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The quest for weird forms

Carl Zimmer

New York: A panel of scientists convened by America’s leading scientific advisory group says the hunt for extraterrestrial life should be greatly expanded to include what they call “weird life”: organisms that lack DNA or other molecules found in life as we know it.

“The committee’s investigation makes clear that life is possible in forms different from those on earth,” the scientists conclude in their report, The Limits of Organic Life in Planetary Systems, published on Frida y by the National Research Council.

Other experts hailed the report as an important rethinking of the search for life. “It’s going to help us a lot to make sure we go exploring with our eyes wide open,” said Dr. Michael A. Meyer, lead scientist for the Mars exploration programme of the National Aeronautics and Space Administration (NASA).

Starfish, sequoias, salamanders and the rest of the earth’s residents may seem very diverse, but they are surprisingly similar on the molecular scale. All species that scientists have studied need liquid water to survive, for example. Further, they all rely on DNA to carry genetic information, and they all use that information to build proteins from the same set of building blocks, known as amino acids.

NASA has long looked to life on the earth to guide its search for life in other worlds. Planets and moons that have hints of liquid water have been ranked high on the list of potential sites for life-detection missions.

But there is good reason to suspect that other kinds of chemistry could support life as well, the authors of the new report argue. Weird life could differ from life as we know it in small or big ways. For example, while DNA uses phosphorus in its backbone, it might be possible to build a backbone out of arsenic instead. And life might exist in liquids other than water, perhaps ammonia or methane.

The report, which is posted on the website of the National Academies, www.nationalacademies.org, even explores the possibility of life based on silicon, not carbon, though Meyer, who had no role in the work, thinks that astrobiologists should limit their search to carbon-based life forms.

The report calls for NASA and the National Science Foundation both to support research into weird life. Scientists should also search the earth for weird life, the authors maintain.

“There’s much about earth life we don’t understand,” said the panel’s chairman, Dr. John A. Baross of the University of Washington. — New York Times News Service

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