The impact origin and evolution of Chryse Planitia on Mars revealed by buried craters

Lu Pan,Sylvain Breton,Chloé Michaut,Cathy Quantin-Nataf

doi:10.1038/s41467-019-12162-0

Abstract

Large impacts are one of the most important processes shaping a planet’s surface. On Mars, the early formation of the Martian crust and the lack of large impact basins (only four unambiguously identified: Hellas, Argyre, Utopia, and Isidis) indicates that a large part of early records of Mars’ impact history is missing. Here we show, in Chryse Planitia, the scarcity of buried impact craters in a near-circular area could be explained by a pre-existing topographic depression with more intense resurfacing. Spatially correlated with positive Bouguer anomaly, this near-circular region with a diameter of ~1090 km likely originated from an impact. This proposed large impact basin must have been quickly relaxed or buried after its formation more than 4.0 billion years ago and heavily modified by subsequent resurfacing events. We anticipate our study to open a new window to unravelling the buried records of early Martian bombardment record.

Highlights

Large impacts are one of the most important processes shaping a planet’s surface
The Martian crust may have formed within a hundred million years from solar system formation[6,7] during which impact flux was expected to be high, currently on Mars only four large basins have been identified with confidence (Hellas, Argyre, Utopia, and Isidis) among which only Isidis impacted onto the dichotomy
Multiple classes of degraded craters are found in the southern highlands[34], most of the impact craters in the northern lowlands can be classified into two distinct groups, the relatively pristine craters, and the degraded craters

Summary

Introduction

Large impacts are one of the most important processes shaping a planet’s surface. On Mars, the early formation of the Martian crust and the lack of large impact basins (only four unambiguously identified: Hellas, Argyre, Utopia, and Isidis) indicates that a large part of early records of Mars’ impact history is missing. Extensive studies on the moon showed circular, positive Bouguer anomalies form in impact basins as a result of a combination of crustal thinning, uplift of the mantle beneath, and later infill of dense materials[12,13,14,15] These features in early basin-forming impacts may be obscured by subsequent crustal relaxation and burial beneath Hesperian and Amazonian aged lava-plains and sediments, especially within the northern lowlands of Mars[16,17]. We identify distinct crater populations within a circular area in Chryse compared to the adjacent region, which could be related to a more intense resurfacing event in a topographic depression This region shows a quasi-circular positive gravity anomaly, which combined with the buried topography from impact crater statistics, suggests that the circular region could be the original Chryse impact basin, which subsequently underwent heavy degradation

Methods

Results

Conclusion