Could life rise in a comet?
Scientists stretch their imaginations to wonder at the possibility of life on comets and noncarbon-based creatures.
Astrobiologist Chandra Wickramasinghe says that what we're learning about the interior of comets suggests they would be havens for organic (i.e., carbon-based) life. Physicist V.N. Tsytovich wonders if all life-forms must be carbon-based. He finds intriguing lifelike processes among supposedly inert dust particles in interstellar space.
Welcome to "The Twilight Zone" of science, where fact melds with speculation. Scientific knowledge consists of verifiable facts and well-tested theories.
But to gain reliable knowledge, scientists often let their imaginations run ahead of what they actually know.
Dr. Wickramasinghe at Cardiff University in Wales has pursued this strategy for decades in search of insight into the prospects for life in outer space. He has been particularly interested in the possibility that simple life-forms could originate in space and travel through it – a concept called panspermia. Now he has joined colleagues Bill Napier and Janaki Wickramasinghe in a paper to be published in the International Journal of Astrobiology that lays out the case for life inside comets.
Earlier this month, the university's announcement of this work noted that, in 2005, the Deep Impact probe to Comet Tempel 1 gouged out a mix of clay particles and organic substances. The Stardust probe that visited Comet Wild 2 in 2004 found numerous hydrocarbon molecules such as those believed to be involved in pre-life chemistry. The research team suggests that radioactive heat could maintain a habitable liquid environment within a comet. Clay, the porous surface of which may have provided a platform for assembling biological molecules on Earth, presumably could be a life-enabling platform within comets as well.
"The findings of the comet missions, which surprised many, strengthen the argument for panspermia," Wickramasinghe explains. "We now have a mechanism for how it could have happened."
Meanwhile, Dr. Tsytovich at the Russian Academy of Science in Moscow and an international team of colleagues explain in the online New Journal of Physics why scientists should look beyond organic matter in their search for the origins of life. They are using computer modeling to study the interactions of particles in interstellar plasmas. (A plasma is made up of equal numbers of positive and negative electrically charged particles.)
The report of these studies issued earlier this month by Britain's Institute of Physics and the German Physical Society, co-owners of the journal, cites lifelike self-organization among some of these particles. They form helical structures that divide and duplicate themselves, as does biological DNA. They evolve into different forms that, over time, sort out the more stable form from those less fit to survive – an evolutionary process.
"These complex, self-organized plasma structures exhibit all the necessary properties to qualify them as candidates for inorganic living matter," Tsytovich concludes. "They are autonomous. They reproduce and evolve."
That's a big stretch to make on the basis of computer modeling. Take it for what it is – a challenge not to be too comfortable with the Earth-centric assumption that all life must be carbon-based.
As for the comet havens that Wickramasinghe's studies, nothing has been proved to substantiate that hypothesis so far. Their value lies in encouraging us to think beyond Earth's biology and adopt a cosmic perspective.