As if we needed another reminder that Mars isn't exactly friendly to life, researchers from Scotland's University of Stirling have revealed that the planet is more arid than Earth's driest deserts. That might not exactly sound surprising, but it's yet another wet (dry?) blanket on the usefulness of surface-level Mars water. The researchers also measured a chemical weathering rate on Mars for the first time, a process that relies heavily on moisture in the atmosphere. It can take between 10 to 10,000 times as long on Mars for meteorites to form equivalent levels of rust as on Earth, according to the research paper.