Alien studs on dwarf's erection baffle boffins

Pics NASA has released images of a smooth-sided dome three miles (five kilometres) high, studded with bright reflective spots, on the surface of the dwarf planet Ceres.

The pictures of the feature – dubbed Ahuna Mons – were sent back by NASA's Dawn probe, which has just completed its first year in orbit around Ceres – a strange small world in the asteroid belt between Mars and Jupiter.

The American space agency described it as "a dome with smooth, steep walls," around 12 miles (20 kilometres) in diameter, and is baffled as to how it got there.

"No one expected a mountain on Ceres, especially one like Ahuna Mons," said Chris Russell, Dawn's principal investigator at the University of California, Los Angeles. "We still do not have a satisfactory model to explain how it formed."

Ahuna Mons was initially viewed as a vague pyramidal structure when Dawn originally arrived. Since then, the probe has swing lower and lower over Ceres and has now taken pictures from as low as 240 miles (385 kilometres) above the mountain, which is the only one on the entire surface.

The feature sits right beside a deep crater of similar size, and is irregularly covered in bright reflective patches, similar to those seen dotted in craters on Ceres. The biggest cluster of these is found in the Occator crater, one of the largest depressions on the planetlet.

Natural feature or super-secret spaceport – probably the former

Despite some getting excited at the thought of a distant species' starbase, the reality is likely to be rather more mundane. Scientists think the spots are caused by reflective salts that have bubbled up out of Ceres' moist interior from comet strikes on the surface – but they need more data.

"Dawn began mapping Ceres at its lowest altitude in December, but it wasn't until very recently that its orbital path allowed it to view Occator's brightest area," said Marc Rayman, Dawn's chief engineer and mission director at NASA's Jet Propulsion Laboratory. "This dwarf planet is very large and it takes a great many orbital revolutions before all of it comes into view of Dawn's camera and other sensors."

That time will come, however, since Ceres isn't going anywhere in the foreseeable future. Ceres is the last planned stop for the spacecraft, and it'll be left in a stable parking orbit sending back images for as long as possible. ®