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Saturday, 30 June 2012


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The pyres of giant stars...

If you're looking for the creation of the solar system, sooner or later you'll run into a paradox: It was born, at least in part, from a force cosmic destruction. One that makes a Death Star look puny: The Supernova.

Video above: A simulation of the collapsing bulk of a supergiant star, as it rips itself apart in a supernova. Anything standing on any planet within about a light year will be in big, big, trouble. It's pretty though, you can actually see the collapsing outer layers and the rebounding shockwave. Music: Wandering Star, by Portishead. Simulation by the Max Planck Institute for Astrophysics. Video uploaded to you tube by m3141592.

Most supernova are the deaths of the largest stars in the universe: Colossal pulses of energy that get given out by huge, old, suns blowing themselves apart [1]......some (called type 1a supernova [2], because 'thing that looks like an exploding giant star but isn't really one' takes up too much room) happen when a white dwarf, a stellar corpse, explodes.

But both types are powerful engines of birth, and the key lies in why they blow themselves apart.

I'll focus on the most common kind, the exploding-giant-star kind, and leave type 1a (white-dwarfs-turned-huge- fusion bombs) for another day:

Why does a giant star explode? A star is a powered by nuclear fusion [3]: The combining of two atomic nuclei [4] into a bigger one. When this happen to elements lighter than iron, part of their mass becomes energy - radiation or the kinetic energy of a high speed particle. Inside our Sun this is going on trillions of times a second, producing a colossal amount of energy. But the Sun doesn't blow itself apart on the spot*, because the Sun also has colossal gravity, so it's also trying to fall towards its own middle. The two forces balance [5], and the star teeters along this knife edge, for most of its life.

Image above: The giant star Betelgeuse, the closest supernova candidate to Earth. The light and dark areas are giant spots on this monsters surface, caused by huge currents of plasma rising and falling. It's 430 light-years away, so for all I know it's already popped. Image courtesy of the Paris Observatory.

A star usually fuses hydrogen into helium. As it ages, hydrogen becomes more scarce. The core shrinks under its own weight, heating up in the middle. When it gets hot enough, it starts fusing helium into carbon, leaving a shell of hydrogen around the edge. The new form of fusion halts the collapse, until core runs out of helium. For a small to medium star, it stops there: The rest of the star puffs away, and the core becomes a white dwarf [6].

But in a big star, the core shrinks again, and starts fusing carbon into silicon, leaving a shell of helium. And so on, and so forth, until, in the very middle of a star layered like a gob-stopper, silicon starts fusing into iron.

Image above: The gob-stopper layering of a huge, old, rickety star. The various layers are still producing energy by fusion, which is why the iron core can be held up for a while. Each layer fuses for a shorter and shorter period of time, so by the time the star has reached silicon as a fuel it only has a week or so left: That's probably the signal to jump in a space ship and leave the area at a large fraction of light speed. Image courtesy of wikimedia commons.

Except fusing iron doesn't produce any energy. In fact nothing heavier than iron fuses to produce when the core can't produce enough energy to hold the growing iron core up ....things for the star things go a bit sideways:

The iron core collapses under its own gravity.

And, this time, there's nothing that can stop it in time to save the star.

Exactly what happens next is fairly complicated, and, in some ways, still quite mysterious. But for our purposes: Imagine a huge bonfire, suddenly collapsing under its own weight. It's falling inwards but the blast definitely goes outwards, spreading a lot of sparks, smoke, and ash. Make the bonfire nuclear powered, and times by.....well just keep multiplying it until your head hurts. You still won't be close to just how huge the blast is, but you wouldn't get too close to something like that anyway.

Astrophysicists, as dedicated as they are, wouldn't either. Well, having known a few, they might. But, in any case, they can't. So instead, they try to understand what happens with computer simulations:

Video above: The moment that everything goes squiffy for our giant star: The core reaches a critical weight and collapses, beginning the process that will result in the star smearing itself across the sky, and flash frying any luckless planets it's got. This bit of the process takes only milliseconds, and you can watch the whole star start to become unstable, and the disruption spreading. Courtesy of the Max Planck Institute for Astrophysics.

Video above: A simulation of the star exploding, seen from the outside this time, and over the course of about nine thousand seconds. So everything you see in the previous simulation has happened so fast that it's invisible in this one. Courtesy of the Max Planck Institute for Astrophysics.

How does this build a solar system? The point is this: Up until now our huge star has made all the elements up to iron for us. It can't make elements heavier than iron and live, because making them won't produce energy to keep it inflated against its own gravity.

Well, it's not living any more.

As the core collapses, and forms a neutron star[7], the rest of the star follows it inwards at about a quarter of light speed. The star stuff hits itself, and the new born neutron star. Now there's a huge shockwave making its way back out of the core. The pressure and temperature goes through the roof, even compared to the kind of pressures and temperatures giant stars usually run at...and in all this chaos....iron is being made to fuse into heavier things:

The iron nuclei are running into each other, and combining. Everything is being bombarded by countless high speed neutrons, which the nuclei absorb, making them even heavier. In seconds, atomic nuclei have been built that are far to heavy to be stable [8]. They begin to fall apart, and the heavier they are, generally , the faster they disintegrate: Some of these will disintegrate so fast they can barely be said to have existed at all. Some may take billions of years to go completely - which is why things like uranium 235 can still be found in nature. This falling apart of nuclei, called fission [9], produces energy to, and the presence of these unstable atoms is what keeps the core of Earth warm.

