Mercury rising: The planet nearest the sun shows the circular marks of volcanoes
Volcanic activity forged the surface of Mercury while also making it shrink, scientists revealed today.
A NASA spacecraft discovered the smallest planet in the solar system has lost 3 miles of its 3,032 mile diameter. This is far more than scientists had expected.
Messenger has begun to resolve some of the mysteries of Mercury, a sun-baked world about a third the diameter of Earth and only slightly larger than the moon. The car-sized spacecraft has seven scientific instruments on board and has measured magnetic activity.
Messenger images from its January 14 fly-by provide strong evidence that volcanoes played a critical role in forming the planet's surface, according to geologist James Head of Brown University in Providence, Rhode Island.
‘Everything we’ve seen so far would suggest that the activity on the surface dates from the first half of solar system history rather than the last half,’ Dr Head said.
The Caloris basin, with a diameter of 960 miles, is one of the solar system’s biggest impact craters, formed more than 3.8 billion years ago when a large space rock hit.
Messenger sent back images of a shield volcano with a distinct orange color about 60 miles wide on the southwestern edge of this basin that may be a source for the lava that formed smooth plains inside the basin.
Inside the shield volcano they detected a kidney-shaped vent with a bright halo around it very similar to halos formed by explosive eruptions on Earth and the moon.
In other findings also published in the journal Science, scientists said Mercury’s magnetic field originates in the planet’s outer core and is powered by the core’s cooling.
Messenger, which stands for Mercury Surface, Space Environment, Geochemistry and Ranging, was launched in 2004.
Nasa’s Mariner 10 flew past Mercury three times, mapping 45 per cent of its surface. Messenger has imaged about 20 per cent more and is due to fly by Mercury again this October and in September 2009 before starting a yearlong orbit in 2011.
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