Laboratory produced this photomosaic using computer software and techniques developed for use in processing planetary data. The images used to construct the Michelangelo Quadrangle were taken during Mariner 10's second flyby of Mercury.

The Mariner 10 spacecraft was launched in 1974. The spacecraft took images of Venus in February 1974 on the way to three encounters with Mercury in March and September 1974 and March 1975. The spacecraft took more than 7,000 images of Mercury, Venus, the Earth and the Moon during its mission.

The Mariner 10 Mission was managed by the Jet Propulsion Laboratory for NASA's Office of Space Science in Washington, D.C.

From Orbit, Looking toward Mercury's Horizon

NASA Image and Video Library

2017-12-08

NASA image acquired: March 29, 2011 MESSENGER acquired this image of Mercury's horizon as the spacecraft was moving northward along the first orbit during which MDIS was turned on. Bright rays from Hokusai can be seen running north to south in the image. MDIS frequently acquired images that contained Mercury's horizon during the mission's three Mercury flybys. (Visit these links to see examples of horizon images from Mercury flyby 1, Mercury flyby 2, and Mercury flyby 3.) However, now that MESSENGER is in orbit about Mercury, views of Mercury's horizon in the images will be much less common. The field of view for MDIS will generally be filled with Mercury's surface as the instrument maps out the planet's geology in high resolution, stereo, and color. Occasionally, in order to obtain images of a certain portion of Mercury's surface, the horizon will also be visible. On March 17, 2011 (March 18, 2011, UTC), MESSENGER became the first spacecraft to orbit the planet Mercury. The mission is currently in its commissioning phase, during which spacecraft and instrument performance are verified through a series of specially designed checkout activities. In the course of the one-year primary mission, the spacecraft's seven scientific instruments and radio science investigation will unravel the history and evolution of the Solar System's innermost planet. Visit the Why Mercury? section of this website to learn more about the science questions that the MESSENGER mission has set out to answer. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Join us on Facebook

Kilometer-Scale Topographic Roughness of Mercury: Correlation with Geologic Features and Units

NASA Technical Reports Server (NTRS)

Kreslavsky, Mikhail A.; Head, James W.; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.

2014-01-01

We present maps of the topographic roughness of the northern circumpolar area of Mercury at kilometer scales. The maps are derived from range profiles obtained by the Mercury Laser Altimeter (MLA) instrument onboard the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. As measures of roughness, we used the interquartile range of profile curvature at three baselines: 0.7 kilometers, 2.8 kilometers, and 11 kilometers. The maps provide a synoptic overview of variations of typical topographic textures. They show a dichotomy between the smooth northern plains and rougher, more heavily cratered terrains. Analysis of the scale dependence of roughness indicates that the regolith on Mercury is thicker than on the Moon by approximately a factor of three. Roughness contrasts within northern volcanic plains of Mercury indicate a younger unit inside Goethe basin and inside another unnamed stealth basin. These new data permit interplanetary comparisons of topographic roughness.

Magnetic mineralogy of the Mercurian lithosphere

NASA Astrophysics Data System (ADS)

Strauss, B. E.; Feinberg, J. M.; Johnson, C. L.

2016-11-01

Mercury and Earth are the only inner solar system planets with active, internally generated dynamo magnetic fields. The MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission recently detected magnetic fields on Mercury that are consistent with lithospheric magnetization. We investigate the physical and chemical environment of Mercury's lithosphere, past and present, to establish the conditions under which magnetization may have been acquired and modified. Three factors are particularly crucial to the determination of crustal composition and iron mineralogy: redox conditions in the planet's crust and mantle, the iron content of the lithosphere, and, for any remanent magnetization, the temperature profile of the lithosphere and its evolution over time. We explore potential mechanisms for remanence acquisition and alteration on Mercury, whose surface environment is both hot and highly reducing. The long-term thermal history of Mercury's crust plays an important role in the longevity of any remanent crustal magnetization, which may be subject to remagnetization through thermal, viscous, and shock mechanisms. This thermal and compositional framework is used both to constrain plausible candidate minerals that could carry magnetic remanence on Mercury and to evaluate their capacity to acquire and retain sufficient magnetization to be detectable from satellite orbit. We propose that iron metal and its alloys are likely to be the dominant contributors to induced and remanent magnetization in Mercury's lithosphere, with additional contributions from iron silicides, sulfides, and carbides.

The development and testing of the fast imaging plasma spectrometer and its application in the plasma environment at Mercury

NASA Astrophysics Data System (ADS)

Koehn, Patrick Leo

The plasma environment at Mercury is a rich laboratory for studying the interaction of the solar wind with a planet. Three primary populations of ions exist at Mercury: solar wind, magnetospheric particles, and pickup ions. Pickup ions are generated through the ionization of Mercury's exosphere or are sputtered particles from the Mercury surface. A comprehensive mission to Mercury should include a sensor that is able to determine the dynamical properties and composition of all three plasma components. The Fast Imaging Plasma Spectrometer (FIPS) is an instrument to measure the composition of these ion populations and their three-dimensional velocity distribution functions. It is lightweight, fast, and has a very large field of view, and these properties made possible its accommodation within the highly mass- constrained payload of MESSENGER (MErcury: Surface, Space ENvironment, GEochemistry, Ranging) mission, a Mercury orbiter. This work details the development cycle of FIPS, from concept to prototype testing. It begins with science studies of the magnetospheric and pickup ion environments of Mercury, using state-of-the-art computer simulations to produce static and quasi-dynamic magnetospheric systems. Predictions are made of the spatially variable plasma environment at Mercury, and the temporally varying magnetosphere-solar wind interaction is examined. Pickup ion studies provide insights to particle loss mechanisms and the nature of the radar-bright regions at the Hermean poles. These studies produce science requirements for successfully measuring this environment with an orbiting mass spectrometer. With these science requirements in mind, a concept for a new electrostatic analyzer is created. This concept is considered from a theoretical standpoint, and compared with other, similarly performing instruments, both of the past and currently in use. The development cycle continues with instrument simulation, which allows the design to be adjusted to fit within the science requirements of the mission. Finally, a prototype electrostatic is constructed and tested in a space- simulating vacuum chamber system. The results of these tests are compared with the simulation results, and ultimately shown to fit within the science requirements for the MESSENGER mission.

Multiscale geomorphometric modeling of Mercury

NASA Astrophysics Data System (ADS)

Florinsky, I. V.