So, by both living and dying, our supernova has given the universe all the other elements we find in nature, as well as a lot that decayed away long before we walked the Earth.

But the influence of a supernova doesn't end there...

Taking a big step back:

The core has collapsed into a neutron star. The remnants of the star that fall back onto the neutron star- one hundred billion degrees warm from the explosion - may make it heavy enough to undergo one final, endless, collapse, and become a black hole.

Image above: A close in view of the Crab Nebula pulsar, taken by the Chandra space telescope in X-rays. What you're actually seeing is the gas around the pulsar, heated up by the radiation coming from it. imaghe courtesy of NASA.

On all sides the rest of the star is speeding away into space, as a massive shockwave. It's carrying with it all those newly formed elements, and that shockwave will do two important things:
It will carry those newly formed elements into the surrounding clouds of dust and gas, and it will make those clouds of dust and gas collapse. The collapsing clouds will form a new generation of stars. And around the new stars, out of the heavy elements from the supernova, and countless others like it.... planets like Earth can grow.

Image above: The Crab nebula, a massive cloud of dust and gas left behind by a supernova. No, I don't see a crab either. Image courtesy of NASA.

And, on it, what can we do? We can take the elements forged in the heart of those supernova, and turn them into..... computers! That's right, anything heavier than iron (like the gold on some of the electrical contacts) in this computer was forged in the heart of a huge, dying  star.

Carl Sagan said: We are stardust.

Almost everything you'll see today is stardust to....

* Little things like that make me grateful.

List of links:
[3]">nuclear fusion

Thursday, 28 June 2012

Ancient, alien stones...

Meteorites bring many things to Earth. Now a new one has joined the list: Panguite [1] an entirely new mineral, found nowhere on Earth. Panguite is a unique form of titanium dioxide, and its structure includes scandium, aluminium, magnesium, zirconium, and calcium as well. 

So.... a mineral from space, that doesn't exist anywhere on Earth...cue the X-files theme tune?


Video above: You're a child of the nineties if you whistle this sarcastically upon hearing someone declare their 'psychic powers'. Although being able to whistle in a sarcastic tone of voice is pretty X-files in itself....

Well...I doubt Mulder and Skully got out of bed for less than an invasion by black alien goo. But more importantly, this is really just confirmation of something that we already knew: That the alien worlds these rocks formed on were alien - sometimes even in the chemistry of their rocks. Because Panguite is not the first material to be found only in a rock from space...
Here are just a few examples:

Image right: A cut and polished section of nickel-iron meteorite, showing the 'octahedrite' texture of the metal inside.

These were first found by the English Geologist W.G.Thompson, who noticed the bizarre triangular patterns forming on the surface of a Krasnojarsk meteorite [3], when he tried cleaning  it with nitric acid. By the way, cleaning things with concentrated acid, of any kind, is a bad idea. Although if you can take one whiff of concentrated acid, and not realise it's best left well alone.... heaven help you, because natural selection certainly won't.
Most nickel-iron meteorites have this unique crystal pattern, which only occurs when molten nickel and iron cool together over millions of years, in microgravity - evidence that these rocks formed in the cores of objects that were no bigger than large asteroids, and yet had an internal heat source that was long lived. The cores of protoplanets are thought to be partly preserved in the M-class asteroids, which were blasted into space when their protoplanets were destroyed in massive collisions.
Meteorites discovered on the surface of Mars [4], by the Opportunity rover, have been identified by finding this crystal pattern in them.

Image above: A false-colour view of a meteorite on the Martian desert surface, named 'block island'. The image was taken by the Opportunity Mars rover [5], which was given a warranty of ninety days, and is still going eight years later. And people say NASA's lost it! I hope someone's boss is buying them regular beers for that little bit of engineering, I really, really, do. Image courtesy of JPL/NASA.

Found in the Onello meteorite [7], Allabogdenite is compound of Iron, Nickel, Cobalt and phosphorous. It's light yellow to cream in colour, and occurs as thin crystal layers. It's similar to steel in hardness, and very brittle.

A compound if titanium, iron, nickel, and phosphorous, Florenskyite is one of only four naturally occurring phosphides, and exists, as far as we know, only in the Kaidun [9] meteorite

Another from the weird Kaidum meteorite, this one based on titanium, vanadium, chromium, iron, cobalt, nickel, and phosphorous. So, everything including the kitchen sink, and the garden table, is in there.

Image above: A projected 3d structure, used to understand the structure of quasi-crystals. What you're actually looking at here is a three dimensional 'slice' through a six dimensional 'cube' or hexacube. See? I told you this stuff was weird. Image courtesy of Wikimedia commons
Don't stare too long, you'll get a headache, and start to feel like you're falling into the screen...

