Wed, 05 May 2010
The EGU conference is packed, and this blog isn't anything remotely like real-time, but some interesting talks came up on Monday evening :
Simon Katterhorn gave a neat presentarion on icy moon tectonics, specifically on Europa and Enceladus. He showed the cycloid tracks on Europa, and how these are probably generated by tidally-driven ice tectonics. The presence of these of different ages shows the existence of a global ocean underneath, and the decoupled ice shell on top. More on this can be seen in Greenbergs book on Europa; but he also showed further follow-on work on Enceladus. Enceladus is small enough that people thought it had cooled and could not support an ocean, explaining the geysers and plumes by "small reservoirs". He shows instead that the 'tiger stripes' at the south pole are also tidally-created stresses, and moreover older generations of stripes, at an angle to the current ones, are also present: the plumes occur at the intersections. This shows free rotation of the ice shell and almost certainly an ocean. As to how to heat it: tidal heating is the primary candidate.
I'm looking forward to Tidal heating and orbital evolution of Enceladus on Thursday.
Tue, 04 May 2010
I'm at the European Geosciences Union (EGU) General Assembly, 2010, the biggest gethering of European geoscientists, in Vienna, May 2-7. This is my first time here and its huge: over 9000 participants. Merely finding the talks and posters is a challenge (they supply a USB stick with the abstracts and agendas as they can't print them all!
The first day I spent mostly at the exoplanet stream (and putting up my own poster). Some neat stuff on show: summaries by Borucki on Keplers findings (on the Hot Jupiters they found :" these things glow like a blast furnace; forget life"). He points out that when they look for Earth sized planets, radial velocity confirmation would take 1000s of hours on 10M telescopes - so it won't happen. hmm.
Steve Unwin on SIM: neat astrometric mission for planet hunting and galaxy measurement. A targeted mission list, unlike the Gaia survey; to fly in 2016 if the Decadal survey says yes. 20% of time available under the general observer program, so get proposals ready ?
Nestest poster idea: Anomalous night-time temps on Mars, Gonzales et al.. Finding hot spots on Arsia Mons, a volcano. Explained by air rising from 100km long lava tubes. We've seen pit entrances to caves on Mars with HiRISE, etc. here they model heat output from a pit entrace/exit and imply 100km caves. Oh to go exploring...
Tinetti points out that we lack proper spectra, both experimental and theoretical, for high temperature and pressure gases such as methane, etc. Hmm, I know a group in Galway that might be able to help ...
Helmut Lammer raised an interesting point at the poster session, that many groups ignore the stellar wind when looking at H2 atmospheres around exoplanets. Theis grossly inflates the apparent H2 atmosphere. Without taking this into acount it would be easy to mistake H2 detections with a Neptune-like atmosphere. He points to a 1.7M UV telescope that the Russians are planning to launch that would help do UV measurements when Hubble is gone.
Lena Noack gave a talk on convection in tidally-locked planets (with related poster Low-lid formation on Super-Earths and implications for the habitability of Super-Earths and Sub-Earths). They argue that no covection can be expected in the mantle, and hence no geodynamo or magnetosphere. This could be a problem for holding an atmosphere. Time to check for planetary magnetic fields. Break out the polarimeter ?
Oh, and it seems that That Damned Volcano is closing Irish airspace on Tuesday. Might be an idea to go to the meeting about it. Hope it clears by Friday ...
Mon, 11 Jan 2010
Thanks to Joey Hess for the request to set up tor bridges. I wholeheartedly agree, and recommend the video he points to. I've installed a Tor bridge at home, and recommend others to do so.
For the most part, I'm not politically active at the moment - I'm doing a PhD Part-time, and thats consuming all my "spare" time, other than work and family. Just given a blog site, however, one subject strikes me as very important - free speech. Hence the side links to Amnesty International, etc. In Ireland this campaign has a particular focus at the moment - the Repeal of the Blasphemy Law. This law came into effect in Ireland this January. While the government claims that this law will 'never be used', its bad in several ways. Firstly, it promotes the ideas of censorship as a method of hiding social issues, and secondly it may actually be used, as pointed out in :
Blasphemy is a Victimless Crime from Limerick Blogger on Vimeo.
Basically, with Europe-wide arrest warrants, if two European countries have criminal blasphemy laws, then someone may be extradited to face prosecution in another country. While the Irish government says they will never prosecute, they open the possibility of say, Irish citizens being extradited to Greece to safe prosecution for blasphemy.
