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Tuesday 31 July 2012

Fire rainbows....

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This is nothing to do with the solar system.... um, that is, apart from being a part of it, the same way everything on Earth is. But you know what I mean*. I just had to show it to someone:

Image above: A fire rainbow. Nature is just awesome. Image courtesy of Environmental Graffiti.

This is a fire rainbow - it only occurs in high altitude cirrus clouds when the condition are just right, and the  sunlight hits the ice crystals at exactly fifty eight degrees.

Have a look here [1] for more very cool fire rainbow stuff.

NuSTAR readying for science operations:

Image above: A copy of NuSTARs first ever image, signed by the science team. The picture is of the black hole Cygnus X-1, which is very bright in the X-ray sky. Yes, I know that sounds ridiculous - google 'black hole accretion disk' to find out why. Image courtesy of Caltech.

The next generation X-ray telescope [2], with the nifty fold away design [3], is getting ready [4] to begin 'phase E' - science operations. This is a bit confusing for me, as Nu-STAR has already been making X-ray observations of the black hole in the centre of our galaxy, and observing quasars with with INTEGRAL [5], Suzaku [6], and XMM-Newton [7]. That sounds a lot like science to me, but then what do I know?

Video above: A quick run down on how the NuSTAR craft goes about unfloding itself in space. Video courtesy of JPL/Caltech.

..And a word on a veteran:

The Japanese Geotail [8] space craft is twenty years old today [9] - Geotail was the first in a small fleet of satellites called the International Solar Terrestrial Physics project, whose mission was to map Earths magnetosphere and its interactions with the Sun.

Image above: A cross section of the magnetosphere of Earth, which keeps solar storms from gradually eroding away our atmosphere. Quite useful then.Image courtesy of NASA.

This fairly unknown craft gave us our first comprehensive look at how the energy from a coronal mass ejection [10] is funnelled into a geomagnetic storm [11] in our magnetosphere, giving rise to aurora -  amongst other things. It's adjusted it's orbit several time to fly through the various parts of the magnetic field of Earth, and get a good collection of information on how it works, what it does, and how it fits into the larger interplanetary environment.

Video above: This is a brilliant excuse for another stunning video of the Aurora seen from space. Although I don't really need an excuse. Video courtesy of NASA.

The space satellite is still going strong, still collecting science data, after twenty years. Today it provides a comparison point for newer Sun and magnetosphere studying craft, like THEMIS [12].

Just goes to show - A veteran craft can do just as much as one o' these flashy young 'uns!.

* That's just a statement of vague hope.

List of links:


Sunday 29 July 2012

Dawn leaves for Ceres....

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Heartfelt congratulations to the Dawn [1] team - this September eighth will mark the end of their year long exploration of the battered protoplanet Vesta [2]. The details of how Dawn has opened up our understanding of this battered world would be several books its own right. But, suffice to say, out view of Vesta has changed from this.....

Video above: A series of images from the Hubble Space Telescope, our best view of Vesta before the Dawn space probe arrived there. Video courtesy of NASA/JPL. this....

Image above: Dawns view of the south pole of Vesta. Or what's left of it. Dawn discovered that the entire south pole had been blown apart, by not one but two massive impacts from asteroids. The ridges you see around the Vestan equator are caused by the shock waves from these blasts rippling through the rock. to give you an idea of the scale of all this: Vesta is about five hundred and fifty kilometres across. So the scale is BIG. Image courtesy of JPL/NASA.

....including shots like this:

Image above: The image on the left is an infra red view of the Vestan surface, where red represents the 750 nanometre wavelength of infra red light, green the 920 nanometre wavelength, and blue the 980 nanometre wavelength. The image on the right shows the different types of rock present, colour coded by the dawn scientific team. Image courtesy of JPL/NASA.

The mission has mapped the protoplanets gravity field and interior structure [3], surface composition [4], and collected literally millions of high resolution spectra [5] of its surface.

Dawns ion engines [6]* have already begun firing, raising the crafts orbit - September the eighth marks the point when Dawn will have gathered enough speed relative to Vesta to be considered free of its gravitational field once more.

The team are planning the 'Hasta La Vesta' webcast [7], and until then I recommend Dr Marc Raymans latest Dawn journal log [8].

