Pingos on Earth and Mars: Morphology and Geographic Distribution

Pingos are massive ice cored mounds that form by pressurized groundwater flow mechanisms. Pingos and their collapsed forms are found in periglacial and paleoperiglacial terrains on Earth, and have been hypothesized for a wide variety of locations on Mars. Given their importance as climate markers, we present a literature survey of pingo-like features (PLFs) on Mars, in order to 1) assess the plausibility of their origin as ice-cored mounds, and 2) map out their distribution. In assessing the plausibility of the features as pingos, we have relied on intercomparison of individual morphology and geological context with those of terrestrial pingos. This assessment also entailed consideration of other possible interpretations for mound or conical features on Mars.

We first discuss the morphology of terrestrial pingos and their geologic contexts. Then we use that information to asses hypothesized pingos on Mars. In our assessment, PLFs in Mars' polar region and equatorial regions may be explained as other landforms than massive ice-cored mounds. PLFs in the mid-latitudes, most notably Utopia basin, are strong candidates for collapsed pingos. The latitudinal distribution of likely pingos and collapsed pingos matches the distribution of other inferred near-surface ground ice features that are attributed to obliquity variations. This correlation suggests that the Martian pingos and collapsed pingos may have also formed during the last period of high obliquity. Hypothesized water sources for the high-likelihood pingo forms included both hydrostatic/near-surface taliks and hydraulic/sub- and intra-permafrost talik flow.