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:

[1] http://iopscience.iop.org/1538-3881/143/1/22/
[2] http://www.universetoday.com/92060/have-complex-molecules-been-found-on-plutos-surface/#more-92060
[3] http://news.discovery.com/space/will-we-find-oceans-on-pluto-111130.html
[4] http://solarsystem.nasa.gov/planets/profile.cfm?Object=KBOs
[5] http://news.nationalgeographic.com/news/2011/12/111215-nasa-comet-harpoon-sample-crossbow-space-science/
[6] http://star.stanford.edu/projects/mgs/
[7] http://www.lpi.usra.edu/books/MESSII/9010.pdf
[8] http://www.lpi.usra.edu/books/AsteroidsIII/pdf/3031.pdf
[9] http://www.physorg.com/news62952904.html
[10] http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=47389
[11] http://carnegiescience.edu/news/half_baked_asteroids_have_earth_crust
[12] http://solarsystem.nasa.gov/planets/profile.cfm?Object=Io
[13] http://solarsystem.wustl.edu/wp-content/uploads/reprints/1999/No89%20Fegley%201999%20Space%20Sci%20Rev.pdf
[14] http://cshperspectives.cshlp.org/content/2/12/a002097.full
[15] http://www.meteorite.fr/en/classification/carbonaceous.htm
[16] http://www.nasa.gov/topics/solarsystem/features/dna-meteorites.html
[17] http://www.pnas.org/content/early/2011/08/10/1106493108

Saturday, 17 December 2011

Roll up roll up, see the amazing death defying comet!

Image left: The brilliant twin tails, one of dust the other of ions, of comet west. Image courtesy of John Laborde.

Comets[1], wandering escapees from the protoplanetary disk that formed our solar system almost 5 billion years ago, usually lead a solitary existence: They move silent and almost invisible out beyond the ice giant Uranus and Neptune [2]. Only occasionally does one break ranks with its fellows and come hurtling into the inner solar system. It does not do this willingly, it must be pushed or pulled by the gravity of some other body. When that happens the comets frozen surface boils away into space, subsurface pockets of more volatile material explode through its skin as jets, and the comet briefly develops a tenuous atmosphere of gasses, called a coma [3]. This coma is shed and renewed as the black (comets are usually covered in a crust of pitch black hydrocarbons) ice ball hurtles inwards, leaving behind tails of dust and gas that catch the sunlight and can be a spectacular display if Earth is in the right position.

Image right: despite their brilliant tails the cores of comets are actually grey to black in colour, as demonstrated by comet Halley here. Image courtesy of ESA.

Other exceptions may be hiding amongst the ranks of D-class asteroids [4]: Volatile rich, covered in hydrocarbon molecules, these may be the burnt out cores of comets gathered along the outer edge of the asteroid belt. They resemble the bizarre Tagish lake meteorite [5], which still poses many mysteries to science: Odd hollow organic globules [6], nano-diamonds, buckyballs and compounds called pyridine carboxylic acids [7]. Some of these odd objects seem not to be so burnt out, and are referred to as main belt comets [8].

And sometimes a comet does not just hurtle sun wards. Sometimes, as if it has lost its way from the safe cool depths, a comet flings itself into the solar systems central inferno [9]. This is what astronomers thought would happen to comet Lovejoy this week. It has been tracked by the Solar Dynamics Observatory (SDO [10]), a spacecraft who's main mission is to study the sun itself. But this was too juicy to miss, so they got the doomed comet in one corner of the spacecrafts eye and are posted updated photos as they got them. They even ran those images together into a time lapse movie of what we all expected to be comet Lovejoys final moments.... enjoy:



Video above: Comet Lovejoy approaches the sun with its tail rippling in the solar winds. Courtesy of JPL/NASA.
You can see the comets tail twitching and kinking in the blasts of plasma from the Suns surface! But it turns out the snowball thrown into hell did have a chance after all......



Video above: Comet Lovejoy takes a seemingly fatal plunge into the sun, only to emerge from the other side hours later! Courtesy of JPL/NASA.