The next target for Dawn is the dwarf planet Ceres [9] - a world nearly a thousand kilometres wide. The surface of Ceres shows signs of alteration by water [10], there's possibility it may have retained a liquid water layer [11] in its interior for billions of years, and even tentative hints of out-gassing [12] over its pole. So the Ceres phase of the mission will prove at least as exciting as the Vesta phase. And it's impossible not to wonder: What will Dawn change our view of Ceres to?

Image above: A gigantic peach, floating in space. Just kidding... I mean the dwarf planet Ceres - this is one of the best images of this embryonic planet that humankind has, via the Hubble Space Telescope. Image courtesy of JPL/NASA.

* If you've ever wondered what the 'TIE' in TIE fighter stands for: Twin Ion Engines. Though Dawn doesn't run armed, unless Marc Rayman is keeping something serious under his hat. What do you mean you've never wondered that? Next you'll be telling me you've never pulled a sickie to watch all six Star Wars films back to back. 

List of links: 

Friday 27 July 2012

Mystery on the edge of fire: Mercury

Sometimes it's too easy to assume that secrets hide in the darkness: The planet Mercury has been hiding its secrets in the light. And, now NASA's MESSENGER  spacecraft  has completed its mission, and JAXA/ESAs Bepi-Columbo under construction, it has begun to reveal them.....

Image above: An enhanced colour view of Mercury, from the MESSENGER space craft - the colours you see here are too subtle for the human eye. Ahh, to be a, being stranded a billion kilometres into deep space isn't worth it. Image courtesy of NASA/JPL.

I grew up reading textbooks that pegged Mercury as being like the Moon - essentially a dead rock.

Well, so much for received wisdom: The Moon has turned out to be a complex place with things still going on, and Mercury..... MESSENGER has shown Mercury to be an riddle wrapped around a large, still active, iron core. And the exploration of this world, that bakes in the full electromagnetic and particle fury of the Sun, is just beginning.

Not so dead:
Mercury is still alive and kicking - both deep inside its core and, possibly, on its surface. And it is a massive core - eighty five percent of the planets volume. Because of the planets small size, before MESSENGER, researchers had assumed that the core had cooled solid, and any magnetic field was residual.

Now we know differently: By measuring changes in MESSENGER's velocity near Mercury, the team has been able to build up a map of the planets gravitational field. Combined with  measurements from Earth based radar, a working idea of the internal structure of Mercury has been built up: There's a solid crust, then a solid, iron sulfide outer core, and then a liquid core further in.

Image above: A comparison of the internal structures of Earth an Mercury - though, as you can see from the 'relative sizes' box Mercury would fit nicely inside the core of Earth. Image courtesy of the Case Western Reserve University.

The planets magnetic field is about a percent of ours, and is off axis - so the north magnetic pole is around twenty degrees from the north geographical pole. This makes it lopsided, being three and a half times stronger in the north than the south - something we don't have a good explanation for yet.  But that means that the south is getting a much harder blasting from the solar wind - the gale of plasma the Sun puts out.

The  field itself is as complex as a very complicated thing

Image above: An infographic of Mercury, showing the magnetics fields place in the grand scheme of things. Image courtesy of ESA.
It's shaped similarly to Earths, with an outer bow shock covering the planets sunward face, and a long magnetotail streaming behind. Huge, moving, bubbles of plasma (called plasmoids) travel down the magnetotail towards interplanetary space. And the whole field is wracked by tornadoes in the magnetic field lines [10] - called flux transfer events - eight hundred kilometres across.

Image above: A simplified map of the magnetic field of Mercury. Yes, that's the simple version. Image courtesy of NASA

All this adds to the idea of the field being generated by a molten core - a solid core with a relic field wouldn't produce such complex behaviour.

In the northern hemisphere are massive expanses of plains, formed by ultra runny komatiite lava, that hasn't been seen on Earth for billions of years. This lava came pouring out of twenty five kilometre long cracks in the crust, and spread to cover six percent of the planets surface. And these lavas are deep - up to two kilometres, judging by the remains of the craters buried underneath them.

In other areas there are very, very strange hollows - clusters of them. These are like nothing geologists have ever seen, on Earth or any other planet. They are bluer in colour than the rest of Mercury, they look fresh, they occur in places where there's no sign of recent volcanic activity. In fact, as one member of the MESSENGER team has said: "There's a distinct possibility [these hollows] are active today."