2018-02-01

Topography is one of the key characteristics of a planetary body. Geomorphometry deals with quantitative modeling and analysis of the topographic surface and relationships between topography and other natural components of landscapes. The surface of Mercury is systematically studied by interpretation of images acquired during the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission. However, the Mercurian surface is still little explored by methods of geomorphometry. In this paper, we evaluate the Mercury MESSENGER Global DEM MSGR_DEM_USG_SC_I_V02 - a global digital elevation model (DEM) of Mercury with the resolution of 0.015625° - as a source for geomorphometric modeling of this planet. The study was performed at three spatial scales: the global, regional (the Caloris basin), and local (the Pantheon Fossae area) ones. As the initial data, we used three DEMs of these areas with resolutions of 0.25°, 0.0625°, and 0.015625°, correspondingly. The DEMs were extracted from the MESSENGER Global DEM. From the DEMs, we derived digital models of several fundamental morphometric variables, such as: slope gradient, horizontal curvature, vertical curvature, minimal curvature, maximal curvature, catchment area, and dispersive area. The morphometric maps obtained represent peculiarities of the Mercurian topography in different ways, according to the physical and mathematical sense of a particular variable. Geomorphometric models are a rich source of information on the Mercurian surface. These data can be utilized to study evolution and internal structure of the planet, for example, to visualize and quantify regional topographic differences as well as to refine geological boundaries.

Development of technology for lightweight Beryllium Cassegrain Telescope for space applications and lessons learnt

NASA Astrophysics Data System (ADS)

Greger, R.; Rugi, E.; Hausner, Th.; Jahnen, W.; Frei, S.; Pellaton, D.; Mueller, P.; Hollenbach, I.

2017-11-01

This paper gives an overview on the development of a light weighted Cassegrain telescope with a 200 mm optical aperture as one key element of the Laser Altimeter which will fly on the BepiColombo mission to Mercury (BELA).The Receiver Telescope (RTL) collects the light pulse transmitted to Mercury and reflected from the planet's surface. Mercury's challenging thermal environment, the thermo-mechanical stability of the telescope and the stringent instrument's mass budget require the implementation of an innovative design solution to achieve the requested optical performance over an extended temperature range.

Librations and obliquity of Mercury from the BepiColombo laser altimetry, radio science and camera experiments

NASA Astrophysics Data System (ADS)

Pfyffer, G.; van Hoolst, T.; Dehant, V. M.

2010-12-01

Through its anomalously high uncompressed density implying a metal fraction of 60% or more by mass, Mercury represents an extreme outcome of planetary formation in the inner solar system. The space missions MESSENGER and BepiColombo are expected to advance largely our knowledge of the structure, formation, and evolution of Mercury. In particular, insight into Mercury's deep interior will be obtained from observations of the obliquity, the 88-day forced libration, the planetary induced librations and the degree-two coefficients of the gravity field of Mercury. We report here on aspects of the observational strategy of ESA’s BepiColombo mission to determine the libration amplitude and obliquity, taking into account the space as well as the ground segment of the experiment. Repeated photographic measurements of selected target positions on the surface of Mercury are central to the strategy to determine the obliquity and libration in the frame of the BepiColombo mission, but a significant constraint is posed by the fact that the planetary surface can only be photographed under very strict illumination conditions. We therefore study the possibility to use the information embedded in the groundtrack crossings (crosstracks) of the BepiColombo laser altimeter (BELA) in addition to the primary photographic data in order to estimate the librations and obliquity of Mercury. An advantage of the laser altimetry data is that it does not depend on the solar incidence angle on the surface nor on the presence of specific surface features as required for the camera data in the camera rotation experiment. Both laser and photographic measurements were simulated in a realistic set-up in order to estimate the accuracy of the reconstruction of the orientation and rotational motion of the planet as a function of the amount of measurements made, the number of different targets and crosstrack points considered and their locations on the surface of the planet. Such an analysis requires the use of an accurate model of the rotation of Mercury, which takes into account longitudinal librations additional to the main 88 day libration due to planetary perturbations on Mercury's orbit. Our simulations show that the achievable level of accuracy on the libration amplitude and obliquity will only be sufficient to constrain the size and physical state of the core of Mercury if certain conditions are satisfied. If the orbiter follows the ESA baseline mission scenario, and at least 25 landmarks are imaged at least twice over the mission duration (360 days), the annual libration amplitude and obliquity can be determined with sufficient accuracy. Also the Jupiter induced libration amplitude can pose an additional constraint on the interior of the planet. We will discuss the relative contributions of the different methods will enable us to determine the optimum combinations of the observations with consequences for the mission planning and the instrument performances.

Detecting negative ions on board small satellites

NASA Astrophysics Data System (ADS)

Lepri, S. T.; Raines, J. M.; Gilbert, J. A.; Cutler, J.; Panning, M.; Zurbuchen, T. H.

2017-04-01

Recent measurements near comets, planets, and their satellites have shown that heavy ions, energetic neutral atoms, molecular ions, and charged dust contain a wealth of information about the origin, evolution, and interaction of celestial bodies with their space environment. Using highly sensitive plasma instruments, positively charged heavy ions have been used to trace exospheric and surface composition of comets, planets, and satellites as well as the composition of interplanetary and interstellar dust. While positive ions dominate throughout the heliosphere, negative ions are also produced from surface interactions. In fact, laboratory experiments have shown that oxygen released from rocky surfaces is mostly negatively charged. Negative ions and negatively charged nanograins have been detected with plasma electron analyzers in several different environments (e.g., by Cassini and Rosetta), though more extensive studies have been challenging without instrumentation dedicated to negative ions. We discuss an adaptation of the Fast Imaging Plasma Spectrometer (FIPS) flown on MErcury Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) for the measurement of negatively charged particles. MESSENGER/FIPS successfully measured the plasma environment of Mercury from 2011 until 2015, when the mission ended, and has been used to map multiple ion species (H+ through Na+ and beyond) throughout Mercury's space environment. Modifications to the existing instrument design fits within a 3U CubeSat volume and would provide a low mass, low power instrument, ideal for future CubeSat or distributed sensor missions seeking, for the first time, to characterize the contribution of negative particles in the heliospheric plasmas near the planets, moons, comets, and other sources.

High-frequency flux transfer events detected near Mercury

NASA Astrophysics Data System (ADS)

Schultz, Colin

2013-01-01

The physical process that creates connections between the magnetic fields emanating from the Sun and a planet—a process known as magnetic reconnection—creates a portal through which solar plasma can penetrate the planetary magnetic field. The opening of these portals, known as flux transfer events (FTEs), takes place roughly every 8 minutes at Earth and spawns a rope of streaming plasma that is typically about half of the radius of the Earth. As early as 1985, scientists analyzing the Mariner 10 observations, collected during their 1974-1975 flybys, have known that FTEs also occur at Mercury. However, using the measurements returned from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft now orbiting Mercury, Slavin et al. found that Mercurial flux transfer events are proportionally much larger, stronger, and more frequent than those at Earth.

Constructional Volcanic Edifices on Mercury: Candidates and Hypotheses of Formation

NASA Astrophysics Data System (ADS)

Wright, Jack; Rothery, David A.; Balme, Matthew R.; Conway, Susan J.

