Radar Sounding Observations Reveal Stratigraphic Similarity Between Ice Deposits at the Polar Cap and in Korolev Crater on Mars

Mars’ polar ice deposits preserve a record of climate throughout their evolution. In addition to the large north polar layered deposit (NPLD) located at Mars’ north pole, smaller outlying ice deposits also are preserved in craters nearby. These outlying deposits may or may not have been deposited due to the same mechanisms that drive the evolution of the NPLD. Identifying whether or not these outlying deposits share the same emplacement history as the NPLD could help to better understand the extent of the mechanisms that have driven the climate evolution of the Martian north polar region over the most recent millions of years. We have analyzed SHARAD (Shallow Radar, an instrument onboard NASA’s Mars Reconnaissance Orbiter) radar depth profiles from 34 locations across the NPLD and 5 locations within the Korolev crater ice deposit. We used Fourier transform analysis to search for dominant periodicities within the radar depth profile at each location. As a second line of analysis, we employed the dynamic time warping (DTW) signal tuning algorithm to quantitatively assess the stratigraphic similarity between the two deposits, because DTW can compare two signals even if they have a nonuniform relationship in time. Through the combination of these two analyses, we quantitatively show that the radar reflectors of the ice deposit in Korolev crater and the NPLD are stratigraphically similar, and were likely formed due to the same climate forcing mechanism. This is the first time the DTW algorithm has been applied to radar sounding data on another Solar System body, highlighting its utility in interpreting remote sensing observations.