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Life, Unbounded

Life, Unbounded


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Astrobiology Roundup

The views expressed are those of the author and are not necessarily those of Scientific American.


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The Ghost of Astrobiology Past

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.

 

Proto-planetary, water-rich, disk (NASA/JPL)

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.

Glorious Greenland

“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?

Cometary pelting (Spitzer/NASA)

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.

Sailing on the Aral Sea

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.

 

 

Caleb A. Scharf About the Author: Caleb Scharf is the director of Columbia University's multidisciplinary Astrobiology Center. He has worked in the fields of observational cosmology, X-ray astronomy, and more recently exoplanetary science. His latest book is 'Gravity's Engines: How Bubble-Blowing Black Holes Rule Galaxies, Stars, and Life in the Cosmos', and he is working on 'The Copernicus Complex' (both from Scientific American / Farrar, Straus and Giroux.) Follow on Twitter @caleb_scharf.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Ehkzu 10:10 pm 11/16/2011

    OK, I’ll bite. Here’s an astrobiological challenge–even though, ultimately, what I’ll propose will never be proven or disproven:

    Intelligent aliens look–and think, and speak–a lot like us.

    When say this to college-educated friends I get consternation. They know I’m smart, and a naturalist, and a scuba diver who’s dived in a dozen countries in both hemispheres. So of all people I should know about the enormous diversity of life–just on this planet, much less on other ones.

    And I’ve laughed at all those Star Trek episodes where every being in the universe, practically, looks like us–only sometimes with funny foreheads or skin color–and all speak colloquial Southern California English. (And all the chicks dig Captain Kirk.)

    I’ve also seen the Star Wars Cantina Scene, which mirrors most people’s assumptions about the diversity of life Out There.

    But. As a diver, along with mind-boggling diversity (I’ve dived the Raja Ampat Islands off New Guinea, which some say is the most diverse habitat on the planet), I’ve seen powerful convergent forces as well.

    And intelligent, technology-using life must satisfy a demanding set of requirements. Especially since Nature is a notorious cheapskate, willing to settle for crummy kludges instead of more elegant solutions. Meaning that evolution proceeds completely blindly, bumping into stuff along the way.

    Those demanding requirements include having something like hands available to manipulate the environment, and sensory apparatus that utilizes pretty much the same part of the electromagnetic spectrum as we do, in order to get useful resolution and reach. And sense organs as close to the brain as possible. And being terrestrial, since you can’t smelt iron underwater. And not being able to fly–can’t have the energy sink of a big brain and flight metabolism at once.

    I could go on. But the more I’ve pondered this, the more I get backed into a corner next to another upright, terrestrial, bipedal hominid that looks a whole lot like us.

    Though I’m a little dubious about them finding Captain Kirk sexually attractive…

    http://www.artzu.blogspot.com

    Link to this
  2. 2. Caleb A. Scharf in reply to Caleb A. Scharf 11:19 am 11/18/2011

    I think these are interesting points. In fact the notion of “convergent evolution” is something that has seen a fair amount of discussion (for example Simon Conway-Morris’s ‘Life’s Solution’ book is an intriguing take, although I personally feel it goes a bit too far where the evidence is scarce). Certainly at a bio-molecule level it does seem plausible that similar acting toolkits are inevitably going to evolve even from distinctly different ‘origin points’ if life is to survive. Exactly how far this goes is unclear. I take your points about vision and manipulative appendages (hands/thumbs etc), although surely an octopus is equally deft and visually skilled? As you say, nature is a cheapskate, and evolution is ‘blind’ – so I think the question really comes down to asking whether being technological (in the sense that we are) is *really* equivalent to evolutionary “success” – and the problem is we’ve been around for such a tiny, short amount of time I’m not sure we can answer that yet.

    Link to this

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