Multiple overspill flood channels from young craters require surface melting and hundreds of meters of mid-latitude ice late in Mars history

TL;DR

This study investigates the formation of tadpole craters on Mars, suggesting they record evidence of surface melting and extensive ice presence in mid-latitudes during late Mars history, indicating prolonged water activity.

Contribution

It provides new measurements and analysis supporting the hypothesis that multiple breach tadpole craters formed through surface melting of ice-filled craters, revealing ancient climate conditions.

Findings

Multiple breach tadpole craters indicate hundreds of meters of mid-latitude ice.

Surface melting and groundwater discharge likely caused crater rim breaches.

Liquid water was intermittently available on Mars for billions of years.

Abstract

Mars' tadpole craters are small, young craters whose crater rims are incised by one or more exit breaches but lack visible inlets. The tadpole forming climate records the poorly understood drying of Mars since the Early Hesperian. A third of tadpole craters have multiple breaches, therefore a process is needed that was able to generate crater rim incision in multiple locations. We use HiRISE data for four multiple breach tadpole craters to measure their crater fill, rims, and exit breaches. We compare these measurements and other data to our calculations of liquid water supply by rain, surface melting, groundwater discharge, and basal ice sheet melting to discriminate between four proposed formation hypotheses for tadpole breaches, favoring scenarios with ice-filled craters and supraglacial melting. We conclude that multiple breach tadpole craters record hundreds of meters of mid-latitude ice and climate conditions enabling intermittent melting in the Late Hesperian and Amazonian, suggesting that liquid water on Mars has been available in association with water ice for billions of years.