Increased hydrogen escape from Mars atmosphere during periods of high obliquity

TL;DR

This study uses a 3D climate model to show that Mars's hydrogen escape rate increased significantly during high obliquity periods, contributing substantially to the planet's drying process.

Contribution

It demonstrates that high obliquity periods can cause over tenfold increases in hydrogen escape rates, highlighting their role in Mars's atmospheric evolution.

Findings

Hydrogen escape rates increased by over an order of magnitude during high obliquity.

Accumulated hydrogen loss accounts for about 80 meters of global water equivalent.

High obliquity periods significantly contributed to Mars's atmospheric drying.

Abstract

It is still unknown how much water has escaped from Mars during its history. Hydrogen escape from Mars's atmosphere probably played a major role in drying the planet, but present-day Hloss rates (about 3x10^26 atoms per second on average) cannot explain the geological evidence for the large volumes of liquid water on ancient Mars. Here we used the three-dimensional Mars-Planetary Climate Model to show that H loss rates could have increased by more than one order of magnitude (6x10^27 atoms per second) during higher spin axis obliquity periods, notably in the last few million years when Mars's obliquity was about 35 deg on average. The resulting accumulated H escape over Mars's history translates into an approx. 80 m global equivalent layer, which is close to the lower limit of geological estimates, assessing the major role of atmospheric escape in drying Mars.