Search This Blog

Saturday 24 December 2011

Happy Christmas! Have a million ton snowball.....

Firstly: If you are reading this page you probably have at least a passing general interest in space, and if you do and follow any of the major space news pages at all you have probably have already seen this:

Video above :Comet Lovejoy seen from the ISS. Courtesy of NASA.

But I wouldn't be Human if I didn't put a copy here. It's comet Lovejoy, which recently made a breakneck death plunge into the sun and came out the other side (see last weeks post) ....And now, as if to rub ol' Sols nose in it, it is putting on a truly spectacular display. The video is made of time lapse footage from the international space station, an what better place to watch a comet from?

Image left: Hubble, still exploring the universe.

Secondly: Tentative evidence[1] from the Hubble space telescope suggests that the low temperature processes on Pluto may be forming complex carbon molecules [2]: Remember that molecules of that broad type are thought to be involved in the chemical processes leading to life, so Pluto joins the list of places where nature may be bearing her greatest secrets for us to see. This and the possibility of a subsurface ocean [3] makes the dwarf planet (and similar objects in the Kuiper belt [4]) more interesting than ever.

Thirdly: NASA has long been hankering after returning a sample of comet  to a well equipped lab beneath Earths blue skies. However landing on such a fragile object is problematic at best. So a team at Goddard space centre, led by Joe Nuth, is working on a 'comet harpoon' [5] to spear the icy beasts and bring back subsurface samples without needing to land. It sounds kind of wacky, so NASA have put together a video explaining the concept:

Video above: The 'Comet Harpoon' concept. Video courtesy of NASA/Goddard.

Today is Christmas, a holiday and a time of reflection, so rather than focus on any specific topic I've decided to post some of the thoughts that make asteroid, comet, hell even space dust, science so fascinating for me:

As I’ve written about before, the study of meteorites has opened up a picture of the kinds of worlds that made up our solar system in the years after its birth. The major planets, especially the terrestrial ones, were still growing. This left a lot of smaller bodies ranging in size from chips of rock to things the size of Mars, roaming about the solar system in chaotic orbits. Given the current state of Mars [6] – a hyper arid, bitterly cold desert where even on a good day the hardiest organisms would struggle on the surface – you’d expect these small worlds to be at least as inhospitable. In fact you’d expect most of them to be like our Moon: Totally unsuitable for the kind of chemical processes involved in or leading to life.

Image above: Modern Mars, an environment that challenges the outer bounds of what even ultra hardy extremophiles may be capable of surviving.But was it always this way? Image courtesy of JPL.

But this is where we have to remember that the rules were different [7] in the early solar system. Many bodies, it is now apparent [8], had enough internal heat form liquid water in the cracks and pores beneath their surfaces. The chief culprits for these heat sources are impacts from smaller bodies, which were many many times more frequent than today, and relatively short lived radioactive isotopes. Internal heat in the Earth and other terrestrial planets today comes, at least in part [9], from the decay of radioactive materials. Back in the day, in fact back before there were days and nights, many radioactive materials that have now decayed away completely (for example Aluminium 26) were still present. This meant that even places as small as Lutetia [10] could have maintained a molten – or at least semi molten – core. There are other lines of evidence supporting this: Meteorite fragments that show signs of having come from parent bodies with Earth like crusts [11], fragments that have signs pointing to liquid water percolating through them, ones that show signs of coming from differentiated bodies, and the giant asteroid Vesta which is covered in frozen basaltic lava, a dead giveaway of a geologically active history.

Image right: Meteorite GRA 06129, composed of material similar to Earths continental crust. Image courtesy of the Antarctic Search for Meteorites.

Ok – so these little planetary pre-cursors were warm (in fact some of them were probably as hot and active as Jupiters mon Io [12]for a while). So..... fascinating for geologists, who get to study the geology of worlds hundreds, even tens of thousands, of times smaller than Earth with consummately lower gravity. It makes a fascinating comparison to the Earth itself, tells them something about how the larger rules that govern its geology work, and what materials it was built from. But who else would be interested?

Image above: Io. Only marginally relevant to what I'm talking about but it's just to spectacular to not put an image of up. The volcano blowing its lid in this picture is called Prometheus. Courtesy of NASA/JPL.

Astrobiologists for a start. You see; these little worlds inherited a legacy or two from the primordial cloud that span up to become our solar system: An abundance of water [13] (one of the most abundant compound in the cloud), and organic chemistry [14]. Some of them were so hot these things were baked out of them, but many were merely warm. Some members of the carbonaceous chondrite [15] meteorite family were never heated above 50 degrees Celsius for example.

Now we have the three big things that astrobiologists wet themselves about all together, on not just one small world but many: Water, carbon based (which is referred to as ‘organic’ by chemists) chemistry, and enough heat to melt the water and allow the carbon chemistry to actually do something.

In fact, as the latest evidence[16] from studies of carbonaceous chondrite meteorites shows, these reactions had got quite a way down the road before their host worlds were either destroyed or froze:
In August this year researchers from the University of California published results[17] showing that nucelobases (basic building blocks from which DNA and RNA are made), and similar molecules referred to a nucleobase analoges, were present inside certain carbanceous chondrites.
Now in a way this isn't all that Earth shaking: Fairly complex carbon compounds, includeing amino acids and nucleobases, have been found in meteorites before. But the discovery, in more than one meteorite, of nucleobase anlouges adds credebility to the idea that these molecules are not contamination from terrestrial biology: Terrestrial biology would have left the nucleobases themselves, not the similar-yet-different anolgues. Further evidence comes from the studies the team did to see if any of these compounds were present in the ice or soil near where the meteorite landed - they weren't. Lastly the team did a series of lab experiments involving liquid water, ammonia and hydrogen cyanide. These experiments were aimed to re-create the chemical environment present beneath the surface of the long dead protoplanet that these meteorites came from. These lab tests produced the same mix of nucleobases and their anogues, in the same proportions.
It seems as though these asteroids, long before Earth as we know it existed, were producing the basic chemical building blocks of life. Watch these tiny specks of matter - they may have even bigger surprises in store for us......

List of links:


No comments:

Post a Comment