Impact inducted surface heating by planetesimals on early Mars

TL;DR

This study examines how impacts of planetesimals and planetary embryos on early Mars contributed to surface heating, influencing the duration of a steam atmosphere and its escape to space under the young Sun's radiation.

Contribution

It combines impact statistics, SPH simulations, and atmospheric models to quantify impact-induced surface heating and its effect on atmospheric escape on early Mars.

Findings

Impact impacts can sustain a shallow magma ocean on early Mars.

Surface heating from impacts prolongs the vapor state of the atmosphere.

Impact-driven heating significantly enhances atmospheric escape within 0.6 million years.

Abstract

We investigate the influence of impacts of large planetesimals and small planetary embryos on the early Martian surface on the hydrodynamic escape of an early steam atmosphere that is exposed to the high soft X-ray and EUV flux of the young Sun. Impact statistics in terms of number, masses, velocities, and angles of asteroid impacts onto the early Mars are determined via n-body integrations. Based on these statistics, smoothed particle hydrodynamics (SPH) simulations result in estimates of energy transfer into the planetary surface material and according surface heating. For the estimation of the atmospheric escape rates we applied a soft X-ray and EUV absorption model and a 1-D upper atmosphere hydrodynamic model to a magma ocean-related catastrophically outgassed steam atmosphere with surface pressure values of 52 bar H2O and 11 bar CO2. The estimated impact rates and energy deposition onto an early Martian surface can account for substantial heating. The energy influx and conversion rate into internal energy is most likely sufficient to keep a shallow magma ocean liquid for an extended period of time. Higher surface temperatures keep the outgassed steam atmosphere longer in vapor form and therefore enhance its escape to space within about 0.6 Myr after its formation.