2018-04-01

Mercury, a planet with a predominantly volcanic crust, has perplexingly few, if any, constructional volcanic edifices, despite their common occurrence on other solar system bodies with volcanic histories. Using image and topographical data from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, we describe two small (<15-km diameter) prominences with shallow summit depressions associated with volcanically flooded impact features. We offer both volcanic and impact-related interpretations for their formation, and then compare these landforms with volcanic features on Earth and the Moon. Though we cannot definitively conclude that these landforms are volcanic, the paucity of constructional volcanic edifices on Mercury is intriguing in itself. We suggest that this lack is because volcanic eruptions with sufficiently low eruption volumes, rates, and flow lengths, suitable for edifice construction, were highly spatiotemporally restricted during Mercury's geological history. We suggest that volcanic edifices may preferentially occur in association with late-stage, postimpact effusive volcanic deposits. The European Space Agency/Japan Aerospace Exploration Agency BepiColombo mission to Mercury will be able to investigate further our candidate volcanic edifices; search for other, as-yet unrecognized edifices beneath the detection limits of MESSENGER data; and test our hypothesis that edifice construction is favored by late-stage, low-volume effusive eruptions.

Google Mercury: The Launch of a New Planet

NASA Astrophysics Data System (ADS)

Hirshon, B.; Chapman, C. R.; Edmonds, J.; Goldstein, J.; Hallau, K. G.; Solomon, S. C.; Vanhala, H.; Weir, H. M.; Messenger Education; Public Outreach Epo Team

2010-12-01

The NASA MESSENGER mission’s Education and Public Outreach (EPO) Team, in cooperation with Google, Inc., has launched Google Mercury, an immersive new environment on the Google Earth platform. Google Mercury features hundreds of surface features, most of them newly revealed by the three flybys of the innermost planet by the MESSENGER spacecraft. As with Google Earth, Google Mercury is available on line at no cost. This presentation will demonstrate how our team worked with Google staff, features we incorporated, how games can be developed within the Google Earth platform, and how others can add tours, games, and other educational features. Finally, we will detail new enhancements to be added once MESSENGER enters into orbit about Mercury in March 2011 and begins sending back compelling images and other global data sets on a daily basis. The MESSENGER EPO Team comprises individuals from the American Association for the Advancement of Science (AAAS); Carnegie Academy for Science Education (CASE); Center for Educational Resources (CERES) at Montana State University (MSU) - Bozeman; National Center for Earth and Space Science Education (NCESSE); Johns Hopkins University Applied Physics Laboratory (JHU/APL); National Air and Space Museum (NASM); Science Systems and Applications, Inc. (SSAI); and Southwest Research Institute (SwRI). Screen shot of Google Mercury as a work in progress

Making Mercury's Core with Light Elements

NASA Technical Reports Server (NTRS)

Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Ross, D. Kent

2016-01-01

Recent results obtained from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft showed the surface of Mercury has low FeO abundances (less than 2 wt%) and high S abundances (approximately 4 wt%), suggesting the oxygen fugacity of Mercury's surface materials is somewhere between 3 to 7 log10 units below the IW buffer. The highly reducing nature of Mercury has resulted in a relatively thin mantle and a large core that has the potential to exhibit an exotic composition in comparison to the other terrestrial planets. This exotic composition may extend to include light elements (e.g., Si, C, S). Furthermore, has argued for a possible primary floatation crust on Mercury composed of graphite, which may require a core that is C-saturated. In order to investigate mercurian core compositions, we conducted piston cylinder experiments at 1 GPa, from 1300 C to 1700 C, using a range of starting compositions consisting of various Si-Fe metal mixtures (Si5Fe95, Si10Fe90, Si22Fe78, and Si35Fe65). All metals were loaded into graphite capsules used to ensure C-saturation during the duration of each experimental run. Our experiments show that Fe-Si metallic alloys exclude carbon relative to more Fe-rich metal. This exclusion of carbon commences within the range of 5 to 10 wt% Si. These results indicate that if Mercury has a Si-rich core (having more than approximately 5 wt% silicon), it would have saturated in carbon at low C abundances allowing for the possible formation of a graphite floatation crust as suggested by. These results have important implications for the thermal and magmatic evolution of Mercury.

NASA's MESSENGER Finds New Evidence for Water Ice at Mercury's Poles

NASA Image and Video Library

2017-12-08

New observations by the MESSENGER spacecraft provide compelling support for the long-held hypothesis that Mercury harbors abundant water ice and other frozen volatile materials in its permanently shadowed polar craters. Three independent lines of evidence support this conclusion: the first measurements of excess hydrogen at Mercury's north pole with MESSENGER's Neutron Spectrometer, the first measurements of the reflectance of Mercury's polar deposits at near-infrared wavelengths with the Mercury Laser Altimeter (MLA), and the first detailed models of the surface and near-surface temperatures of Mercury's north polar regions that utilize the actual topography of Mercury's surface measured by the MLA. These findings are presented in three papers published online today in Science Express. Given its proximity to the Sun, Mercury would seem to be an unlikely place to find ice. But the tilt of Mercury's rotational axis is almost zero — less than one degree — so there are pockets at the planet's poles that never see sunlight. Scientists suggested decades ago that there might be water ice and other frozen volatiles trapped at Mercury's poles. The idea received a boost in 1991, when the Arecibo radio telescope in Puerto Rico detected unusually radar-bright patches at Mercury's poles, spots that reflected radio waves in the way one would expect if there were water ice. Many of these patches corresponded to the location of large impact craters mapped by the Mariner 10 spacecraft in the 1970s. But because Mariner saw less than 50 percent of the planet, planetary scientists lacked a complete diagram of the poles to compare with the images. MESSENGER's arrival at Mercury last year changed that. Images from the spacecraft's Mercury Dual Imaging System taken in 2011 and earlier this year confirmed that radar-bright features at Mercury's north and south poles are within shadowed regions on Mercury's surface, findings that are consistent with the water-ice hypothesis. To read more go to: 1.usa.gov/TtNwM2 Image Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington/National Astronomy and Ionosphere Center, Arecibo Observatory NASA image use policy. NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission. Follow us on Twitter Like us on Facebook Find us on Instagram

Carbon Solubility in Silicon-Iron-Bearing Metals during Core Formation on Mercury

NASA Technical Reports Server (NTRS)

Vander Kaaden, Kathleen E.; McCubbin, Francis M.; Ross, D. Kent; Rapp, Jennifer F.; Danielson, Lisa R.; Keller, Lindsay P.; Righter, Kevin

2016-01-01

Recent results obtained from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft showed the surface of Mercury has high S abundances (approximately 4 wt%) and low Iron(II) Oxide abundances (less than 2 wt%). Based on these extreme values, the oxygen fugacity of Mercury's surface materials was estimated to be approximately 3 to 7 log(sub 10) units below the IW buffer (Delta IW-3 to Delta IW-7). This highly reducing nature of the planet has resulted in a large core and relatively thin mantle, extending to only approximately 420 km depth (corresponding to a core-mantle boundary pressure of approximately 4-7 GPa) within the planet. Furthermore, MESSENGER results have suggested the presence of carbon on the surface of the planet. Previous experimental results from have also suggested the possibility of a primary floatation crust on Mercury composed of graphite, produced after a global magma ocean event. With these exotic conditions of this compositional end-member planet, it begs the question, what is the core composition of Mercury? Although no definitive conclusion has been reached, previous studies have made advances towards answering this question. Riner et al. and Chen et al. looked at iron sulfide systems and implemented various crystallization and layered core scenarios to try and determine the composition and structure of Mercury's core. Malavergne et al. examined core crystallization scenarios in the presence of sulfur and silicon. Hauck et al. used the most recent geophysical constraints from the MESSENGER spacecraft to model the internal structure of Mercury, including the core, in a iron-sulfur-silicon system. More recently, Chabot et al. conducted a series of metal-silicate partitioning experiments in a iron-sulfur-silicon system. These results showed the core of Mercury has the potential to contain more than 15 wt% silicon. However, with the newest results from MESSENGER's low altitude campaign, carbon is another potential light element that could be incorporated into Mercury's core. The goal of this study is to determine the carbon concentration at graphite saturation in various silicon-iron bearing metals relevant to possible mercurian core compositions. Future experiments will include the addition of sulfur into these metals.

