Water Ice Resources Identified In Martian Northern Hemisphere

Areas featuring subsurface frozen water ice that could benefit future human explorers have been identified in the northern mid-latitudes of Mars, a new paper led by Planetary Science Institute Senior Scientist Gareth A. Morgan says.
Through the integration of orbital datasets from several NASA spacecraft – Mars Reconnaissance Orbiter, Mars Odyssey, and Mars Global Surveyor – in concert with new data-processing techniques, the Subsurface Water Ice Mapping (SWIM) on Mars project assessed the likelihood of ice by quantifying the consistency of multiple, independent data sources with the presence of ice.

“The goal of SWIM is to provide maps of potential buried ice deposits to support the selection of human landing sites. Ice is a critical resource that has many uses, like the generation of water for human consumption, growing plants for food, and for the generation of methane fuel and breathable air. But the most important is to provide fuel for the return trip home to Earth,” said Morgan, lead author of the paper “Availability of Subsurface Water-Ice Resources in the Northern Mid-Latitudes of Mars” (https://www.nature.com/articles/s41550-020-01290-z) that appears in Nature Astronomy. “Taking all the fuel you need for the round trip to Mars is basically not feasible and as a result pretty much every mission concept study from the last 30 years considers exploiting the Martian environment for fuel.”

PSI scientists Nathaniel Putzig, Matthew Perry, Hanna Sizemore, Zachary Bain, Isaac Smith and Asmin Pathare are co-authors on the paper.

“The good news is that Mars is an icy planet. The challenge is locating ice at a latitude that is conducive for a human landing site. Earlier studies have shown that ice buried within 3 meters of the surface should be stable in the current climate at latitudes above 50 degrees in each hemisphere, but these regions are colder and subject to long seasons of extended night. Lower latitudes are warmer, have a manageable length of night and plenty of solar radiation for power generation,” Morgan said. “In a nutshell SWIM is all about reconciling the need for ice with the need for plenty of sunshine.”

Focusing across a significant portion of the northern hemisphere of Mars, the team’s composite ice consistency map indicates that broad regions of the mid-latitudes, equatorward of the present-day northern ice-stability zone, exhibit evidence for ice. The detected ice is buried at depths ranging from a few centimeters to about 1 kilometer. The validity of the team’s ice consistency methodology and map products was shown when the team compared their results with the locations of fresh, Ice-exposing impacts that have recently been detected by the Mars Reconnaissance Orbiter spacecraft. As new impacts are detected, the team will continue to compare them to the SWIM maps.

“Our methodology leverages five independent remote sensing techniques: neutron spectroscopy, thermal analysis, radar surface analysis, radar subsurface compositional (dielectric) analysis, and geomorphic mapping of periglacial features. In our analysis of each of these five datasets, we attempt to isolate distinct properties of the subsurface that provide proxies for the presence – or absence – of ice,” Morgan said. “For example, we use the thermal datasets to look for regions with high subsurface thermal inertia, consistent with ice, while we apply the radar surface analysis to track evidence of ice-like low-density materials. The majority of these techniques also represent significant advancements on previous, similar methodologies.”

PSI Senior Scientist and co-author Putzig said the paper does not select specific sites best suited for future human exploration of Mars: “Constraints imposed by the limitations of the data sets and the time available for the work meant that we were only able to evaluate ice consistency at relatively coarse resolution across the northern hemisphere. The results point to areas for further study at higher resolution with existing and future data sets that will be needed to select the most promising sites to send humans.”

“Of course, safely delivering humans to Mars and ensuring their survival requires many other considerations beyond in situ utilization of water resources, including landing-site safety and solar and thermal specifications. Defining such site requirements is beyond the scope of the SWIM project and would be premature, given that all human Mars mission plans are still in the conceptual stage,” Morgan said. “We provide a hemispheric perspective of ice distribution to support initial landing-site studies and enable the community to explore the range of Martian terrains that host ice.”

Funding for this project came from a subcontract (1611855) to PSI from the Caltech Jet Propulsion Laboratory, supported by NASA.