In Real Science: What are the odds?

Nicholas Albertini

With both satellites and nuclear submarines colliding this week, one does wonder about the odds. Life on Earth was the theme of this year’s meeting of the American Association for the Advancement of Science in Chicago, taking place Feb. 12-16. Several scientists made astounding conjectures in their fields.
Astrophysicist Alan Boss of the Carnegie Institution for Science suggested that there could be more than 100 billion Earth-like planets orbiting within the habitable regions of their sun-like stars just in our own galaxy. Considering that there are somewhere in the neighborhood of a few hundred billion galaxies in the visible universe, such prevalence would be staggering.
Physics professor Paul Davies of Arizona State University proposed a search for a second genesis of life on Earth. He suggested that there could exist what he calls a “shadow biosphere” where “shadow life” may be hiding. He also suggested that this “shadow life” would likely consist of forms that have different biochemical metabolisms and do not process the same chemicals as normal life.
Such differences would be due to a separate biogenesis and would prove that life started on Earth more than once. He suggested that areas rich in arsenic may be especially prone to harboring this kind of biosphere. Davies believes that that the main reason that we have not found such life before is probably that we have not looked for it.
Meanwhile, biochemistry professor Steven Benner of The University of Florida and The Foundation for Applied Molecular Evolution unveiled his evolving DNA in a beaker. This DNA has six base nucleotides rather than four and requires polymerase chain reaction cycling to replicate. That is, it has to be cooked and cooled in a vat of chemicals each time. But the DNA is evolving, in the sense that it makes errors, which might be more likely to be replicated in future cycles. Professor Benner conjectures that we may one day find life forms with such a six base genetic code on other planets. His research is funded by NASA.
A more accurate theme for the meeting might have been life on other planets. Conjectures are not weighted very heavily in science, but when they come from people of such high expertise in their fields, it is advisable to take heed.
If there really are so many habitable planets in the universe, and if it can be demonstrated that life has arisen on ours more than once, then it is assured that there are not only other life forms out there, but intelligent life as well.
If Benner is successful in creating a self-replicating version of his evolving biochemical set of polymers, we will see the mechanism of this self-creation for ourselves. If we can detect a telltale biological light spectrum from another planet, we will know without a doubt.
With the Kepler space telescope scheduled to launch Mar. 5 to search for Earth-sized extrasolar planets, at least one of these conjectures with be put to the test very soon.

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