Space-qualified laser system for the BepiColombo Laser Altimeter.

PubMed

Kallenbach, Reinald; Murphy, Eamonn; Gramkow, Bodo; Rech, Markus; Weidlich, Kai; Leikert, Thomas; Henkelmann, Reiner; Trefzger, Boris; Metz, Bodo; Michaelis, Harald; Lingenauber, Kay; DelTogno, Simone; Behnke, Thomas; Thomas, Nicolas; Piazza, Daniele; Seiferlin, Karsten

2013-12-20

The space-qualified design of a miniaturized laser for pulsed operation at a wavelength of 1064 nm and at repetition rates up to 10 Hz is presented. This laser consists of a pair of diode-laser pumped, actively q-switched Nd:YAG rod oscillators hermetically sealed and encapsulated in an environment of dry synthetic air. The system delivers at least 300 million laser pulses with 50 mJ energy and 5 ns pulse width (FWHM). It will be launched in 2017 aboard European Space Agency's Mercury Planetary Orbiter as part of the BepiColombo Laser Altimeter, which, after a 6-years cruise, will start recording topographic data from orbital altitudes between 400 and 1500 km above Mercury's surface.

Experimental Study of Hollow Formation

NASA Astrophysics Data System (ADS)

Parman, S. W.; Orlando, T. M.; Milliken, R. E.; Head, J. W.; Jones, B. M.; Anzures, B. A.

2018-05-01

Hollows are enigmatic features on the surface of Mercury caused by sublimation and/or space weathering. Here we propose a comprehensive experimental study in which candidate hollows materials are exposed to a range of relevant conditions.

Characterization of the 300 K and 700 K Calibration Sources for Space Application with the Bepicolombo Mission to Mercury

NASA Astrophysics Data System (ADS)

Gutschwager, B.; Driescher, H.; Herrmann, J.; Hirsch, H.; Hollandt, J.; Jahn, H.; Kuchling, P.; Monte, C.; Scheiding, M.

2011-08-01

The Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) onboard the European-Japanese space mission BepiColombo to Mercury will be launched in 2014. The MERTIS scientific objective is to identify rock-forming minerals and measure surface temperatures by infrared spectroscopy (7 μm to 14 μm) and spectrally unresolved infrared radiometry (7 μm to 40 μm). To achieve this goal, MERTIS utilizes two onboard infrared calibration sources, the MERTIS blackbody at 700 K (MBB7) and the MERTIS blackbody at 300 K (MBB3), together with deep space observations corresponding to 3 K. All three sources can be observed one after the other using a rotating mirror system. The leaders of the project MERTIS are the Westfälische University of Münster, institute for planetary investigation, Mr. Prof. Dr. H. Hiesinger (PI) and the DLR, Institute of Planetary Research Berlin-Adlershof, Mr. Dr. J. Helbert (CoPI). Both blackbody radiators have to fulfill the severe mass, volume, and power restrictions of MERTIS. The radiating area of the MBB3 is based on a structured surface with a high-emissivity space qualified coating. The relatively high emissivity of the coating was further enhanced by a pyramidal surface structure to values over 0.99 in the wavelength range from 5 μm to 10 μm and over 0.95 in the wavelength range from 10 μm to 30 μm. The MBB7 is based on a small commercially available surface emitter in a standard housing. The windowless emitter is an electrically heated resistor, which consists of a platinum structure with a blackened surface on a ceramic body. The radiation of the emitter is expanded and collimated through use of a parabolic mirror. The design requirements and the radiometric and thermometric characterization of these two blackbodies are described in this paper.

How Tiny Collisions Shape Mercury

NASA Astrophysics Data System (ADS)

Kohler, Susanna

2017-07-01

If space rocks are unpleasant to encounter, space dust isnt much better. Mercurys cratered surface tells of billions of years of meteoroid impacts but its thin atmosphere is what reveals its collisional history with smaller impactors. Now new research is providing a better understanding of what were seeing.Micrometeoroids Ho!The inner solar system is bombarded by micrometeoroids, tiny particles of dust (on the scale of a tenth of a millimeter) emitted by asteroids and comets as they make their closest approach to the Sun. This dust doesnt penetrateEarths layers of atmosphere, but the innermost planet of our solar system, Mercury, doesnt have this convenient cushioning.Just as Mercury is affected by the impacts of large meteoroids, its also shaped by the many smaller-scale impacts it experiences. These tiny collisions are thought to vaporize atoms and molecules from the planets surface, which quickly dissociate. This process adds metals to Mercurys exosphere, the planets extremely tenuous atmosphere.Modeling PopulationsDistribution of the directions from which meteoroids originate before impacting Mercurys surface, as averaged over its entire orbit. Local time of 12 hr corresponds to the Sun-facing side. A significant asymmetry is seen between the dawn (6 hrs) and dusk (18 hrs) rates. [Pokorn et al. 2017]The metal distribution in the exosphere provides a way for us to measure the effect of micrometeoroid impacts on Mercury but this only works if we have accurate models of the process. A team of scientists led by Petr Pokorn (The Catholic University of America and NASA Goddard SFC) has now worked to improve our picture of micrometeoroid impact vaporization on Mercury.Pokorn and collaborators argue that two meteoroid populations Jupiter-family comets (short-period) and Halley-type comets (long-period) contribute the dust for the majority of micrometeoroid impacts on Mercury. The authors model the dynamics and evolution of these two populations, reproducing the distribution of directions from which micrometeoroids strike Mercury during its yearly orbit.Schematic of Mercury in its orbit around the Sun. The dawn side leads the orbital motion, while the dusk side trails it.Geometry of an OrbitMercurys orbit is unique in our solar system: it circles the Sun twice for every three rotations on its own axis so if you were on Mercury, youd see a single day pass over the span of two years. As with all prograde planets, the edge leading the Mercurys orbit marks the dawn terminator, while the edge trailing the planets orbital motion marks the dusk terminator.Pokorn and collaborators find a significant asymmetry in the impact vaporization that occurs on Mercurys dawn side versus its dusk side. This is due to impact geometry (since the dusk side is shielded from impacts in the direction of motion) and seasonal variation of the dust/meteoroid environment around the planet. The authors show that the source of impact vaporization shifts toward the nightside as Mercury approaches aphelion, and toward the dayside when the planet approaches the Sun.Importance of Long-Period CometsSeasonal variations of the relative vaporization rate from the authors model (black line) compared to measurements of Mercurys exospheric abundance of Ca. The contribution of long-period comets is shown by the blue line. [Pokorn et al. 2017]The dawn/dusk asymmetry and the seasonal variations predicted by the model are all nicely consistent NASAs MESSENGER spacecraft observations of the metal distribution in Mercurys exosphere.What makes Pokorn and collaborators model work so well? Their inclusion of the long-period, Halley-type comets is key: the high impact velocity of the micrometeoroids produced by this family play a significant role in shaping the impact vaporization rate of Mercurys surface.This work successfully demonstrates that we can use measurements of Mercurys exosphere as a unique tool to constrain the dust population in the inner solar system.CitationPetr Pokorn et al 2017 ApJL 842 L17. doi:10.3847/2041-8213/aa775d

