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Mercury Exploration Assessment Group (MExAG) Meeting

February 6–8


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MExAG Posters

Wednesday, February 7, 2024, 11:00 AM

Grava C.
Mercury's Exosphere: BepiColombo's Prospects [#6038]
The two spacecraft Mariner 10 (1974-1975) and MESSENGER (2008-2015), in addition to several ground-based observation campaigns, have improved our understanding of the complex surface-exosphere-magnetosphere system of Mercury, but many mysteries remain unsolved. For example, what is the fate of oxygen, one of the most abundant species expected in the Mercurian exosphere, that has nevertheless eluded detection by both spacecraft? I will summarize the properties of species detected in the exosphere of Mercury, how it responds to changes in the external drivers (micrometeoroids, solar wind, solar photons), and how its constituents provide important clues to understanding source and loss processes of exospheres of other airless bodies. The arrival of BepiColombo, with instruments that sense the Mercurian exosphere both in situ and remotely, promises to revolutionize our understanding of the formation and evolution of not only Mercury but also rocky exoplanets orbiting close to their star.
Travnicek P. Schriver D. Lapenta G. Delitsky M. L. Ho G. et al.
Ion and Electron Acceleration, Transport, and Precipitation at Mercury [#6045]
We examine plasma transport and energization processes within Mercury’s magnetosphere and the loss of ions and electrons through precipitation at the dayside cusps and nightside auroral regions. We study the consequences of charged particle precipitation, including space weathering effects on frozen icy volatiles within high latitude craters and the emission of particles from the surface (e.g., sodium) via sputtering and desorption. To capture the physics of these processes correctly on a local and global scale, fully self-consistent kinetic simulations are required. To model the interaction of the solar wind with Mercury’s magnetosphere, a three-dimensional global kinetic simulation approach is used that combines a fully self-consistent particle in cell (PIC) simulation (particle ions, particle electrons), a hybrid simulation (particle ions, fluid electrons) and large scale kinetic (LSK) particle tracing simulations.
Dutta A. A.
Unraveling Mercury's Exosphere: Exploration and Experimentation [#6007]
Mercury's enigmatic exosphere, a dynamic ballet of particles around the planet, is a celestial mystery waiting to be unveiled. Composed mainly of hydrogen, helium, sodium, and potassium, this ethereal expanse influences Mercury's environment profoundly. The MESSENGER and BepiColombo missions have been pioneers, providing a front-row seat to the exosphere's spatial nuances influenced by solar activity. The delicate balance between these forces crafts the exosphere's composition—a testament to the intricate interplay of planetary and extraplanetary dynamics. Solar radiation, particularly in the ultraviolet and X-ray spectrum, acts as the maestro shaping the exosphere's behavior. The absorption and re-emission of solar radiation create a tail-like structure—a signature of Mercury's interaction with the solar wind. Understanding these processes not only illuminates the exosphere's current state but also unveils insights into Mercury's historical evolution under the relentless gaze of the Sun.
Sonke A. J. Robinson M. S.
MESSENGER-Based Control Network for Mariner 10 Images [#6006]
Mariner 10 imaged approximately forty percent of Mercury’s surface in 1974. Subsequently, the MESSENGER Mercury Dual Imaging System (MDIS) acquired global high-resolution multispectral images of Mercury from 2011 to 2015. The MDIS images, combined with Mercury Laser Altimeter (MLA) observations, enabled a global image-based control network, resulting in a global image mosaic and digital elevation models. We are deriving a new Mariner 10 image-based control network tied to the MDIS and MLA products, which will allow for more accurate analytical triangulation calculations and, subsequently, the reconstruction of instrument pointing and spacecraft location kernels for the Mariner 10 image set ahead of BepiColombo’s orbital phase at Mercury. In conjunction with MDIS images, improved kernels will enable color unit mapping on Mercury in an extended spectral range and temporal analysis of surface processes on multi-decadal time scales.
Chabot N. L. Malaret E.
