I attended (most of) the Royal Society discussion meeting on
The detection of extra-terrestrial life and the consequences for science and society
on Monday and Tuesday. Here are some quick notes on what (I think) I've learned from the more scientific part of the meeting (there were also talks about impact of any ET discovery on society, religion etc. which are a bit less relevant to me but may find more coverage in the mainstream media):
Some notes from the RS astrobiology meeting 25./26.1.2010
Charles Cockell (Open University) about life in the lithosphere. He insists “there is no such thing as a biosphere,” as the living part of the spherical planet is so thin it should be called a biofilm covering the geosphere. (Not sure that helps, as biofilms are something else entirely.) Attempts to cultivate iron oxidizers from rocks not successful yet. Very difficult for microorganisms to make a living from lithosphere, which is thermodynamically tasty but kinetically inaccessible. Therefore, when looking for life, follow the kinetics. Example Chessapeeke impact crater. Lithospheric austerity can be overcome by tectonism, volcanism, impacts. Habitats in solar system: Europa would be promising, but we don’t know redox status of subsurface ocean.
Simon Conway Morris (Cambridge) talked about extremophiles and potential habitat, mentioned Venus clouds and high pressure biology. No good explanation why microbial life dominated for so long except if step up to complex life is unlikely. Convergent evolution on Earth, => ET life may have developed similar features to adapt to similar environments, e.g. will also have camera eyes and similar sensory systems as we have. Violent behaviour could also be convergent, => need to be very careful with any ETs we find.
Michel Mayor (Geneva) on hunt for exoplanets, how boundaries have shifted so that now we can detect Neptune sized planets and even super-Earths with 1-10 Earth masses. Surprising diversity of extrasolar planets. Importance of migration of planets to orbits far from where they must have originated, e.g. very hot Jupiters. Eccentricity of extrasolar planets: huge scatter in distribution of orbit parameters. Transit, Doppler, and microlensing studies cover different areas of the planet spectrum, thus complementary. In order to find Earth twin need to improve methods even further.
Malcolm Fridlund (ESA) on COROT mission and how to spot life on extrasolar planets. Take Earth as model, move it 10 Parsecs away, what would we see? Need 1-pixel observations of Earth from distant space probes, not published yet. ESA looking into possibilities since 1995. Challenge equivalent to studying a firefly next to a lighthouse from 10,000 km away. COROT looking at acoustic vibraitions in stars, operated more than 1000 days so far, studied over 20 exoplanets, mission extended for further 3 years. E.g. Corot7B: 1.58 Earth radii, 4.8 Earth masses, density 5.5g/cm3 similar to Earth, orbiting Sun-like star, but only 5 star radii away from star, so very hot. Competitors: Kepler (now running), Plato (due 2018).
Chris McKay (NASA Ames) on life in solar system. Why we want to find some: Two examples of life more powerful than one, and could do comparative biochemistry. Case for Mars: evidence of past water, atmosphere, dry climate means good preservation of traces. Downside: exchange of meteorites with Earth could confound case for separate origin, may just find distant relatives. Fossils not enough, need guts. Phoenix Lander at Mars North Pole. Found soil pH 8, carbonate buffered, with 1% perchlorate (totally unexpected). If perchlorates generally present in Martian soil, conventional methods of organics detection by combustion won’t work, as organics won’t make it to receptor. Sensitivity would be reduced from ppb to 0.1 %. Phoenix couldn’t adapt its protocol to presence of perchlorate, this speaks in favour of sample return mission. Phoenix also found segregated ice, indicative of past liquid water. Habitability of Phoenix landing site 5 Myears ago: only thing missing is nitrogen. Europa, Enceladus, Titan, better prospects for “second genesis” as much less likely to have shared bio history with Earth. On Enceladus all basic requirements for life are met: C, H, N, energy … If it’s like us, easy to spot, but not interesting. If alien, interesting, but hard to find.
Colin Pillinger (Open University) on chemical methods to find life. Involved in Apollo 11 sample analysis, made proposal for Viking analysis but wasn’t selected. Favours C isotope analysis, as (terrestrial) life has preference for 12C over 13C. analysis of Martian meteorite EETA79001, with carbonate inclusions (light) and organics (heavy). Step combustion can find every C atom in every form. Organics from ALH84001 very enriched in 12C, would fit methanotrophic organisms. Analysis of Nakhla meteorite (fell 1911) – 80% of organic matter contains no 14C. Beagle2, or how to shrink 1t of equipment to 5.5 kg. Would have detected C isotopes by 2 independent methods.
Paul Davies (Arizona State Univ) Shadow biosphere on Earth as test of cosmic imperative. Chance or law, or where on the spectrum in between ? There may be 1020 Earth like planets, but odds against could easily exceed that number. Looking for “second genesis” on Earth. As 99.9 % of microbial species remain uncharacteriseed, there may be extant or extinct second type of life, which could be ecologically separate or integrated with the kind we know. Places to look: extreme conditions, high atmosphere. Tested for “mirror life” looking for organisms that can digest mirror nutrients, found Anaerovirgula multivirulans which is normal but can live on mirror nutrients, not sure yet how it metabolises the sugars. Looking for “arsenic” life with As instead of P in arsenic-rich environments, results expected soon.
Frank Drake (SETI institute) on 50 years of SETI. 50 years ago, only considered sun-like stars, but now know that M stars also have planets, and multiple stars may have planetary system as well, so range of targets has expanded. How to look – radio signal still most promising, and today 14 OM more powerful than 1960. also consider picking up laser pulses from civilisations that actively try to communicate. Problem: progress in our communications technology means Earth radio has become much fainter than it was in 1960. Search parameters still based on old technology. Advanced civilisations may emit much less radio waves than thought.
PS my tweets from the meeting are tagged #outthere
PPS Oops, I just noticed I already used the title for a blog entry in September, will try to remember not to use it for a third time ...