That would make Mercury geologically active - although we still have no firm idea of what kind of active geology is forming these things.

These pits look as though something blasted its way up from the subsurface, and one of the leading theories right now is that subsurface deposits of something volatile did just that: Something in the rocks is affected by either the solar wind or the Suns intense heat, and breaks down, either erupting through the crust as a gas, or leading to massive rock collapse as the stones chemical structure falls apart. Or both.

Image above: Mercury looks like it's going rotten, like the surface of a an old tomato going mouldy. Although the mould is tens of kilometres across, and is actually huge pits in the ground that are opening for no apparent reason. But it sure looks like blue mould. Image courtesy of NASA.

There has long been a huge question mark hanging over the poles of Mercury. Not literally, although - as there is a huge hexagon imprinted on Saturn's south pole - I suppose we should never rule anything out. But radar probing from Earth has long shown something that looks suspiciously like ice at the bottom of some of the polar craters.

Messenger has been able to confirm that these mystery deposits are only found at the bottom of craters of eternal night, where the Sun never, ever rises above the crater rim mountains. That's not proof of water, but it is suggestive, and MESSENGER is equipped with a neutron spectrometer that should find out for sure

Image above: Some of the radar bright deposits, hidden in the bottom of eternally dark craters. Left image from NRAO, Muhleman, 1992; right north polar image from Harmon, NAIC, 2000.

The overall chemical composition of Mercury is different to the other terrestrial planets, and measurements of the ratio of potassium to thorium show that the planet had a cooler past than expected, and may retain a supply of volatile materials. In fact this puts a lot of theories of how Mercury grew back to the drawing board -  and suggests that the little planet might have grown from metal rich chondrite asteroids.

In fact it's been back to the drawing board for a lot of our assumptions about Mercury. And I couldn't be more thrilled to have bunch of new mysteries to wonder over.....

Wednesday 25 July 2012

Magnets forged in supernova.....

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I love magnets. A great time waster is to make up some ferrofluid [1], get a nice strong rare earth magnet [2], and just muck about.

Video above: These things, made using elctromagnets, are called Morpho towers [3]. Video courtesy of  Sachiko Kodama.

But sometimes the universe takes things a bit far.

A perfect example of this is the magnetar [4]: a rare type of neutron star [5]. Neutron stars take the word 'extreme' and run with it anyway. Born in the supernova deaths of the most massive stars in the universe, they are so dense that a pinhead of their matter would outweigh a supertanker. Their surface gravity is a hundred billion times stronger than Earths - strong enough to visibly warp the starlight that passes too close to them. Magnetars add a new trick to the act - the most insanely powerful magnetic fields known to exist.

The magnetic field of Earth is about fifty microtelsas. A good rare earth magnet is about one tesla. The most powerfull magnetic fields [6] created on Earth are around a hundred tesla.

Magnetars field reaches about ten gigateslas. That would erase your credit card at a distance of a hundred thousand kilometres. It would tear you apart - due to the diamagnetism of your bodies water [7] - at a thousand kilometres. The field is so strong [8] it turns the surface of the magnetar into a place, so strange, it's hard to credit they are part of the same universe as Earth. Under the influence of that hurricane field space becomes birefringent [9]. Photons - particles of radiation - perform weird acrobatics. Atoms stretch out tubular - I have no idea what what effect that will have on rules of chemistry, but I'd bet on oddness.

To make these objects even more fun, their unstable: Their internal magnetic field gets twisted up by their own rotation, until the energy it's stored gets released in a massive starquake. Unlike an earthquake, one of the side effects of a magnetars starquake is the release of a massive pulse of gamma rays*.

We've learned to study them: As well as massive gamma ray flares the magnetars field decays away as X-rays, reducing down to the .... frankly still insanely high.......  strength of an ordinary neutron star over tens of thousands of years.

Only twenty or so confirmed magnetars have been found - and now there's a new twist in this tale of warped space time and supernova powered magnets:  A new breed of neutron star, that is 'normal' on the outside, but hides the colossal field of a magnetar on the inside, has been coming to light. Astrophysicist are calling these 'low field magnetars [10]' because their external fields are comparatively weak. But their internal fields are still magnetar strength, and when they star quake X-rays come pouring out of cracks in their crusts.