KSC-04pd1448

NASA Image and Video Library

2004-07-06

KENNEDY SPACE CENTER, FLA. - The Boeing Delta II Heavy second-stage engine, the Aerojet AJ10-118K, is lifted up the mobile service tower on Pad 17-B, Cape Canaveral Air Force Station. At right can be seen the first stage of the Delta II and the nine Solid Rocket Boosters surrounding it. The Delta II is the launch vehicle for the MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) spacecraft, scheduled to lift off Aug. 2. Bound for Mercury, the spacecraft is expected to reach orbit around the planet in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

Expected Geochemical and Mineralogical Properties of Meteorites from Mercury: Inferences from Messenger Data

NASA Technical Reports Server (NTRS)

McCubbin, F. M.; McCoy, T. J.

2016-01-01

Meteorites from the Moon, Mars, and many types of asteroid bodies have been identified among our global inventory of meteorites, however samples of Mercury and Venus have not been identified. The absence of mercurian and venusian meteorites could be attributed to an inability to recognize them in our collections due to a paucity of geochemical information for Venus and Mercury. In the case of mercurian meteorites, this possibility is further supported by dynamical calculations that suggest mercurian meteorites should be present on Earth at a factor of 2-3 less than meteorites from Mars [1]. In the present study, we focus on the putative mineralogy of mercurian meteorites using data obtained from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft, which has provided us with our first quantitative constraints on the geochemistry of planet Mercury. We have used the MESSENGER data to compile a list of mineralogical and geochemical characteristics that a meteorite from Mercury is likely to exhibit.

Kilometer-scale topographic roughness of Mercury: Correlation with geologic features and units

NASA Astrophysics Data System (ADS)

Kreslavsky, Mikhail A.; Head, James W.; Neumann, Gregory A.; Zuber, Maria T.; Smith, David E.

2014-12-01

We present maps of the topographic roughness of the northern circumpolar area of 30 Mercury at kilometer scales. The maps are derived from range profiles obtained by the 31 Mercury Laser Altimeter (MLA) instrument onboard the MErcury Surface, Space 32 ENvironment, Geochemistry, and Ranging (MESSENGER) mission. As measures of 33 roughness, we used the interquartile range of profile curvature at three baselines: 0.7 km, 34 2.8 km, and 11 km. The maps provide a synoptic overview of variations of typical 35 topographic textures. They show a dichotomy between the smooth northern plains and 36 rougher, more heavily cratered terrains. Analysis of the scale dependence of roughness 37 indicates that the regolith on Mercury is thicker than on the Moon by approximately a 38 factor of three. Roughness contrasts within northern volcanic plains of Mercury indicate a 39 younger unit inside Goethe basin and inside another unnamed stealth basin. These new 40 data permit interplanetary comparisons of topographic roughness.

New Morphometric Measurements of Peak-Ring Basins on Mercury and the Moon: Results from the Mercury Laser Altimeter and Lunar Orbiter Laser Altimeter

NASA Technical Reports Server (NTRS)

Baker, David M. H.; Head, James W.; Prockter, Louise M.; Fassett, Caleb I.; Neumann, Gregory A.; Smith, David E.; Solomon, Sean C.; Zuber, Maria T.; Oberst, Juergen; Preusker, Frank;

The gravity field and orientation of Mercury after the MESSENGER mission

NASA Astrophysics Data System (ADS)

Mazarico, E.; Genova, A.; Goossens, S. J.; Lemoine, F. G.; Neumann, G. A.; Zuber, M. T.; Smith, D. E.; Solomon, S. C.

2015-12-01

After more than four years in orbit about Mercury, the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft impacted the planet's surface north of Shakespeare crater (54.44° N, 210.12° E,) on 30 April 2015. One of the main goals of the mission was to determine the gravity field of Mercury in order to learn about Mercury's interior. Together with ground-based radar measurements of the obliquity and forced librations, MESSENGER-derived gravity models helped revise models of Mercury's interior. Nevertheless, the refinement of Mercury's orientation with the latest data from MESSENGER can further improve the interior modeling of the planet. The last eight months of the mission provided a special opportunity to conduct low-altitude measurements, with extensive radio tracking coverage below 200 km altitude north of ~30°N. MESSENGER's Mercury Laser Altimeter (MLA) mapped the topography of Mercury's northern hemisphere with a sub-meter vertical precision, an along-track sampling of ~500 m, and a longitudinal resolution (~0.1°) limited by the number of spacecraft orbits (~4,000). The combination of gravity and topography helps determine crustal thickness and interior properties. Altimetric ranges provide geodetic constraints to improve the spacecraft orbit determination, and thus the gravity field model. In particular, whereas the MESSENGER spacecraft was not tracked at each periapsis passage, MLA operated nearly continuously (outside of thermally challenging periods). From an analysis of the entire radiometric and altimetric datasets acquired by MESSENGER, a new gravity field to degree and order 100 has been obtained, resolving features down to ~75 km horizontal scale. The altimetric data help reduce the uncertainties in the determination of the pole position. A reanalysis of the Mercury flybys also constrains the spin rate over the longest available time span.

Space and planetary environment criteria guidelines for use in space vehicle development. Volume 1: 1982 revision

NASA Technical Reports Server (NTRS)

Smith, R. E. (Compiler); West, G. S. (Compiler)

1983-01-01

Guidelines on space and planetary environment criteria for use in space vehicle development are provided. Information is incorporated in the disciplinary areas of atmospheric and ionospheric properties, radiation, geomagnetic field, astrodynamic constants, and meteoroids for the Earth's atmosphere above 90 km, interplanetary space, and the atmosphere and surfaces (when available) of the Moon and the planets (other than Earth) of this solar system. The Sun, Terrestrial Space, the Moon, Mercury, Venus, and Mars are covered.

KSC-04pd1465

NASA Image and Video Library

2004-07-12

KENNEDY SPACE CENTER, FLA. - Technicians at Astrotech Space Operations in Titusville, Fla., work on the back side of the MESSENGER spacecraft, mating it with the Payload Assist Module, the Boeing Delta II third stage, below. The white panel seen here is the heat-resistant, ceramic cloth sunshade that will enable MESSENGER to operate at room temperature. MESSENGER (Mercury Surface, Space Environment, Geochemistry and Ranging) is scheduled to launch Aug. 2 aboard a Boeing Delta II rocket from Pad 17-B, Cape Canaveral Air Force Station, Fla. It will return to Earth for a gravity boost in July 2005, then fly past Venus twice, in October 2006 and June 2007. It is expected to enter Mercury orbit in March 2011. MESSENGER was built for NASA by the Johns Hopkins University Applied Physics Laboratory in Laurel, Md.

