“The discovery of abundant siderite in Gale Crater represents both a surprising and important breakthrough in our understanding of the geologic and atmospheric evolution of Mars,” Benjamin Tutolo, associate professor at the University of Calgary, Canada, and lead author of the paper, said in a statement.

NASA's Perseverance rover on Mars has discovered unusual "float" rocks on the rim of Jezero Crater while searching for signs of ancient microbial life. Scientists are investigating their origin.