20 December 2009

AGU 2009: Day 3 – Astrobiology and Society

Posted by Ryan Anderson

Wednesday was full of particularly interesting stuff: in between the Venus and moon talks there was also the Sagan lecture and an afternoon session about astrobiology and its implications in society.

The Sagan lecture was given by Tori Hoehler, a scientist at NASA Ames. He discussed the fundamental thermodynamics behind life, and showed that even if alien life relies on completely different molecules, there are basic requirements, such as the availability of free energy, that should be universal because they are rooted in the way the universe works. To paraphrase, he said: Life must evade the decay into equilibrium by reproducing extremely low probability results. There is a lot of thermodynamics behind this, but everyone has common sense experience with it. The world tends toward entropy unless energy is applied. Just take a look at the nearest college dorm room.

The DNA molecule is an incredibly complicated "aperiodic crystal" that is highly unlikely to form spontaneously. Energy is needed to make unlikely things like DNA assembly happen.

Hoehler used real world examples showing that living systems, be they simple bacteria colonies or all the complex cells involved in a human being, tend to grow until they are using all of the free energy available. There is a certain minimum amount of energy required to add a new piece (such as a cell) to the system, so the system can’t grow unless that amount of energy is available.

Tori concluded with a quote from Carl Woese: “Organisms are resilient patterns in a turbulent flow.” Hoehler argued that when thinking about biosignatures, we need to look at the fundamental requirements of any life. Regardless of its specific chemistry: energy use is the ultimate biosignature.

Later in the afternoon on Wednesday there was a really thought-provoking section about the societal implications of astrobiology. One of the first talks that I saw in the session was by David Koch, discussing the Kepler telescope. Kepler is a mission designed to stare at a single large patch of the sky for years, monitoring the brightness of hundreds of thousands of stars. Why? Well, occasionally a star will have planets that orbit in just the right configuration so that they “transit” – pass between their star and Kepler’s detector – blocking out a tiny fraction of the star’s light. Kepler was specifically designed so that it will be able to detect even the tiny dip in starlight caused by an earth-sized planet passing in front of a sun-like star. Koch showed an example of Kepler data, as compared with ground-based data of a star with a known transiting giant planet. The ground-based data was very noisy because of the turbulent atmosphere, but the Kepler data was so good that it looked like a solid line rather than a series of data points. The Kepler data was good enough that you could see the change in brightness as the planet went through phases like the moon. Koch also showed a tantalizing signal from a binary system that may have a planet orbiting both stars, much like everyone’s favorite binary-orbiting plant, Tatooine.

Sunset on a world orbiting binary stars. However, the planet detected by Kepler is likely a gas giant, not a rocky world like Tatooine. Image copyright Lucasfilm Ltd.

Next, Jacob Haqq-Misra, author of the new book “Planetary Messenger”, talked about how life and climate are intertwined. One example of this was the early climate, when the only life was methane-producing bateria. Methane is a powerful greenhouse gas, and so the global climate would warm rapidly with a world full of methane-making critters, but methane also undergoes chemical reactions when exposed to UV light and forms a thick haze. Just take a look at present-day Titan for proof of this! The haze would eventually get thick enough to cool the planet’s surface, balancing out the warming due to methane and preventing the planet from overheating.

Of course, then along came oxygen-producing life, which destroyed the methane and organic haze and poisoned most ofther forms of life, relegating them to dark anaerobic places like the stomachs of cows. Haqq-Misra also pointed out that the modern climate is pretty unusual: we have ice caps. Models suggest that Earth typically is quite warm, with no ice caps even at the poles, or it enters a “snowball” phase, where everything freezes up and ice extends down to the equator. In either case, live persists, and it may be the action of life that nudges the Earth out of these extremes. Haqq-Misra’s bottom line was that life is extremely resilient and can have a powerful effect on climate. Modern-day climate change could have serious consequences for humans, but life in general will adapt in the long run. “We’re not saving the world, but ourselves,” he said. It’s not quite that simple, since many species other than humans are threatened by climate change, but his basic point still is valid.

The Earth likely oscillates between a “snowball” and “hothouse” climate, with life-driven cycles, particularly the CO2 cycle, playing a major role.

The last few talks in the session strayed from science into social science and philosophy. Linda Billings spoke about the relationship between astrobiology and culture. She pointed out that astrobiology has gained credibility from large agencies like the National Research Council, and has always been popular with the public, but that the public and scientific perception is somewhat different. The public tends to assume ET life is common and like us, while science focuses more on extremophiles and the origin of life. One thing that I wish she had addressed a bit more was whether the public perception of ET life is necessarily a bad thing. Yes, there are powerful misconceptions to work against, but the public’s interest in astrobiology makes it a perfect “entry point” into all sorts of science!

The last few talks in the session considered the interplay between astrobiology and religion. Richard Randolph, presenting for Ted Peters who couldn’t make it, showed the results of a survey asking the question “Could the confirmation of another civilization in the universe cause a religious crisis?” The findings were not that surprising: Religious people did not think it would cause them to lose their faith, but were somewhat more likely to think that other people might lose faith. Non-religious people were almost all sure that such a discovery would cause religious people to have a crisis of faith. I would like to see the results of the survey if the word “crisis” was removed from the questions. I suspect more people would be willing to admit that discovering ET would make them think hard about their religion, but that they wouldn’t consider that a “crisis” of faith.

Next, Connie Bertka talked about astrobiology and evolution. She said that we really can’t avoid discussing science versus religion because, to paraphrase, “nature and creation are no longer purely in the theological domain”. Thus, she said that astrobiologists should encourage dialog with religious people. I think it’s a fine line to walk. We don’t want to give people like creationists legitimacy by engaging them on equal ground, but we equally can’t just avoid the interface between religion and science.

Finally, Richard Randolph discusses the Christian ethical implications of astrobiology. He asked two primary questions: What ethical obligations would Christians owe non-intelligent extraterrestrial life? and Is there a Christian obligation to spread life in the universe?

Based on his reading of Genesis, Randolph extended the common interpretation of humans as “stewards” or “god’s authority on earth” to extraterrestrial life. I was disappointed that he so obviously avoided talking about the elephant in the room for this issue though. Sure, the bible gives us stewardship over extra-terrstrial microbes. He even said that predation, in moderation, is “acceptable” just as it is for life here on earth. That’s all well and good. But what happens when we find aliens who are as smart or smarter than us? Does the bible give us stewardship over them? Permission for “predation in moderation”? Why would a creator make mere humans stewards over equally intelligent or possibly much more advanced species?

Ok, we are stewards over alien microbes, but what if we meet these guys?

As for the obligation to extend life in the universe, Randolph said that, since the bible repeated describes creation of life as “good” then by extension, spreading that life elsewhere qould also be good. Thus he said that there was “qualified affirmation” of the assertion that we are obliged to extend life elsewhere. Again he dodged a big question: do we extend terrestrial life at the expense of possible more primitive extra-terrestrial life? (a.k.a. when is it morally justified to terraform Mars?) What if spreading terrestrial life is at the expense of more advanced ET life?

It was refreshing to have these more philosophical talks after so much science. I may not have agreed with much of what Randolph said, but it definitely made me think, and it was a good reminder that science does not operate in a cultural vacuum.