This really is odd stuff: Quasi-crystals are a form of matter that has an order, but no translational symmetry [12]. Its crystal pattern never repeats, making each part of the structure unique. The discovery of quasi-crystals led to new advanced materials, and changed our understanding of how nature builds ordered structures
But when materials scientist Dan Shechtman first reported it in 1982, he was ridiculed, and accused of 'quasi-science'. Nearly thirty years later, in 2009, the first, and so far only natural quasi-crystal [13] was discovered, in rocks that isotope analysis [14] suggest is from an ancient asteroid impact. Shechtman, I'm happy to say, was awarded the Nobel prize [15] for chemistry shortly afterwards.

So, what is the significance of this bunch of cosmic misfits? Well, they all come from meteorites that were fairly untouched since the solar systems birth. So they tell us that, four and a half billion years ago, in the molten cores of protoplanets, nature smelted things into existence that are alien to terrestrial geology. That gives us a signpost - that the bodies these meteorites came from were genuinely different to Earth, right down to their cores -  and so we need to be careful about making assumptions on how these worlds worked..

It's also a brilliant reminder: That we don't know it all, that how things are here on Earth certainly isn't how they are everywhere. And that, as we go into space, we will be visiting places where even the rocks are strange....

List of links:


Wednesday, 27 June 2012

The Chaos of Miranda

A little while ago I posted about the Uranian system but, like Voyager 2 [1] when it visited, I was barely able to scratch the surface. To fix that a little, I thought I'd take a look at the most bizarre moon of Uranus.

Geologically it's, perhaps, the most bizarre moon in the solar system:

A moon with many faces: 

When Voyager 2 arrived at Uranus it was met with a blank sphere of cerulean blue, as if the god of the sky was refusing to give up it's mysteries. But it's moons....ah. They had stories they were willing to share with the visitor.

Image above: Uranus, hiding its secrets beneath a veil of opaque turquoise cloud. This is the view from Voyager two, and the ice giant seems clear it's giving nothing away easily. Image courtesy of JPL/NASA

And one of them, Miranda [2], the innermost large moon, had a story that was written on its face in scars and landscapes like nothing the team controlling Voyager had ever seen before....

 Image above: Miranda looms out of the darkness. The 'tick' feature near the middle top is called the Chevron and, like most of Mirandan geology, we have no idea how it got there. Image courtesy of NASA/JPL.

Voyagers cameras showed the 480km wide moon to be a mix of odd landscapes wedged together. The Voyager team saw...

.....compressed, crumpled, valleys and cliffs, reaching 5km into the black sky above the little moon...

Image above:  Miranda boasts the highest cliff known to exist: Fall off it, and between the low gravity and height you'd take ten minutes to hit the bottom. So at least you'd have time to work on your famous last words... Image courtesy of NASA/JPL.

.....massive parallel ridges, next to ancient rolling hills dotted with craters...

Image above: Ancient, heavily cratered, hilly terrain sits right next to a sea of massive parallel ridges, and a young (geologically young -  so still really hugely old) area of chaotic landscape. Landscape isn't supposed to do that. Why this one does....we simply don't know for sure. Image courtesy of JPL/NASA.

......fractures exposing different light and dark materials....

Image above: The deformed edge of Miranda, where huge rifts eat into the surface and expose subsurface layers of darker and lighter material. And, once again, we're not entierly sure what any of it means.... Image courtesy of JPL/NASA..

......Miranda looked like it had been shattered, the pieces squashed clumsily back together, and then told 'stay!'

And, at first, that's exactly what the geologists thought had happened: That Miranda had been broken by a massive asteroid or comet [3], and gravity had crudely bought the fragments back together. And that then it had been pulverised again. And again. And again. Five times in fact [4]. Five cycles of destruction, and rebirth, each time becoming more confused and twisted. Each time bits of the core wound up on the surface, so the theory goes,  and bits of surface wound up in the core.


There were a few problems with this idea - one being that the re-accretion process itself should have ground the surviving fragments down to no bits bigger that ten kilometres. So other explanations have been sought.
There is another explanation [5] for the jigsaw moon, one now more widely regarded than the first. It begins in a different part of the Uranian system: The moon Umbriel [6]. At one point in its history Miranda may have been in a 3:1 orbital resonance [7] with Umbriel - so for every orbit Umbriel made, Miranda did three. Because of the resonance,  the two moons were always closest to each other at the same point in the orbit of Miranda, and Umbriels gravity distorted Mirandas path.

Video above: I couldn't find a video showing the Miranda - Umbriel orbital resonance, so here's one with Titan and Hyperion instead, two moons of Saturn. Titan - the inner, faster moving moon - drags Hyperion along behind it. Since a faster moving object must orbit higher, the orbit of Hyperion orbit gets distorted into an egg shape.

