Comets and life

Updating Comets and Magic Universe

Did comets spark life on Earth?

Part 1

A French team’s find of extraterrestrial dust grains rich in carbon in the snow of Antarctica is thrilling for any of us who have pondered the cosmic ancestry of life. A scarcity of carbonaceous material in the samples that NASA’s Stardust mission brought home from Comet Wild 2 in 2006 was a little disappointing – especially after the high hopes raised by molecular results radioed from ESA’s Giotto and the Soviet Vega spacecraft that intercepted Halley’s Comet in 1986, and by organic materials seen when NASA’s Deep Impact probe hit Comet Tempel 1 in 2005.

Collecting ultra-clean snow to be melted and sieved for meteoritic particles, in a trench at the French-Italian Concordia station in Antarctica. Photo Jean Duprat/CSNSM-CNRS.

But the Antarctic report by Jean Duprat and his colleagues, in the current issue of Science (7 May) puts us back on track to look for credible links between the complex carbon compounds seen interstellar space and the first living things to appear in the waters of the early Earth. That’s not just my opinion. Larry Nittler of the Carnegie Institution says in closing a commentary on the Duprat report:

The very high carbon contents of UCAMMs [ultra-carbonaceous Antarctic micrometeorites] may well have profound implications for the original delivery of organic molecules to the early Earth, with possible consequences for the earliest prebiotic chemistry.

It’s is a huge subject, stretching from the chemistry of dying stars and the search for extraterrestrial life to issues about chemical thermodynamics, the climate of the young Earth, and what surviving genes may tell us about the earliest viable entities. It’s peppered with hypotheses that I discuss in Giotto to the Comets as well as in Comets and Magic Universe. To deal adequately with this Update will take some time, so “Part 1” is a signal that there’ll be more to come.

Let me just mention that in Comets, written 30 years ago, I made fun of propositions from Fred Hoyle and Chandra Wickramasinghe about viable entities living in comets and being delivered ready-made to the Earth, scattered from the comets’ tails. Fred is dead, but Chandra thrives in Cardiff and has refreshed his ideas in “The origin of life in comets” (2007, Napier ref. below) and just last month in “The astrobiological case for our cosmic ancestry”. I’ll comment on those too, in the follow-up.

References

J. Duprat et al., Science, Vol. 328, pp. 742-5, 2010

L.R. Nittler, Science, Vol. 328, pp. 698-9, 2010

W.M. Napier, J.T. Wickramasinghe and N.C. Wickramasinghe, International Journal of Astrobiology, Vol. 6, pp. 321-323, 2007

C. Wickramasinghe, International Journal of Astrobiology, Vol.9, pp. 119-129, April 2010

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