Volcanism and hollows on Mercury

A very interesting update today from the MESSENGER mission, the spacecraft which is orbiting the innermost planet, Mercury. Superficially, Mercury resembles our Moon, and is usually thought to be very similar (or even boring compared to some other planets and moons), but new data is showing that it is indeed a unique world in its own right.

MESSENGER has been taking the best photographs ever obtained of Mercury, and collecting a wealth of data about its composition, geology and origin. The question of whether Mercury has ever been volcanically active has now been answered (yes) with extensive lava deposits seen in detail for the first time, which can be up to 2 kilometres (1.2 miles) thick. There are also apparent lava vents up to 25 kilometres (16 miles) long. They are probably not active now, but indicate that Mercury, just like other rocky planets and moons in our solar system, had been very volcanically active when it was younger.

Even more interesting are the many small “hollows” – small irregular depressions often found in clusters, the origins of which are a new puzzle. Their younger appearance suggests they may still be forming today, acoording the the mission scientists.

An example of the "hollows" on Mercury. Click for larger version. Credit: Science/AAAS

MESSENGER has already shown that Mercury is actually quite different from the Moon, and that some old assumptions were wrong, which happens frequently in the space exploration business, but that is the point; the more we explore and discover, the more we learn.

Many more images from today’s media briefing are here.