On a wider level, I recommend Index on Censorship. It keeps documenting the cost of censorship around the world, and has been instrumental in campaigning for Libel reform in the UK, which is ncreasingly important for open scientific discussion.
Mon, 24 Aug 2009
Up on arxiv.org today is a paper, "Title: The perihelion precession of Saturn, planet X/Nemesis and MOND", by Lorenzo Iorio.
The perihelion is the point of the planets orbit where it is closest to the Sun. Over the millennia, this point moves, or precesses, under the gravitational pull of other objects. This is a tiny effect, spotted because we have accurate measurements for Saturn thanks to measurements with the Cassini probe. (We have no such measurements further out, for Neptune and Uranus; but we have a more famous case: the Pioneer Anomaly, unexplained changes in the path of the Pioneer probes). Iorio comes up with measurements for a potential planet X to explain this; an Earth-sized planet around 80-150 AU out, up to a Jupiter-sized object at 1000 AU. (1000 times the Earth-Sun distance).I've written before about this: such a planet is remotely feasible to detect by ground-based systems (or perhaps Herschel). It would certainly help explain the architecture of the outer solar system. Perhaps we should start seriously looking for such an object ?
The Brown Dwarf possibility is also interesting; Centauri Dreams has an article on the Wide-field Infrared Survey Explorer (WISE) mission, due for November launch, thats expected to be capable of finding many cold brown dwarfs nearby.
read more »
Thu, 20 Aug 2009
In this weeks Astronomy & Astrophysics was a paper by M. Reidemeister et al., A possible architecture of the planetary system HR 8799.
This revisits HR 8799, one of the few planetary systems seen by direct imaging, actually observing the planets.
These are believed to be three Jupiter-sized planets (of about 5, 7 and 7 times the mass of Jupiter: the exact numbers depend on the precise viewing angle from Earth; Reidmeister think this is nearly pole-on). They were discovered last year by Marois et al..Summarizing all available data, they decide that HR 8799 is less that 50 Million years old, practically still forming. Their proposed layout of the system has at least three dust rings, still coalescing and cooling. By comparison, our Solar system at that stage had formed the main planets but the four outer giants were still moving into position, working their way through the remains of a dusty, gassy disk : another 500 million years or so before Jupiter and Saturn settled into their current orbits, and bombarding the inner system as they did so, leading to the cratering we see on the moon and resurfacing Mars, Earth and Venus.
What makes the HR 8799 system so interesting is that its a good test for theories of planetary or stellar formation. Its unclear whether it formed as a 'planetary system', with the planets formed in the debris disk of the star, or as a "multiple star" system; for the latter. Modelling the formation of HR 8799 will be a good test of Alan Boss's 'Gravitational Instability' theory, vs the 'core accretion' model which has been gaining ground in recent years.
In the meantime for non-theorists, its pole-on orientation gives us a good view of planets in formation. Roll-on the clearer images of the James Webb Space Telescope.
Thu, 13 Aug 2009
WASP-17b is the first planet to be discovered in a retrograde orbit: it rotates about its star in the opposite direction to the spin of the star. (See the nice BBC News write-up, or the ArXiv preprint for the more technical details).
We think planetary systems are formed from a disk of debris as the star forms, and the disk and star would rotate the same way, so most planets rotate pro-grade, in the same direction of the star. For retrograde motion, it would have to have been hit early-on by some large object (another planetary embryo, for example, being ejected from the stars 'solar system' in the game of cosmic billiards as they coalesce to form planets).
Within our solar system we see retrograde motion in Venus as it spins (on its own axis) in the opposite direction of other planets, but this is the first time we've seen a planet orbit in retrograde. Similarly, Uranus' spin axis is tilted at 89 degrees, but it orbits in a pro-grade manner; its thought that Uranus was hit by a giant object causing its tilt. As we find more exoplanets, the statistics of how many are pro-grade or retrograde will help us learn about the formation of planetary systems.
WASP-17b is a "Hot Jupiter", discovered by the Wide Area Search for Planets (WASP) consortium of UK Universities by Radial velocity methods.
Sun, 21 Jun 2009
Unfortunately I won't be able to make it to DebConf9, so as an aid to those who are going, here's a summary of current work:
I've just uploaded terralib 3.3.1 to Debian, and its sitting in the NEW queue, as the older version was removed from the archive due to lack of maintenance (it had an RC bug in both including its own copy of libtiff and failing to link against it - now it links against an external copy of libgeotiff and libtiff).
