A Large New Crater Exposes the Limits of Water Ice on Mars

Water ice in the Martian mid-latitudes has advanced and retreated in response to variations in the planet's orbit, obliquity, and climate. A 150 m-diameter new impact crater near 35 degrees N provides the lowest-latitude impact exposure of subsurface ice on Mars. This is the largest known ice-exposing crater and provides key constraints on Martian climate history. This crater indicates a regional, relatively pure ice deposit that is unstable and has nearly vanished. In the past, this deposit may have been tens of meters thick and extended equatorward of 35 degrees N. We infer that it is overlain by pore ice emplaced during temporary stable intervals, due to recent climate variability. The marginal survival of ice here suggests that it is near the edge of shallow ice that regularly exchanges with the atmosphere.

Automated summary

Water ice in the mid-latitudes of Mars has fluctuated due to the planet's orbit, tilt, and climate changes. A new impact crater near 35 degrees N has revealed the lowest-latitude exposure of subsurface ice on the planet. This crater, the largest of its kind, provides valuable information about the history of Martian climate. The relatively pure ice deposit in the crater was once much thicker and extended beyond 35 degrees N, but it has now mostly vanished and is covered by surface ice.