Confirmation has come from analysis of the first photos taken by the Perseverance rover. On the Red Planet, about 3.7 billion years ago, there was a river flowing to a reservoir of water in Jazero crater.
There was a lake where there is now a wasteland, namely Jazero crater. A river flowing to a body of water was present on Mars about 3.7 billion years ago. Then the climate would have changed, and now the surface of the Red Planet is a collection of rocks and soil. That water had been present on the planet had long been suspected, but confirmation came from scientific analysis of the first images taken by Perseverance. The NASA rover landed in that area in February to search for life forms and traces of Mars' past.
The lake in the Jazero crater on Mars
The results of the study were published in the journal Science by an international team of experts led by Nicolas Mangold of the University of Nantes and coordinated by NASA's Jet Propulsion Laboratory (JPL). The images analyzed were taken by Perseverance in the first three months of the mission and show the details of the fan-shaped rock formation that is located in the western part of Jazero crater near the Kodiak knoll. Observations of the layering show that the first structure was really the delta of a small river, which 3.7 billion years ago flowed carrying fine sediments.
A drastic climate change would then cause violent flooding and the movement toward the delta of huge boulders, which are still visible. Some of these rocks are a meter in diameter and appear to weigh several tons. According to experts, they were part of a bedrock that was located on the edge of the crater or perhaps about fifty kilometers further upstream. These very boulders, which were deposited on top of the finer layers of sediment, may hold signs of past life. "We now have the opportunity to look for fossils," comments Tanja Bosak, a geobiologist at the Massachusetts Institute of Technology (MIT). "It will take time to get to the rocks we want to analyze for signs of life. So it will be a marathon, with great potential." The most striking thing to emerge from the Perseverance images, according to MIT planetologist Benjamin Weiss, "is the ability to capture the moment when the crater transformed from a habitable environment to the wasteland we see today. These rock layers may have recorded the transition, something we haven't yet seen in other places on Mars."
Recently Perseverance has also managed to capture rocks on Mars that scientists are analyzing to understand the Red Planet's ecosystem even better.