15 July 2010
Last updated at 19:03
Scientists analysing data from Nasa's Messenger spacecraft say they have located some of Mercury's most recent volcanic activity. This portion of Mercury's surface had remained unseen until Messenger's most recent third flyby.
Rather than being a tiny, long-dead planet, that scientists had assumed, researchers now say Mercury may have been active for much of its "life". This merged image shows an area that appears to have experienced a high level of volcanic activity.
These clues about Mercury, the closest planet to our Sun, could help reveal how other planets of our Solar System, and beyond, evolved. The findings are reported in the journal Science.
In another Science paper, James Slavin, a space physicist at Nasa's Goddard Space Flight Center in Maryland, and his colleagues, reported evidence of very intense "magnetic substorms" on Mercury. This enhanced-color image shows the planet's Titian crater.
Mercury's rough surface is pockmarked by craters of all sizes. Messenger principal investigator Sean Solomon said: "Every time we've encountered Mercury, we've discovered new phenomena."
Messenger has enough fuel to maintain its orbit around Mercury until at least 2013, scientists say. Dr Solomon said: "Once Messenger has been safely inserted into orbit about Mercury next March, we'll be in for a terrific show."