That would mean Miranda was significantly further from Uranus - and feeling a different gravitational pull - at some points in its orbit than others. The changing gravitational pull would cause tides in the 'rock' making up Miranda, like those on the seas of Earth. Rocks that get stretched and squeezed by a huge changing force rub against each other, producing heat. Add up all that heat across the whole of a small moon.... and you can melt it.

Which is exactly what has happened to acne riddled Io, and this is a perfect excuse to put in a picture of the angriest moon in the solar system:

Image above: Io. The colours are due to sulphur compounds all over its surface. Io has volcanoes the same way that a car in a scrapyard has dings. After it's been through the crusher. Miranda may once have been a cooler, water-ammonia, cousin to the seething chaos of Io. Image courtesy of NASA/JPL. 

That melting turned Miranda into a pit of cryovolcanic [8] chaos, perhaps more wracked even than Io. Miranda started to belch its core onto its surface: Huge blobs of warm, ice called diapirs [9] would have forced their way out of the mantle, driving older terrain aside and compressing it. Water-ammonia slurry bursting out of fissures as cryolava, covered thousands of square kilometres. The changes in internal distribution of its mass made the whole moon shift on its axis [10], like a.......a 500 km wide ice and rock moon melting and shifting about, and that's impressive enough to need no metaphor. Imagine if a cluster of volcanoes popped up on Earth, a cluster so big the poles became the equator, because the plume of magma underneath the volcanoes was throwing the whole planet off axis.

But then Umbriel and Miranda drifted out of resonance, the tidal forces faded, and Miranda froze again - halfway through turning itself inside out like an old sock - leaving a surface that bears an odd resemblance to one in places.

Both theories might hold water - or cryolava - up to a point. The solar systems history is long enough to leave room for a lot of events.

Image above: A photo-montage of the moons of Uranus, revealing Miranda as the tiddler of the bunch. The huge unmapped regions on Ariel just serve to underline how much exploring we still have to do out there. Image courtesy of JPL/NASA.

Although we will have to wait a long time for answers, there has been a resurgence of interest in the ice giant [11] planets: New missions have been proposed [12], and the advent of new space drives like the solar sails [13] and ion engines [14] might ease the path to making them a reality. The New Horizons [15] probe to Pluto shows us again what Voyager did decades ago: That, even with conventional engines, the old gravitational slingshot manoeuvre can get a probe out further even than Uranus.

Oh, one other thing: Remember I posted a soundtrack of the radio wave 'song' of Uranus, recorded by Voyager as it passed by? Well, Miranda sings one to, but where Uranus's 'song' was kinda beautiful, Miranda's is...  frankly creepy.

Fitting, perhaps, for a world that has been racked by such violence and turmoil.....


Video above: The radio waves recorded by voyager two as it passed Miranda, made audible. It sounds... literally like nothing of this world. Image courtesy of NASA/JPL, audio taken from "Symphonies of the Planet vol.2 - Miranda", NASA Voyager Recordings, Brain/Mind Research, 1990.

List if links:


Tuesday, 26 June 2012

Hayabusa 2: Putting holes in an asteroid.

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JAXA, the Japanese space agency, is considering the 'exploration by blowing holes in things' approach for its now-under-construction Haybusa 2 space probe: Something called the 'Crackup installation [1]'  may be added to the probes suite of abilities.

The Crackup has two parts: An explosive charge and a solid, 2 kilogram, 'bullet'.

Yes, that sounds like a cannon to me to.

While the Crackup is deployed over one side of the target asteroid, Haybusa 2 will sensibly fly around to the other side. The explosive will go off, shooting the 'bullet' into the asteroids surface, blowing a two meter crater in its hide. Haybusa 2 will then come back, probably trying to look innocent, to inspect the hole and take samples from inside it.

There's a good track record of learning about things in space by hitting them with other things and seeing what gets splattered out. From the Deep Impact [2] mission to comet 9P/Tempel [3], to the LCROSS [4] mission that drove a used centaur rocket into the Moons south pole to look for water.

Image above: An artist impression of Hayabusa 2 approaching its target. Image courtesy ofAkihiro Ikeshita/JAXA.

OK, it smacks of brute force, but if brute force works...

...Look, it's not just an excuse to buy a white cat, complain about your goons incompetence, and go 'mawahahaha!' Drilling neat holes in things in space is nothing like as simple as taking a power drill to a chunk of wood. Without gravity to hold everything down you'd need to press the whole probe hard against the thing it's drilling, for starters. That means more weight, more complexity, and more money. And that money stuff is hard to come by.....blowing holes in things is much easier.

And more fun. Mwhah- sorry.


Video above: The Deep Impact space craft demonstrates how NASA goes about digging a hole, as its 370 kilogram copper 'bullet' hits the surface of comet 9P/Tempel. Haybusa 2 won't be aiming to make nearly such a big bang - comet Tempel is seven kilometres across, 1999 JU3 is less than one, so too big a bang could take it apart completely. Um, so maybe that makes the video less than perfectly relevant.... well it's still cool to watch. Video courtesy of JPL/NASA, uploaded to you tube by mynameisdim.

But why put a hole in asteroid 1999 JU3, specifically? Why not just scrape some stuff off the surface?

