October 21, 2011 | 2
The range of topics relevant to astrobiology is pretty staggering – from microbial populations, chemistry, geo-chemistry, geobiology, climate, non-linear systems, solar system exploration, robotics, planetary science, exoplanets, astrophysics, and even cosmology. I often call astrobiology an ‘inter-discipline‘, since so much of it is about the connecting threads, the metaphorical synapses between highly specialized areas of science. So in that spirit here is a small collection of links to some fascinating recent stuff that all (somehow) falls under the umbrella.
The waters of TW Hydrae. The far-infrared instruments on the Herschel space telescope have probed into the outer, cooler, parts of this young (pre-main sequence) stellar system, and find an enormous reservoir of what is likely tiny grains of frozen water in the proto-planetary disk – precisely the kind of material we think provides a major building block for planets. The water totals several thousand times all of Earth’s oceans in mass. Intriguingly these measurements also have implications for our own solar system, suggesting that our cometary bodies consist of a great mixture of water that was originally spread across many zones 4 to 5 billion years ago.
“800,000 Years of Abrupt Climate Variability” is the title of a new study in Science this week. In it the authors present an investigation of a ‘synthetic’ (i.e. mathematical) model of changes in the Greenland ice cores that appears to match at least the past 100,00 years of temperature and glaciation records rather well. During the last ice-age there were many large and rapid shifts in Northern Hemisphere climate. The bottom line is that planetary cycles (e.g. ocean circulations) on thousand year timescales combined with the known orbital variations on longer timescales can sometimes conspire to pop us in and out of ice-age conditions. The astrobiological relevance? Who’s to say that when we find a nice terrestrial-like planet it won’t be in the throes of one of these variations and therefore extremely confusing to study with limited data?
In another study of a distant stellar system the Spitzer telescope has found remarkable evidence for an ongoing episode of intense comet-on-planet collision around the billion year old star Eta Corvi. Surrounding this star are two dusty, watery rings of material. One is some 150 astronomical units in radius, a potential reservoir of cold cometary material. The other is merely 3 astronomical units from the star, a warm mixture of carbon-rich dust and water that cannot be long-lived. The conclusion by Lisse and co-authors is that this inner ring of material is the result of a rocky, possibly terrestrial sized, planet being bombarded by cometary bodies – the fallout if you will. Why is this interesting? We think that something similar happened here on Earth about 3.8 to 4 billion years ago – the so-called Late Heavy Bombardment may have resulted from the orbital evolution of the outer giant planets and the Kuiper Belt – flinging cometary material inwards to irrevocably alter the Earth, and possibly supplying much of its outer layers, including water. Incredibly, the Spitzer data show a similar composition of the dusty, watery mix to a 2008 meteorite fall in Sudan – suggesting that those chunks originated in our own outer system, part of the Kuiper belt.
Using an exoplanetary system to perform real detective work on our own is part of what astrobiology is all about – finding the proper context for our own origins and evolution.
And finally, for something completely different. Lest we forget that our own habitable planet, Earth, is not all roses and sunshine, this rather sobering little survey of the world’s least habitable places came to my notice. The Top 10 Most Inhospitable Places in the World is very human-centric, especially given that we’re the ones mucking up these spots, but much like Eta Corvi 60 light years away it provides some interesting food for thought on how life can interact with its planetary host.