Monday, 29 November 2010

Another quick note:


Image above: Asteroid Itokawa, Hayabusas target. Image courtesy of JAXA

[1]Hayabusa goes from strength to strength! The [2]Yomiuri newspaper reports that the second of the sample return canisters contains hundreds of grains, thought to be from Itokakwa. The grains range in size from a tenth to a hundredth of a millimeter.Apparently they turned the container upside down and shocked it (I think that means tapped it) and the things just fell out! Thanks to [3]Pandaneko over on unmannedspaceflight.com for tipping us non-japenese speakers off.

List of links:
[1]http://www.jaxa.jp/projects/sat/muses_c/index_e.html
[2]http://www.yomiuri.co.jp/dy/
[3]http://www.unmannedspaceflight.com/index.php?s=&showtopic=6648&view=findpost&p=167194

Friday, 26 November 2010

Bad tummy!

Image courtesy of city-data.com

My apologies for what will be a bit of a delay ( a few days only I hope) before my next post; My daughter and I both have tummy bugs and a 1 year old with a bad tummy is very time and energy consuming. But I can't miss pointing out this story on space.com : It seems that new born stars and the deadliest of stellar corpses, black holes, share some things in common. I wonder what this means for our own Suns youth?

List of link:
http://www.space.com/scienceastronomy/star-cosmic-jets-light-speed-101125.html

Saturday, 20 November 2010

Stories of fragments and fragments of stories...

I have a few items sitting in my 'half written' pile that I'd like to mention but don't have enough detail on to write up in full. So here, in the spirit of jumbled collections of things (from asteroid rubble piles to dirty laundry), is a collection of stories of fragments and fragments of stories for your perusal:

Firstly, it is with sadness that I note the passing of Brian Marsden, former director of the minor planet centre. A full obituary can be found [1]here. He died aged 73.


Image above: From left to right, Dan Greene, Allan Hale, Charles Morris, Brian Marsden. Image courtesy of Comethunter.de.

I am also saddened to note the passing of Allan Sandage. He was one of the mot prominent researchers into observational cosmology, and a former assistant to Edwin Hubble. The Carnegie Observatory has [2]a full obituary here. He died aged 84.


Image above: Allen Sandage. Image courtesy of the Carnegie Observatory.

On a happier note there is some great news from Japan:

Hayabusa has collected pieces of asteroid Itokawa:
This has been a good couple of weeks for missions to small solar system bodies: Last week we had the successful  Deep impact flyby of comet Hartley 2 (more on that in a sec). This week [3]JAXA, the Japanese space exploration agency, have announced that its epic, disaster dodging [4]Hayabusa space mission has succeeded in bringing home fragments of the tiny stony asteroid [5]Itokawa.

Image left: Asteroid Itokawa and the international space station to scale. Image courtesy of JAXA/NASA

Hayabusa was launched in early 2003 to fly, using ion engines, to 500 meter long Itokawa and study its make up and  structure. The craft then landed on the lonely peanut shaped fragment of matter and tried to collect a sample of its surface. The images and spectrometer data from the mission have already changed our understanding of small asteroids, revealing that Itokawa was a [6]pile of rubble covered with odd looking smooth patches. The spacecraft itself has [7]flight proven new technologies like the [8]ion engines. Now the cake has its icing, and JAXA can truly claim Hayabusa rests in a state of 'mission accomplished'.

The word Hayabusa means peregrine falcon, and this Japanese mission to bring home fragments of an asteroid has indeed soared. But perhaps it ought to have been named 'plucky little phoenix'  for Hayabusa suffered set back after setback and returned from the edge: [9]Huge radiation storms, [10]malfunctioning ion engines, [11]faulty sample collection mechanisms, and then an agonising wait after its a sample return capsule made it back to Earth while JAXA scientists tried to determine if any of the ultra fine dust found in the pod was indeed from the asteroid.



Video above: Hayabusa is immolated in the upper atmosphere, as the sample return capsule returns to Earth. Courtesy of Fairfax Media.

Well [12]JAXA have announced that most of the 1500 or so micron sized dust grains are from asteroid Itokawa. [13]By comparing the grains in the capsule to the rocks and fine particles found at the launch site and the landing site the science team were able to rule out terrestrial contamination. In particular the  ratio of iron to magnesium is a much better match for Itokawa ( as measured by the probe) than for Earth rock.
Most of the grains are less than 10 microns (0.01 mm) across, making them difficult, but not impossible, to analyse. In addition the Japanese [14]Asahi news paper reports that 50 or 60 larger particles with sizes from 0.01mm to 0.1 mm have been recovered.  And this is just pod A, Pod B has yet to be opened!
Which means that the Hayabusa mission and team have made it, perhaps tired and bruised but made it, across their final finishing marker......

Hartley 2 flies in a swarm of snowballs:

Getting back to Deep Impact and Hartley 2: Wednesday saw a [15]NASA press briefing revealing some more results from [16]last weeks flyby of comet Hartley 2: Things just get more interesting. Firstly the CO2 coming from either end of this deep space wanderer is confirmed, and to make the picture more complex the smooth neck connecting the two lobes is emitting water vapour more like a regular comet. This comet seems to have something of a Jekyll and Hyde personality.


Image above: Infra red images tuned to detect the various components of the blizzard coming off of Hartley 2's tiny surface. Image courtesy of NASA/JPL

 And then the plot thickens further: the CO2 jest have liberated  'snowballs', or particles of ice from golf to football size which are fired off into space by the jets:
"When we first saw all the specks surrounding the nucleus, our mouths dropped," said Pete Schultz, EPOXI mission co-investigator at Brown University. "Stereo images reveal there are snowballs in front and behind the nucleus, making it look like a scene in one of those crystal snow globes."



Video above: Chunks of ice and snow whirl through Hartley 2's tenuous coma. Courtesy of NASA/JPL-Caltech/UMD/Brown.

The probe even bulldozed through a number of 'snowflakes'. There is little doubt that the data from Hartley 2 will be getting more interesting still.....

Study of protoplanetary disks takes a step forwards:

Two Masters students, Rik van Lieshout and Tullio Bagnol, for the [17]University of Amsterdam's (UvA) Anton [18]Pannekoek Astronomical Institute (IAP) have used a new instrument to produce a [19]detailed study of a protoplanetary disk around a [20]Herbig Be star, a star withe around six times the mass of our sun.