Mercury QuickMap: New Features to Support BepiColombo and for the Mercury Community [#6001]
Mercury QuickMap is a public, easy-to-use, web-based tool developed by Applied Coherent Technology (ACT): https://mercury.quickmap.io/ Mercury QuickMap was supported by and heavily used during NASA’s MESSENGER mission and is an important bridge between the MESSENGER and BepiColombo datasets. Through NASA’s support of a BepiColombo Interdisciplinary Scientist position, it has been possible to add new product layers and new capabilities to Mercury QuickMap. These additions benefit the BepiColombo team but are also publicly available to the entire Mercury community. In this presentation, we will introduce those new capabilities added to Mercury QuickMap within the last year, which include the addition of features identified by geologic mapping studies, illumination at Mercury's south pole for the duration of BepiColombo's mission, local high-resolution DEMs, and thermal modeling results of craters nearest to Mercury's north pole.
Jozwiak L. M.
Overview of the State of Volcanism on Mercury [#6016]
The Encyclopedia of Volcanoes is a preeminent resource for students and professional volcanologists. The most recent edition of the Encyclopedia was published in 2015 and presented an overview of the most recent MESSENGER discoveries. Now preparing for its third edition, this new volume plans to include a significantly updated section devoted to the understanding of volcanism on Mercury and its place in the wider context of planetary volcanology. Here, we will provide an overview of the proposed outline of the chapter, the framing of volcanic processes on Mercury, and a discussion about the relative importance of included concepts and ideas for the overarching framing of Mercury in a global volcanic context. The upcoming edition will also include significant amounts of online, open-access material. We seek community input on the most valuable materials to include in these collections.
Lark L. H. Head J. W. Huber C. Parmentier E. M.
Influence of Crustal Layering on Mercury’s Volcanic, Magnetic, and Tectonic Evolution [#6020]
Mercury’s surface records evidence of a puzzling thermal history. Early yet long-lived volcanism overlapped with magnetic field generation (also currently active); these indicate billions of years of heat loss from Mercury’s core and mantle that nevertheless resulted in only moderate total loss of heat as indicated by the tectonic record. We consider this history in the context of Mercury’s highly reduced chemistry, which may have influenced the compositional structure of its mantle. Could magma ocean solidification have concentrated the heat-producing elements at the top or bottom of Mercury’s mantle, as we may see on the Moon? We explore the consequences of this concentration for planetary thermal and geological evolution. We conclude that Mercury’s evolution bears characteristics (e.g., slow cooling, flood lavas) of both upward sequestration of heat-producing elements and heat loss from the interior that was controlled by the insulating properties of Mercury’s crust.
Gwyn R. G. Lambart S. L. McCombs T. M. Boujibar A. B.
Investigating Mercury’s Mantle Phase Equilibria Through the Partial Melting of Enstatite Chondrites [#6026]
Mercury, the innermost terrestrial planet of our solar system, exhibits unique features, including a reduced and chemically heterogeneous surface. The effect of oxygen fugacity on magmatic differentiation is poorly explored, limiting our understanding of mantle-crust differentiation on Mercury. To address this lack of knowledge, we conducted experiments at high pressure and temperature using a synthetic enstatite chondrite powder. Preliminary experimental data is compared with predictions from thermodynamic models (pMELTS) and Mercury’s surface composition, provided by MESSENGER. Melting experiments of enstatite chondrites at 1 GPa and an fO2 of IW-5 show that olivine is in the liquid phase. In addition, the liquidus is found lower than in more oxidized conditions: 1600 degrees C at IW-5 and 1675 degrees C at IW-4.
Pommier A. Tauber M. J. Pirotte H. Cody G. Steele A. et al.
Experimental Investigation of the Bonding of Sulfur in Highly Reduced Silicate Glasses and Melts [#6009]
Elucidating the role of sulfur on the transport properties of Mercury's magma ocean is key to model the planet's evolution. Despite several investigations, questions remain regarding the effect of S on complex glasses at highly reducing conditions. Using multiple spectroscopic methods and microprobe analyses, we studied compositions representative of the Northern Volcanic Plains, with S contents up to 5 wt%. In situ impedance spectroscopy results at 2 and 4 GPa and up to 1740 K indicate that sulfide improves Na+ transport and may overcome a known impeding effect of the divalent cation Ca2+. Melt conductivity varies from 0.7 to 2.2 S/m (the sample with 5 wt% S is the most conductive). 29Si NMR spectra reveal that a high fraction of S bonds with Si in these glasses, a characteristic that has not been recognized previously. Raman spectra show regions rich in Ca–S or Mg–S bonds. Our results suggest that alkaline earth sulfides are weak network modifiers under highly reduced conditions.