In the NEW queue it joins g2clib, hdf-eos4, hdf-eos5 and udunits. These are there as dependencies of other Meteorology-related packages I'm working on: magics++ needs terralib and gshhs; zygrib needs gshhs (it has a copy built-in). NCL (NCAR Command Language) has a rake of dependencies including udunits, hdf-eos, g2clib and vis5d+ (ITP'd) . I'm also packaging VISIT for visualization.
Then there is the GSHHS issue: I think I'll end up packaging 'gmt-coastline-high', but the format of the coastline maps needs to be decided (netCDF or its own binary format) and updating the sundry packages to read the latest version needs tackling.
I'm packaging these as they are used at ICHEC and i've experience building them. One of the main aims I had in setting up Debian Meteorology (beyond adding the software to Debian) was to help integrate all the Free and Open Source code in the Earth-sciences field, and sort out dependency and build issues. I hadn't expected to encounter quite so many so quickly, though. I don't expect to get more done before vacation-time, but I'll be happy if I get these done this summer.
Thu, 18 Jun 2009
As mentioned before, I've started working on Debian Meteorology, adding "standard" meteorology-related packages to Debian. Part of the aim of this is to jump-start an effort of integrating the FLOSS in the field: all the usual libraries that people working in the field use and expect to be on the supercomputers and workstations they use.
So, two packages I've been working on are Magics++ and zyGrib, which are plotting and visualisaton tools. respectively. So they both contain coastline maps of the world. Digging deeper shows they use the same files : a binary database called 'GSHHS', or Global Self-consistent Hierarchical High-resolution Shorelines. Some scope for integration here.
So, I start investigating GSHHS in order to create a 'coastline data' package to be shared. It turns out that building GSHHS depends on GMT, the Generic Mapping Tools, already present in Debian, and this coastline issue has been explored before, and a package gmt-coast-low created.
"gmt-coast-low" is 5.5 MB in size, and as its name suggests, there was once a "gmt-coast-high", but this has since been dropped for taking up too much space in the Debian archive (in its place, a script which will download this data for you has been created. But the files in gmt-coastline-low are in netCDF rather than GSHHS's own binary format; what to do? Posting a mail for help and it turns out that another package is being considered, Basemap, an add-on for Mathplotlib, that also includes the GSHHS data.
I've summarized the files, sizes and versions here in the Debian Wiki. Offhand it appears that there is scope for re-adding a gmt-coastline-high package (with perhaps additional small datafiles on states boundaries, etc. seen in Basemap), though some questions remain:
Fri, 08 May 2009
Adrian von Bidder raises an interesting discussion on why public health care is difficult. Basically, it comes back to the challenge:
The problem is, the majority of health costs are in the last few years of a persons life: when the body is breaking down. If viewed from the problem of health-care funding vs. eg. education, you have an ethical dilemma: is it worth it ? Here there are no easy answers.
Nick Bostrom wrote a very interesting and persuasive essay a while back, The fable of the Dragon Tyrant. In short, we are getting somewhere with regenerative medicine While cures are hard to come by at this stage, there is a growing realization in medicine that senesence, what we used to call "old age", is curable. But we have a lot of psychological defensive mechanisms to help us cope with the carnage of old age that make us deny the problem: if we look afresh at "old age" knowing it to be curable, any delay in doing so is abhorrent.
From a public, societal perspective, we spend a fortune every year on health. But we do so in a very disjointed way: we pay colossal amounts for health care, but also for basic health science: in the US, for example, the budget for the National Institutes of Health is about 30 billion dollars. Nearly twice that of NASA. Similar figures are spent in Europe, but there is this strange gap in the middle: the drug companies and medical industry. We start the development of new drugs with public money, and we buy the drugs with public money, but the choice of what drugs and treatments are developed are left to private industry, that is, a profit motive. This results in many cases in expensive treatments to treat symptoms rather than necessarily cure the problem. Faced with the huge costs of geriatric medicine and senesence, the response should be co-ordinated: funding a cure will be expensive, but save a fortune (Think, instead of a pensioner slowly dying and 'being a drain on resources', of 'experienced citizen in the prime of their productive, tax-paying years'). Instead of funding the basic science alone, we should be funding the complete drug and treatment development publically, only farming out the actual manufacture to private industry.
It is silly to spend a fortune to keep merely keep someone alive at the age of eighty or so, when we know for a larger investment (bigger than a private company can do), we can cure them properly. The solution to the dilemma, then, is to stop thinking of the elderly being a drain, but actually applying our public efforts in a co-ordinated manner to solving the carnage of old age.