The IAP specialises in the study of stars living in a dusty environment- whether these be [21]elderly stars belching ash into space or [22]sputtering young ones still gnawing at the [23]remnants of their birthplaces. The two students, overseen by Professor Rens Waters, were exploring the question of whether or not a star so much chunkier than the Sun could still form planets. To look for clues they chose to study the nature of the disk around a star called MWC 142, and the students have manged to wring a remarkable amount of data on this place form the relatively meager amount of light that makes the journey here to Earth. The star is surrounded by a protoplanetary disk, and by measuring the spectrum of light coming from parts of the disk at different distances from the central star the two intrepid explorers have shown that the pancake flat inner disk is composed only of gasses.


Image right: A rendering of the structure of the protoplanetary disk around MWC 142. Image courtesy of the University of Amsterdam.

This confirms models of disk structure around such stars, which predict that the Herbig Be stars radiation should vapourise all dust particles within a distance roughly the same as the orbit of Mars. This is important to the study of other , older , star systems of the same type as we now know that any planets found within that distance must be immigrants from the outer parts of that star system.
The students were also able to measure the shape of the disk: the inner disk is a flat as an Amsterdam pancake, though not perhaps as tasty, and the outer disk is flared at the edges. From the intensity of one of the emission lines corresponding to magnesium the students are even able to have a stab at how far from the surface of the star the inner edge of the disk lies - they find it to be about a tenth of an astronomical unit.

The press release mysteriously mentions that the study was done using a 'new instrument' developed by staff from K.U Leuven. A bit of research and background reading leads me to believe that the new instrument is probably a device named [24]HERMES.


Image left: The HERMES adaptor attached to the Mercator telescope. Image courtesy of the Catholic University of Leuven.

HERMES ([25]High Efficiency, high-Resolution Mercator Echelle Spectrograph) and was built by the IvS ([26]Catholic University of Leuven), the IAA ([27]Institut d’Astronomie et d’Astrophysique, Universit√© Libre de Bruxelles), the [28]Royal Observatory of Belgium and smaller partners of the [29]Landessternwarte Tautenburg (Germany) and the [30]Geneva Observatory (Switzerland). HERMES is a [31]spectrograph, a device that spreads the incoming light into a spectrum, and measures the intensity of various wavelengths within that spectrum with great sensitivity, and in this case unprecedented [32]spectral resolution.

Image above: The Roque de los Muchachos Observatory sits atop its mountain eyerie on La Palma island. Image courtesy of JPL/NASA.

Image right: The Mercator telescope in full. Image courtesy of the Catholic University of Leuven

It is attached to the [33]1.2 meter Mercator telescope at [34]Roque de los Muchachos Observatory on La Palma Island, on the Canary islands. The size of the telescope used in this study is a humdinger advance in itself - before now studies of disks around other stars have only been possible with space based instruments, or the largest telescopes here on Earth. That a [35]relative lightweight like the the Mercator can now study the protoplanetary disk around a distant star promises a slew of further enlightenment on the growth of solar systems.

Whizzing fragments and sundry beauty:

......in other news [36]asteroid hunters spotted a space rock only ten feet across that buzzed Earth this week: The little scamp, called 2010 WA, is zero threat but it is a good example of how searches for asteroids crossing Earths path are becoming more sensitive. Despite being tiny 2010 WA is not as dull as you might think; it tunrs out that [37]it has the second fastest rate of spin of any asteroid measured to date, and is surpisingly light in colour.....

.....And, while it has nothing directly to do with the Ancient Solar System this stunning (real life) image, taken in the cupola of the [38]International Space Station is just too succulent to pass unmentioned:

Image above: Tracy Caldwell Dyson ponders the Earth below her. This looks like it should be on the cover of Alastiar Reynolds latest book! Image courtesy of JPL/NASA.

[39]Read 'blue' by Stuart Atkinson on universetoday.com.

I hope you enjoyed the mish of mash -  next week back to something a bit more focused: Remnants of an age when our solar system was home to hundreds of active terrestrial planets......

List of links:
[1]http://www.minorplanetcenter.org/mpec/K10/K10W10.html
[2]http://obs.carnegiescience.edu/research/asandage/
[3]http://www.jaxa.jp/index_e.html
[4]http://www.jaxa.jp/projects/sat/muses_c/index_e.html
[5]http://www.daviddarling.info/encyclopedia/I/Itokawa.html
[6]http://www.newscientist.com/article/dn9257-rubbly-itokawa-revealed-as-impossible-asteroid.html
[7]http://www.hayabusa.isas.jaxa.jp/e/index_31.html
[8]http://www.jaxa.jp/article/special/hayabusa/kuninaka_e.html
[9]http://science.nasa.gov/missions/hyabusa/
[10]http://www.spacedaily.com/reports/Asteroid_Explorer_HAYABUSA_Ion_Engine_Anomaly_999.html
[11]http://www.universetoday.com/44642/hard-luck-hayabusa-in-more-trouble/
[12]http://www.jaxa.jp/press/2010/11/20101116_hayabusa_e.html
[13]http://www.planetary.org/blog/article/00002779/
[14]http://www.asahi.com/information/english/
[15]http://www.nasa.gov/mission_pages/epoxi/epoxi20101118.html
[16]http://epoxi.umd.edu/7press/news/20101104.shtml
[17]http://www.english.uva.nl/start.cfm
[18]http://www.astro.uva.nl/
[19]http://www.english.uva.nl/news/news.cfm/C8C8F4CC-04A5-4159-A821477397170075
[20]http://www.daviddarling.info/encyclopedia/H/Herbig_AeBe_star.html
[21]http://www.daviddarling.info/encyclopedia/C/carbon_star.html
[22]http://www.universetoday.com/24802/t-tauri-star/
[23]http://www.physorg.com/news194877369.html
[24]http://hermes.ster.kuleuven.ac.be/papers/HermesSpie2004.pdf
[25]http://www.mercator.iac.es/instruments/hermes/
[26]http://www.kuleuven.be/
[27]http://translate.google.co.uk/translate?hl=en&sl=fr&u=http://www.ulb.ac.be/rech/inventaire/unites/ULB105.html&ei=z63lTOrdA4WAhQfJz6TdDA&sa=X&oi=translate&ct=result&resnum=2&ved=0CCcQ7gEwAQ&prev=/search%3Fq%3DInstitut%2Bd%25E2%2580%2599Astronomie%2Bet%2Bd%25E2%2580%2599Astrophysique%26hl%3Den%26rlz%3D1T4MEDB_enGB318GB331%26prmd%3Div
[28]http://www.astro.oma.be/
[29]http://translate.google.co.uk/translate?hl=en&sl=de&u=http://www.tls-tautenburg.de/&ei=Mq7lTMCbA5yAhAfn6p3cDA&sa=X&oi=translate&ct=result&resnum=1&ved=0CB0Q7gEwAA&prev=/search%3Fq%3DLandessternwarte%2BTautenburg%26hl%3Den%26rlz%3D1T4MEDB_enGB318GB331%26prmd%3Div
[30]http://www.unige.ch/sciences/astro/an/
[31]http://outreach.atnf.csiro.au/education/senior/astrophysics/spectrographs.html
[32]http://www.lightforminc.com/Spectral_Resolution/index.html
[33]http://www.mercator.iac.es/general/presentation
[34]http://www.ing.iac.es/PR/tour/orm.html
[35]http://www.wired.com/wiredscience/2008/04/the-race-to-bui/
[36]http://www.space.com/spacewatch/small-asteroid--passing-earth-101116.html
[37]http://www.space.com/scienceastronomy/tiny-asteroid-passing-earth-spins-fast-101120.html
[38]http://www.nasa.gov/mission_pages/station/main/index.html
[39]http://www.universetoday.com/78802/stunning-image-heartfelt-poetry-could-become-icons-of-space-age/