McCombs T. Boujibar A. Anzures B. A.
Thermodynamic Modeling of Calcium and Magnesium Partitioning between Sulfide and Silicate and Implications for Mercury's Differentiation [#6027]
Mercury is the least oxidized terrestrial planet of the solar system and is enriched in sulfur, which may be saturated in its mantle, possibly forming Ca- and Mg-rich sulfides. Using literature experimental data, we developed a thermodynamic model for calcium and magnesium partitioning between sulfide and silicate melts to enhance our understanding of the chemical equilibria involved in Mercury’s mantle-crust differentiation. Our models show that temperature and carbon abundance in sulfide have a positive effect on Ca partitioning into sulfides while pressure decreases it. In addition, carbon abundance and sulfur concentration in the silicate melt are the primary controls on Mg partitioning, both favoring Mg partitioning into sulfides. Our results will be used to better understand the abundance as well as the presence of calcium and magnesium sulfides within Mercury’s mantle and crust.
Roberts J. H.
Thermochemical Evolution of Mercury's Mantle and the Formation of the Volcanic Plains [#6030]
Large portions of Mercury’s surface are covered by smooth plains, which are interpreted to be volcanic in origin. Volcanic plains are also associated with impact basins, which exhibit compositional and age differences from other plains units. Extensive volcanism implies an era of convection in the Mercurian mantle, widespread partial melting, and secondary crustal production. Gravity observations from MESSENGER suggest that the mantle of Mercury is quite thin and would require internal heating in order to convect. This requires that a significant fraction of radiogenic isotopes remain in the mantle, and effectively places a limit to the degree of crustal production before mantle convection shuts down. Here, we explore the formation of volcanic plains on Mercury, infer the evolution of the mantle as a result of this crustal production, and investigate the effects of large basin-forming impacts on melt production, with the goal of identifying source regions for plains materials.
Blanco-Rojas M. Hauck S. A.
An Initial Approach to Assessing Mercury’s Seismicity Over Time [#6031]
Seismicity provides a window into the inner structure and operation of planetary bodies, as demonstrated by NASA’s InSight mission to Mars. Mercury, with surface features suggesting a radial contraction between 1-7 km since the Late Heavy Bombardment, is a key next target for such studies. Our work aims to estimate Mercury’s seismic moment over time with the intention of guiding future seismic mission design. Using a contraction-based model adapted from Mars studies, we establish upper and lower bounds for Mercury’s annual seismic moment. We find the correlation between planetary contraction and quake frequency indicates an order of magnitude variation in a yearly cumulative seismic moment for the contraction values explored. Our predictions suggest an annual release between 5.4x10^15 Nm and 2.1x10^17 Nm, with up to 12 events exceeding magnitude 4. These results are a vital step toward determining the total seismicity that could be observed on Mercury by a future lander.
Blance A. J. Rothery D. A. Balme M. R. Wright J. Galluzzi V.
Flow Features Around Craters on Mercury: Lunar Comparisons and Investigating Formation Mechanisms [#6048]
Flow features around impact craters occur across the Solar System. Some are interpreted as ejecta flows: ground-hugging flows of ejecta during an impact event, where volatiles may fluidize ejecta material. In contrast, some flows around craters are probably landslides, especially on bodies with minimal volatiles like the Moon. Mercury provides an interesting point of comparison: an intermediary step between volatile, abundant Mars and the volatile, depleted Moon. We did a global survey of Mercury for flow features around craters and surveyed the Moon for comparison. We find both bodies have a similar number of flow features (Mercury 84, Moon 87). Mercury is larger, but the Moon has a higher crater density, so flow abundances are comparable. Most features identified are landslides, with formation controlled by uneven pre-impact topography. However, Mercury also has 2 clear examples of ejecta flows and a significant population of enigmatic flow features that we are still investigating.
