Life in the cosmos » The Thinking Meat Project

The meaning of life

Dec 122008

A time-worn joke about humans is that we’re nothing more than water’s way of getting from one place to another. What if living things in general began as just another of nature’s ways of moving energy from one place to another? (Or more precisely, of minimizing energy differences by increasing energy flows from one part of their environment to another.) This article fromPhysOrg.com describes the work of a father-son team of Finnish scientists whose investigations into why life began blur the line between animate and inanimate matter. Their recent paper in the International Journal of Astrobiology describes living processes as being simply one of the mechanisms by which entropy increases. [Annila, Arto and Annila, Erkki. “Why did life emerge?” International Journal of Astrobiology 7 (3 & 4 ): 293-300 (2008)] Seen from a thermodynamic point of view, all the cool complexity that characterizes the natural world and that fascinates us is perhaps simply a byproduct, but, as with so many human behavioral and emotional phenomena, it’s quite a fascinating by-product.

While you’re pondering that, consider also some fascinating new bits of information about the possibility of life elsewhere in the universe. First, we have news from Hubble about the discovery of carbon dioxide in the atmosphere of a roughly Jupiter-sized planet orbiting another star (a planet where methane and water vapor have already been identified in the atmosphere). Although this particular planet is too hot to support life, this finding is an encouraging indicator of our growing ability to detect specific life-related molecules in the atmospheres of distant planets.

And, in a striking observational feat, a group of astronomers has been able to measure the size of an extrasolar planet using an extremely sensitive new detector. The news is summarized in this ScienceDaily article; the paper is available from arXiv.org. The camera, which can detect minute changes in the brightness of a star, imaged the transit of the planet across the star’s surface (like what we saw with the sun and Venus in 2004). From the resulting (tiny) drop in the star’s brightness as the planet progressed across its surface, the astronomers were able to determine the planet’s size, finding that it is smaller than previously estimated and in fact is one of the denser extrasolar planets found so far. Again, this new capability bodes well for the future.

Unexpected perspectives

Being human, Life in the cosmos 1 Response »

Jul 222008

The EPOXI mission of NASA’s Deep Impact spacecraft took pictures of Earth late in May 2008 from 31 million miles away, with the goal of examining Earth as if it were an extrasolar planet and looking for signs that would indicate life. The result is some interesting observations and a stunning movie that shows a full rotation of Earth with the moon passing across the field of view. It’s one of the most spectacular views of Earth from space that I’ve ever seen. For information about the observations and links to a second video, visit the EPOXI transit press release. Thanks to Mark for passing this one along.

I was surprised and equally delighted by another video that showed up as today’s Astronomy Picture of the Day. It’s a little unusual for APOD, but when I thought about it, I realized that in a way, it makes for an interesting counterpart to the EPOXI video. It’s an example of what you might get if you could zoom in on that spinning blue planet: a video montage of people all over the world dancing along with Matt Harding, who has taken to the road with an informal, energetic dance he does, and has found that if you start dancing, people in many parts of the world are happy to dance along with you. I was utterly charmed by the video; there is something beautifully goofy and joyous in the sight of all these people sharing moments of happy commotion. The wide range of natural and man-made environments was also impressive. I’m not sure why I found this video so emotionally moving. On the whole I find human diversity fascinating; I still remember a line from the original Star Trek where Spock said something about IDIC (infinite diversity in infinite combinations) and “the ways our differences can combine to create meaning and beauty.” But we so often have a hard time dealing constructively or even non-destructively with our differences, on levels from the individual up to the national. Maybe I just needed a reminder that for all the things that divide humans, we share some things in common as well.

Hello, anybody home?