Tuesday, 9 November 2010

Hartley 2 roundup: A dry ice comet?

All links are numbered, and listed at the end.

Last week, as most space nuts can tell you, [1]the cunningly re purposed Deep Impact spacecraft and its veteran control team managed to blast past the core of comet [2]Hartley 2. The probe took images by the thousand, and [3]infrared spectral data by the bucket, which will be keeping researchers busy for decades.

Right: The Deep Impact spacecraft, undergoing preparation at Ball Aerospace. Image courtesy of Ball Aerospace.

The probe, and the team, have performed amazingly well. The team has made this look easy- but its not! The Deep Impact craft shot by the comet at around 27,000 miles an hour and the pointing and programming of [4]the imaging sensors had to be bang on. The probe has, over the whole course of the flyby delivered tens of thousands of images, 23,000 from the medium resolution imager alone, and all told they plan to bring down 120,000 images.

The probe was launched in 2005 to explore comet Tempel 1 in a unique way: by bombing it with a huge copper projectile, blasting parts of its subsurface into space where the flyby probe ( the Deep Impact craft proper ) could scan it.

Image above: Deep Impact watches as a copper slug slams into the crust of comet Tempel 1. Image courtesy of Cal tech.

[5]The initial mission was a resounding success, and it transpired that the robot explorer had enough fuel in its tanks for another mission. Originally the craft was to fly to [6]comet Boethin, but this comet has basically vanished, so Deep impact was re targeted to Hartley 2.
The extended mission has been dual purpose; prior to the approach to Hartley 2 the spacecraft was using its telescopes to [7]search nearby stars for exoplanets

Why comets? Why Hartley 2?


Image above: Comet Hartley 2, as seen from Earth in this long exposure. Image courtesy of JPL. 

Comets are complex and constantly changing places, despite their small size. Among the most often quoted reasons for their study are: To study the carbon ([8]possibly pre-biological) chemistry that goes on in them and on their surfaces, to learn about their origins and how they fit into the history of our solar system, to decipher their structure and composition, to find out [9]what they contributed to the chemistry of early earth, and to (hopefully) understand how one on a collision course with us could be deflected or destroyed.

Image above: In 1908 [10]a comet core came down over Tunguska, Siberia. Only a small one, around 50 meters across, and it detonated before it hit the ground; but the blast did this to a thousand acres of forest. Such events are thankfully very rare. Image courtesy of Time Magazine.

Comets are the ancient solar system in capsule form, and part of the history of Earth, and perhaps the chemistry that gave rise to life in the bargain. And they keep throwing us [11]curve balls, which makes scientist all the more eager.

Which comet was question of what Deep Impact could reach with its remaining fuel reserves. Originally comet Boethin was to be targeted, but it disappeared, perhaps because it disintegrated naturally - comets are unstable things made of material that can be [12]less strong than fresh snowfall.

Hartley 2 was picked specifically because a small, cheekily active, comet like this had never been seen up close before. The science team are hoping that the comparison will help them determine which parts of the comets are due to ongoing processes, and which are relics from ancient times that can inform us on how the solar system formed, and what role comets played in that.

The price is also something worth boasting about: By re-using an existing spacecraft NASA has been able to pull off a [13]discovery class space mission for a tenth of the normal cost (around $40 million US compared to $350 million US for a full mission)- here's to many more examples of lowering the cost of visiting new worlds by using our heads!

So what has [14]Deep Impact/Epoxi found?

To kick off a review of the very very preliminary findings, we go straight to the horses mouth:



Video above : The press briefings on the preliminary results of the EPOXI mission. Courtesy of NASA/JPL/UMD.

The first thing that strikes me is the feel of this press conference: They've done something amazing and they know it! The elation in the clip shown of the control room  just as the first image came down is palpable, and flows out of the recording into the press conference. The human experience is important- that elation at those 'exploration moments' and seeing something never seen before- it is the reason why so many people find space exploration so compelling! The comment by Ed Weiler: "This is not virtual, this is Earth seeing the nucleus of Hartley 2 for the first time" sums it up well.

The science return will take a long time to work through, but even on approach the surprises began to mount up. Even from a distance the the could tell that the nucleus wasn't a nice spherical shape, by watching the jets coming from the comet. Data from scans run by the mighty [15]Arecibo radio dish seemed to [16]confirm this.

But a much bigger surprise followed: The emission of dust grains seems to be tied to the emission of dry ice- frozen CO2, the gas humans exhale when we breath. This suggests that the most active region of the comet is not powered by sublimating water, but [17]by primordial CO2, something that is literally unheard of for a comet. [18]On most comets the main gas being released is water vapour - and [19]water is present in this comet. But the water does not seem to go up and down with the dust emission anything like as much as the CO2 does.

