Robotic vehicles set to unlock secrets of space

At the end of last month came news that Nasa has ideas for a novel robotic space vehicle. Dubbed a "super ball bot" by the US space agency, this would be roughly spherical, built of interlocking rods and cables that would allow it to compress and bounce when landing on another world, before regaining its shape and rolling around to explore. Dozens of the bots could be folded and packed together for a single mission.

It seems a weird concept for space exploration, but our solar system is a weird place, as recent discoveries have shown. Several of these discoveries involve moons, but planets yield surprises too. Mercury, the planet nearest the sun, has a thin atmosphere despite relatively feeble gravity and daytime temperatures soaring to around 450 degrees Celsius. This might be formed by particles from the solar wind, which reach the surface thanks to vortex-like magnetic "tornadoes", forming windows in the overall magnetic field that otherwise deflects them. And despite the intense heat, in 2012, Nasa's Messenger satellite made observations consistent with ice on Mercury - in polar craters shaded from the sun.

Two scientists have suggested that diamonds form in the atmospheres of Saturn and Jupiter. Their scenario involves lightning zapping methane molecules apart to form hydrogen and carbon, with the latter clumping together to become soot particles that fall and experience increasing pressures to become diamonds. These in turn become so hot they liquefy, and turn to diamond rain. Nature quoted one of the researchers, Kevin Baines of the University of Wisconsin-Madison, as saying, "If you had a robot there, it would sit there and collect diamonds raining down," while also noting some are sceptical about the story.

At the south pole of a Saturn moon, Enceladus, there's a cryovolcanic area reaching a relatively toasty minus 116 degrees. It's known as the Tiger Stripes, for four almost parallel ridges that are 130 kilometres long, and split by central fractures. In 2005, observations by the Cassini spacecraft included a plume of icy material extending 500 kilometres above these stripes. Further research has shown that this is mainly water vapour and ice crystals, together with other chemicals including ammonia and carbon dioxide. The plume is brightest when Enceladus is at the furthest point in its orbit from Saturn, probably as the fractures become wider as Saturn's influence weakens a little.

The observations suggest that there may be a watery ocean beneath Enceladus' icy shell.

Last month came news of another moon that might similarly have a sub-surface ocean with extraterrestrial life - Europa, which orbits Jupiter. Europa had been considered one of the most intriguing objects in the Solar System since 1995, when observations by the Galileo orbiter led to theories it has a watery ocean beneath ice, and above a rocky interior.