The Perseverance rover, which has spent months traveling to Mars, could hardly have landed in a more interesting location.
Jezero Crater – an area of dry, windswept Martian rock where the rover landed in February – was once the bed of a lake fed by an ancient river whose flooding was so powerful it could move boulders, according to scientists.
The findings, published last week in the journal Science, confirmed scientists’ suspicions that the crater contained a lake millions of years ago, and also suggest that this part of Mars had a hot and humid past with a water cycle more complicated than previously known.
“There were tumultuous rivers here,” Katie Stack Morgan, assistant scientist for the March 2020 project and author of the article, said of Jezero’s landscape around 3.5 million years ago. “Jezero could have been a great place to live and that environment has changed over time.”
Further studies could help researchers understand why the planet has dried up and provide new clues as to whether the planet once supported life.
A view from the ground
A new perspective – thanks to Perseverance – and geological detective work by scientists made this information possible.
The rover, which transmitted images of the crater’s surface to Earth, provided scientists with new views that could not be seen from space.
“What you think you see from orbit around Mars may not be what you see when you enter the crater at eye level,” Stack Morgan said.
The surface-level images supported scientists’ theory that Jezero once featured a deep lake.
The images also gave scientists, including the 39 authors of the Science article, the ability to further analyze rock layers on an outcrop called Kodiak. The researchers found that these layers matched the appearance of river deltas on Earth, suggesting that water had flowed into the ancient lake.
But the visuals also contained a few surprises. On other cliffs near Kodiak, scientists noticed large boulders – some as wide as five feet in diameter and shaped by water – in the top layers of the formations, according to the Science article.
They suspect the boulders were deposited during massive flash floods powerful enough to quickly transform the Martian watershed.
They don’t know what caused the flooding, but speculated in the document that intense precipitation, rapid snowmelt or changes in glacier ice could have made the floodwaters rage.
“It could be very difficult to rebuild that sort of thing,” Stack Morgan said.
Looking for signs of life
Perseverance is the first rover to collect and cache Martian rock samples.
Stack Morgan said it was exciting to know for sure the rover will visit and collect samples from an ancient river-fed lake.
This means that the rover will have access to a variety of rock types that have been deposited in the crater. The rover should also be able to reach and sample portions of old lake beds, which are “exactly the kind of beds on earth that are great for organic matter and biosignatures,” she said. .
The rover might be in the right place to answer some of humanity’s deepest questions.
“This is why we have come to Jezero with perseverance,” she said. “So far, Jezero has not disappointed.”