As Deep impact tore towards the chunk of ices and organic chemistry the [20]crafts infrared spectrometer measured a huge spike in the abundance of the gas cyanogen, but there was no accompanying release of dust particles, making it a mystery how this gas was released (jets would have released dust particles to). Exactly what this means isn't yet clear, but if the origin of the cyanogen can be pinned to a specific area, or specific jets,  then the combined data could give a clearer pictures of how the comet is spinning.

The close up images begin to unravel the story:



Video above: The first five Deep Impact images of the close encounter released have been nicely made into this 5 X real speed video, courtesy of Machi on [21]unmannedspaceflight.com.




Video above: NASA animation of the flyby. Courtesy of NASA/JPL/UMD

The animations show some firsts for space exploration right away: The mission has imaged the jets and the surface features that they are  related to, all at once. Looking at the dumbbell structure of the comet, with a smooth neck connecting two rough surface lobes, it is clear that the jets are coming from the rough, active areas- in fact they appear to be coming from specific features. The team also spots weird 'clumps' of unknown material, which they believe may be the remnants of past activity.

The clumps were a surprise: The smooth area is thought to be fine grains that have collected in the middle, and resembles smooth areas on asteroids, such as [22]Itokawa which was visited by the epic [23]Hayabusa mission. However Hartley 2 is a very different beast than Itokawa, so while the boulders on Itokawa are likely to be rock, the 'clumps' on Hartley 2 are a complete mystery as a frozen comet is mainly ices! Clumps of ice should be seared down to almost nothing by solar radiation sublimating them, leaving a relatively smooth surface.


Image left: An enhanced version of  one of the close flyby images of Hartley 2. The brilliant white columns of jets are clearly visible in daylight, on the terminator, and over the night side of the nucleus. Image courtesy of NASA/JPL/UMD.

The images also show that the jets are running on the day side, on the terminator, and on the night side- as Dr Sunshine says this means the science team has a lot of work to do, as the comet jets are presumed to be driven by heat from the sun! There have been indications of this before, but this is the first clear evidence. Exactly how long the jets can last isn't known, it depends on how the jets end - do they clog up, or to they run dry? But the comet looses around a meter of material across its whole surface  every time it swings through the warm inner solar system, so it may have  relatively short lifespan left. The shape of the comet is itself a clue, but so far the team is unsure what direction it is pointing them in.

On the subject of the comets spin- at the moment, given what we know about comets its unlikely that the spin  will provide enough [24]centripetal force to snap the comet at its neck and leave it smeared across the sky as rubble. If the jets were pushing the comet to spin much faster then it might- but at the moment it seems that if anything they are slowing the spin. Right now they can only say its probably spinning about its shortest axis, and unlikely to break up due to centripetal force anytime soon.

The close flyby data from the infra red spectrometer hasn't been  looked at yet, but should give us a detailed idea of what gasses this odd comet is releasing, and clues to its internal makeup.

The future of Deep Impact?
The probe doesn't have enough fuel do fly to another comet, but it is in good health, and has enough fuel and power to run its instruments. The team are waiting on instructions from NASA and input on how  the probe could still be used for a future mission, for example [25]asteroid tracking. Currently they are looking to finish operations at the end of this year.

Hartley 2 itself had one more spectacle up its sleeve: As the Earth has passed through its wake the planet may have been been bombarded by [26]a storm of small debris from the comet. This would show up in our skies as a meteorite shower informally nicknamed the '[28]Hartleyids'

There will undoubtedly be much more follow up to these preliminary results over the months and years to come, but for now I'd just like to say; My heartfelt congratulations to the Deep Impact team!

List of links

[1]http://epoxi.umd.edu/
[2]http://cometography.com/pcomets/103p.html
[3]http://www.springerlink.com/content/t81x2g12h59p220l/fulltext.pdf
[4]http://deepimpact.umd.edu/tech/instruments.html
[5]http://www.universetoday.com/10657/deep-impact-smashes-into-tempel-1/
[6]http://cometography.com/pcomets/085p.html
[7]http://epoxi.umd.edu/2science/targets.shtml
[8]http://news.bbc.co.uk/1/hi/sci/tech/5173992.stm
[9]https://www.llnl.gov/news/newsreleases/2010/Sep/NR-10-09-03.html
[10]http://en.wikipedia.org/wiki/Tunguska_event
[11]http://www.space.com/scienceastronomy/071224-mm-comet-mysteries.html
[12]http://www.lpi.usra.edu/meetings/lpsc2008/pdf/1015.pdf
[13]http://discovery.nasa.gov/missions.html
[14]http://epoxi.umd.edu/
[15]http://www.naic.edu/
[16]http://www.planetary.org/blog/article/00002742/
[17]http://www.sciencedaily.com/releases/2010/11/101110171430.htm
[18]http://www.nasa.gov/worldbook/comet_worldbook.html
[19]http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=47909
[20]http://deepimpact.umd.edu/tech/hri.html
[21]http://unmannedspaceflight.com/
[22]http://www.planetary.org/blog/article/00000969/
[23]http://www.jaxa.jp/projects/sat/muses_c/index_e.html
[24]http://hyperphysics.phy-astr.gsu.edu/hbase/cf.html
[25]http://www.universetoday.com/33187/asteroid-tracking/
[27]http://www.universetoday.com/77320/hartley-2-spawns-meteor-shower/
[28]http://science.nasa.gov/science-news/science-at-nasa/2010/27oct_hartleyids/

Friday, 5 November 2010

Worlds on the edge of knowledge: Triton.

As always, links are numbered and listed in order at the end.

Following the excitement of yesterdays Deep Impact flyby I thought I'd try to provide something to decompress to. And what better place to decompress and chill than the outer solar system?

Far out in space, where only a handfull of robots have dared to venture, a  huge group of icy [1]protoplanets and [2]planetesimals have survived in great numbers since our solar systems earliest days.
These worlds are the protoplanets of the [3]Kuiper belt; a wide and deep doughnut of icy objects beyond the orbit of Neptune, surrounding the worlds of our solar system.