Libration and obliquity of Mercury from the BepiColombo radio science and camera experiments

NASA Astrophysics Data System (ADS)

Pfyffer, G.; van Hoolst, T.; Dehant, V.

2008-12-01

Mercury is the most enigmatic among the terrestrial planets, but the space missions MESSENGER and BepiColombo are expected to advance largely our knowledge of the structure, formation, and evolution of Mercury. In particular, insight into Mercury's deep interior will be obtained from observations of the 88-day forced libration, the obliquity and the degree-two coefficients of the gravity field of Mercury. Of those quantities, the libration is the most difficult to measure and will hence be a limiting factor We report here on aspects of the observational strategy to determine the libration amplitude and obliquity, taking into account the space and ground segment of the experiment. Repeated photographic measurements of selected target positions on the surface of Mercury are central to the strategy to determine the obliquity and libration in the frame of the BepiColombo mission. We simulated these measurements in order to estimate the accuracy of the reconstruction of the orientation and rotational motion of the planet, as a function of the amount of measurements made, the number of different targets considered and their locations on the surface of the planet. From this study, we determine criteria for the distribution and number of target positions to maximize the accuracy on the orientation and rotation determination, from which the obliquity and libration are extracted. We take into account the errors arising from the relative positions of the spacecraft, Mercury and the Earth. We consider various error sources such as the solar thermal influence on the spacecraft bus and the Earth based tracking constraint near solar conjunctions of Mercury. The accuracy on the retrieved parameters is then interpreted in terms of accuracy on the constraints on the interior structure of the planet. Our simulations show that the achievable level of accuracy on the libration amplitude and obliquity will be sufficient to constrain Mercury interior structure models, if the orbiter follows the ESA baseline mission scenario and at least 50 landmarks are imaged at least twice over the mission duration, the libration amplitude can be determined in two Mercury years (176 days) with an accuracy of 3 arcsec or better, which is sufficient to constrain the size and physical state of the planetary core.

Sodium Ion Dynamics in the Magnetospheric Flanks of Mercury

NASA Astrophysics Data System (ADS)

Aizawa, Sae; Delcourt, Dominique; Terada, Naoki

2018-01-01

We investigate the transport of planetary ions in the magnetospheric flanks of Mercury. In situ measurements from the MErcury Surface, Space ENvironment, GEochemistry, and Ranging spacecraft show evidences of Kelvin-Helmholtz instability development in this region of space, due to the velocity shear between the downtail streaming flow of solar wind originating protons in the magnetosheath and the magnetospheric populations. Ions that originate from the planet exosphere and that gain access to this region of space may be transported across the magnetopause along meandering orbits. We examine this transport using single-particle trajectory calculations in model Magnetohydrodynamics simulations of the Kelvin-Helmholtz instability. We show that heavy ions of planetary origin such as Na+ may experience prominent nonadiabatic energization as they E × B drift across large-scale rolled up vortices. This energization is controlled by the characteristics of the electric field burst encountered along the particle path, the net energy change realized corresponding to the maximum E × B drift energy. This nonadiabatic energization also is responsible for prominent scattering of the particles toward the direction perpendicular to the magnetic field.

First in-situ observations of exospheric response to CME impact at Mercury

NASA Astrophysics Data System (ADS)

Raines, J. M.; Wallace, K. L.; Sarantos, M.; Jasinski, J. M.; Tracy, P.; Dewey, R. M.; Weberg, M. J.; Slavin, J. A.

2017-12-01

We present the first in-situ observations of enhancements to Mercury's He exosphere generated by CME impact. We analyzed both plasma and magnetic field measurements from the Mercury Surface Space Environment, Geochemistry and Mapping (MESSENGER) spacecraft over a 60-hour period as a coronal mass ejection (CME) passed by the planet. We identified the shock, magnetic cloud and cavity regions of the moderate intensity CME while MESSENGER was in the solar wind. Inside the magnetosphere just after the CME shock passage, we observed a very active dayside magnetosphere, as evident from the high flux plasma parcels passing through the dayside and a broad northern magnetospheric cusp with exceptionally high planetary ion content. All of these signatures indicate substantial reconnection at the dayside magnetopause, making conditions that were excellent for solar wind access to Mercury's surface. The CME appeared to have been particularly enriched in He2+, causing the observed density of solar wind He2+ in the cusp to rise above 0.1 cm-3 and putting it in the top 1% of the over 3200 cusps analyzed. As the low-density CME cavity passed over the planet on the next orbit, the magnetosphere appeared much quieter, with smoother magnetic fields and a smaller, less intense northern cusp but with greatly enhanced He+ content. The elevated He+ observed density continued to increase on subsequent cusp crossings, peaking at 0.1 cm-3 36 hours after CME impact, the highest observed throughout the entire MESSENGER mission. We suggest that the enhancement in He+ indicates an increase to the neutral He exosphere density from the He-enriched CME, a phenomenon observed at the moon, possibly acting as follows: Increased access to the surface from CME-enhanced reconnection, combined with high He2+ flux, enhanced surface implantation. Neutral He atoms were then liberated at an increased rate by surface processes supplying the exosphere, causing a gradual increase in He exosphere density. This led to an increase in He+ abundance through photoionization and charge exchange, which, after acceleration on the dayside, was measured by MESSENGER. These first in-situ observations of exospheric response to CME impact at Mercury have implications for understanding exosphere generation and loss processes, as well space weathering of the planet's surface.

Space Weathering in the Mercurian Environment

NASA Technical Reports Server (NTRS)

Noble, S. K.; Pieters, C. M.

2001-01-01

Space weathering processes are known to be important on the Moon. These processes both create the lunar regolith and alter its optical properties. Like the Moon, Mercury has no atmosphere to protect it from the harsh space environment and therefore it is expected that it will also incur the effects of space weathering. However, there are many important differences between the environments of Mercury and the Moon. These environmental differences will almost certainly affect the weathering processes and the products of those processes. It should be possible to observe the effects of these differences in Vis (visible)/NIR (near infrared) spectra of the type expected to be returned by MESSENGER. More importantly, understanding these weathering processes and their consequences is essential for evaluating the spectral data returned from MESSENGER and other missions in order to determine the mineralogy and the Fe content of the Mercurian surface. Additional information is contained in the original extended abstract.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is secure after transfer to the work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is secure after transfer to the work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is lifted off the pallet for transfer to a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, NASA’s MESSENGER spacecraft is lifted off the pallet for transfer to a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - In the high bay clean room at the Astrotech Space Operations processing facilities near KSC, workers remove the protective cover from NASA’s MESSENGER spacecraft. Employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - In the high bay clean room at the Astrotech Space Operations processing facilities near KSC, workers remove the protective cover from NASA’s MESSENGER spacecraft. Employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, workers check the placement of NASA’s MESSENGER spacecraft on a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, workers check the placement of NASA’s MESSENGER spacecraft on a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities near KSC, workers move NASA’s MESSENGER spacecraft into a high bay clean room. Employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities near KSC, workers move NASA’s MESSENGER spacecraft into a high bay clean room. Employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane moves NASA’s MESSENGER spacecraft toward a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane moves NASA’s MESSENGER spacecraft toward a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane lowers NASA’s MESSENGER spacecraft onto a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - At the Astrotech Space Operations processing facilities, an overhead crane lowers NASA’s MESSENGER spacecraft onto a work stand. There employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

