A Martian rock formation that looked like an ancient coastline from space now appears to preserve a much more surprising water history. Since 2021, NASA’s Perseverance rover has explored Jezero Crater, a 45-kilometer-wide basin on Mars where rivers once fed a lake. Scientists hoped to find sedimentary rocks along the crater rim, a clue that would support the lake shore prediction. But, in a twist, the rover discovered that these rocks are igneous, meaning their origins are volcanic and they did not form in the lake. The rover discovered that water had soaked the rocks at least three different times, in three different ways. This new understanding of the Jezero landmark, called a “margin unit,” gives scientists a more complete picture of ancient Mars, revealing a planet where water continued to find new ways to move across the landscape. Although the rover’s data revealed no evidence of life, it did show an abundance of carbonates, minerals known to be good at retaining traces of past microbes. On Earth, these minerals often form in oceans and shallow lakes that support life. “Jezero Crater lies within one of the largest carbonate exposures on Mars,” Candice Bedford, a scientist at Purdue University in Indiana, said in a statement. “What we learn here goes far beyond this crater.” SEE ALSO: Artemis III delays could threaten 2028 moon landing For the study, Perseverance explored an elevation range of about 870 feet across the fringe unit. He used his SuperCam instrument to identify minerals in rocks based on the light they reflect. In total, the rover examined 185 rocks. The article analyzing this data, led by Bedford, appears in the journal Communications Earth & Environment. For scientists, the biggest surprise of the study may be that this strip of land did not initially form at the bottom of a lake. It started earlier, when the magma deep underground cooled. As the temperature dropped, olivine, a common mineral in volcanic rocks, formed. Much later, after erosion exposed the rocks on the surface, carbon dioxide-rich groundwater began seeping into its cracks. That interaction gave rise to threads of carbonate minerals. Over time, the surrounding rock was worn away, leaving only the crack fillings standing. Mashable Light Speed Perseverance investigates rocks and samples in the marginal unit on September 6, 2024, while climbing the rim of Jezero Crater on Mars. Credit: NASA/JPL-Caltech The researchers then found evidence of a subsequent episode of water that could have come from the lake. “Converting olivine to carbonate can leave behind silica, and we see more of that silica in rocks below the water line,” said Eleni Ravanis, co-author and planetary scientist at the University of Hawaii at Manoa. Want more science and technology news delivered straight to your inbox? Sign up for Mashable’s Light Speed newsletter or receive push alerts from Mashable today. The rocks preserve other signs of the lake. In some places, the water appears to have broken and moved pieces. The researchers found layered rocks that could reflect activity along the lake’s shore, as well as a messy deposit that resembles mud and rocks carried by a stream of water. In a particular part of the strip of land, Perseverance detected mineral veins of calcium sulfate and fluorite. Those minerals hint that the site experienced a third wet episode in which hot water passed through the volcanic rocks, a bit like a hot springs system. This water story is important in the search for ancient life. Scientists want to know what type of water existed, what chemicals it carried, and whether it created environments where microbes could obtain the food they needed to live. The Perseverance team can determine the order of these ancient water events, but not when they occurred. Still, a place that was repeatedly wet provides more opportunities for life to emerge and more chances to leave evidence behind. The rover has collected samples of the formation, which could shed more light on the environment if NASA can figure out how to bring the extraterrestrial material back to Earth. Congress canceled future funding for the Mars Sample Return mission in January. “If there’s one thing I’ve learned after 10 years working with Mars explorers, it’s that Mars constantly throws you surprises,” Bedford said. “It’s very rare that things are as we expect from the orbital data.”