Image left: A map of our solar system showing the Kuiper belt. Image courtesy of orderoftheplanets.com


The Kuiper belt is the solar systems deep freeze storage, home to many [4]weird ancient relics from the sunless far edge of the [5]protoplanetary disk, some of which reached the size of a a small planet before their growth was stunted. But how can we learn about this historical treasure trove when it lies so far away? To get a feel for these distant worlds there is one place we can look that has had the kind of detailed look only an on site spacecraft can bring: [6]Triton.

An enigma writ in pink

Image above: Neptune and Triton, in false colour to bring out Neptune's weather patterns. Image courtesy of the Palomar observatory.

The largest moon of [7]Neptune (2700 km in diameter), Triton orbits in the opposite direction to its planetary hosts rotation, suggesting that it does not come from the Neptune system at all- it is instead a wanderer from further out, in the black depths of the Kuiper belt.
This strange orb of rock and ice has been visited by just one human spacecraft, [8]Voyager two. Voyager two is the grandaddy of deep space probes, [9]still making ground breaking discoveries from the farthest edge of explored space.


Image above: Triton, one of the enigmas of the outer solar system, one of the solar systems most enticing moons, and one that is very very difficult to get to and study. This makes the data gathered so far truly precious. Image courtesy of NASA.

Voyager sent back pictures of Triton. They are images, not of a frozen chunk of ice that died eons ago, but of an active world of alien geology, based on processes we little understand and using [10]materials we only encounter as liquids or gasses. Triton, despite being cold enough that Earths atmosphere would freeze solid on its surface as snow, is active.

Triton surface tells a story of of intense geological history: Based on its density, and [11]spectroscopic analysis of reflected light from its surface, the best guess to date is that it consists of a [12]fat rocky core, maybe making up as much as two thirds of its internal volume, wearing a mantle of ices. The presence of the large core is based on [13]Triton's strangely high density, 2.062 g/cm3, which is far too high for an ice world. Yet the surface is composed of water and carbon dioxide ices, with a cap of frozen nitrogen studded nitrogen geysers that greet the dawn of far distant sol with fountains of gas and dust.  Triton appears to be some kind of hybrid world.

The surface is bitterly cold, only 38 kelvin, but the surface suggests that in the geologically recent past this might not have been so: [14]the surface is very free of craters, indicating that unlike most worlds the same size its [15]geology has been active as recently as a few million years ago, and could even be still running hot ([16]at least less cold) today. The large size of the core makes it possible that there could still be enough residual heat, [17]from radioactivity or tidal heating,  to power [18]convection in the mantle, as occurs on Earth with rock, and possible even sustain a [19]layer of liquid water deep beneath the surface.

Aside from the infrequent impact craters there beautiful and complex valleys and ridges seem to be formed by icy analogues of Earths own tectonic processes.  There are [20]massive high plains in the east, believed to have been formed by a massive eruption of [21]cryolava, and are dotted with pits, such as [22]Leviathan Patera, from which the molten material emerged. Four huge walled plains ave also been found and are thought to be due to volcanic eruptions.



Video above: Candy Hansen, a member of the Voyager team, demonstrates how tectonic activity has altered parts of Triton. Courtesy of NASA.


Image right : Leviathan Patera, the smooth floored depression center left, is believed to have been a source of massive cryovolcanic eruptions. Image courtesy of JPL

One pole is covered entirely with a [23]bright pink cap of frozen nitrogen. Nitrogen, which is a gas on Earth, is usually colourless to human eyes. But mixed in with the nitrogen ices is methane, which  breaks down under the suns ultraviolet light and other space radiation to give unknown carbon compounds, giving Tritons  surface a pinkish hue.

But Tritons most spectacular surface feature by far must be its [24]nitrogen geysers: These geysers are larger than any found on Earth, and are based in the polar cap of solid nitrogen. Right now the leading theory for how they function is that when the sun is directly over heat its radiance is able to pas through the top layer of nitrogen shell, and weak though it is, heat is trapped beneath the surface in a sort of 'solid state greenhouse effect'. Over time this vapourises enough nitrogen ice to produce a buildup of gas pressure that blasts through the ice in a pillar of nitrogen gas, carrying dust from the surface and subsurface up to 8000m high.

Image above: The geysers of Tritons polar cap, visible here by the dark streaks of wind-blown dust they deposit. Image courtesy of NASA.

These geysers may last for up to year, a river of gas to the black sky, and Tritons ultra thin nitrogen atmosphere helps to transport the dust about, slowly changing the face of the little world over time: it lofts the dust particles down wind producing spectacular ribbons of black against the pink nitrogen shell.

Triton geology had one last surprise for the team working on the Voyager images as they flashed back to Earth: The [25]cantaloupe terrain, a huge area of Triton western hemisphere, contorted by strange depressions and folds, making up circular dimples 30 to 40 km wide. Despite its lack of old craters it is thought to be the oldest ground on the mysterious moon, and theories for how it formed are [26]wide ranging, from cryovolcanic flooding, to subsurface collapse, to diaperism, where blobs of warm material rose like sea monsters from the core. This terrain exists only on Triton, and is made mainly of water ice with ...... Many of these causes would have had an incredible effect on Triton, spreading cryolavas of liquid water across the surface, and releasing gasses that could have left the place with a [27]short lived thick atmosphere.

Yet Tritons surface and interior aren't the only interesting things about it: Unusually for such a small world [28]Triton boasts an atmosphere. Not much of one, barely a hundredth of a millibar of pressure, but enough. Tritons surface sees a troposphere with weather patterns like Earth or Mars, and tenuous clouds were imaged by Voyager.


Image left: Tenuous clouds creep over Tritons surface, The image is a composite courtesy C. Hamilton.

These clouds are vaguely analogous to [29]cirrus on Earth, composed of crystals of nitrogen, and there are hazes, where the thin methane component of the atmosphere reacts under UV light to produce Triton [30]tholins, complex carbon based materials related to the [31]organic chemistry believed to have precipitated life on Earth.

How Triton got its lumps:




Video above: A lecture by Dr Gary Peterson of San Diego State University, on Triton and its geological history. Video courtesy of San Diego State University.


