This week's news from Nasa's Curiosity rover provides the best evidence yet that Mars was once much more amenable to life than it appears now. Drilling in Gale crater, where it landed in spectacular fashion last August, it has found that the bedrock was once wet clay alongside a mix of chemicals that could have supported living organisms. It is a long way from this to proving that life ever existed on the early Mars, but the discovery fulfils a major objective of Curiosity's mission.
That mission suffered its first mishap on 28 February when a memory glitch in Curiosity's main computer forced it to switch to a backup system and suspended operations for a few days.
Another issue that might just affect the rover's future, and those of our other current Mars probes such as the Mars Express and the Mars Reconnaissance orbiters, concerns a comet that might pass dangerously close to the planet.
Recently discovered Comet 2013 A1 Siding-Spring is due to pass about 110,000 km from Mars on 19 October next year. Its path is still uncertain, though, and there is a slim chance that it could hit the planet. Moving at 56 km per second, and with a likely diameter of several km, any impact could rival the one that put paid to Earth's dinosaurs 65 million years ago. Even a close approach could pose problems for the orbiters if they were to be sand-blasted by the dust that surrounds the comet's nucleus. However, they and the Curiosity and Opportunity rovers could enjoy a grandstand view.