Impact sculpting of the early martian atmosphere

TL;DR

This study models how early impact bombardment caused the depletion and isotopic fractionation of xenon in Mars' atmosphere, shedding light on planetary atmospheric evolution and timing of solar system events.

Contribution

It provides a quantitative model linking impact-driven atmospheric escape to xenon isotopic signatures on Mars and Earth, offering new insights into early planetary atmospheres.

Findings

Impact bombardment explains Xe depletion and fractionation on Mars.

The process constrains the timing of giant planet instability.

Impacts contributed to atmospheric evolution of terrestrial planets.

Abstract

Intense bombardment of solar system planets in the immediate aftermath of protoplanetary disk dissipation has played a key role in their atmospheric evolution. During this epoch, energetic collisions will have removed significant masses of gas from rocky planet atmospheres. Noble gases are powerful tracers of this early atmospheric history, xenon in particular, which on Mars and Earth shows significant depletions and isotopic fractionations relative to the lighter noble gasses. To evaluate the effect of impacts on the loss and fractionation of xenon, we measure its ionization and recombination efficiency by laser shock and apply these constraints to model impact-driven atmospheric escape on Mars. We demonstrate that impact bombardment within the first $200$ to $300\,\text{Myr}$ of solar system history generates the observed Xe depletion and isotope fractionation of the modern martian atmosphere. This process may also explain the Xe depletion recorded in Earth's deep mantle and provides a latest date for the timing of giant planet instability.