The blatant scars of active geology across Tritons surface give mute testament to its origins elsewhere in the universe: Some of the most plausible explanations for how Triton remained so active for so long are rooted its, possibly devastating, [32]capture by Neptune. There are three main mechanisms for this proposed:

1: Protoplanetary pile up.
One leading theory has Triton actually smashing into a preexisting satellite of Neptune to slow itself down, but that theory has problems- the hit satellite must be just the right size, too big and Triton gets totally pulverized, too small and it won't loose enough speed.

2: Skimming off of Neptune:
A second theory has Triton skimming off of the early accretion disk around Neptune, or even off of a vastly extended Neptune atmosphere. Neptune would have been puffed out like a cheek after a tooth extraction from accretion heat- but Triton is big, and this is a scenario that works much better for a smaller object

3: Sundered twins:
A third theory is that [33]Triton was part of a twin planet system, and that when these twins passed by Neptune one was captured, and the other was shot off into space, taking Tritons excess kinetic energy with it.

Whatever the mechanics of the union, Triton would have wound up in an elliptical orbit, which would have let Neptune gravity set up [34]huge tidal forces within its crust, flexing the whole moon. Back in the [35]Jupiter system this effect drives the terrifying [36]volcanoes of Io, and warms the [37]ocean of Europa and Ganymede.
In Tritons case eventually the very tides themselves forced its orbit to become more circular, and the heating died down, leaving behind a shell of bitter ices. Models suggest that Triton could have remained active or up to a billion years after its capture- and some heat left in its rock core could [38]drive residual activity even today.

Tritons immense distance from Earth makes putting a probe in orbit to do a detailed study difficult with today's engines, and there are no flyby missions planned for the Neptune system.

What do these places tell us about the deep past?

Triton represents one possible path an icy protoplanets can take we, know from our analysis of the Kuiper belt that there are almost as many paths to follow as their are worlds in the belt. Places like Makemake, [39]the Haumea system (a very odd place), [40]Sedna, the Pluto system; each has its own character. Tritons ath ahs ben that if a world that remained 'alive' long after the protoplanetary disk dissipated, and continued to evolve. There have probably many different geological epochs on Triton: Times when water slush lava was common on the surface, the entry into the Neptune system and the long icy days before it, leading back to birth at the edge of the pre-solar nebula, watching our star system grow from a distance. Unravelling Triton's mysteries tell us about how an icy protoplanet can evolve, and what kind of weird world it can grow into.
Next in this series of articles we'll look at one believed to be almost pristine from the ancient solar system...

How do we know these things?
There are two main ways of learning about distant, oddball little worlds: Use advanced telescope technologies to view them from afar, and put a robot space ship with cameras and sensors up close to one.
Image left: A model of Voyager 2. image courtesy of NASA.

In Triton's case, advanced telescope technologies is where its at for the foreseeable future- a pity given the fascinating world Voyager 2 gave us a glimpse of. On of the major tools for the study of Triton is our old friend [41]spectroscopy. The [42]European southern observatory is [43]very active in this field, making use of [44]adaptive optics in instruments that adjust the shape of the telescopes main mirror to cancel out the distortions of Earths atmosphere. [45]The Hubble has also spent a lot of time looking at Triton, and has seen [46]changes on its surface as its seasons have progressed.
But for the real goodies, the data that only a spacecraft like Voyager could reveal to us, we're stymied right? Not quite. Although there are no plans for a mission to the Neptune system, there is a spacecraft on its way to visit a world that is thought by many to be Triton's near twin: the [47]New Horizons mission to Pluto. Pluto and Triton are often held to be closely related objects, and the fun doesn't stop at Pluto. New Horizon's is planned to investigate other Kuiper belt worlds as it hammers out of our solar system. It will provide us with a larger picture of the Kuiper belt story, and we will be able to apply much of what it teaches us to our studies of Triton, this distant, slightly garish, and very mysterious world.

List of links:

