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Friday, 10 April 2015

The MESSENGER nears the end of the journey - but what’s that in the shadows?

The MESSENGER mission to Mercury is winding down. The navigation thrusters are exhausted, and the team have directed their probe to make series of ultra low altitude passes over the surface, so that they can make the most use of the magnetometer and the neutron spectrometer (which measure the magnetic field and the surface composition respectively). They're already getting pretty low over the surface, but now they'll come within a few kilometres of Mercury's rocks and take videos like this:

Above: This video was taken by the MESSENGER  spacecraft as it flew low over Mercury - keep your eyes open, there are some of the surface features mentioned in tHis post wizzing past the camera! Courtesy of NASA
This will be the final phase of the mission - but fascinating things about Mercury are still emerging. They will keep doing so for years I expect - it needs a lot of time to sift through the mountains of data a space probe collects, and find that thar gud stuff. But at the 46th Lunar and Planetary Science Conference this year there were two tantalising mercury findings from MESSENGER, both pointing to alien geological processes at work:

Something hidden in the eternal night:

Above: Permanently shadowed craters at the poles of Mercury. Yes, I know they're all red and yellow, that's just the graphics. Courtesy of NASA
Mercury, like our Moon, has permanent regions of darkness near the poles, and these have a layer of reflective water ice coating their floors. That ice might have come from comet impacts, or might have been caused by the rocks of Mercury chemically interacting with the solar wind. Although it's weird that a world so near the Sun would have lots of ice, it makes sense because Mercury has no atmosphere to level out its temperatures. So, although the surface of Mercury is oven-hot in the sunlight, in the shadowed regions it's incredibly cold - cold enough for the ice to accumulate and be stable.

Above: Colder than that. Colder than that if you had to spend the night at the bottom of those stairs. After your wife caught you spending the kid's college fund on beer and Doritos. Courtesy of NASA.
That's a big deal in itself, but the story takes a twist when we look at craters and valleys that are a bit further from the poles, and just a touch too warm to let ice be stable over the long term. Here MESSENGER doesn't see a layer of reflective water ice. Instead it sees craters filled with a layer of .....something. Something very dark.

Above: Something even darker than the lyrics of black metal band Marduk. And, in case the outfits and the genre weren't a clue, they write... well, not nursery rhymes. At least I hope none of you are playing your kids Marduk as nursery rhymes. Mind you, have you ever read the originals of fairy stories? Courtesy of MusicTimes
Black materials are common in the solar system, but what's strange here is this: Over Mercury’s lifespan the relentless bombardment of meteorite impacts should have blurred and smeared the boundaries of any patch of material on the surface, but the edges of the black layer are almost razor sharp. It could just be one of those odd coincidences that this stuff formed just as MESSENGER arrived, but it seems more likely that the edges are somehow being repaired.

Self repairing black masses, hiding in the bottom of permanently shadowed craters, on a sun drenched planet -  now that's the kind of alien phenomena we go into space to discover.

Other sensors carried by MESSENGER, like the radar sounding experiment, suggest that there’s a layer of water ice beneath the black material, so the leading theory is that the ice in the craters has some kind of organic material mixed in with it. As ice in these these craters isn't stable over the long term the ice gradually evaporates, leaving behind a layer of organic chemicals on the surface. The layer then protects and preserves the remaining ice. If the layer is breached then the newly exposed ice repeats the processes. These organic materials could even contain compounds related to the origin of life, as similar deposits on the moon are thought to.

But right now this is just our best guess - this might be possible if the ice was mainly due to accumulated comets strikes, as they’re rich in both ice and organics. But if the water molecules are formed chemically from solar wind and the rocks it’s harder to see where the organics could be coming from.

Different flavours of hollows:

Above: These weird hollows seem to be caused by something undermining the top layer of rock and soil, and are growing all over the planet (BTW, this is a very exaggerated colour image, to bring out the details). I'm not saying it's Mercurian mole people. That'd be crazy, and besides they might have agents here on Earth who'd undermine my house if I gave them away... Image courtesy of NASA.
These weird looking holes in the Mercury's crust have been  showing up in MESSENGER images since the probe arrived: They’re areas of ground that have been eroded away in a mould-like pattern by some unknown process, all to roughly the same depth, all across the planet. Crater counting shows them to be geologically young, and probably forming still today. But exactly what process has created them… it’s a mystery.
One idea is that there are stores of volatiles below the surface, and that, as these evaporate beneath the blazing Sun, they cause the ground to collapse. But again, we're into 'best scientific guess' land here. To thicken the plot: At LPSC some of the UV spectrometer results from MESSENGER were revealed, showing that some of the hollows have different surface compositions – this might represent inherent differences, or it might be that some of the craters are older and space weathering has changed their surfaces.

Mercury has turned out to be far from a dead chunk of rock  -  the above are just a couple of the mysteries we've found there. Wouldn't it be great if there was a follow up mission being developed? well there is, it's called Bepicolumbo!

Above: A quick rundown on the upcoming Bepicolumbo mission, courtesy of ESA.

Elsewhere in the universe:
Above: A depiction of the Methyl Cyanide molecule. The 'H's are hydrogen atoms, the 'C''s are carbons, and the N is a nitrogen

Molecules implicated in the origins of life have been spotted in a still forming solar system. The Methyl cyanide molecule, and its simpler sibling hydrogen cyanide, are thought to be amongst the ground level molecules for the chemical evolution that leads to life, so their detection suggests that they’re present in a lot of young planetary systems – great news for alien hunters as it raises the possibilities of finding worlds with the chemistry needed for life. This isn’t the first time complex , life related molecules have been found – sugars have been found, amino acids have been shown to form on interstellar dust, and tar like compounds have been found in distant reaches of the universe. But this is the first time molecules so directly life related have been found in a growing solar system – not too dissimilar to the way our own is thought to have been 4.5 billion years ago.

SpaceX is going to make another attempt to land and re-use it's Falcon 9R rocket. their last attempt came close but...well here's the video:

Above: Owch. But, I should point out, SpaceX shared this video themselves - that's how sure they are they know what went wrong and can get it right.

Lastly, this is pure science fiction, but it's awseome. And it's being made into a movie!

Elsewhere on the internet:

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