Despite passing just 120,000km from the suns surface, and despite the solar behemoth tearing off part of its tail, the enigmatic comet has proved to be made of stern stuff; tearing past the surface of the sun at incredible speeds and back out the other side. At the size of two football fields it is hardly an obvious challenger to the Suns 3 light second wide majesty, yet this underdog has at least survived to tell the tale. Others have not been so lucky: Another comet met a truly spectacular demise at the suns hands in may of this year:



Video above: A comet dies spectacularly as it careens into the Sun. Image courtesy of JPL/NASA.

Now Lovejoys (presumably) melted and altered surface will take a story of peril and fire surmounted back into to cool of deep space....and perhaps one day we will catch up with it to read that story in greater detail.

List of links:

[1] http://www.rmg.co.uk/explore/astronomy-and-time/astronomy-facts/comets-meteors-asteroids/comets
[2] http://www.solarviews.com/eng/oort.htm
[3] http://www.universetoday.com/40872/comet-coma/
[4] http://www.daviddarling.info/encyclopedia/D/D-class_asteroid.html
[5] http://www.meteoritestudies.com/protected_TAGISH.HTM
[6] http://www.astrobiology.com/news/viewpr.html?pid=21384
[7] http://www.astrobio.net/exclusive/206/the-tagish-lake-meteorite
[8] http://www.astronomynow.com/nam2010blog/2010/04/the-truth-about-main-belt-comets.html
[9] http://cometography.com/sungrazers/sungrazer.html
[10] http://sdo.gsfc.nasa.gov/

Saturday, 10 December 2011

Rosetta visits an ancient relic of Earths birth.... and we watch Vesta go 'Boom'

A double post this time: One of the big small body events from the past year and a plan from NASA that is right up my street!

Rosetta at asteroid Lutetia:
Deep into the darkness that no human and few machines have ever penetrated you wouldn't expect to run across a literal piece of home.  But you'd be wrong.

Image to the right: the enigmatic contours of Lutetia catch the distant sunlight. Courtesy of NASA/JPL.

In July 2010 the ESA space craft Rosetta [1] tore past the asteroid Lutetia at a distance of around 3000 km - a long way for a human but nothing for a space faring robot. As it did so it took images and spectra of this enigmatic 120km long boulder. Even its changes in speed as it passed by gave us information on this little worlds mass and density - Lutetia is denser than an ordinary stony chondrite meteorite [2], meaning it almost certainly is metal rich. Now scientist have had the chance to study the data beamed back and draw some conclusions: Lutetia may be a left over building block of the four terrestrial planets, Mercury, Venus Earth and Mars.
The Rosetta spacecraft observed the asteroid, which, when combined with telescopic observations from European Southern Observatory [3] New Technology Telescope gives us the most complete surface spectrum of an asteroid ever. The spectrum - the wavelengths of sunlight reflected and absorbed by the surface - gives us an idea of what an object is made of. Luetetias spectrum is very similar to a type of meteorite called estatic chondrites - these are thought to have formed close to the sun, making up the earliest Lego's from which planets like ours were born  Hence Lutetia may have been grown in the same place -  a piece of Earths own ancient history, stranded out of deep time [4].
Another revelation about Lutetia is that it may have once had enough internal heat - from internal radioactivity or left over accretion heat - to have had a warm core smouldering sullenly behind its rocky face. An incredible thing for a place so small its gravity cannot even squeeze it into a rough sphere.
Image above: The geological regions of Asteroid Lutetia. Image Courtesy of ESA.

The surface of Lutetia has been mapped into seven areas:  Baetica, Achaia, Etruria, Narbonensis, Noricum, Pannonia, and Raetia. Achaia and Noricum are truly ancient places; based on crater counting Achaia is nearly 4 billion years old.

Image right: A set of grooves on the Lutetian surface. Grooves like these are seen on many asteroids, but their exact origins are still a matter of debate.

The surface is studded by immense, monolithic blocks of impact ejects, blankets of solidified lava up to 600 meters thick, grooves [5] a hundred meters deep, and landslides creeping down crater walls under the low low gravity. Finding such an active geological history on a world so small is a treasure trove for planetary geologists.


Image left: A huge landslide has slithered down onto the bottom of this crater in the Baetica region of Lutetia. Massive boulders on the overlooking slopes cast black shadows that are reduced to pinpricks by distance.

Why wasn't this massive rock incorporated into one of the main planets? Luck, and gravity. Lutetia probably had a gravitational slingshot [6] type close encounter with at least one major planet as they were growing, and ended up in the asteroid belt instead. Only 2% of asteroids in the belt are from the inner solar system, so scientists will be keeping Lutetia in their thoughts- a mission dedicated to Lutetia itself (Rosetta is on its way to meet comet Churyumov-Gerasimenko in 2014) could help shed light on the origin and earliest, most hidden, years of Earths existence.

Vesta go BOOM!

Speaking of things that happened when Earth was still young: Check out this computer model of the titanic impact that pulverised the south pole of Vesta: 


Video above: A computer model of a 50km wide asteroid smashing apart Vestas south pole. Courtesy of Martin Jutzi. First seen on The Planetary Society blog [7]. No protoplanets were harmed in the making of this video.

The big sphere is a primordial Vesta, and the little one is a 50 km wide impactor. However even the simulations authors admit they are a way from having an accurate handle on the impact yet. Eric Asphaug and Martin Jutzi who authored the model suggested there might be several reasons for this: the impact speed could have been lower than in the model, Vesta may have been harder, or there might have been effects that did not kick in until some time after the explosion that had more influence over the final shape.

Vesta it seems is proving difficult to interpret - it's uniqueness as a world surviving from the deep past and its unusual history makes it difficult to interpret. However a few tentative conclusions are being drawn: Vesta is differentiated like a planet for starters. For more on this follow the link above for the planetary society report, or go to the website for the 2011 American Geophysical Union meeting [8].

List of links:

[1]http://www.esa.int/export/esaSC/120389_index_0_m.html
[2]http://www.daviddarling.info/encyclopedia/C/chondrite.html
[3]http://www.eso.org/public/
[4]http://www.sciencedirect.com/science/article/pii/S0019103511003848
[5]http://www.lpi.usra.edu/meetings/lpsc2011/pdf/1366.pdf
[6]http://www.esa.int/esaCP/SEMXLE0P4HD_index_0.html
[7]http://www.planetary.org/blog/article/00003293/
[8]http://sites.agu.org/fallmeeting/scientific-program/

Tuesday, 6 December 2011

I turn my back for five minutes.......

Well a year in fact. But that said a helluva lot has happened since I last got a chance to blog. I've deliberately left it until I've begun to have enough free time to make a decent commitment to it. I've had a thesis to write, small people shouting things like 'dada, come!' before jumping in muddy puddles, things like that. So, to get back into the groove, I'll start with a series of posts devoted to the biggest and most stunning ancient solar system developments of the last Earth orbit. As always a list of links is provided at the bottom of the post.
First up:

Dawn arrives at Vesta.

I wish, really wish, that I could get someone to play something suitably jaw dropping every time I hear that. Actually there are lots of jaw dropping bits of music out there, so here's a good one [1] - just imagine the music starts as Dawn leaves Earth orbit, then the Sun rises over Vesta's monumental impact scars as the string section really kicks in....On the July 16th of this year the ion engine [10]powered Dawn spacecraft [2] pulled into a survey orbit around the immense 400km bulk of asteroid Vesta. Alone with this devastate majesty it moved into a  high altitude mapping orbit (HAMO), and recently moved into a low altitude mapping orbit (LAMO). As soon as it arrived at this tortured and primordial place this sophisticated space faring machine began collecting images, scans, and data of all kinds [3] on its surface, its composition.... and its cataclysmic history.

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Video above: An introduction to the Dawn probe. Courtesy of NASA/JPL.

This is a neat little video released shortly before Dawn pulled into orbit about its first lonely port of call, and it serves as a nice introduction to the mission. The next video snippet shows Vesta as Dawn closed with it: it's immediately an illustration of why Vestan history gets the description 'cataclysmic':



Video above: Dawn closes with the first target: Vesta. Courtesy of NASA/JPL.

The evolution of the images from fuzzy blob to (still fuzzy) monstrous space rock highlights one of Vestas main, primeaval, features: From this video we can see that the bottom 1/4 of the protoplanet [4] has been obliterated by a gigantic impact.

In fact it gets worse for Vesta:

Left: A false colour relief map of the south polar region of Vesta. Blue is lower, yellow/red is higher. Image courtesy of NASA.

Look at the two arcs of thrown up mountains making the rim - there are two distinct arcs. Each arc is the right size and shape to have been thrown up by a giant impact, which tells us that the Vestan south pole got blasted not once, but twice by smash ups with its brethren space rocks. These blasts made the Asteroid hit implicated in the dinosaur extinction [5] look seriously puny: Vesta had its entire south pole blasted apart and replaced with these giant basins and their mountains.
However this is a good explanation for one other mystery: How pieces of Vesta got launched into space and eventually arrived on Earth as meteorites! These are known as Howardite–Eucrite–Diogenite (HED) meteorites [6] and have long been suspected to be portions of Vesta's crust.



Image above: A fragment of the monomict eucrite Millbillillie which fell in October 1960 near Jundee Station, Wiluna district, Western Australia.  Today scientists agree that the source of the known eucrites is Asteroid 4 Vesta and its smaller companions, the Vestoids. Image courtesy of www.niger-meteorite-recon.de/en/meteorite_eucrite.htm


Dawn provides more evidence for these vast calamities from long before humankind looked to the sky, with pictures like these:

Image above: A view from Dawn of the face of Vesta, showing the destruction of its south pole and how the whole asteroid was forced into a new shape.

The above image shows, on the lower right, the crushed depression where Vesta should have a south pole. It also shows, on the lower left most visibly, grooves, steep walled, flat bottomed, that encircle the dead world like a grim garland.
There are two sets of grooves, one older, the other younger, and guess what? Their epicentres line up almost with the epicentres of the two giant impacts. These two titan events made the basaltic rock of Vesta ripple like waves on a pond and then settled into these strange new shapes.
The newest of these giant crater has been named Rheasilvia. But the discovery doesn't stop with the obvious Vestan wounds. Mysteries abound here:

Right: A close up shot of the Vestan surface. Notice how some craters show ejecta that is both light and dark -as though the impacts have broken into different layers of material.

The surface is splotchy in places, with odd light and inky dark patches that show little relief, as you would expect if they were related to craters or hills. And even amongst those that clearly are related to craters the mix of light an dark material is confusing - we'd have expected Vesta to be fairly homogeneous beneath the surface, but some craters that seem to have had landslides of light and dark material, as if Vesta were layered inside like a gobstopper.


Image above: A beautiful shot of a crater on the plains of Vesta, within which streams of light and dark rubble can be seen.

And going back to the abyss that was once the south pole: In its centre lies the giant central peak of the crater. Measuring tens of kilometres from base to peak it is one of the biggest mountains in the solar system:

Image above: A profile of the remains of the Vestan south pole. Courtesy of NASA/JPL.

There's so much in these pictures we don't understand. Some of these oddities are almost like a Vestan signature, unique to this giant amongst asteroids: Craters cut in half:

Image above: A Vestan crater that has been partly erased. Courtesy of NASA/JPL.

A varied surface composition (false colour image).

Image above: A false colour image of Vesta. Very subtle colour variations have been enhanced here to make variations in surface composition stand out. Courtesy of NASA/JPL.

It goes on and on.... You'd think Dawn would have its own blog wouldn't you? Well it does[7]! And to round off this frankly inadequate introduction to Dawn and Vesta here is a conference presenting the finding from the team themselves... enjoy!

Video above: Science briefing by the Dawn team.Courtesy of JPL/NASA.

And this is not the end of Dawn and her teams mission into the deep mysteries of the asteroid belt: Dawn will be the first spacecraft to visit the dwarf planet Ceres [8], a world suggested to have once had a subsurface ocean [9], and hints of activity over its south pole. That will be a whole new voyage in to the unknown.........

List of links:

[1] http://www.youtube.com/watch?v=XrZ7E2WC3RI&feature=related
[2] http://dawn.jpl.nasa.gov/
[3] http://dawn.jpl.nasa.gov/technology/
[4] http://www-ssc.igpp.ucla.edu/personnel/russell/papers/CeresVesta.pdf
[5] http://www.youtube.com/watch?v=5qJPTjMnwNk
[6] http://www.planetary.brown.edu/~hiroi/MAPS2001Burbine.pdf
[7] http://dawn.jpl.nasa.gov/mission/journal.asp
[8] http://www.sciencedaily.com/articles/c/ceres_(dwarf_planet).htm
[9] http://dsc.discovery.com/space/im/asteroid-belt-dawn-sykes.html
[10] http://nmp.nasa.gov/ds1/tech/ionpropfaq.html