Mars rover Perseverance lists, among its mission objectives, a first for red planet exploration. The robotic explorer has been tasked with searching for signs of ancient microbial life on the dusty, dry planet – tiny microfossils that would be evidence that Mars was once habitable. That would indeed be an astounding, incredible discovery – but the new paper urges caution in interpreting what we find, in both this and future sources. According to astrobiologist Sean McMahon of the University of Edinburgh and geobiologist Julie Cosmidis of the University of Oxford in the UK, scientists will have to keep an eye...