Discussion and news about the modern effort to understand the nature of life on Earth, finding planets around other stars, and the search for life elsewhere in the universe

Monday, April 11, 2011

Rotten Eggs

Posts here have been a bit more threadbare than usual. Mea culpa. Can be blamed on a number of projects, including a fun writing one that you will be able to find in the May 7th issue of New Scientist magazine as their "Instant Expert" piece on Astrobiology - a lavishly illustrated 8 page spread. Hats off to the editorial and graphics staff there.

It's also been a hard time to summon the courage to move on after the kind of dreadful, gray news coming recently from NASA as missions are abandoned left, right, and center. Not good. The trickle down from this kind of mass slaughter is going to be significant.  NASA's entire budget is a miniscule 0.5% or so of the federal budget of the USA, and the projects being cut are an even smaller fraction of that. Between this and the shutdown of the Tevatron it would seem that the shining city upon a hill is getting a little dilapidated, when it comes to fundamental science.

Onto better stuff. Hydrogen sulphide, in fact. An interesting result appeared recently in the Proceedings of the National Academies, by Parker et al. that re-analyzes the products of an experiment performed half a century ago. Back in the early 1950's Stanley Miller and Harold Urey performed a number of experiments on the chemistry of a mix of 'raw' ingredients of water, methane, ammonia and hydrogen gas. By subjecting this gaseous stew to electrical discharges they attempted to reproduce conditions that might have existed on a very young planet Earth. The basic idea was to see if the rudimentary molecules for life, the prebiotic organics, might arise. Some indeed did, a smattering of amino acids for example, along with a lot of chemical muck.  There were big uncertainties though, not least of which was the true composition of the young Earth's atmosphere.

Quite recently some of Miller's later experiments came to light, by way of the analysis of sealed glass vials stored in his lab from the 1950's. Modern chemical analysis techniques are far more sensitive and precise than those that had been available to Miller, and it became clear that many more amino acids had formed inside his experiments than he had realized at the time.

Now Parker and colleagues have taken a look at a particular batch of vials from 1958 where Miller included hydrogen sulphide (H2S) in his starter mix. He had never reported the results. Hydrogen sulphide is a widespread compound, from volcanoes on Earth to extraterrestrial environments. Remarkably, these experiments seem to have produced the highest yields of amino compounds in any such conditions. The finger points to the presence of sulfur. A whiff of that could be truly magic for building bio-molecules on a primordial world.

Quite incredibly, the mix of amino acids is also a very close match to that of a number of carbonaceous chondrite meteorites. Given that hydrogen sulphide is certainly found in these meteorites the indication is that the same kind of chemistry could have taken place off-world in the proto-planetary environment. So, that wonderfully malodorous substance hydrogen sulphide could provide a critical boost to the abiotic chemical synthesis of some of life's building blocks - both here on Earth, and further afield.

Thank goodness Stanley Miller didn't like to throw things away.


Mini said...

Interesting piece, and very well written, Caleb!

Hehe, I love your final comment! :D One mans "trash" can be our future treasure! :)

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