A version of this article first appeared in Astrobiology Magazine, http://www.astrobio.net.
The fossil remains of a natural nuclear reactor in Oklo, Gabon. It entered a fission state some 2 billion years ago, and so would not have been involved in any origin of life scenario. But is a proof of concept that these natural reactors have existed and some were widespread on earth Earth. It is but one possible source of high energy particles on early Earth. The yellow rock is uranium oxide. (Robert D. Loss, Curtin University, Australia)
Life on early Earth seems to have begun with a paradox: while life needs water as a solvent, the essential chemical backbones of early life-forming molecules fall apart in water. Our universal solvent, it turns out, can be extremely corrosive.
Some have pointed to this paradox as a sign that life, or the precursor of life, originated elsewhere and was delivered here via comets or meteorites. Others have looked for solvents that could have the necessary qualities of water without that bond-breaking corrosiveness.
In recent years the solvent often put forward as the eligible alternative to water is formamide, a clear and moderately irritating liquid consisting of hydrogen, carbon, nitrogen and oxygen. Unlike water, it does not break down the long-chain molecules needed to form the nucleic acids and proteins that make up life’s key initial instruction manual, RNA. Meanwhile it also converts via other useful reactions into key compounds needed to make nucleic acids in the first place.
Although formamide is common in star-forming regions of space, scientists have struggled to find pathways for it to be prevalent, or even locally concentrated, on early Earth. In fact, it is hardly present on Earth today except as a synthetic chemical for companies.
New research presented by Zachary Adam, an earth scientist at Harvard University, and Masashi Aono, a complex systems scientist at Earth-Life Science Institute (ELSI) at Tokyo Institute of Technology, has produced formamide by way of a surprising and reproducible pathway: bombardment with radioactive particles.
In a room fitted for cobalt-60 testing on the campus of the Tokyo Institute of Technology, a team of researchers gather around the (still covered) cobalt-60 and vials of the chemicals they were testing. The ELSI scientists are (from left) Masashi Aono, James Cleaves, Zachary Adam and Riquin Yi. (Isao Yoda)
The two and their colleagues exposed a mixture of two chemicals known to have existed on early Earth (hydrogen cyanide and aqueous acetonitrile) to the high-energy particles emitted from a cylinder of cobalt-60, an artificially produced radioactive isotope commonly used in cancer therapy.… Read more
