A set of archived chemical samples discovered in the UC San
Diego lab of the late scientist Stanley Miller offer glimpses of
the primordial Earth and into Miller's famous 1950s experiments on
the building blocks of life, according to an article published
Monday in the Proceedings of the National Academy of Sciences.
The study, by researchers at Scripps Institution of Oceanography
and other organizations, sheds new light on Miller's experiments,
showing that a slightly altered gas mixture yielded a richer trove
of amino acids ---- the basic component of the proteins that form
Miller came into prominence in 1953, when he charged a brew of
water, hydrogen, methane and ammonia with an electric spark to
mimic the effects of lightning on the atmosphere of early Earth.
That experiment yielded a handful of amino acids, providing greater
insight on how the precursors to life could form amid the gases of
the young planet.
Shortly before Miller's death in 2007, Jeffrey Bada, Miller’s
former student and now a professor of marine chemistry at Scripps
Institution of Oceanography, found untouched samples that Miller
had concocted, then shelved, in 1958.
"It's very surprising that these historic samples were just
sitting around, without anyone's knowledge, and a lot of them
haven't been analyzed," Eric Parker, a graduate student at the
Georgia Institute of Technology, and a former researcher in Bada's
lab, said in an interview Monday.
Bada, Parker and other researchers analyzed some of the samples
that included hydrogen sulfide, a gas that would have been present
in the atmosphere and plentiful around the planet's raging
volcanoes, but which was not included in the earlier
Hydrogen sulfide, it turns out, was the missing ingredient in
the primordial soup. Adding it to the mix of gases yielded a
greater range of chemical complexity. While Miller's original
experiment produced about five amino acids, researchers detected 23
in the latter samples, creating a better simulation of conditions
that scientists believe led to the first forms of life.
"One of the things we're interested in is the diversity of
organic compounds that might have been available in the early Earth
to set the stage for life," Bada said Monday. "If you include
hydrogen sulfide as a component in the early atmosphere, you really
make a richer selection of organic compounds than you do if it's
In addition, Bada said, modern analytical tools are far more
sensitive than the methods Miller used, allowing researchers to
detect a wider array of compounds in his extracts.
Researchers also found that the chemical components of the
samples is similar to those of meteorites, Bada said, revealing
that similar compounds could develop throughout the universe.
"The building blocks of life are probably quite widespread, and
if you have water, the possibility of moving from simple to more
complex molecules to something involving a living entity is quite
high," Bada said.
Although Miller became famous because of his early experiments,
Bada said, he may have overlooked his subsequent, more powerful
samples for a simple reason.