Mercury, the smallest and innermost of all planets has always been thought to be rather dull, one where no evolution takes place. Besides the fact that it has no atmosphere and a strong iron core, It's most exciting feature was the narrow ridges that scientists believed evolved millions of years ago, when the planet was first formed - Now it turns out, there may be more to this tiny mysterious planet, than meets the eye.

New photos captured by NASA's MESSENGER spacecraft has revealed large hollows on the surface of the planet - ranging in size from 60ft. to over a miles across and between 60-120ft. deep. Since the hollows seem to be much younger than the craters they were found inside, scientists believe they are freshly made - A major surprise considering they had previously thought the planet was not evolving at all.

What makes this 'Swiss cheese' like depressions unique, is that this is the first time they have been found on a rocky surface. While Mars has similar hollows, they are present only in the carbon dioxide ice that covers the planet's South Pole.

Though scientists are not sure what is causing these, they have ruled out the effects of wind or water erosion for sure - That's because this tiny planet has no atmosphere and therefore, no wind or rain!

Since Mercury is so close to the sun, the hollows maybe a result of exposure to fierce heat and extreme space weather. One theory is that the sulfur and other volatile minerals present on the planet may be vaporizing thanks to the heat, solar wind and the micrometeoroid attacks the planet is subjected to every day. This in turn, leaves only a few minerals behind, weakening the rock and making it all spongy.

MErcury Surface, Space ENvironment, Geochemistry and Ranging AKA MESSENGER, is a spacecraft commissioned by NASA to study the surface of Mercury. Launched in 2004, it made several flybys of the planet before finally getting into orbit around the planet in March, 2011. Since then, it has been sending back some images of the planet - We wonder what it will discover next - Some aliens perhaps?

Resource: science.nasa.gov