KENNEDY SPACE CENTER, FLA. - In the high bay clean room at the Astrotech Space Operations processing facilities near KSC, NASA’s MESSENGER spacecraft is revealed. Employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

NASA Image and Video Library

2004-03-10

KENNEDY SPACE CENTER, FLA. - In the high bay clean room at the Astrotech Space Operations processing facilities near KSC, NASA’s MESSENGER spacecraft is revealed. Employees of the Johns Hopkins University Applied Physics Laboratory, builders of the spacecraft, will perform an initial state-of-health check. Then processing for launch can begin, including checkout of the power systems, communications systems and control systems. The thermal blankets will also be attached for flight. MESSENGER - short for MErcury Surface, Space ENvironment, GEochemistry and Ranging - will be launched May 11 on a six-year mission aboard a Boeing Delta II rocket. Liftoff is targeted for 2:26 a.m. EDT on Tuesday, May 11.

Compiling Mercury relief map using several data sources

NASA Astrophysics Data System (ADS)

Zakharova, Maria; Lazarev, Evgeniy

2015-04-01

There are several data of Mercury topography obtained as the result of processing materials collected by two spacecrafts - the Mariner-10 and the MESSENGER during their Mercury flybys. The history of the visual mapping of the Mercury begins at the recent times as the first significant observations were made during the latter half of the 20th century, whereas today we have no data with 100% coverage for the entire surface of the Mercury except the global mosaic composed of the images acquired by MESSENGER. The Mercury relief map has been created with the help of four different types of data: - global mosaic with 100% coverage of Mercury's surface created by using MESSENGER orbital images (30% of the final map); - Digital Terrain Models obtained by the treating stereo images made during the Mariner 10's flybys (10% of the map) (Cook and Robinson, 2000); - Digital Terrain Models obtained from images acquired during the Messenger flybys (20% of the map) (F. Preusker et al., 2011); - the data sets produced by the MESSENGER Mercury Laser Altimeter (MLA) (40 % of the map). The main objective of this work is to collect, combine and process the existing data and then to merge them correctly for one single map compiling. The final map is created in the Lambert azimuthal Equal area projection and mainly shows the hypsometric features of the planet. It represents two hemispheres - western and eastern. In order not to divide data sources the eastern hemisphere takes an interval from 50 degrees east longitude to 130 degrees west longitude and the western one takes respectively the interval from 130 degrees west longitude to 50 degrees east longitude. References: Global mosaics of Mercury's surface. Available mosaics include one created prior to MESSENGER's orbital operations, high resolution versions that use MESSENGER's orbital images that are available in NASA's Planetary Data System (PDS) (http://messenger.jhuapl.edu/the_mission/mosaics.html). Cook, A.C., Robinson, M.S., 2000. Mariner 10 stereo image coverage of Mercury. J. Geophys. Res. 105, 9429-9443. Preusker, F., Oberst, J., Head, J.W., Watters, T.R., Robinson, M.S., Zuber, M.T., Solomon, S.C., 2010. Stereo topographic models of Mercury after three MESSENGER flybys. Planetary and Space Science 59 (2011), 1910-1917. The MLA is a time-of-flight laser rangefinder that uses direct detection and pulse-edge timing to determine precisely the range from the MESSENGER spacecraft to Mercury's surface (http://pds-geosciences.wustl.edu/missions/messenger/mla.htm).

Planetary Science from NASA's WB-57 Canberra High Altitude Research Aircraft During the Great American Eclipse of 2017

NASA Astrophysics Data System (ADS)

Tsang, C.; Caspi, A.; DeForest, C. E.; Durda, D. D.; Steffl, A.; Lewis, J.; Wiseman, J.; Collier, J.; Mallini, C.; Propp, T.; Warner, J.

2017-12-01

The Great American Eclipse of 2017 provided an excellent opportunity for heliophysics research on the solar corona and dynamics that encompassed a large number of research groups and projects, including projects flown in the air and in space. Two NASA WB-57F Canberra high altitude research aircraft were launched from NASA's Johnson Space Center, Ellington Field into the eclipse path. At an altitude of 50,000ft, and outfitted with visible and near-infrared cameras, these aircraft provided increased duration of observations during eclipse totality, and much sharper images than possible on the ground. Although the primary mission goal was to study heliophysics, planetary science was also conducted to observe the planet Mercury and to search for Vulcanoids. Mercury is extremely challenging to study from Earth. The 2017 eclipse provided a rare opportunity to observe Mercury under ideal astronomical conditions. Only a handful of near-IR thermal images of Mercury exist, but IR images provide critical surface property (composition, albedo, porosity) information, essential to interpreting lower resolution IR spectra. Critically, no thermal image of Mercury currently exists. By observing the nightside surface during the 2017 Great American Eclipse, we aimed to measure the diurnal temperature as a function of local time (longitude) and attempted to deduce the surface thermal inertia integrated down to a few-cm depth below the surface. Vulcanoids are a hypothesized family of asteroids left over from the formation of the solar system, in the dynamically stable orbits between the Sun and Mercury at 15-45 Rs (4-12° solar elongation). Close proximity to the Sun, plus their small theoretical sizes, make Vulcanoid searches rare and difficult. The 2017 eclipse was a rare opportunity to search for Vulcanoids. If discovered these unique, highly refractory and primordial bodies would have a significant impact on our understanding of solar system formation. Only a handful of deep searches have been conducted. Our observations will only be the second time ever a search for Vulcanoids will have been conducted in the NIR. In this presentation, I will review our NASA flight program, and focus on the planetary science observations that came from the Great American Eclipse of 2017.

Mercury

NASA Technical Reports Server (NTRS)

Gault, D. E.; Burns, J. A.; Cassen, P.; Strom, R. G.

