Perseverance took this photo of Jezero Crater in April. The flat-topped hill, named Kodiak, has ancient layered rocks. (NASA)
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NEW ORLEANS — Lava once flowed at the site of an ancient lake on Mars.
The Perseverance rover landed on the planet just 10 months ago, but it has already made that surprising discovery.
The rover’s latest finding suggests that the bedrock it has been driving over since landing was once formed by volcanic lava flows — something that was “completely unexpected,” according to mission scientists. Previously, they thought the layered rocks Perseverance took photos of were sedimentary.
The rocks that Perseverance has sampled so far also revealed that they interacted with water multiple times, and some of them include organic molecules.
These discoveries could help scientists create an accurate timeline for the events that have taken place in Jezero Crater, the site of an ancient lake, and has wider implications for understanding Mars.
The finding was announced Wednesday during the American Geophysical Union Fall Meeting in New Orleans.
For years, scientists have questioned if the rock in this crater was sedimentary rock, comprised of layers of material deposited by an ancient river, or igneous rock, which forms when lava flows cool.
“I was beginning to despair we would never find the answer,” said Ken Farley, Perseverance project scientist at the California Institute of Technology in Pasadena, California, in a statement.
Everything changed when Perseverance began using a drill on the end of its robotic arm to scrape away at the surfaces of rocks.
“The crystals within the rock provided the smoking gun,” Farley said.
Perseverance is armed with a suite of sophisticated instruments that can image and analyze these scraped rocks, revealing their composition and mineral content. Ones of these instruments is PIXL, or the Planetary Instrument for X-ray Lithochemistry.
In November, Perseverance used its instruments to study a rock, nicknamed “Brac” by the team. The analysis revealed large olivine crystals surrounded by pyroxene crystals, both of which pointed to the fact that the rock came from volcanic lava flows.
“A good geology student will tell you that such a texture indicates the rock formed when crystals grew and settled in a slowly cooling magma — for example a thick lava flow, lava lake, or magma chamber,” Farley said.
“The rock was then altered by water several times, making it a treasure trove that will allow future scientists to date events in Jezero, better understand the period in which water was more common on its surface, and reveal the early history of the planet. Mars Sample Return is going to have great stuff to choose from.”
Now, the team wants to know if the rocks containing olivine were formed by a cooling lake of lava, or if they originated from a subsurface chamber of lava that was later exposed due to erosion.
“This was completely unexpected, and we are struggling to understand what it means,” Farley said. “But I will speculate that this is not…