Ice Exploration on Mars: Whereto and when?

Identifying, characterizing, and inventorying the ground ice on Mars is an essential element of any Mars exploration strategy, with direct linkages to: (1) questions concerning Mars’s paleo-climate and the stability or non-stability of liquid water at or near Mars’s surface through its geological history; (2) concepts for astrobiological reconnaissance; and (3) support for human exploration needs tied in particular to water ice as a resource (Planetary and Astrobiology Sciences Decadal Survey, NASEM, 2022). Here we summarize the electromagnetic sensing methods documented to have been the most effective thus far in following the story of ice on Mars, at least within the upper active surface layer (<10m thick), and the path forward towards possibly understanding its sources, sinks, and, writ large, cycles. Building on the seminal experiences with ice reconnaissance on Earth and the exploration of Mars, we describe the in situ, orbital, and proposed ice-relevant sample-return steps constitutive of this path.