Well, the following is just my guess, but if you'll indulge me:
1999 JU3 [5] is a C-class asteroid [6]. These are especially interesting  because they are both rich in carbon compounds (life on Earth is carbon based) and show signs of being in contact with liquid water [7] on the protoplanets they came from. Fragments of C-class asteroids that hit Earth - carbonaceous chondrite meteorites [8] - have been found to contain chemical compounds [9] relating to the start of life on Earth, and contain some of the best preserved material [10] from the solar nebula [11] that the solar system formed from. We really, really, want pristine bits of 1999 JU3 for study here on Earth.


The surface of 1999 JU3 won't be pristine. It will have been exposed to high energy UV photons, x-rays, high speed protons - all the raw and deadly stuff from the Sun that Earths atmosphere filters out - for four and half billion years. So the material on the surface will be irradiated to buggery, and we want to get at the unaltered good stuff below the surface.

That'd be my excuse for shooting up yet another object in space anyway.......

Image above: Asteroid 253 Mathilde, the only other C-class asteroid to be visited by a spacecraft from Earth. On the left is true colour, on the right enhanced colour, showing subtle variations in the surface The NEAR [12] probe flashed by it, on its way to the asteroid Eros. See, they both got cool names... Image courtesy of NASA/JPL/Cornell .

Incidentally, the Hayabusa 2 website describes the probes target as "the asteroid temporarily named 1999 JU3". So here's hoping they've got an inspiring real name for it in the works....

List of links:


Sunday, 24 June 2012

Suncream....from spaaaaace....

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Super bugs:
No, not that kind of super bugs. Image courtesy of  J. K. Moore.

Here's two interesting facts about life: It can survive exposure to space for over a year, and it can turn a continent wrecking meteorite impact to its advantage.

No, not you, unless Superman is reading this. I'm talking about some of the simplest life there is: Microbes.

If Superman is reading this: Please could you do something about the rush hour traffic for me tomorrow morning? Thanks.

Microscopic lifeforms, including the well known tough guy B. subtilis [1], were sent into space as part of the Expose-E [2] experiment. Expose-E simply sat on the outside of the International Space Station [3], with two trays of micro-organisms exposed to space, and a third exposed to simulated Martian surface conditions - the Martian surface being a little friendlier than open space in some ways, but with 200 mile an hour sandstorms and occasional CO2 frost. The B.subtilis organism has a means of surviving adverse conditions: It forms a endospore [4], a dried out, almost crystallised, version of itself.

Image above: B. Subtilis, as seen under an electron microscope. Each one is about a micrometer long, but their tough. I mean, they couldn't beat you up single handed, but they can survive almost anything. Image courtesy of NASA.

The results are an impressive underlining of how tough some life forms are: On the stations outer hull these spores took the full beating of the Suns electromagnetic fury, the dessication and radiation of space, and the 90 minute swings from minus twelve degrees Celsius to plus forty.
The killer in space was found to be the high power UV from the Sun, which the Earths atmosphere shields us from the worst of. When exposed to the Suns fire-hose of high energy UV light most (although not all!) of the organisms were dead after 18 months. But the spores that were shielded from the suns UV laughed at the rest of it: Eight percent of the B.Subtlis exposed to hard space survived, as compared to control samples on the ground, an incredible percentage considering that you or I would last seconds at best.

The B.subtlis in the Martian simulation? They all survived. All of them.

 Image above: The Martian surface, on a frosty morning. Pretty, but making a cup of tea there is hard work. And I wouldn't survive without tea. Or oxygen... Image courtesy of NASA/JPL.

And some of the lichens that were sent up survived even the UV [5]... which has attracted the interest of pharmaceutical companies looking to develop better sun cream -  if the lichens can be persuaded to tell how they do it... well, eighteen months of resistance to space strength UV....

.....kinda leaves SPF 50 in the shade, doesn't it? 'In the shade', geddit?


There is a lot more to it than that - in fact there's a whole special issue of Astrobiology magazine devoted to it. Follow this link [6]; even if you don't have access to the full articles, the abstracts alone are worth running your eye over.

Evolutionary Judo:

So, critters can walk the walk when sat on the hull of a space station for 18 months. But how do they cope with a clobbering by a mile wide space rock?

Well, to answer this one, Charles Cockell from the University of Edinburgh took a team to the site of Chesapeake Bay impact crater -  and Aaron Gronstal was kind enough to make a diary of the expedition [10] for us all. This buried impact crater marks the spot where a kilometre wide asteroid (thats the same size as 2012 LZ1 [7] that passed Earth last week) smashed into the waters just off the North American continent.

 Image above: The Chesapeake bay crater. Eighty five kilometres wide. Bang goes the neighbourhood. And that neighbourhood. And that one. And that one, and that one, and that one....Image courtesy of the United States Geological Survey.

Now being anywhere near that explosion.... doesn't bare thinking about, unless you like thinking about being flash fried, pulverised, and then hit by a three hundred meter tall tidal wave. But the team went to investigate how subterranean life - and life has been found happily living at depth of up to 1400 meters [8] -  had responded to the event. The surprise was that, in the rocks under the impact crater, there were more micro-organisms [9] than had ever been found at such depth before.