Video above: A visualisation of how the internal magnetic field, of a low field magnetar, re-aligns. Since all that stored energy has to go somewhere it comes pouring out as X-rays. Video courtesy of ESA.

We have only found two of these hybrids, and one in particular has been scrutinised by...well let's see...NASA’s Rossi X-Ray Timing Explorer, the Chandra X-ray Observatory, ESA’s XMM-Newton, Japan’s Suzaku satellite, as well as the ground-based Gran Telescopio Canarias and the Green Bank Telescope.

From this, you might get the impression astronomers are quite interested in these things.

The reason for all this attention has been that, until April of this year, it was going through a sort of 'slow burn' starquake, giving off X-rays instead of higher energy gamma rays, allowing this weird member of a weird species of object to be studied in detail.

The existence of these hybrids suggests that magnetars may be just a phase that some neutron stars go through. That would mean that many of the neutron stars we know of might be hiding a magnetar like inner core, or might have had phases of magnetar like behaviour in the past. And that adds to their usefulness - by studying neutron stars, even from great distances, we can learn how the laws of physics act under unimaginably extreme conditions, which all adds to our knowledge of how the universe (including things that happen here on Earth) works. Adding the most intense magnetic fields in the galaxy to neutron stars makes for nice icing on the cake.

And it's a good thought -  that some of the most deadly objects in the universe can actually help us to learn about it.....

* What zapped Bruce Banner to turn him into Hulk. Although that doesn't actually work. As far as I know.

List of links:


Sunday 22 July 2012

Dry planet

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Why is Earth so dry? OK, I realise that this is a bit of U turn when, not so long ago, I ran a story about how much water Earth has gained [1] from asteroids and comets. But here's the kicker - at least some large percentage of the water on Earth was imported by asteroids or comets. And, even with that, Earth is only about than a percent water by weight.

Image above: The huge carbonaceous asteroid Mathilde. Space rocks like these can hold a lot of water within themselves, and are thought to have been the source of much of the water on Earth. Image courtesy of Pearson Prentice Hall, Inc.

That's pointing to a big plot hole in the theories of our planets formation [2]. A plot hole that runs like this:

Earth formed from the protoplanetary disk, of dust and gas and debris around the growing Sun. Within this disk is a temperature boundary called 'the frost line', running around the Sun: If you're outside it, things are cold, water can condense to form solid ice, and massive amounts of water should get incorporated to any growing body. If you are inside it things are warm, water cannot condense, and anything that grows in that area is dry.

Video above: a very cool artist impression of the solar system forming out of the protoplanetary disk. Why is it in here? Why not? Video courtesy of University of Copenhagen/Lars Buchhave.

Yes, Earth was born from the collision between two protoplanets [3], which should have dried it out a bit. Temperatures of ten thousand degrees Celsius do that. But our models of planet growth predict that, at least for some of the time, Earth should have been growing beyond the frost line.

So Earth should not merely be wet, with oceans up to eight thousand metres deep. It should be at least ten percent water, potentially with oceans hundreds of kilometres deep.

So what gives?

Well, what gives - paradoxically - is that the young Sun didn't heat the protoplanetary disk as well as we thought. In the previous models of the accretion disk, the material near the inner edge of the disk is fully ionised [4] -  which allows the Suns magnetic field to gulp matter down [5] onto its surface. While this is going on the inner disk is hot. But this phase doesn't last long enough for a planet like Earth to grow, and when it ends the disk cools, the frost line migrates inwards, and the Earth should be growing in a region where water ice is abundant.

A Tale of Two Disk Models

Image above: The standard model of the protoplanetary disk, and the new model. The 'dead zone' around the Sun heats up by gravity, and actually warms more of ther disk than the Sun could. Image courtesy of [6]
In a new version of the model [7], the Sun doesn't have enough power to fully ionise the inner disk, so it can't scoop material off the inner edge. Dust and gas builds up on the inner edge, and it heats up of its own accord, by gravitational compression [8]. This heat source is steady, and warms the inner disk for long enough to keep the region Earth grows in dry.


*If simple means years of painstaking work, simulations run on a super computer, all checked against observations of young star systems by the Hubble Space Telescope [9].

List of links:

Friday 20 July 2012

The Valley of Ghosts...

