Tracing the fate of carbon and the atmospheric evolution of Mars

TL;DR

This paper models Mars' atmospheric evolution, showing how carbon escape and carbonate formation explain current isotopic signatures and atmospheric pressure, aligning with geological data and testable by ongoing missions.

Contribution

It presents a family of solutions for Mars' climate evolution that do not require missing reservoirs, linking atmospheric isotopic data with carbonate formation processes.

Findings

Early Mars had a surface pressure less than 1 bar.

Carbon escape processes enrich heavy isotopes in the atmosphere.

Open lake carbonate formation could raise pressure estimates to 1.8 bar.

Abstract

The climate of Mars likely evolved from a warmer, wetter early state to the cold, arid current state. However, no solutions for this evolution have previously been found to satisfy the observed geological features and isotopic measurements of the atmosphere. Here we show that a family of solutions exist, invoking no missing reservoirs or loss processes. Escape of carbon via CO photodissociation and sputtering enriches heavy carbon (13C) in the Martian atmosphere, partially compensated by moderate carbonate precipitation. The current atmospheric 13C/12C and rock and soil carbonate measurements indicate an early atmosphere with a surface pressure <1 bar. Only scenarios with large amounts of carbonate formation in open lakes permit higher values up to 1.8 bar. The evolutionary scenarios are fully testable with data from the MAVEN mission and further studies of the isotopic composition of carbonate in the Martian rock record through time.