London, Jan 22 : Latest images from NASA's Messenger spacecraft have hinted at the presence of solidified lava flows on the surface of Mercury, which should provide vital clues to unlocking the planet's history.
The car-sized spacecraft, which had successfully completed its mission of flying by mercury on Jan 14, released the first image of the planet that were taken from a distance of 27,000 kilometers.
A report in New Scientist said that this image shows dark areas near the top of the globe.
"Those dark splotchy regions look like lava flows to me," said David Rothery, a planetary scientist at the Open University in the UK.
According to Rothery, the suspected flows appear to lie on top of the original crust, implying that they formed after the end of the cratering that scarred Mercury's surface during the planet's first half-billion years of existence.
If so, then when Messenger gets a closer look at the planet's surface, scientists will be able to compare the composition of the lava flows with the surrounding, older crust. That should provide a window onto the processes that took place in the interior of the planet after the crust formed.
Previous research by planetary scientists to understand the moon's history also suggests that these dark regions on Mercury might be formed by lava flows.
The significance of this mission is that there was no equivalent lava flows visible on Mercury in the Mariner images from the 1970s.
"The big question we had before going back to Mercury is whether we can identify two crustal regions," said Rothery, "This is very encouraging that we are actually going to see lava flows," he added.
But, it is not the only sighting that has got planetary scientists excited.
The Messenger has also drawn attention to the sharp cliffs and escarpments visible on the close-up images.
"These features indicate that the whole planet shrank as it cooled," Messenger team member Jeffrey Gillis-Davis told New Scientist.
During the flyby, Messenger recorded 1000 images, as well as other scientific data. "The increased resolution makes Mercury look like a whole new planet to discover," said Gillis-Davis.
Messenger returns for another fly-by of Mercury on 6 October this year, before finally going into orbit in March 2011.