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The Moon has a complex, violent history. And, although it was born from Earth [1], it has always been a very alien world. 

 Image above: The Schroter Valley, as seen from orbit by the crew of Apollo 15. No sniggering, you aren't ten. Unless you are. In which case go for it - but remember: A silly name doesn't make this place any less terrible and fascinating. Image courtesy of NASA.

Nowhere is a better example of this than the Schroter valley [2]*: Carved into the Aristarchus plateau, the one hundred and eighty five kilometre long valley is the longest ‘sinuous rille [3]' on the Moon  Starting at Cobras head, a six kilometre wide hole in crust, the valley snakes through the lunar rock, first north, then north-east, then south, until it crosses the kilometre high drop into Oceanus Procellarum - a sea of crystallised lava..

Off to the east is the ultra bright, 40 kilometre wide Aristarchus crater [4] - for which the plateau is named - and south of there lies a set of smaller valleys: The 121 kilometre long Rimae Aristarchus.

Though the Moon is a smaller world than Earth, Schroter shows that it likes its geology big: In places the valley is ten kilometres wide, a kilometre deep, and has a second, smaller, track carved along it's bed [5].

Take a good look at it. Looks an awful lot like a river, doesn't it?

Video above: A virtual flyover of the two kilometre high Aristarchus plain, built from images by the Hubble Space Telescope. Video courtesy of NASA/Goddard Space Flight Center Scientific Visualization Studio.

That impression isn't wrong - we just have to abandon one preconception: That the river ran with water. Lunar rivers didn't. 

They ran with molten rock. 
Many researchers believe they ran with komatiite [6] - a very hot, very runny lava, not seen on Earth for three billion years. Because of its high temperature, turbulence, and ability to flow komatiite would have eroded the lunar soil much more effectively than regular lava, which tends to build up (more like cold syrup - yum) -  leading to a river like valley, rather than a frozen lava flow.

The smaller channel cut into the base of Schroter is a mystery - the best guess to date is that the komatiite flow slowed to a trickle, dribbling along the bottom of the older channel. It's hard to tell for sure without being able to visit - as the cancelled Apollo eighteen expedition would have done. 
But bizarre geology, with no 'living' counterpart on Earth, isn't the only strange thing about this valley. Schroter has the third highest rate for Transient Lunar Phenomena [7] on the whole Moon. And there's a chance that the whole Aristarchus plain isn't as geologically dead as it seems... 

TLP's are sudden, short lived, changes in the brightness of the lunar surface. Lots of explanations have been put forward, from good old 'you're imagining it' to telescope lens flares, to meteorite impacts. 

Image above: A TLP (the bright spot in the middle), caught on camera by Leon Stuart, in 1953. Image courtesy of Columbia University.
Many scientists are still sceptical about TLPs. But a statistical analysis [8], by Arlin Crotts of the University of  Columbia, suggests that there is reality to many reports. The Apollo missions reported signs of radon gas [9], leaking from the Moons interior - from some of the same locations [10] TLP's are often reported.

To researchers like Crotts that suggests an explanation: Ancient, radon bearing, gas builds up just beneath the Moons surface, until it burbs its way out in a cloud of dust. Voila, one TLP.  
Is the Aristuchus plain where the ghosts of the Moons fiery past are seeping to the surface? It's hard to be sure. There are oddly fresh patches [11] of the Moon, that may well have been shaped by gas [12] eruptions, as little as a million years ago.

Image above: The strange Ina formation, which shows a very young (by which I mean less incredibly old) surface - suggesting it may have been altered by recent geological activity. Image courtesy of NASA.

Until we can get back to the lunar ground [13], to do some close up work on the rocks, places like Schroter and Aristachus will keep their secrets.... it's nice to hear that ESA's lunar lander mission [14] is making progress.

Video above: A run down on the ESA lunar lander mission, the first European attempt to soft land a robot on the Moon. Video courtesy of ESA.

....not to mention the Google Lunar X-prize [15] contestants....

Video above: The announcement for the Google Lunar X-prize contestants. Gist of it is: The Moon is brilliant, lets start exploring it again. Well said. Though my version is quicker. Video courtesy of Google.

...who intend to land there for a pittance. Or perhaps a pittance plus a few million quid.

But the point is this: The Moon might not be the dead place we thought. And it is certainly alive in a lot of peoples hopes....

