The Solar System is full of surprises. Mercury, the planet closest to the Sun, is a baking hot world, as would be expected. It is one of the last places where you would think anything would or could be frozen, but things aren’t always as they seem. There has been tantalizing evidence already for water ice deposits in craters at Mercury’s north pole, and now the MESSENGER spacecraft in orbit around the small planet has visually confirmed it for the first time.
As we have explored the solar system, we have found evidence for different kinds of oceans. Earth of course has its water oceans, while some icy moons like Europa have subsurface water oceans and Saturn’s largest moon Titan has seas and lakes of liquid methane.
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.
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.
Until now, the innermost and smallest planet, Mercury, had been relatively unexplored apart from the brief flyby by Mariner 10 in the 1970s. But the orbiting MESSENGER spacecraft is changing that, revealing new details about this little world.
New images now surface at an average of 250 metres per pixel and a global base colour map at about 1.2 kilometres per pixel. The extensive volcanic plains near the north pole may be several kilometres deep. Some of the most interesting features are clusters of irregular, rimless pits which vary in size from hundreds of metres to several kilometres in size, and photographed with a resolution down to only 10 metres per pixel. They are often surrounded by some sort of higher-reflectance material.
Despite Mercury’s accurate reputation of being a searingly hot world so close to the sun, MESSENGER is also providing new data indicating that there may be water ice on the floors of craters which are permanently in shadow, which have also been observed by radar with the Arecibo Observatory on Earth. Since there is no atmosphere to speak of to distribute heat, temperatures in daylight can be hundreds of degrees, yet far below zero in the shade, similar to the Moon.
An additional good overview of the results so far is here.
The first spacecraft to ever orbit the innermost planet Mercury, MESSENGER, has started sending back some beautiful photos, the first of thousands to be taken over the course of the mission. Appearance-wise, Mercury is very similar to our moon, mostly gray and covered in craters, so perhaps not as exciting as the views from some of the other planetary locales in our solar system, but this mission is the first to study Mercury in unprecedented detail from the vantage point of orbit. As the MESSENGER web site notes, Mercury is “the smallest, the densest (after correcting for self-compression), the one with the oldest surface, the one with the largest daily variations in surface temperature, and the least explored.” That’s good enough for me to make it another interesting place to go to.
A few photos are posted below; additional ones are (and will be added) here.