1977-01-01

Prior to the flight of the Mariner 10 spacecraft, Mercury was the least investigated and most poorly known terrestrial planet (Kuiper 1970, Devine 1972). Observational difficulties caused by its proximity to the Sun as viewed from Earth caused the planet to remain a small, vague disk exhibiting little surface contrast or details, an object for which only three major facts were known: 1. its bulk density is similar to that of Venus and Earth, much greater than that of Mars and the Moon; 2. its surface reflects electromagnetic radiation at all wavelengths in the same manner as the Moon (taking into account differences in their solar distances); and 3. its rotation period is in 2/3 resonance with its orbital period. Images obtained during the flyby by Mariner 10 on 29 March 1974 (and the two subsequent flybys on 21 September 1974 and 16 March 1975) revealed Mercury's surface in detail equivalent to that available for the Moon during the early 1960's from Earth-based telescopic views. Additionally, however, information was obtained on the planet's mass and size, atmospheric composition and density, charged-particle environment, and infrared thermal radiation from the surface, and most significantly of all, the existence of a planetary magnetic field that is probably intrinsic to Mercury was established. In the following, this new information is summarized together with results from theoretical studies and ground-based observations. In the quantum jumps of knowledge that have been characteristic of "space-age" exploration, the previously obscure body of Mercury has suddenly come into sharp focus. It is very likely a differentiated body, probably contains a large Earth-like iron-rich core, and displays a surface remarkably similar to that of the Moon, which suggests a similar evolutionary history.

Monte Carlo Modeling of Sodium in Mercury's Exosphere During the First Two MESSENGER Flybys

NASA Technical Reports Server (NTRS)

Burger, Matthew H.; Killen, Rosemary M.; Vervack, Ronald J., Jr.; Bradley, E. Todd; McClintock, William E.; Sarantos, Menelaos; Benna, Mehdi; Mouawad, Nelly

2010-01-01

We present a Monte Carlo model of the distribution of neutral sodium in Mercury's exosphere and tail using data from the Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft during the first two flybys of the planet in January and September 2008. We show that the dominant source mechanism for ejecting sodium from the surface is photon-stimulated desorption (PSD) and that the desorption rate is limited by the diffusion rate of sodium from the interior of grains in the regolith to the topmost few monolayers where PSD is effective. In the absence of ion precipitation, we find that the sodium source rate is limited to approximately 10(exp 6) - 10(exp 7) per square centimeter per second, depending on the sticking efficiency of exospheric sodium that returns to the surface. The diffusion rate must be at least a factor of 5 higher in regions of ion precipitation to explain the MASCS observations during the second MESSENGER f1yby. We estimate that impact vaporization of micrometeoroids may provide up to 15% of the total sodium source rate in the regions observed. Although sputtering by precipitating ions was found not to be a significant source of sodium during the MESSENGER flybys, ion precipitation is responsible for increasing the source rate at high latitudes through ion-enhanced diffusion.

Mercury accumulation in periphyton of eight river ecosystems

USGS Publications Warehouse

Bell, A.H.; Scudder, B.C.

2007-01-01

In 2003, the U.S. Geological Survey (USGS) National Water-Quality Assessment (NAWQA) program and U.S. Environmental Protection Agency studied total mercury (THg) and methylmercury (MeHg) concentrations in periphyton at eight rivers in the United States in coordination with a larger USGS study on mercury cycling in rivers. Periphyton samples were collected using trace element clean techniques and NAWQA sampling protocols in spring and fall from targeted habitats (streambed surface-sediment, cobble, or woody snags) at each river site. A positive correlation was observed between concentrations of THg and MeHg in periphyton (r2 = 0.88, in log-log space). Mean MeHg and THg concentrations in surface-sediment periphyton were significantly higher (1,333 ng/m2 for MeHg and 53,980 ng/m2 for THg) than cobble (64 ng/m2 for MeHg and 1,192 ng/m2 for THg) or woody snag (71 ng/m2 for MeHg and 1,089 ng/m2 for THg) periphyton. Concentrations of THg in surface-sediment periphyton had a strong positive correlation with concentrations of THg in sediment (dry weight). The ratio of MeHg:THg in surface-sediment periphyton increased with the ratio of MeHg:THg in sediment. These data suggest periphyton may play a key role in mercury bioaccumulation in river ecosystems. ?? 2007 American Water Resources Association.

Remote X-ray fluorescence experiments for future missions to Mercury

NASA Astrophysics Data System (ADS)

Clark, P. E.; Trombka, J. I.

1997-01-01

To date, the only deep space mission to Mercury, Mariner 10, as well as ground-based observations have failed to provide direct measurements of that planet's composition. Such measurements are fundamental for the understanding of Mercury's origin and the inner solar system's history. The spin-stabilized Mercury Orbiter proposed for launch in the first or second decade of the twenty-first century as part of the ESA's Horizon 2000-plus plan could address this problem by including the X-ray spectrometer proposed here. X-ray spectrometers act as detectors for the X-ray emission induced by the solar flux incident on planetary surfaces. This emission is strongly dependent on the chemical composition of the surface as well as on the solar spectrum. Characteristic fluorescent lines, the most prominent being the K-alpha lines, are of sufficient intensity for major elements (Mg, Al, Si, Ca, Fe) to allow orbital measurement by remote X-ray detectors. The X-ray spectrometers described here will all have established heritage for space missions by 2000. These instruments have previously flown, are being flown as part of the NASA NEAR (Near Earth Asteroid Rendezvous) or Clark SSTI (Small Science and Technology Initiative) missions, or are now under development as part of NASA Facility Instrument Development Program. The instrument package would probably consist of an array of solid state detectors for surface measurements, as well as one which would act as a solar monitor. Calculations of anticipated results have been done for a variety of orbital and instrument configurations, and a variety of lunar soil compositions which could be analogous: anorthositie gabbro bearing soils from lunar highlands (Apollo 16), high-Mg basalt-rich soils from a KREEP-bearing area (Apollo 15), and mare basalt bearing soils (Apollo 12). The mission being considered here should result in maps of abundances of major elements, including Mg, Al, Si, Ca, and Fe, for much of Mercury's surface, with resolutions ranging from tens to hundreds of kilometers depending on the element, the orbital eccentricity and altitude of the spacecraft.

Solar wind controls on Mercury's magnetospheric cusp

NASA Astrophysics Data System (ADS)

He, Maosheng; Vogt, Joachim; Heyner, Daniel; Zhong, Jun

2017-06-01

This study assesses the response of the cusp to solar wind changes comprehensively, using 2848 orbits of MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) observation. The assessment entails four steps: (1) propose and validate an approach to estimate the solar wind magnetic field (interplanetary magnetic field (IMF)) for MESSENGER's cusp transit; (2) define an index σ measuring the intensity of the magnetic disturbance which significantly peaks within the cusp and serves as an indicator of the cusp activity level; (3) construct an empirical model of σ as a function of IMF and Mercury's heliocentric distance rsun, through linear regression; and (4) use the model to estimate and compare the polar distribution of the disturbance σ under different conditions for a systematic comparison. The comparison illustrates that the disturbance peak over the cusp is strongest and widest extending in local time for negative IMF Bx and negative IMF Bz, and when Mercury is around the perihelion. Azimuthal shifts are associated with both IMF By and rsun: the cusp moves toward dawn when IMF By or rsun decrease. These dependences are explained in terms of the IMF Bx-controlled dayside magnetospheric topology, the component reconnection model applied to IMF By and Bz, and the variability of solar wind ram pressure associated with heliocentric distance rsun. The applicability of the component reconnection model on IMF By indicates that at Mercury reconnection occurs at lower shear angles than at Earth.