Curiosity Surveys the 'Ubajara' Sampling Site on Mars

NASA's Curiosity Mars rover captured this 360-degree panorama at a site nicknamed "Ubajara" on April 30, 2023, the 3,815th Martian day, or sol, of the mission. Taken by the rover's Mastcam, this panorama was stitched together from 141 images after they were sent to Earth. Dark rover tracks recede into the distance in the center of the scene. Curiosity used the drill on the end of its robotic arm to take a sample from Ubajara, then dropped the pulverized rock into instruments within the rover's body. One of those instruments, called CheMin (Chemistry & Mineralogy), used X-ray diffraction to discover the presence of an iron carbonate mineral called siderite in samples from this site and two others: one above and one below Ubajara in a region enriched with salty minerals called sulfates. The discovery of siderite may help solve one of Mars' mysteries: There is strong evidence that liquid water coursed over the planet's surface billions of years ago, suggesting Mars had a thick, carbon-rich atmosphere rather than the wispy one it has today (a thicker carbon dioxide atmosphere is required to provide enough pressure and warmth for water to remain liquid on a planet's surface; otherwise, it rapidly vaporizes or freezes – which is the case on Mars today). That carbon dioxide and water should have reacted with Martian rocks to create carbonate minerals. However, when scientists study the planet with satellites that ample carbonate hasn't been apparent – even at Curiosity's site. It's possible that other minerals may be masking carbonate from satellite near-infrared analysis, particularly in sulfate-rich areas. If other such layers across Mars also contain hidden carbonates, the amount of stored carbon dioxide would be part of that needed in the ancient atmosphere to create conditions warm enough to support liquid water. The rest could be hidden in other deposits or have been lost to space over time. https://photojournal.jpl.nasa.gov/catalog/PIA26554