Warm, Wet Mars: New Research Suggests a Tropical Past in Jezero Crater

New analysis of samples collected by NASA’s Perseverance rover suggests that early Mars was far warmer and wetter than previously understood, potentially possessing a climate capable of supporting life for extended periods. The findings, focused on the presence of kaolinite clay within Jezero crater, indicate sustained rainfall and a greenhouse-like climate billions of years ago.

For decades, the prevailing view of Mars has been one of a cold, arid world. However, the discovery of kaolinite – a clay mineral that forms on Earth through prolonged weathering by water – challenges this narrative. Unlike clays formed by brief bursts of meltwater from volcanic activity or impacts, the kaolinite found in Jezero crater points to a long-term, stable wet environment. This is significant because it suggests the rocks were altered under modest temperatures and persistent heavy rainfall, rather than in scalding hydrothermal conditions.

The research, published in Communications Earth & Environment, details how the chemical composition of these clay pebbles closely resembles similar clays found on Earth dating back to periods of warmer, wetter climates. The authors suggest that these conditions may have persisted for thousands, or even millions, of years, creating potentially habitable environments on the red planet.

The Jezero crater, once a lake fed by an ancient river delta, has been a primary focus for Perseverance. The rover’s exploration has revealed evidence of ancient coastlines, river valleys, and lakebeds, all indicative of a past where liquid water flowed freely across the Martian surface. The presence of kaolinite within the crater’s delta further strengthens the case for a warmer, wetter Noachian epoch – a period spanning from approximately 4.1 to 3.7 billion years ago.

This period in Martian history coincided with the Late Heavy Bombardment (LHB), a time of intense meteorite impacts throughout the solar system. Despite the cataclysmic nature of the LHB, the evidence suggests that Mars was not only habitable during this time but may have been *most* habitable then. The enormous Hellas and Argyre impact basins, both over a thousand miles across, are scars from this era, yet the presence of water-sculpted landforms indicates that the planet could still support liquid water and potentially, life.

The findings also have implications for the search for past life on Mars. The sustained wet conditions indicated by the kaolinite deposits would have provided a stable environment for the development of microbial life. Perseverance has already collected samples from within Jezero crater that show possible biosignatures, and these samples are currently cached on the rover awaiting a future sample return mission.

However, the future of that sample return mission is now uncertain. NASA recently cancelled the planned mission, leaving the crucial analysis of these samples potentially delayed for years. The samples represent a unique opportunity to apply the “Knoll criterion” – a standard in astrobiology that requires evidence of life to be inexplicable without biological processes – but this will only be possible with advanced laboratory analysis on Earth.

The discovery of kaolinite and the evidence for a warmer, wetter Mars represent a significant shift in our understanding of the planet’s history. It paints a picture of a Mars that, billions of years ago, may have resembled a tropical oasis, a stark contrast to the cold, desolate landscape we see today. The possibility that a living ecosystem once thrived in Jezero crater, during a time when Earth was still in its early stages of development, is a compelling thought and underscores the importance of continued exploration and research.

Gareth Dorrian is a Post Doctoral Research Fellow in Space Science at the University of Birmingham.

This article is republished from The Conversation under a Creative Commons license. Read the original article.