Wright J. Caminiti E. Rae A. S. P. Besse S.
Source of Mercury’s Hollow-Forming Materials: Preliminary Results from Geological Mapping, Spectra, and Impact Simulations [#6044]
Mercury’s large iron core has been hypothesized to have formed by energetic processes. Paradoxically, Mercury’s surface is volatile-rich. Thus, it is important to learn what thickness of Mercury’s silicate portion is volatile-rich to constrain how and when Mercury acquired its volatiles and large core. We are studying Caloris, the largest, well-preserved impact basin on Mercury, using three techniques. First, we are making a geological map of Caloris to ascertain the distribution of its ejecta, which has previously been shown to contain hollows and landforms formed by volatile loss. Second, we are analyzing MASCS data of the mapped Caloris ejecta to determine how much of it is generally volatile-rich by comparing these spectra with the known spectra of hollows. Third, we are performing iSALE impact simulations to establish what depth in the subsurface hollow-forming Caloris ejecta was excavated from. Here, we present progress and preliminary results from our tripartite analysis.
Meyer H. M. Jozwiak L. Kinczyk M. Klima R. Blewett D.
Tyagaraja and Zeami: Maximizing Compositional Diversity in a Single Exploration Target [#6032]
Although the surface composition of Mercury remains mysterious, data from the MESSENGER mission were used to distinguish a range of distinct terrains, including those related to some of the oldest crustal material (low reflectance material, LRM), and potentially some of the youngest features (hollows). Previous work has shown that there is a marked association of hollows with LRM, which is thought to be excavated from depth, and, to a lesser degree, an association between hollows and pyroclastic deposits. Tyagaraja (97km) and Zeami (129km) are both relatively young, large impacts that exhibit LRM, pyroclastic materials and hollows in close proximity. Further, both craters have hollows and explosive volcanic features directly associated with their central peaks/rings. As such, they are ideal landing sites to study hollows formation in both LRM and pyroclastic terrains, the compositional diversity of Mercury’s crust, and the association of hollows with impact structures.
Meyer H. M. Fassett C. Denevi B.
Basin-Scale Science with a Landed Mission to Mercury [#6042]
Impact basins excavate deeper than any other impact and, as such, provide an opportunity to investigate Mercury’s crustal stratigraphy. For example, the Odin formation at the Caloris basin is thought to be Caloris ejecta, implying material excavated from great depths due to the basin size. A landed mission could perform detailed imaging and compositional analyses to better understand the origin of the Odin formation and could provide substantial insight into the composition of the deep crust of Mercury.
Meyer H. M. Rivera-Valentín E. G.
Optimizing Geologic Diversity in a Single Exploration Target: A Non-polar PSR Target [#6025]
MESSENGER revealed permanently shadowed regions (PSRs) exhibiting heterogeneity in their reflectance and are associated with radar-bright deposits. Further, the compositional diversity of Mercury’s surface includes some of the oldest crustal material (low reflectance material, LRM) and potentially some of the youngest features (hollows). A non-polar crater (71.750N, 104.323E) within Mendelssohn exhibits a PSR with high radar backscatter and both LRM and hollows on its floor. Its relatively low latitude with respect to the poles makes it more accessible for a landed mission. Such a mission, including data collection on descent in particular, would provide invaluable insight into the geologic context and development of these terrains. Locations with multiple science opportunities enhance the intrinsic value of a given mission.
Glantzberg A. K. Chabot N. L. Hamill C. D.
Exploring the Thermal Environment and Composition of Mercury’s Northern Ice-Bearing Deposits [#6037]
MESSENGER results indicate that permanently shadowed regions (PSRs) on Mercury have temperature conditions suitable for the presence of water ice and low-reflectance volatiles at or near the surface. There are a number of craters near the north pole with PSRs that have been characterized by MESSENGER and show intriguing features worthy of future landed exploration. Once such crater is Laxness (25.9 km) — situated at 83.3 deg N, it has a low-reflectance surface, likely composed of complex organic molecules, along with a radar-bright deposit indicative of subsurface water ice. The position and topography of Laxness keep one side in perpetual shadow while the other side receives up to 30% direct sunlight, offering a lander both refuge from extreme heat and access to solar power within the crater. Adjacent to a similarly endowed crater, Fuller, Laxness also presents the prospect of a dual-site exploration mission.
