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Wednesday, 25 March 2015

Big stories of little planets...

The earliest days of the solar system would have been a very strange place for us -  the planets had not yet formed and instead there were hundreds of protoplanets in the inner solar system, and massive accretion cores of developing gas giants in the icy outer solar system.
Some protoplanets survived, like Ceres and Vesta, and some collided and merged over and over, until they got up to the size of full grown planets. Even in the roomier outer solar system, where there were only a few massive proto-giants, there was a lot of chaos...

Above: A simulation of what was going on in the outer regions of the protoplanetary disk. Those blobs zipping all over the place like pingping balls in a hurricane? Those are bigger than Jupiter. watch, near the end two of them smash into each other. Courtesy of 

This was a sky filled with hundreds of protoplanets, thousands of giant asteroids, millions of asteroids and comets, all filled with radioactive elements that hadn't had time to decay. Their orbits weren't that stable. And at some point it all got hit by a supernova. Possibly two, in fact.

So, when I said strange, I didn't mean 'ooh, how odd' strange. I meant strange like this guy...

Above: Hooray! I have finally managed to work a joker reference into a blog about the history of the Solar System. I can tick that off my bucket list.
We know that there were lots of head on collisions between giant asteroids and protoplanets, because today we can turn our telescopes onto young stars with protoplanetary disks and see the clouds of dust and debris blasted into space by such events.

Above: One of the wonders of modern space telescopes is that we can get to see just how terrifying the universe is .. but from the comfy confines of planet Earth. Courtesy of geobeats.

The irony is that the radioactivity and violence of these worlds made them, in some ways, more like Earth: All that heat meant that even tiny worlds had a geology like that of a full grown planet, with a core, a mantle, and a crust. Their molten metal cores produced magnetic fields that lasted for millions of years, not unlike Earth's. The warmth of impacts (a very explosive kind of warmth I'll grant you), and short lived radioactive nuclei, produced volcanic activity. That volcanic activity melted ice into water, and could have spewed out gas to create tenuous atmospheres.
Above: Pallasite meteorites, like this one, can contain gem quality crystals, a sign of active geology at work.Courtesy of the Natural History Museum.

It all makes for a very interesting ancient solar system - one that we'll never see, but which we can explore through the meteorites, comets, dust and debris it left behind. Which is why some new results presented at last week's Lunar and Plantar Science Conference have caught my eye:

Protoplanets may well have had liquid water for longer than thought:
It had been believed that any occurance of water on these proto-worlds would have been confined to the time when the hyperactive energy of the short lived isotopes kept everything warm. However a team from Nanjing university has challenged this, finding evidence that there was still water flowing through the subsurface of some protoplanets over a hundred million years after the radioactive heat is thought to have died out. They've found this by using a technique called uranium-lead dating* on a mineral called apatite that forms in the presence of water - in this case the apatite was found inside a meteorite, so it seems pretty likely the world this meteorite was blasted free from had running water at some point.

.. and that water moved through the rocks more easily than we thought...
There's been a lot of debate down the years about how far the underground water would have been able to move through the rocks of a protoplanet.  - it's kind of important because water that can travel a long way can mix up the protoplanets chemistry, change isotope signatures, and erode or dissolve features in the rocks themsleves. As the fragmented rocks are all we have left we need to undertsand how they were shaped. A team from MIT have done experiments showing that vapourising water can open up fractures in the rocks, allowing water to move more easily. And if you're wondering how vaporising water can break rock....

Above: Volcanic heat plus ice = BOOM. Courtesy of ITN.

Protoplanets produced right handed sugar molecules:
It's not new news that some natural process on proto-worlds was processing precursor molecules from interstellar space into sugars and other pre-biological materials. But NASA Ames researchers have done an analysis on sugars from the Murchison meteorite, and found  that these sugars  showed signs of having and excess of the right handed version of the sugar molecules. If you're not quite sure what I man by that, then check out this video:

Above: Chriality. Which is not an Armenian girl group. Although, the world being what it is, I should probably add 'yet'. Courtesy of TED.

 The NASA Ames find is definately weird, as most processes produce these molecules in equal amounts of left and right handed versions. This could be pretty important for research into how life began: It suggests that meteorites bringing organic molecules to Earth could have delivered those precursor molecules with an excess of one handedness of molecules, and so influenced which kind life preffered.

It was all born from a massive star forming complex:
A University of California team has been looking at what we know about the short lived radioactive isotopes, and concluded that it's more likely the Sun was born in a massive complex of gas and dust, which had had radiactive material pumped into it over and over by many supernova. There're are massive star forming regions like this today, such as the Vela Molecula Ridge.

Comets recycle their chemicals:

Above: Comet McNaught. that pretty green colour? that's caused by Cyanogen, which is very, very, poisonous. And you thought astronomy was a safe hobby. Courtesy of
Mostly it's assumed that cometary processes are pretty much one way - bye bye, down the jet and off into space, goodbye! But, as it turns out, in the inner portion of an active comets very  extended atmosphere some molecules can be recycled. One such molecule is HCN (hydrogen cyanide) - a chemical which also has the odd distinction of simultaneously being an important precursor molecule for biological life, and an extremely deadly poison.

Impacts in the early solar system were more likely to spread life around:
Dialling the clock forwards to the early days of worlds like Earth and Mars we have a paper on lithopanspermia - the idea that microscopic life could have ridden he debris from major meteorite impacts across space to other worlds - is an idea that has sometimes struggled to get taken seriously. But, over the years, a growing body of evidence has suggested that such trips could really have taken place - something that has serious implications for the hunt for alien life, as it would meant hat any alien microbes we found elsewhere in the solar system could in fact be distant relatives of us.  Now researchers from the university of Kent have presented simulations showing that a range of microbes could survive the impact on another planet - and even one higher life form, the tardigrade - could have survived the landing on a Moon or protoplanet.

Above: The Tardigrade. This is a real life Earth creature that can survive... well, almost anything. Seriously, if they weren't so tiny they'd kick Superman and the Hulk around the room like rag dolls. CVourtesy of Eye Of science.
A lot of more main planet themed papers have made the headlines, but even a quick trawl through the abstracts shows that there was once a very different solar system, and we are slowly learning to look back in time and explore it...

Elsewhere in the universe...

Charon may be broken:
The biggest Moon of Pluto, Charon, may have tides beneath its surface strong enough to result in surface fractures -   this is based on a series of computer simulations, but it's an interesting prediction to read about as the Pluto system is about to get a visit from the New Horizons Space probe!

Jupiter wandered around the early solar system wrecking things:
The giant planet Jupiter migrated from it's original orbit, then migrated again, resulting in our oddball solar system.

Mars looks a little more promising for microbial life:
The red desert in the sky has both chemical energy sources, and the kind of nitrogen that microbes can use, making the prospects of past or present life there look a little rosier.

Robert Downey Junior gives Iron Man fan a real life bionic arm:

Elsewhere on the internet:

Pluto's moons formed from a ring of debris?
 *There's a joke about heavy metal dating to be made here, but then I'd be too ashamed to continue writing

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