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Saturday, 24 January 2015

Rossetta, Philae, and the comet that wants to be a world...

My apologies for the way the font changes part way through - I'm working to fix this but blogger isn't playing tonight - I'll keep trying and I hope it doesn't spoil your read! JF

Rosetta, Philae, and the comet that's trying to be a world...

Late last week a whole bunch of reports and papers from the Rosetta mission - a space probe on a mission to explore a comet - were released This is a link to all the reports, and here's the quick version. I've been reading through them, because, well, I'm space nerd.

I might even have a set of Star Trek PJ's. Maybe

But never mind that - it seems as though this comet doesn't know it's meant to be just a big chunk of ice...
Above: Rosetta has a camera called 'Navcam'- it's the robotic equivalent to your night vision; black and white, good enough to let you find your way about in the dark, and the comet is very dark. This is what Navcam sees. Courtesy of ESA 

Firstly, the comets resemblance to a gigantic rubber duck still defies explanation - either this is two comets that have somehow stuck together, or one comet shaped by some weirdly selective force of erosion.

There's a space alien out there, watching us all scratch our heads, and it's sniggering.
What can be said for sure is that the head, neck and body all give off different kinds of gas and dust, at different rates, with the neck giving out the mostly water vapour, and the body giving out CO2 and CO. That sort of suggests this is two comets stuck together, but that begs the question 'how the hell did that happen?' A collision at the sped things travel in space should have pulverised them both..

Above: This is actually far slower than things would happen in a real space collision - in reality you'd never see the debris, it's going too fast for you eye to pick up. Everything around you would just start sprouting massive holes and exploding ... hard to get anything to stick together!

On the comets surface things don't look like people were expecting either: Ever since the first images came back people have been looking at these things:
Above: ESA travelled billions of miles into deep space, and found a scene out of Lawrence of Arabia.
...and going  'those can't be dunes, dunes need an atmosphere and wind to form'. It turns out that these are dunes- the gas surrounding the comet is thin, but the winds in it blow at up to 300 meters a second - fast enough to blow surface material into dunes. 

The surface is covered in several distinct varieties of terrain, including deep, circular-ish pits, like this:
Above: The dark and twisted surface of comet 67P. Definite proof that even the laws of nature have gothic moments.... Courtesy of ESA
At the moment they're choked with dust and debris, but when the comet is warmer they are probably where a lot of gas a dust shoots out - some of them are already starting to 'geyser':

Above: This over exposed image is bright enough to show the jets growing from the pit. Courtesy of ESA.
One of the pits has a formation that looks as though the comet has erupted some kind of fluid material:

Above: Theory says this strangely flat material was probably the result of something that flowed like a fluid.. in a place where fluids should be impossible.... Courtesy of ESA
This fluid probably isn't water - although signs of liquid water have been seen in comet material. It might be something like a cold version of a pyroclastic flow - a terrifying fluid-like flow of  ash, rock and scalding gas that comes out of volcanoes:

Above: Not as bad as it looks, much, much worse.

Another oddity is the presence of clusters of bright bluish objects at ten or so locations. They seem to be ice rich, but the rest of the surface has had the ice baked out of it by the Sun, so where did they come from, and why are they gathered together in particular spots?

Above: The clusters of icy objects. Um... snowmen, perhaps? Courtesy of ESA.
67P also has a structure like no iceberg: The comet overall has the density of cotton wool, and must have a structure something like frozen foam, getting less dense towards the middle. The surface actually has hardly any ice at all, and is made of  a very red-black, brittle material, that acts as an amazing thermal insulator - even though the surface temperatures are already getting up to - 40 deg C (That's very surprisingly warm considering how far it still is from the sun) the heat hardly penetrates any depth into the comet.

Above: Mmmm... chocolate truffle.. no.. wait, huge space thing! I keep making ta similar mistake with the Sun, and calling the electricity company when my light switch won't turn it off...

Then there are these odd 'goosebumps' . Regular lumps in the comets flesh. There're all about three meters across, composition unknown, and show up anywhere the comets subsurface has been recently exposed. Current best guess is that they could be the basic building blocks of the comet itself - whatever they are, the similarities make it likely they all formed the same way....

Above: The 'Goosebumps' are everywhere on this comet - it is chilly there, but 10 foot wide bumps seems excessive. Courtesy of ESA.

The last thing I'm going to mention - although not the last odd thing or mystery in the reports by any means - are the jets of gas. Now, at the moment these seem to be blasting out of the neck region. As far as anyone knows the only possible way these jets are powered is from sunlight heating the comets surface. But measurements of which jets are strongest seem to show that the strongest jets are coming rom regions that re in the shadows - and the shadows of a comet are deep, cold, and sunless places. This really suggests that either we've got the way the comets internal structure transports heat very wrong, or we've somehow got how the jets themselves are powered wrong - we'll need more time to figure that out.
OK, not the last thing I'll mention: Rosetta has captured dust grains being ejected from the comet, and studied them with its mass spectrometer - a device that gives chemical composition. It's found a fantastically complex mix of organic chemicals, and the team are still trying to unravel the readings. But they've found alcohols, carboxylic acid (which goes into making proteins) and aromatic and aliphatic molecules (aromatic = organic molecule with rings of carbon atoms aliphatic  = organic molecule with no rings) These could include amino acids, which are an important chemical step towards life, and have been seen in comets before.
As for Philae, the MIA lander that is somewhere on the comets surface? The robot is still missing, but its results are rumoured to be up for release soon.
This is going to be an interesting mission....
Elsewhere on the internet:


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