* Yes, I was once ten as well, I know what it sounds like.Go on, giggle if you have to. People will stare if you're reading this on the train though.....

List of links:

Thursday 19 July 2012

Worlds lost in time: The Ancient Moon

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Firstly, my apologies for the patchy blogging this week - that annoying real life stuff has been getting in the way.

Now: This week the 2012 Lunar Science Forum [1]is on - and some one at work has asked me  "So it's all about craters then?"

Looking at the Moon today, you'd be forgiven* for thinking that it had never seen anything more than asteroid strikes.

You'd be wrong - the Moon, for hundreds of millions of years, was world in geological agony.

The Earth and Moon were born from a massive collision [2] between a Mars sized protoplanet, and an Earth-sized world called Theia. The blast briefly outshone the Sun, and may have exceeded ten thousand degrees Celsius. So the Moon formed hot. As it cooled, it began to crystallise - the heavy materials, like pyroxene [3], sank into its core, and the lighter ones floated to the surface and solidified as its crust.

Video above: A potted history of the Moon, as revealed by the new clues from NASA's Lunar Recconasiaence Orbiter space craft. Video courtesy of NASA Goddard Space Flight Center.

That was the just the beginning: Fifty kilometres beneath the surface, the Moon was still molten, and the crust faulted and cracked - under its own stresses, and under the massive asteroid impacts.

The Moon became a world of  many small volcanoes -  lunar lava is very runny and doesn't pile up into huge mountains well.... 

Image above: Twin lunar volcanoes, photographed by the Lunar Reconnaissance Orbiter. They're only about a mile across each. Aren't they  sweet? Awwww........ What? Image courtesy of NASA/JPL

...which meant the surface was covered in rivers of molten rock, hundreds of kilometres long...

Image above: Both volcanism and impacts can melt enough rock to produce rivers of runny lunar lava: This one flowed from the site of the impact that created Tycho crater, and ends in a small lake of once molten rock on the right.. Image courtesy of NASA/JPL. 

....these flooded the low lying areas, creating the dark areas you can see from Earth: 'Maria' or plains flooded with magma.....

 Image above: Mare Crisium. The 'Maria' were mistaken for seas in ancient times. There was, in fact, no mistake: They were formed by seas of lava spilling into giant impact basins... Image courtesy of NASA.

....there were massive eruptions of gas rich lava from pyroclastic vents leading into the lunar mantle....

Image above: The dark stain, around the long cold vent, is believed to be the signature of a pyroclastic eruption, where magma containing dissolved gas flowed to the surface. At depth, the gas was kept dissolved by the pressure. Like the carbon dioxide in a sealed cola bottle. Shake the cola bottle, and then open the lid. Now imagiune the lid coming off a volcanic vent, and the cola being magma.
Image courtesy of NASA/GSFC/Arizona State University.

....not that unlike this one.....

Video above: Infra red and visible images of a pyroclastic flow, showing temperatures of up to four hundred degrees Celsius. In all seriousness, if you ever see one of these coming your way, run across its path not directly away - they can out race anything alive. Video courtesy of montserratvolcanoobs via You-tube.

......and these scattered beads of volcanic glass across the plains.....

Image above: Beads of orange volcanic glass under the microscope, bought back to Earth by the Apollo  mission. These beads only form in pyroclastic eruptions, which means erupting gas under pressure, as well as molten rock. Image courtesy of  NASA.

...and, while all this was going on, the surface was getting pummeled to pieces by massive asteroid impacts, forming really, really huge impact craters.

Image above: The Giordano Bruno crater. Image courtesy of NASA/JPL.

This was one very, very active world. The Moon we see today is only a shadow of its former self, but everything the Moon ever did is recorded on its surface. There are signs that some of its volcanoes may have been active for as long as three billion years [4] - and there may have been tectonic activity as little as fifty million years ago [5]. The latest evidence shows the core is still cooling, and as it cools the whole Moon contracts...

Video above: NASA's Lunar Reconnaisience Orbiter has forund evidence of relatively (Thats a geologists relatively, which is even longer than a paleantologists relatively) recent tectonic activity, forming new valleys on the Moon. Video courtesy of NASA Goddard Space Flight Centre

....and asteroids and comets have slammed into the surface, mixing everything [6] into a gigantic geological puzzle.