[1]http://www.universetoday.com/37053/protoplanets/
[2]http://www.universetoday.com/35974/planetesimals/
[3]http://nineplanets.org/kboc.html
[4]http://www.astroengine.com/?p=2047
[5]http://www.daviddarling.info/encyclopedia/P/protoplandisk.html
[6]http://nineplanets.org/triton.html
[7]http://www.solarviews.com/eng/neptune.htm
[8]http://voyager.jpl.nasa.gov/
[9]http://science.nasa.gov/science-news/science-at-nasa/2009/23dec_voyager/
[10]http://www.gps.caltech.edu/~mbrown/papers/ps/volatiles.pdf
[11]http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6WGF-45GMFFX-3K&_user=10&_coverDate=06%2F30%2F1999&_rdoc=1&_fmt=high&_orig=search&_origin=search&_sort=d&_docanchor=&view=c&_searchStrId=1510687655&_rerunOrigin=google&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=80c02725afd216a03e6b8cb21dbd124a&searchtype=a
[12]http://science.jrank.org/pages/4592/Neptune.html
[13]http://books.google.co.uk/books?id=dw2GadaPkYcC&pg=PA836&lpg=PA836&dq=measurements+of+tritons+density&source=bl&ots=TqMbzP093c&sig=eecC1bJc9ebvz84f2Yyy4g4ThpI&hl=en&ei=0KnFTPezKY734AbIu4S6Aw&sa=X&oi=book_result&ct=result&resnum=5&ved=0CDUQ6AEwBA#v=onepage&q&f=false
[14]http://www.planetary.org/blog/article/00002726/
[15]http://www.universetoday.com/12108/how-old-is-tritons-surface/
[16]http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/35791/1/93-1517.pdf
[17]http://iopscience.iop.org/1538-3881/119/2/945/990318.text.html
[18]http://www.see.leeds.ac.uk/structure/dynamicearth/convection/
[19]http://eprints.ucm.es/10454/1/11-Trit%C3%B3n_1.pdf
[20]http://books.google.co.uk/books?id=G7UtYkLQoYoC&pg=PA490&lpg=PA490&dq=eastern+plains+triton&source=bl&ots=jDVn2Yu_DU&sig=c7rgXpbAde3p0Jso1iH6qJnJ2M4&hl=en&ei=vrnFTPCnOamL4gbxsrm5Aw&sa=X&oi=book_result&ct=result&resnum=2&ved=0CBsQ6AEwAQ#v=onepage&q=eastern%20plains%20triton&f=false
[21]http://www.psi.edu/pgwg/images/dec08image.html
[22]http://books.google.co.uk/books?id=G7UtYkLQoYoC&pg=PA490&lpg=PA490&dq=leviathan+patera&source=bl&ots=jDVnb3qZyN&sig=IKXF7EVJoiuAotpd0LZ5joRp-qo&hl=en&ei=knbUTKmuCsbA4garhrj7Bg&sa=X&oi=book_result&ct=result&resnum=7&ved=0CDIQ6AEwBg#v=onepage&q=leviathan%20patera&f=false
[23]http://books.google.co.uk/books?id=9kxz5AZj8lwC&pg=PA22&lpg=PA22&dq=triton+polar+cap&source=bl&ots=z7vmwW3awA&sig=ajkHeU3BrQxWNz35Io1T6ycwKlI&hl=en&ei=v-HFTOGqI5aO4gbL1Yi6Aw&sa=X&oi=book_result&ct=result&resnum=7&ved=0CDsQ6AEwBjgK#v=onepage&q=triton%20polar%20cap&f=false
[24]http://www.lpi.usra.edu/meetings/lpsc1995/pdf/1174.pdf
[25]http://www.nasa.gov/mission_pages/voyager/pia12186.html
[26]http://books.google.co.uk/books?id=dw2GadaPkYcC&pg=PA838&lpg=PA838&dq=cantaloupe+terrain+origin&source=bl&ots=TqMbzQ75Zf&sig=AxQsU2zoHdNsGtu9yE545p4tdVQ&hl=en&ei=b-rFTLbWAom9jAfs3Oy4BQ&sa=X&oi=book_result&ct=result&resnum=8&sqi=2&ved=0CEAQ6AEwBw#v=onepage&q=cantaloupe%20terrain%20origin&f=false
[27]http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1993LPI....24.1245S&db_key=AST&page_ind=1&plate_select=NO&data_type=GIF&type=SCREEN_GIF&classic=YES
[28]http://www.windows2universe.org/neptune/moons/triton_atmosphere.html
[29]http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/cld/cldtyp/hgh/crs.rxml
[30]http://www.daviddarling.info/encyclopedia/T/tholin.html
[31]http://www.geochemsoc.org/publications/geochemicalnews/gn142jan10/complexorganiccarbononabio.htm
[32]http://www.planetary.org/blog/article/00000577/
[33]http://www.sciencedaily.com/releases/2006/05/060511083934.htm
[34]http://www.suite101.com/content/tides-and-volcanoes-on-io-a15323
[35]http://www.nasa.gov/worldbook/jupiter_worldbook.html
[36]http://science.nasa.gov/science-news/science-at-nasa/1999/ast04oct99_1/
[37]http://news.nationalgeographic.com/news/2008/12/081210-europa-oceans.html
[38]http://www.lpi.usra.edu/meetings/LPSC99/pdf/1766.pdf
[39]http://web.gps.caltech.edu/~mbrown/2003EL61/
[40]http://www.mikebrownsplanets.com/2010/10/there-is-something-out-there.html
[41]http://www.ipac.caltech.edu/Outreach/Edu/Spectra/spec.html
[42]http://www.eso.org/public/
[43]http://www.eso.org/sci/publications/messenger/archive/no.129-sep07/messenger-no129-58-61.pdf
[44]http://cfao.ucolick.org/ao/
[45]http://hubblesite.org/
[46]http://iopscience.iop.org/2041-8205/723/1/L49
[47]http://www.nasa.gov/mission_pages/newhorizons/main/index.html

Thursday, 4 November 2010

A quick and dirty roundup.....

....of what I came away from the NASA/JPL press event on the Hartley 2 flyby with:

The comets jets seem to be powered by CO2, unlike any comet observed so far

The water signature goes up and down a little (tentatively, they aren't 100% sure on that data yet), suggesting some H2O involvement but by and large this comet is driven by dry ice. The comet is giving off water vaour but at a steady rate that does not go up and down with the amounts of dust given off (the CO2 emissions do) suggesting its not the main thing powereing the jets.

The dry ice activity seems to be mainly coming from one end of the comet (the one with all the clustered jets in the images released so far).



Image above: One of the close by mages of Hartley 2. The most active, apparently CO2 driven, vents are clearly visible at the far right end. The 'dusty' smooth patch in the middle resembles the asteroid Itokawa visited by [1]Hayabusa. The 'boulders'almost certainly aren't rock, and may be related to the jet activity! Image courtesy of JPL/NASA/UMD, via some processing by Hungryforinfo over on [2]unmannedspaceflight.com.

The 'boulders' littering the ends of the comet definately aren't rocks, they're probably not even very solid, and they don't yet know what they are or how they got there.

This comet definately has jets coming out of its night side, so there is some mechanism driving them even out of the suns heat. This has been hinted at in previous comet encounters, but this is the first solid confirmation.


Image above: Enhanced image showing jets coming out of the comets night side.Image courtesy of JPL/NASA/UMD.

The IR spectral data has not yet been analysed, so they can't say much beyond the overabundance of CO2 in the jets about Hartley 2's composition.

The smooth mid section is likely caused by fairly fine dust particles filling a topographic low, resembling (it is thought) the [3]asteroid Itokawa. If the jets were oriented so that the comets spin were to increase it would likely snap at the neck around the one revolution every 3 to 4 hours mark.


Image above: Asteroid Itokawa, courtesy of [4]JAXA.

 
The comets rotation is not well understood, although it probably spins about its shortest axis.

Deep Impact travelled to Hartley 2 specifically to study a comet smaller than any that  had been looked at before. Comets are of interest because they supplied the raw materials for the cores of giant planets, and may well have been involved in bringing water and organic matter to Earth (I know that, and I've menioned it here  before, but it bears repeating).

Once again comet exploration throws science a basketfull of challenging surprises! I can't wait to hear some more detailed analysis, and especially the infra red spectral data on precisely what the comet is giving out. I'll leave it there for now, but I will endeavour to do a better presented and more detailed follow up post within the next week or so.

Today I have seen things no human being has seen before - so I'll tag today a good one, and go to bed smiling.

