Try not to panic – Mercury, the smallest resident of our close-knit solar system, is shrinking. Scientists studying data sent back by the Messenger probe, launched in 2004, reveal that it’s disappearing; withering away like a long-forgotten prune (not their words).
Before you pack up the car and head over to Aunt Margaret’s place in the highlands, you should know that this galactic disaster isn’t happening very quickly but at a considerably faster rate than previously suspected. Nonetheless, NASA reckons the old girl could last another few billion years yet.
So far, the planet has lost around 3 miles from its 3,000 mile diameter over the course of its existence. This is being caused by the molten core cooling and solidifying.
The Messenger probe has now performed four sweeps over Mercury, snapping some 1,200 photos from 120 miles above the planet’s surface. This has also been used to answer the pressing question of what created the areas of smooth plains covering the planet’s surface.
Scientists were previously unable to decide whether these were impact craters from space debris or volcanic deposits. It is now believed that Volcanism has been the major cause of Mercury’s surface structure and given an answer to the 30 year old question.
Some impact craters could have been as much as 1.3 miles deep and filled with hot lava. “That’s a lot of lava,” said Dr James Head of
The University of the Bloody Obvious Brown University. “It shows the planet was really active in its early history,” he added.
This information was published in a special collection of 11 papers in the journal Science. Messenger is going back for another fly-by in October, again in September 2009 and then will take up residence in orbit from 2011. Now that the volcano vs impact question can be answered, it is hoped that it might find evidence of ongoing volcanic activity.