Isn't mother nature helpful?

And there is so very much we still don't have a clue about, when it comes to out nearest planetary neighbour:

What are the mascons - the massive anomalies [7] in its gravitational field?

 Image above: A map of the Moons odd mass concentrations - mascons - that make it's gravity so uneven that no spacecraft can stay in orbit for long... Image courtesy of NASA.

Why are some areas so enriched with thorium [8]?

 Image above: The patterning of thorium deposits on the Moon. Map courtesy of Nature magazine.

Why did the lava floods affect the nearside of the Moon more than the far-side?

 Image above: The near and far sides of the Moon, as mapped by the Clementine mission. Even though the far side has basins as deep as those of the near side, they didn't become seas of frozen magma. Image courtesy of SDIO/NASA.

How did all that ice [9] get to its poles?

What else is frozen there [10], besides water ice?

How does the ultras thin layer [11] of water molecules on its surface form?

Video above: Archived news report on the discovery, and confirmation, of water in the upper millimetres of the lunar soil, by the Indian Chandraayan 1 space probe. Video via YouTube by NTDTV.

The list goes on, and on, and on and on....

We'll have to go back to the surface to find out....

* Not sufficiently to avoid being bored to tears by yours truly, explaining that there's more to the Moon than that, though.

List of links:

Tuesday 17 July 2012

Waters older than the oceans....

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I blog today from a bus in the Scottish highlands. It's spectacular, but it's a miracle there's any Internet connection at all up here.

So bear with me.

In 1983 a research team led by Jeffrey L Warner, studying samples of stony meteorite [1], found something unusual inside them: Luridly purple salt crystals [2] called Halite - common enough on Earth, but fragile, and seldom found in meteorites.

Inside those crystals they found tiny cavities, only a few microns across (one micron is one thousandth of a millimetre, or about the length of a smallish bacterium).

Image above: A super close-up of a tiny reservoir of water, trapped inside a blue halite (rock-salt) crystal, from the Monahans meteorite. The bit marked 'V' is a bubble of vapour, within the inclusion, and the bit marked 'L' the liquid part.. If you held it up to your ear, would you hear the whisper of ancient underground, that's just tinnitus. Image courtesy of Virginia Tech.

Inside those cavities they found water. Incredibly ancient water, that had been sitting inside the salt crystals for 4.5 billion years. Water carrying chemical clues; to what existence had been like for the rocky parent bodies, and how they had formed.

No.. hang on. I’m starting this story in the middle, aren’t I?

Meteorites, generally, are chips off larger objects: Protoplanets, many of which are thought to have been warm enough for an active geology, melting the ices inside them, and giving rise to subsurface water flows.

Water is an excellent carrier for chemical reactions, that’s why your insanely chemically complex body is better than three quarters water. So, when immersed in water, things could happen that otherwise wouldn’t have, especially if that water is saturated enough with something that crystals of it start to grow – and so the wet, underground rocks on these protoplanets began to grow salt crystals.

Crystals are funny things: They grow, they seed off pieces of themselves, and as they grow, sometimes a tiny bubble of the water they’re growing out of gets trapped on all sides by crystal, without filling up with crystal itself - Geologists call this a ‘fluid inclusion’

Image above: Protoplanets running into each other head first, at speed -  that's why the sky is full of rocks!

Then the protoplanet gets run into by something big: Another protoplanet, and possibly big enough to do totally pulverise it, scattering rocks across space.

Four and bit billion years go by. The rocks are preserved by the vacuum of space. Then a huge wall of green-blue makes an appearance – Earth. And a few minutes of violence, heat, and plasma later the rock is sitting on Terra Firma, for the first time in longer than the age of our world.

The rocks get picked up by one of the meteorite hunting expeditions that scour the ground after a large meteorite is seen, and get given names, like…. um, ALHA 77256. Well, no-one said life would be fair.

Research monkeys* chopped the rocks up, and looked at them with microscopes, electron microscopes, Raman spectrometers [5], and ion microprobes [6]. They found the water, still waiting, after all that time.

And, because the water still contains the chemicals that were reacting in it when the crystal formed, that water is a snapshot of what was going on at that time. Even if it’s only the tiniest droplet.

