NASA rover's latest rock sample offers new clues about Mars' watery past

The latest rock core sample collected by NASA's Perseverance Mars rover offers new clues about Jezero Crater and the lake it may have once held.

Scientists believe that Jezero Crater, the landing site of Perseverance, was once flooded with water and was home to an ancient river delta. The rover is on a mission to collect samples of rock and soil that might preserve the signs of microbial life in this area.

Analysis by instruments aboard the six-wheeled rover indicates that the 24th Martian rock sample, collected on March 11, was awash in water for an extended period of time in the distant past, perhaps as part of an ancient Martian beach.

"Nearly all the minerals in the rock we just sampled were made in water; on Earth, water-deposited minerals are often good at trapping and preserving ancient organic material and biosignatures. The rock can even tell us about Mars climate conditions that were present when it was formed," said Ken Farley, project scientist for Perseverance at Caltech in Pasadena, California.

Such compositions are key indicators of past habitable environments on Mars and are vital for selecting samples for the ambitious Mars Sample Return mission.

The rock, nicknamed "Bunsen Peak" is about 5.6 feet wide and 3.3 feet high (1.7 meters by 1 meter) and boasts an interesting texture on one of its faces. Scientists were also intrigued by Bunsen Peak’s vertical rockface, which offers a nice cross-section of the rock and, because it’s not flat-lying, is less dusty and therefore easier to investigate.

Bunsen Peak is likely composed of about 75% carbonate grains - a mineral linked to habitability - cemented together by almost pure silica. This makes it good at trapping and preserving signs of microbial life if any was once present, NASA says.

"The silica and parts of the carbonate appear microcrystalline, which makes them extremely good at trapping and preserving signs of microbial life that might have once lived in this environment," said Sandra Siljeström, a Perseverance scientist from the Research Institutes of Sweden (RISE) in Stockholm.