DNA sugar can form in space, experiments show
Lab work adds to evidence that extraterrestrial organic compounds may have seeded life on Earth. Andrew Masterson reports.
Laboratory experiments have shown that a sugar critical to the structure of DNA arises when ice formed on planets, asteroids and meteorites is subjected to ultraviolet radiation.
The result adds to evidence that organic molecules can form under non-biological conditions, and extends the argument that the substances needed for life to emerge on Earth may have originally come from outer space.
In a paper published in the journal Nature Communications, Michel Nuevo, George Cooper, and Scott Sandford, all from NASA’s Ames Research Centre in the US, report detecting 2-deoxyribose – the sugar component of DNA – and several deoxysugar derivatives in residues produced from the ultraviolet irradiation of ice mixtures under standard astrophysical conditions in the laboratory.
They also tested samples from selected meteorites and detected the presence of deoxysugars. However, quantities were too small to permit the unambiguous identification of the DNA sugar.
Nevertheless, the results are highly significant.
“The presence of sugar derivatives in primitive meteorites, together with other compounds of biological interest such as amino acids, nucleobases, and amphiphiles is consistent with a scenario in which a significant fraction of the inventory of compounds from which biological processes started on the primitive Earth may have been delivered via comets, meteorites, and interplanetary dust particles (IDPs),” the authors write.
The researchers reached their conclusions after blasting ice comprising water and methanol with ultraviolet irradiation and held at the extremely low temperatures that are typical of space.
The work continues about 25 years of experimentation regarding the formation of sugars as a result of non-biological astrophysical processes. In 2001, for instance, a team demonstrated that in conditions analogous to those impacting ice on planets or asteroids in deep space, ultraviolet exposure induced the formation of amino acids.
Research in 2016, researchers conducted a similar experiment, reported in the journal Science, in which ice formed from water, methanol and ammonia was irradiated “under conditions similar to those expected during the formation of the solar system”.
The result produced a variety of simple sugars – including ribose, a key component of RNA.
For Nuevo and his colleagues, the latest findings add another piece to the puzzle of how life emerged on Earth, and whether that event was unique in the universe, or a predictable, even unavoidable, outcome.
“Though terrestrial processes must also have contributed to the emergence of life on our planet over 3.8 billion years ago,” they write, “the formation of complex organics in astrophysical environments and the delivery of compounds of biological importance to telluric planets are believed to be universal events that may have occurred elsewhere in the Universe.”