Kinczyk M. J. Meyer H. M. Rivera-Valentín E. G.
Icy Hot: A Case for a Landed Investigation of Mercury's Permanently Shadowed Regions [#6035]
Previous work identified radar-bright deposits in many of Mercury’s permanently shadowed regions (PSRs) consistent with the presence of ice. A PSR landed mission could address several high-priority science questions related to volatile transport, as well as the importance of microclimates on other planets. Two potential landing sites are the floors of Stieglitz (91 km, 72.5°N, 67.3°E) and Egonu (24 km, 67.1°N, 61.4°E) craters situated in Mercury’s northern smooth plains, which contain PSRs that host radar-bright deposits. Both craters appear to be morphologically young, but the continuous ejecta deposit of Egonu is spectrally distinct from the surrounding terrain. Thus, in situ analysis of Egonu could additionally elucidate the nature of crater formation and composition on Mercury. Landing in or near a PSR could also potentially extend the lander's life since PSRs have lower average temperatures than lower-latitude non-PSR locations.
Jozwiak L. M. Meyer H. M.
Mercury's Pyroclastic Deposits as a Target for Future Exploration [#6015]
Pyroclastic materials represent a compositionally distinct terrain on Mercury and were one of the most significant discoveries of the MESSENGER mission. These deposits were formed by gas-rich eruptions from the Mercurian mantle, and GRS/XRS data suggest that the deposits are depleted in carbon and sulfur. The composition of Mercury’s mantle, and in particular, its volatile composition, remains unknown but has large implications for the formation and evolution of Mercury. Pyroclastic deposits represent a singular location for tackling questions related to the volatile evolution of Mercury, as well as the thermal evolution of the planet. The deposit known as Nathair Facula (formerly NE Rachmaninoff) would provide a prime target, consisting of a several meters thick pyroclastic deposit and smoothly mantled landing regions; however, any pyroclastic deposit with a preserved spectral anomaly would be sufficient for pursuing these investigations.
Fischer E. L. Lark L. H. Parman S. W.
Another Fe-Enriched Geochemical Terrane? [#6046]
An Fe-enriched region, located within basin b56 and antipodal to the westernmost expression of the high-Mg region (HMR), was identified through MESSENGER XRS measurements. This region is not associated with significant LRM, except as ejecta from craters. The geochemistry of this region is unique because it is depleted in Mg, Al, Ca, and S. Higher resolution mapping with MIXS-T on BepiColombo will help to assess the surface expression and origin of this region. For example, it is of interest to determine its geochemical relationship to the HMR, which also exhibits an enrichment in Fe but also shows an enrichment in S, Mg, and Ca. New data as a targeted region during solar flares will further contribute to our understanding of the geochemical terranes on Mercury and their relationship to mantle conditions such as composition, temperature, and oxygen fugacity.
Parman S. W. Mustard J. F. Pieters C. M. Kremer C. H. Bramble M. S. et al.
Mercury Scout: Mapping Minerals and Ices [#6041]
Mercury Scout is an orbiter concept that will fill several knowledge gaps concerning the innermost planet: 1) what is the distribution (and identity) of minerals on the surface, 2) what is the distribution of ice in the permanently shadowed regions (PSRs) and 3) where are there smooth areas for future landed missions. The mission consists of three main components: 1) a newly developed intermediate wavelength IR (IMIR=4-8 micron) imaging spectrometer, 2) a narrow-angle visible wavelength camera with 1 meter per pixel resolution, and 3) a ~1500 square meter solar sail to serve as the primary propulsion and as a light source to illuminate the PSRs. The spectrometer is based on Lunar Trailblazer’s HVM3 and uses a unique HOT BIRD detector developed at JPL. TRL6 testing of the solar sail will occur in early 2024. The mission would provide new insights from Mercury’s early differentiation to its recent volatile cycle and will provide key information for future missions.

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