You won’t see rain in the weather forecast on Mars this week. In fact, rain probably hasn’t fallen on Mars in billions of years. The Martian climate is arid and the tiny bit of water that does exist is frozen solid or vaporized in the atmosphere. It wasn’t always this way. The discovery of ancient river valleys, river deltas, and minerals known to form only in liquid water provide clear evidence that the Martian surface once had an active water cycle. Jezero crater features such evidence. It was formed by a meteorite impact on early Mars and hosts an ancient river delta, providing clues about the red planet’s wet past.

An international team of scientists recently confirmed that Jezero crater not only hosts a river delta, but also a dried lake bed. Scientists have been remotely exploring Jezero crater since 2021 with the Perseverance rover. The discovery was made possible by radar that penetrated the crater surface to a depth of about 20 meters (66 feet). The measurements revealed numerous layers of fine, rocky particles called sediments carried by a once flowing river. On Earth, deltas form when rivers deposit sediments in a stagnant body of water like a lake. The recent discovery shows that a river likely emptied into Jezero crater to form a lake billions of years ago. Irregularities in the lake bed layers reveal periods of sediment deposition and erosion, reflecting large-scale climate fluctuations in the Martian environment. The question remains as to which (if any) of these chapters in Martian history may have supported life.

On our beloved Earth, the water cycle plays a vital role in supporting life. Evidence for an ancient water cycle on Mars begs the question: did Mars ever host life? With the Perseverance rover positioned directly in an ancient lake bed, we may be much closer to finding the answer.

This study was led by David Paige, a professor in the Earth, Planetary & Space Sciences department at the University of California, Los Angeles (UCLA).

Managing Correspondent: Collin Cherubim

Press Article: Confirmation of ancient lake on Mars builds excitement for Perseverance rover’s samples (UCLA Newsroom)

Original Journal Article: Ground penetrating radar observations of the contact between the western delta and the crater floor of Jezero crater, Mars (Science Advances)

Image Credit: NASA/JPL-Caltech/MSSS/JHU-APL