The Distribution and Age of Martian Icy Permafrost

NOTE: This subaward was originally Project Number 1465 from Johns Hopkins University for a ROSES 2016 MDAP award, which was transferred to Cornell University in 2018.

Water on Mars has played a central role in most aspects of the planet s geology, geochemistry, and climate throughout history. Ice in particular is as a reservoir of water, a driver of geological processes, and a signature of past and present hydrological processes. Observations from Mars Odyssey s Neutron Spectrometer (MONS) indicate that ground ice is, in many regions, highly concentrated (>90 vol. %) in excess of soil pore space that is in atmospheric equilibrium. Two limitations are present in the global MONS data: 1) a coarse 600 km spatial resolution; and 2) a depth limit of 1-2 cm into the icy layer (the ice table), a result of a short mean-free-path of neutrons in ice. Near-surface ice below 1-2 cm and on smaller spatial scales is largely unknown.

Ubiquitous to martian permafrost is polygonal patterned ground, which forms by repeating thermal cracking of ice-cemented permafrost. Polygon morphology depends heavily on the depth, concentration, and long-term stability of ground ice. This relationship is valuable because polygons: i) sense ice concentration at depths of a few meters, below that sensed by MONS; ii) develop over thousand-to-million years, helping to constrain the age of icy deposits on which they rely; and iii) sense variations on local horizontal scales not resolved by MONS.

We propose to examine the morphometric characteristics of polygonal patterned ground as seen in high-resolution image data over the middle and high latitudes, correlate those observations with other remote sensing data sets, and develop an understanding of the local scale and depth distribution of ground ice not otherwise discernable in existing observations. Such correlations can shed light on the origin of the excess ice, through better understanding of the distribution and age, enabling comparisons with other data sets, and providing constraints on near-surface hydrological processes in the modern martian climate.