There are many knob formations is the southeastern Acidalia region of Mars. All show a hilltop crest except one which has a summit crater that resembles a cone volcano.

Knobs like these likely formed from interactions between water ice and lava. For instance, the crater at the top of the center knob is likely from a steam explosion when lava vaporized ice. As such, this summit crater is not an impact crater.

This caption is based on a public target suggestion from HiWish.

ID: ESP_038877_2135
date: 11 November 2014
altitude: 292 km

https://uahirise.org/hipod/ESP_038877_2135
NASA/JPL-Caltech/UArizona
#Mars #science #NASA