International Mars Ice Mapper Mission: The combined scientific potential of Synthetic Aperture Radar, Very High Frequency (VHF) Sounding, Submillimeter Sounding, and High-Resolution Imaging for Climatology, Geology, Habitability and Human Exploration

In development by ASI, CSA, JAXA, and NASA (the Italian, Canadian, Japanese, and U.S space agencies, respectively), the International Mars Ice Mapper (I-MIM) mission concept (phase 2) includes two complementary goals and five cross-cutting objectives:

Goal 1:  Map and characterize accessible, near-surface (within the uppermost 10 m) water ice and its overburden in mid-to-low latitudes to support planning for the first potential human surface missions to Mars.

Goal 2:  Analyze evidence of ice-related subsurface, surface, and atmospheric interactions planetwide and their relation to geological and climatological processes and potential habitable environments on Mars.

Drawn from findings of the competitively selected, international, multidisciplinary I-MIM Measurement Definition Team (MDT), the mission objectives provide traceability to the two mission goals: 

• Water Ice. Identify the presence or absence of near-surface water ice, measure its depth and abundance, and map its distribution.
• Overburden. Constrain the structure, stratigraphy, roughness, and compactness of near-surface lithic material.
• Candidate Sites. Assess the scientific and engineering suitability of candidate sites for future robotic and human exploration requiring access to near-surface water ice.
• Planetary Evolution. Investigate Mars’ past and present environmental processes and implications for habitability through its geological and atmospheric record.
• Volatiles. Characterize the role of atmospheric structure and dynamics in the exchange of volatiles amongst the Martian subsurface, surface, and atmosphere.

These scientific objectives guide the design and development of I-MIM’s proposed instrument suite:

• a Synthetic Aperture Radar (SAR), centered at 930 MHz (the mission concept’s anchor payload provided by CSA);
• a Very High Frequency (VHF) sounder provided by ASI;
• a High-resolution Imager provided by NASA; and,
• a Submillimeter Sounder provided by JAXA.

These instruments are based on the MDT Final Report (2022) [1], which concluded that augmenting the mission concept’s anchor payload with the above complementary instruments would provide the opportunity to accomplish unique new science covering a broad range of international science priorities.  Mapping the unstudied near surface of Mars thanks to the synergic observations L-band SAR and the VHF Sounder, augmented by the High-resolution Imager, has the potential to fill a major data gap unmet by prior instruments sent to Mars and provide a broad evaluation of the abundance of water-ice reservoirs at mid latitudes.  The addition of the submillimeter sounder enables atmospheric profiling for studies of volatiles exchanges among the subsurface, surface, and atmosphere, as well as wind profiles, another major data gap of high priority to the science community.

When combined, these complementary instruments have the potential to address high-priority scientific investigations shared by the international science community:

Climatology:  In order to characterize variability in the ionosphere, both the SAR and the submillimeter sounder further address key questions about the connections in Mars’s dynamic climate regions and seasonal interactions of shallow subsurface volatiles with the atmospheric structure, of critical importance to both science and human-robotic mission planning.

Geology: A VHF sounder would provide depth resolution and penetration that bridges a critical gap between the core payload and current sounders at Mars. A high-resolution imager would provide key information on surface geomorphology at spatial scales that complement the capability of the core payload and would have capability, in concert with context information potentially provided by a supplemental imaging spectrometer, to constrain present day cratering rates.

Habitability: In the context of international Moon to Mars objectives, the MDT work showed that I-MIM would provide important advances toward outstanding ancient and modern habitability questions related to astrobiology.

Human Exploration: by providing critical precursor data (e.g., characterizing the presence and seasonal variabilities of liquid brines, subsurface void detection, and environmental characterizations for designing planetary-protection and human-health safeguards) relevant to future human-robotic missions dedicated to the search for life.

With science priorities and potential identified, the partner agencies are considering these recommendations in their ongoing multilateral concept study, intending to generate a viable mission architecture that maximizes the scientific return to the greatest extent possible.  The four agencies view the multilateral approach as a way of achieving “big science” for the individual agency cost of a small mission.  The mission concept’s new models of multilateral governance pave the way to future international collaborations related to both human and robotic exploration, in pursuit of shared scientific outcomes relevant to Mars, and by extension, to planetary systems in our solar system and around other stars.

References: [1] I-MIM MDT Final Report (2022) 239 pp., online: https://science.nasa.gov/researchers/ice-mapper-measurement-definition-team.