Science Goals and Mission Concept for a Landed Investigation of Mercury

Abstract

Mercury holds valuable clues to the distribution of elements at the birth of the solar system and how planets form and evolve in close proximity to their host stars. This Mercury Lander mission concept returns in situ measurements that address fundamental science questions raised by the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) mission’s pioneering exploration of Mercury. Such measurements are needed to understand Mercury's unique mineralogy and geochemistry, characterize the proportionally massive core's structure, measure the planet's active and ancient magnetic fields at the surface, investigate the processes that alter the surface and produce the exosphere, and provide ground truth for remote data sets. The mission concept achieves one full Mercury year (∼88 Earth days) of surface operations with an 11-instrument, high-heritage payload delivered to a landing site within Mercury's widely distributed low-reflectance material, and it addresses science goals encompassing geochemistry, geophysics, the Mercury space environment, and geology. The spacecraft launches in 2035, and the four-stage flight system uses a solar electric propulsion cruise stage to reach Mercury in 2045. Landing is at dusk to meet thermal requirements, permitting ∼30 hr of sunlight for initial observations. The radioisotope-powered lander continues operations through the Mercury night. Direct-to-Earth communication is possible for the initial 3 weeks of landed operations, drops out for 6 weeks, and resumes for the final month. Thermal conditions exceed lander operating temperatures shortly after sunrise, ending operations. Approximately 11 GB of data are returned to Earth. The cost estimate demonstrates that a Mercury Lander mission is feasible and compelling as a New Frontiers–class mission.

The Gravity Signal of Mercury's Inner Core

“…Gravity measurements made at a specific location at Mercury's surface by a future lander (e.g., Ernst et al., 2022) may also permit a detection of the degree 2, order one internal gravity signal. Unlike global gravity observations made by an orbiting spacecraft, measurements at one location at the surface would not give direct information on the contrast between the amplitudes of $${\Delta}{C}_{21}^{\mathit{int}}(t)$$ and $${\Delta}{S}_{21}^{\mathit{int}}(t)$$ signals.…”

A Geostratigraphic Map of the Rachmaninoff Basin Area: Integrating Morphostratigraphic and Spectral Units on Mercury

“…Mercury is less well‐explored than Mars and the Moon, so these maps rely on the geomorphology‐led approach. Until landed Mercury science commences (Byrne et al., 2021; Ernst et al., 2022), it seems unlikely that lithological or definitive rock origin information could be included in a geological map of Mercury, for example, the geological map of H05 (Wright et al., 2019). Recently, structural measurements of the shallowly dipping faults associated with some lobate scarps on Mercury have been made (Galluzzi et al., 2015; Pegg, Rothery, Conway, & Balme, 2021), but the remote sensing techniques used rely on rare cross‐cutting relationships, and so cannot be employed widely enough to adorn Mercury maps with strike and dip measurements.…”