Life in the cosmos 1 Response »

May 072008

This article from Technology Review presents an interesting twist on the question of whether we’re alone in the universe. The author hopes that we are alone, mainly because, as he explains, if the road to the emergence life is easy, then the fact that we’re unable to find any other intelligent life to talk to is likely to result from stumbling blocks on the road to space-faring life. In other words, there’s likely some kind of bottleneck that lowers the likelihood of space-faring civilizations. If the bottleneck lies in the long process that results in the emergence and evolution of living things, then that bottleneck is in the past for our species; we somehow dodged all the hazards and here we are, alive and intelligent. There may be other hazards in our future, but at least we’ve evidently surmounted obstacles that have prevented life from even getting this far on other worlds. On the other hand, if simpler life forms are common, then we can assume that life arises with relative ease, and the reason that we find the universe devoid of other intelligent life is that living things generally do not negotiate some existential crisis on the road to advanced technology and space colonization. It’s an interesting argument, and it may make you think twice about whether you dream of or dread the day we learn of fossil bacteria on Mars or the spectral signature of life in the atmosphere of an extrasolar planet.

Life born of ice?

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Feb 232008

As I look out the window on this February afternoon, it’s hard to see ice as anything other than an impediment to travel. However, this article from Discover Magazine describes several lines of evidence that indicate that ice might have been the birthplace of life on Earth.

The classic scientific image of how life began is that of a shallow pool on a warm early Earth, an organic soup sparked by lightning, perhaps, and giving rise to the amino acids that became the basis of life. But ice, rather surprisingly, possesses several qualities that might have made it a better incubator for life. For one thing, although chemical reaction rates go down in cold conditions, a process called eutectic freezing concentrates the impurities in water so that they are crowded together and forced into interactions with each other, canceling the effect of the slow-down due to the chill. This is a good way to concentrate and preserve fragile or volatile compounds, giving them the chance to assemble into something more interesting. Experiments also indicate that freezing temperatures offer favorable conditions for the formation and development of RNA.

It’s impossible to say for sure where life really originated, whether in ice or on mineral dust or as the result of volcanic outgassings. It might be some combination of the three. If the “snowball Earth” hypothesis, which suggests that a thick crust of ice covered the Earth at one point fairly early in its history, is correct, an icy origin for life might explain how life could have ever gotten started on such a snowball. More intriguingly, if freezing a planetary body makes it suitable for the emergence of life, that puts a new light on the possibilities for life in the ices to be found on places like Mars, Titan, and Europa.

Methane on extrasolar planet

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Feb 122008

Methane has been identified in the atmosphere of a planet orbiting another star, the first time that astronomers have found an organic compound on a planet outside of our own solar system. Earlier observations suggested that the planet also had water vapor in its atmosphere, and these new observations confirm that as well. This particular Jupiter-class planet is too close to its parent star, and thus too hot, for conditions there to be favorable for life, but the ability to analyze its atmosphere and detect methane there is still an exciting development. Someday the technique should prove useful for examining extrasolar planets that offer more potential as homes for extraterrestrial life.

Plate tectonics and life

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Jan 092008

The American Astronomical Society is holding its annual meeting in Austin, so you might notice that Thinking Meat is taking on a definitely star-struck feel this week. A story that made the news today is about plate tectonics on Earth-like planets.

The processes of plate tectonics are believed to be responsible for some crucial features that make Earth habitable, including the cycling of carbon dioxide between rock and atmosphere and back again (essential for temperature control, which in turn is essential for maintaining liquid water on the surface). Not to mention the creation of the continents and the maintenance of the magnetic field that helps keep our planet from being pasteurized by cosmic radiation—plate tectonics are good for living things. (Peter Ward and Donald Brownlee spend a whole chapter on plate tectonics in their book Rare Earth: Why Complex Life Is Uncommon in the Universe.)

But the news from Austin is that Earth appears to be at the small end of the range for planets with suitable conditions for plate tectonics. Simulations of rocky planets much larger than Earth showed that the movements of continental plates become easier on bigger planets, where the plates are thinner. Based on the simulations, scientists would expect to find plate tectonics operating on rocky planets three times as massive as the Earth and larger (with an upper limit of about ten times the Earth’s mass, because any bigger than that planets start to turn into gas giants). Perhaps the presence of water on Earth adds enough subterranean pressure to get the plates moving even though our planet is so small. Note that Mars and Venus, both smaller than Earth, do not have plate tectonics, and as far as we know have no life, certainly no complex life. It looks like rocky “super-Earth” planets might be relatively common in the cosmos, which makes this good news for anyone who hopes to someday find evidence for extraterrestrial life.