Since Jeffrey Warner looked into those salt crystals [3], fluid inclusions have been found in a wide variety of meteorites, including the carbon rich rocks [4] that are thought to preserve the earliest materials and processes of the solar system.

What have they taught us?

The most important thing, is how hot the waters were: Some rocks show that they were rinsed by waters up to one hundred and fifty degrees Celsius. Others were never warmed above thirty. Ther’re suggestions that the water ebbed and returned, causing episodes of crystal growth. These waters were rich in salts, and contained carbon based chemistry, even in the relatively carbon-compound poor ordinary chondritic meteorites. Through these measurements we are beginning to build up a picture of the character, history, and processes, at play on these worlds that were gone long before the Sun rose over a molten early Earth.

Scientists hope for more: The fluid bubbles might act as time capsules, preserving structures such as organic carbon globules from the pre-solar nebula.

A four point five billion year journey, carrying capsules of water from deep space, delivering us on Earth the story of a long dead world.

Not a bad result, for someone pausing to pick up a rock lying on the floor….

List of links:


Sunday 15 July 2012

Not alone......

When people think of the asteroids*, they probably think of a nice, doughnut shaped, belt of a few thousand rocks going around the Sun in ...well, a nice, well behaved, doughnut shape.

It's not like that. It's a snowstorm, with snowflakes up to nine hundred kilometres wide. 

So, ladies and gentlemen, I present to you a youtube 'map': The asteroids of the inner solar system, in the order they were discovered, from 1980 to the present day. New discoveries in white, main belt asteroids in green, non-threatening Earth approachers in orange, potentially hazardous Earth crossers in red.

Stick with it until the end - put the video to full screen, in a dark room, for maximum effect. Then look up at the sky, and remember how damn crowded it is.....

Video above: A map of the inner solar system, showing the discovery of asteroids from 1980 to the present day. That's a lot of rocks. What really strikes me, though, is that by the end of the animation all the terrestrial planets are embedded in a swirling disk of flying rocks! It's worth remembering:  These blips are the remnants of the Suns protoplanetary disk  that gave birth to all the planets... Video courtesy of Scott Manley

As the automated sky surveys come on-line in the mid 1990s the count rate rockets, and around 2010 you can see the pattern of finds changes to one more parallel with direction of motion of Earth - that's the WISE space observatory coming on-line. And yes, I've posted this before, but this is the high definition, updated version...

Complex Dust Disk, Expected Birthplace of Planets, Around Star HD 141569A
Image above: Protoplanetary disks around star HD 141569A. Yes, it looks light pretty swirls of light, but what you're standing on right now came out of something a lot like that - and the asteroids are the leftovers. Image courtesy of [4].

Most of those rocks are less than half a kilometre across - which is plenty big enough to ruin your country, and there are lot of bigger ones. But although we do need to be aware of the potential hazard, those fragments of shattered protoplanets are an incredible scientific, and potentially material, resource.

And, from time to time, they treat us to spectacular displays of small fireworks.....

Video above: The Leonid meteor shower - the Leonids are a stream of dust and debris left behind by comet Tempel-Tuttle, so what you're seeing here are pieces of comet raining out of the sky. That's fine, and beautiful. Whole comets raining out of the sky would be more of a problem... Video courtesy of

......Big fireworks.....

Video above: A huge meteorite explodes over south Africa, and gets caught on CCTV. The explosive force of such an 'air-burst' is usually comparable to a small nuke, but the meteorite goes bye-bye so far above the ground the damage is nil. Footage uploaded to youtube by knightskross

.......And leave us clues to what things are like beyond our blue skies.....

Image above: A cut and polished nickel-iron meteorite, showing the strange Thomson structure that occurs when the metal has cooled very, very, slowy, under microgravity - which means in the dying core of a protoplanet. Bits of the iron cores of protoplanets just fall out of the sky! But it's too rare to justify always wearing a hard hat. And a hard hat wouldn't be much good against most of these things anyway. 
But if you just like hard hats, feel free.......Image courtesy of The National Museum of Wales.
.... as well as likely delivering water , and the organic chemistry life is based on, to Earth.

So, if anyone ever tells you space is empty, do them a favour: Point them in the direction of the top video, and ask them how that qualifies as 'empty'...

* I  realise that most people don't think about asteroids on a daily basis. Look at that video - that's enough to get me thinking....