The teams explanation is nicely simple: The impact pulverised the rock beneath the it, opening up cracks and crannies that microbes could then move into, and allowing fluids containing nutrients to get down to them. And microbes are still in the process of moving into this new habitat today.

This has a strong bearing on the history of life on Earth: It's always been up for debate whether life existed in any form during the Late heavy Bombardment [11]. The LHB was a time of non-stop hits by large asteroids, and many have thought that the Earth must have been totally sterilised by it - although some of the evidence for it was recently questioned [12]. Yet the homesteading bacteria under the Chesapeake impact show that life could actually have found a way to make use of the blasts, sinking deeper into Earths crust, and find the most protected nooks.

Many martial arts teach that an attack can, if treated the right way, be turned against itself. Well these critters were applying the same principle at least thirty-five million years before Bruce Lee ever donned his Gi....

List of links: 

Saturday, 23 June 2012

An ice giant planet, in the twilight....

First up, some quick news bites:

Below average asteroid fools astronomers: 

Asteroid 2012 LZ1, which passed Earth [1] not ten days ago, has turned out to be twice as big as previously thought, and half as bright. What threw off estimates of its size was its dark surface: Astronomers assumed that it was reflecting an about average amount of light for an asteroid. So, surface brightness and distance being equal, a big rock will look brighter than a small one, and they estimated 2012 LZ1 was 500 meters wide.

In fact it was reflecting a below average amount of sunlight, and was really 1000 meters wide. Sneaky!

Image above: The asteroid that hid in plain sight, 2012 LZ1. Image courtesy of USRA.

We know about this thanks to the Arecibo radio observatory [2]. Arecibo can 'probe' a passing object with radio waves. What it does is similar to a RADAR, but more subtle than just getting a 'ping'. I refer you to Emily Lakdawalla of the Planetary Society for a further explanation of how images can be made using radio waves [3].

The unusually dark surface probably points to this being a carbon rich chunk of four and a bit billion year old rock. That means a 1 kilometre wide chunk of fairly unaltered material from the very beginning of the solar system - and there it goes, sailing off into the black... oh well...

Although if it had hit us, for a lot of us, its exact size and type would have been academic. By which I mean that millions would have been cooked by the blast, and wouldn't care just how big 2012 LZ1 was.


But it missed us and, thanks to the Arecibo observations, we know it's no danger to Earth for at least 700 years. So.... that's all OK. Just remember, when you go to the polls: One day one of them won't miss. And funding for science and space exploration is what might give us the tools to do something about it.

Nu-STAR stretches, gets ready for the job ahead:

Remember Nu-STAR [4], the space satellite with the revolutionary X-ray optics? No? Really?
Fair enough, I once forgot that American mains power is different to British mains power, and blew up a very, very, expensive computer. As a side note: The bang deafened my firms managing director in one ear for twelve hours..... so I didn't get away with that one.

Image above: An artists impression of Nu-STAR, big boom extended to catch images of the biggest X-ray bangs in the universe. Image courtesy of NASA/JPL/Caltech.

Nu-STAR is a micro-satellite - a fridge sized satellite -  with a remarkable X-ray imaging system, part of which needs to be extended away from the main craft on a long unfolding boom. The satellites mission is to provide unprecedentedly sharp X-ray images, of some of the most violent events in the universe, such as black holes and the aftermath of supernova. After a successful launch, the next big hurdle for the Nu-STAR team was getting the boom unfurled.

In a turn of events that is wonderful, but lacking in Hollywood style drama: They have successfully unfurled the boom [23]. Well done to the whole Nu-STAR team!

Portrait of an ice giant:

Out near the edge of our solar system lies a strange, cold, collection of worlds: The Uranian system.

Yes: The system centred around Uranus. Anybody want to make that very, very, tired joke?

Go ahead, I'll make a cup of tea while you get it out of the way.

While I'm slurping my tea like an old granny, consider this: The planet, that has amused generations of school kids, has also been inspiring great art ever since its discovery. Just listen to the music it has inspired down the ages:

From Holst......

Video above: The Planets Suite: Uranus. Music by Gustav Holst. Images courtesy of NASA/JPL..  Hendrix...

Video above: Uranus Rock, by Jimi Hendrix. Say 'Who?' and I'll cry. Seriously.

... to metal band 'Uranus explodes'....


Video above: 'Oblivion' by Uranus explodes. Yes, they're a metal band, which means mosh pits, crowd surfing, and that the bands name is almost certainly meant to be interpreted that way. Incidentally, never be in the front of a Motorhead gig if Lemme decides to go crowd surfing. Learn from my mistakes folks. where you need to remember: Music is patterned sound, and your brain is a genius at finding patterns.
Here's the music:

Video above: Uranus sings into space. The random EM frequencies coming from the planet and its rings sound like music to the human ear.  That's.... wonderful. Weird. The reason I love this sciency stuff. Planets sing into the eternal night, and some people claim science robs us of a sense of wonder. Go figure. Track from Symphonies of the Planets vol.4 - Rings of Uranus" NASA Voyager Recordings. Images courtesy of NASA/JPL..