However, it’s a little disconcerting to realize that Earth is somewhat marginal in the plate tectonics department, especially in light of another news story about how the process might occasionally quit working. Geochemical evidence suggests that about a billion years ago, the volcanism associated with plate tectonics stopped. Around the same time, an ocean basin closed and the subduction zones surrounding it (where rock on the ocean floor collides into continental rock and gets pushed beneath it) were shut down, evidently bringing plate tectonics to a halt. Today subduction, an important driver for volcanism, earthquakes, and associated disturbances, is mostly happening in the Pacific basin, which is predicted to close in about 350 million years, when North and South America run into Eurasia. When this happens, plate tectonics might again grind to a halt (I know that phrase is a cliche, but it seems appropriate for something that involves the collision of continents). So it may be that our planet is not just borderline geologically active, but only intermittently geologically active as well.

Prebiotic chemistry around another star?

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Jan 072008

Chalk up another staggering discovery for the Hubble Space Telescope. Nine years ago, results from Hubble seemed to indicate that the disk of dust orbiting a youngish star called HR 4796A is restricted to a fairly narrow ring; the ring structure indicates that the dust is gravitationally constrained, presumably by planets or protoplanetary bodies that have formed from larger pieces of debris circling the star.

Now spectroscopic data from Hubble indicate that the ring of dust contains tholins, complex organic molecules that may be the antecedents of the biomolecules that on our planet gave rise to life. (Our atmosphere is no longer hospitable for tholins, but they’re believed to have been present on Earth billions of years ago; they also occur on Saturn’s moon Titan and in comets.) This is the first evidence of complex organic molecules in the dust surrounding another star. HR 4796A is very different from the sun–bigger, brighter, hotter, younger; it’s about 220 light years away and we see it in the sky among the stars of the constellation Centaurus. This press release has more information about the latest discovery. If we are indeed seeing the late stages of planet formation in an environment containing the precursors of life, it’s fun to speculate about what might lie ahead for this planetary system.

If you could talk to ET…

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Dec 272007

Judging by the plethora of self-help books on the topic, it’s hard to know what to say to people you don’t know, even ones who are leading lives fairly similar to your own. Intercultural communication can be even more challenging, and we’re still in the fairly early days of some kinds of interspecies communication (e.g., communicating with dolphins, whales, or some kinds of birds). But we’re an optimistic species, and some of us are trying to figure out how to successfully introduce ourselves to, and communicate with, any intelligent beings in the cosmos within reach of our signals.

This article from Seed Magazine addresses the question of whether the search for extraterrestrial intelligence should include actively broadcasting a message to the stars as well as passively listening. Some argue that it’s our moral responsibility to let any other civilizations out there know that we exist; others argue that by announcing our presence, we’re laying ourselves open to unknown but possibly catastrophic dangers. Of course science fiction has already explored the latter possibility, and your estimation of the danger is likely to vary with your ideas of who might be out there and who we’d meet first (Vulcans or the Borg? the Minbari or the Shadows?).

And furthermore, if we broadcast a message, what should it say? This article from New Scientist suggests that the data we’ve sent out into the void so far doesn’t give ET intelligence any interesting news about us other than that we exist and we are intelligent enough to understand some things about physics and chemistry. We’d be electrified and our societies might well be convulsed by learning such a thing about an ET civilization, but perhaps a more advanced civilization would be looking for specifics and would be bored by learning only the basics. (The record albums sent along with the Voyager spacecraft on their journey into deep space do give a brief glimpse of human culture, but I would guess the odds of anyone finding and understanding them are slim.) The article describes the efforts of two astrophysicists who have created a language for composing messages to ET civilizations and sent two messages so far. They’re looking for ways to make their next message more intriguing to possible extraterrestrials by encoding information about our social structures and practices. They hope to tell the universe about some of the more difficult challenges we’ve had to face as intelligent animals. I wish them well, although I wonder if the biggest payoff from their work might be a better understanding among ourselves of the problems they’re trying to describe, even if ET never does hear about them.

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