The Timing of Alluvial Fan Formation on Mars

TL;DR

This study uses a combination of global databases and statistical models to estimate that alluvial fan formation on Mars persisted into the last ~2.5 billion years, indicating prolonged surface liquid water activity during the Amazonian period.

Contribution

It introduces a global approach and improved statistical modeling to estimate the timing of alluvial fan formation across Mars, extending previous regional studies.

Findings

Alluvial fan formation likely continued into the last ~2.5 Gyr.

Current data insufficient to constrain the duration of fan formation.

More crater data needed for tighter model constraints.

Abstract

The history of rivers on Mars is an important constraint on Martian climate evolution. The timing of relatively young, alluvial fan-forming rivers is especially important, as Mars' Amazonian atmosphere is thought to have been too thin to consistently support surface liquid water. Previous regional studies suggested that alluvial fans formed primarily between the Early Hesperian and the Early Amazonian. In this study, we describe how a combination of a global impact crater database, a global geologic map, a global alluvial fan database, and statistical models can be used to estimate the timing of alluvial fan formation across Mars. Using our global approach and improved statistical modeling, we find that alluvial fan formation likely persisted into the last ~2.5 Gyr, well into the Amazonian period. However, the data we analyzed was insufficient to place constraints on the duration of alluvial fan formation. Going forward, more crater data will enable tighter constraints on the parameters estimated in our models and thus further inform our understanding of Mars' climate evolution.