Regards,

John Freeman

Links:
[1]http://www.isas.jaxa.jp/e/enterp/missions/hayabusa/index.shtml
[2]http://unmannedspaceflight.com/
[3]http://www.newscientist.com/article/dn9257-rubbly-itokawa-revealed-as-impossible-asteroid.html
[4]http://www.jaxa.jp/index_e.html

I can't pass this up.....

..... one of the first animations of the while flyby of Hartley 2, courtesy of cassioli, one of the imaging wizards over on [1]unmannedspaceflight.com. I don't know how to embed said animation from where it is right now, so I'll just link you to the [2]relevant post.

Links
[1]http://www.unmannedspaceflight.com/index.php?
[2]http://www.unmannedspaceflight.com/index.php?s=&showtopic=5177&view=findpost&p=166201

Deep Impact reveals another strange new world...

A brief note here: My congratulations to the Deep Impact/ EPOXI team on their successful flyby of comet Hartley 2. Closest approach was at 1400 hours UTC, and the first close up images hit the web at 1500.


Image above :My favorite view of Hartley 2 to come down so far! Note the twin lobe structure, connected by an oddly smooth neck. Courtesy of NASA/JPL/UMD

The mission website is [1]here, and there are already fascinating analysis of these images being made over at the [2]planetary society blog. I won't clutter things with my own attempt at analysis - over the coming months and years these and the many images yet to come will be subjected to exhaustive analysis by minds far more informed by mine.

What I'd like to do is offer my thoughts on what has been achieved here: 23 million kilometers away a space craft built, launched, and operated by us very imperfect humans has torn past a 4.5 billion year old relic of the solar systems birth, and given us all a chance to learn a bit more about where we came from, and what this tiny strange world is like.

The comet itself has a stark and alien beauty about it. The achievement these images represent is something the whole of humankind can take pride in. And I will, of course, be keeping an ear close to the ground for the knowledge that will inevitably be sifted from these pictures.

John Freeman
EDIT There will be a NASA press conference on the data recieved so far at 20:00 hours UTC, or 16:00 EDT. Availaible [3]here as Ustream, or [4]here on NASA TV. Enjoy, I know I will!
Links:

[1]http://epoxi.umd.edu/
[2]http://www.planetary.org/blog/
[3]http://www.ustream.tv/nasajpl2
[4]http://www.nasa.gov/multimedia/nasatv/index.html

Monday, 1 November 2010

An old friend visits a new (if very small) world...

I'd be remiss not to mention the continuing exploits of an old friend; A veteran space explorer with telescopes for eyes and a radio antenna for ears that started its journey aboared a [1]Delta 2 rocket and feeds of the Sun using solar cells.The good ship [2]Deep Impact is about to show us all how its done again.



Video above: The launch of Deep Impact in 2006. Courtesy of hackreik via YouTube.

This week sees the fly by of the Deep Impact space craft with comet [3]Hartley 2. In preparation the comet has been given the once over by both the [4]mighty Arecibo radio telescope and the [5]Hubble space telescope.
Hartley 2 is the smallest comet ever visited by a space craft at roughly a mile across, and observations from Arecibo radio telescope show it to be [6]almost peanut shaped.

Image right: The Deep Impact space craft in its clean room. Image courtesy of Ball Aerospace.

Deep impact (re-christened [7]EPOXI for this new mission) will map its tightly curved surface and study the make up of gasses emitted by it.The mission has already thrown up [8]at least one surprise: The comets emission of the gas [9]cyanogen was seen to wax and then wane by five times its initial value, without any signs of a new pocket of gas being violently released. Outbursts, particularly of cyanogen, like these are usually accompanied with and increase in the amount of dust emitted by a comet, by this has not been seen. And Hartley 2, despite its small size, is throwing out as much water vapour as the much larger [10]Tempel 1, suggesting it surface is a cauldron of activity.


Image left: Comet Hartley 2 captured by an amateur astronomer. Image Courtesy of Andrew Cooper.

The various differences between comets, and the plethora of [11]surprises they keep flashing at science makes the exact origins of these wanderers form the deep dark of the outer solar system a [12]tantalising mystery. The current best model is that these are icy stragglers left behind by the great [13]protoplanetary disk that birthed our solar system. But the many and varied behaviors they show suggests that they may not all have the same origins.


Punters can [14]follow the mission on its blog, or if you prefer there will be a [15]u-stream lecture given by the comets discoverer tomorrow. Deep impacts first target was the comet Tempel 1 which was analysed in a unique fashion by blowing a hole in it with a huge copper projectile. Since then the probe has been moonlighting by [16]studying extrasolar planets, and now is set to fly past Hartley 2 at a distance of 700km on November the 4th. Hopefully the fly by will give us back here on Earth a better understanding of where this little wandered came from, how old it is and what is is made of. Emily Lakdewalla over at the Planetary Society has [17]a good write up on this, and their website includes [18]a timeline of what the long serving spacecraft will be doing and when!

Image above: The bizarre surface of comet Tempel 1, Deep Impacts first voyage of exploration. Courtesy of NASA.

List of links:
[1]http://www.boeing.com/defense-space/space/delta/delta2/delta2.htm
[2]http://www.space.com/deepimpact/
[3]http://cometography.com/pcomets/103p.html
[4]http://www.naic.edu/
[5]http://www.sciencedaily.com/releases/2010/10/101006131443.htm
[6]http://www.naic.edu/~pradar/103P/
[7]http://epoxi.umd.edu/1mission/index.shtml
[8]http://epoxi.umd.edu/7press/news/20101021.shtml
[9]http://www.britannica.com/EBchecked/topic/147747/cyanogen
[10]http://deepimpact.umd.edu/science/tempel1.html
[11]http://news.bbc.co.uk/1/hi/sci/tech/4801968.stm
[12]http://www.nature.com/news/2010/101026/full/4671013a.html
[13]http://www.daviddarling.info/encyclopedia/P/protoplandisk.html
[14]http://epoxi.umd.edu/6outreach/daily.shtml
[15]http://www.jpl.nasa.gov/events/lectures_archive.cfm?year=2010&month=11#myComet
[16]http://epoxi.umd.edu/2science/targets.shtml
[17]http://www.planetary.org/blog/article/00002744/
[18]http://www.planetary.org/explore/topics/deep_impact/hartley2_timeline.html