Beautiful, yes?

The planet Urtanus didn't inspire it.

The planet Uranus performed it.

Image above: Voyager 2 passes Uranus. CGI image, created using Celestia. Image courtesy of Wikimedia commons.

The Voyager 2 probe [5] carried an instrument called the Radio Astronomy Investigation instrument [6]. It recorded the various frequencies of radio waves, emitted by the worlds it passed, for future study. The 'sounds' of solar storms [7] hitting planetary magnetic fields [8], the emissions of magnetosphere's, the fluxes of ionised particles following curved field lines, and hitting atmospheres, or ring systems...
....and these are the 'sounds', the radio wave songs, of the Uranian system.

The man who recognised the planet as a planet, William Herschel in 1781 [9], was inspired to try naming it 'Georgium Sidus' (George's planet). A planet named George wasn't popular (beyond King George who Herschel was trying to honour), so the name Uranus was proposed instead, and stuck.

Mercury, Venus, Earth, Mars, Jupiter, Saturn, George.... see?

The closest of the ice giant planets was probably quite indifferent to all this, as it never comes closer to Earth than two and a half billion kilometres. The gulf is so vast that only one spacecraft has ever been there, and that was Voyager 2, in January 1986.Voyager taught us that this system doesn't give up its secrets easily. It gave us most of what we do know about this twilight collection of worlds, but the short time it had there was barely enough to scratch the surface.

Voyager found an huge, inscrutable, planet. A gravitational linchpin for a complex system of rings and moons, all with their own personalities. 

Image above: Uranus seen in visble light by Voyager 2 (left),and infra red by the Keck telescope (right).. Image courtesy of Keck observatory.

Proposed missions back there, like the Uranus Pathfinder [10], have been knocked back. mainly this is due to the time, money, and technical difficulties of reaching such a distant target. Conventional engines will only allow a ship to flyby Uranus, unless it takes a very very slow route, due to the weight of fuel it would need to carry.

All is not lost for exploring this strange realm further though: Over the years our sensors on and near Earth have improved. High end telescopes, from Keck [11] to Hubble, have scrutinized the baffling blue orb [12], and slowly, when added to the Voyager data, some of the mysteries have begun to unravel:

Image above: the Keck observatory, one of the 'eyes' that let humanity explore the parts of the universe we can't physically reach, at dusk. image courtesy of NASA.

Uranus itself is thought to be a thing of ice, with a rock core, surrounded by an atmosphere of hydrogen and helium. As the pressure grows, beneath the clouds, the atmosphere gradually changes into an ocean of liquid gasses with no definite surface. Mixed into its atmosphere are water, ammonia, methane (which makes it blue), and hydrocarbons formed by UV light hitting the methane. The winds howl around the planet at up to 900km an hour, and massive storms occasionally dance around its atmosphere.

Seen from afar Uranus seems like a mad parody of the other giant planets: The whole planet spins tilted violently to one side, almost at right angles to it's own orbit, and like Venus spins west to east. The magnetic poles are nowhere near the actual poles for some reason, which is probably related to the planet being sideways. And, because of the extreme tilt, the poles get twenty years of night in the winter, and twenty years of day in the summer.

The histories of both the ice giants -  Uranus and Neptune - are surrounded in question marks: Computer modelling of the suns protoplanetary disk shows that a world like Uranus couldn't have formed where it is today -  according to the leading theory of giant planet growth, the core accretion model [13], Uranus would simply run out of building material before it reached its present mass.

And, obviously, it didn't. Unless it's hollow. Which is incredibly unlikely. I'm a scientist, so I have to say 'incredibly unlikely' rather than 'impossible'. That's almost part of the job description, along with bad pay and putting up with occasional explosions and electric shocks....

Another model, the disk instability model [14], acts faster, but isn't as widely accepted. These differing theories give different internal structures: Core accretion predicts an Earth sized chunk of rock at the core, but disk instability lets them grow without such a 'seed' in the middle..

Or did they simply form elsewhere, and move home later in life?  Luckily scientist love a good theoretical argument. But not as much as they love being able to find out who's right using evidence. If you're reading this NASA, ESA, or JAXA, hint hint....

The planet is encircled by thirteen rings, a dark cousin of Saturns bright halo. Uranus has rings that are almost black, and their chemical composition is an unknown. The best candidate for what composes them are of chunks of water ice, contaminated by radiation altered carbon compounds (think ice with asphalt and tar frozen into it). The theory is that these chunks are debris from a collision between two small moons, around 600 million years ago.

Image above: A map of the Uranian ring system, incuding some of the small, asteroid like, moons. Imnage courtesy of Wikimedia commons.

How the rings are kept in place is also a mystery. Saturns rings have tiny Shepherd moons [22], that tug the ring particles into their places. But only one pair of shepherds has been found at Uranus.

Ah.. that brings me to the moons....

There are five major moons, swinging around the blue central orb. Named for characters from the plays and poems of Shakespeare and Alexander Pope, these distant worlds of ice and rock share the extreme seasons of Uranus, and have complex histories and unknowns of their own.

Chaotic Miranda [15], a jigsaw of randomly assembled landscapes, like it was smashed to pieces and then squashed the remains back together....

Image above: A photo-mosaic of Miranda, made from shots taken by Voyager 2 as it flew past. Image courtesy of JPL/NASA.

Ariel [16], with ancient cratered sliced up by scarps and canyons, indicating the most recent geological activity of the five large moons...

Image above: Ariel, as seen by Voyager at its closest approach. The rift valley-like features may indicate that Ariel had internal activity, driven by tidal heating, more recently than the other moons. Image courtesy  of JPL/NASA.

Umbriel [17], with it's dark surface of crystalline ice and tholins [21]....

Image above: A re-processed image of Umbriel. Re-processing courtesy of Ted Stryk. The white feature on the 'top' is actually on the equator, and this view is almost straight down onto the south pole. No idea what it is. A crater? A giant crash landed iced doughnut? Probably a crater, but feel free to correct me. Image courtesy of NASA/JPL.

Titania [18], a world that may hide a subsurface ocean [19] of ammonia and water....

Image above: The pockmarked face of Titania. The queen of the fairies would not be flattered methinks.... Image courtesy of JPL/NASA.

And, farthest out of the big moons, Oberon [20], a world  covered in gigantic cracks......

Image above: The Uranian moon Oberon, with its ruddy tint. Image courtesy of JPL/NASA.

I'm sure you can guess my opinion..... I think we should be going back, if only to hear the rings singing again....

Image above: As it left Uranus Voyager 2 took this picture, looking abck towards its sunlit crescent/ Image courtesy of NASA/JPL.

List of links:

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[19]">subsurface ocean

Tuesday, 19 June 2012

A quick note: Voyager nears the edge....

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Thirty five years ago the Voyager 2 space craft [1] was launched. With its sister ship, it opened up a new solar system for us. It revealed the clouds, and moons, of the giant planets as never before. It showed us the volcanoes of Io, the smogs of Titan, the enigmatic moons clustering around Uranus and Neptune.

Image above: One of the volcanoes of Io, among the Voyager missions greatest discoveries, blows sulphur based lava into the moons sky. Beautiful. From my armchair. Up close, probably a brown trousers experience, although a short lived one. Image courtesy of NASA/JPL.

It may be about to make another first: First space ship to reach interstellar space.

Almost 18 billion kilometers from Earth the stubbornly long lived probe is showing signs that it is about to leave the heliopause [2], the edge of the Suns magnetic field.

The grandaddy of space probes had already reached the 'stagnation region'[3], where the solar wind starts to loose speed, and the solar magnetic field starts to pile up..
Clues that the edge is coming up fast have been arriving, as a steady rise in the number of hits from high speed cosmic particles, since 2009. These are microscopic debris from supernova explosions, debris that our Suns magnetic field keeps out of the solar system. The number of hits has increased by nine percent in the last month, and Voyager controllers are waiting for the final confirmation that Voyager has broken through -  a change in the direction of the magnetic field lines surrounding the little ship from east-west to north-south.

Video above: The story of the Voyager mission, as told by the people who've worked on it. Be warned it's almost an hour long, but well worth it if you have an hour to spare. Go on, get a glass of wine and a bar of chocolate and give it an hour. Video courtesy of NASA/JPL.

Although there's not much to see that far out - well there's the majesty of the entire Universe on display, but aside from that not much - scientists have been hoping to see Voyager become our first toe dipped into interstellar space for a long time. Before the event it is impossible to say for sure when the crossing will occur, and Voyagers on board nuclear batteries will only be able to keep it alive out there for so long. The penciled in date of possible last contact with the probe is 2025.
That seems a long way off, but then so does the deadline for my tax return, and I know from past experience what a mess I can get into with that one.

Image above: The IBEX ribbon. The IBEX mission, designed to monitor the incoming neutral particles from the solar systems boundary, found a 'ribbon' of higher energy particle emission.  The image above is an 'unwrapped' full sky image, with higher energy particles shown in yellow to red and lower energy particles shown in green to blue. Image courtesy of NASA.
It's not just the 'first to' that has space nerds excited: The exact nature of interstellar space has been tantalizing us. There was the discovery of the IBEX ribbon [4] by the Interstellar Boundary EXplorer craft [5], and the discovery the gas in interstellar space is much more strongly magnetized [6]than expected. The strong magnetic field and the ribbon may well be related, with the field reflecting energetic solar particles to create the ribbon [7]. It all adds up to... well, no-one's quite sure. But the thinner-than-thin gas between the stars is the stuff that goes into the molecular clouds, that birth the next generation of stars So understanding it is the root of understanding our solar systems history.

What we do know is that we don't yet fully understand the way interstellar space works. And Voyager, it seems, will soon be able to experience it first hand....

List of links: