March 26, 2002

Amino Acids From Interstellar Space

Dr. Max Berstein

A team of scientists including SETI Institute and NASA researchers today announced the successful creation of amino acids, chemicals essential to life, in a laboratory simulation of conditions found in deep space.

At NASA's Ames Research Center, Moffett Field, CA, the team reproduced the freezing conditions that exist in the gigantic interstellar clouds of dust, gas, and ice that are the birthplaces of new stars and planetary systems.

In their experiment, NASA scientists simulated space-like conditions by freezing mixtures of common molecules found in interstellar clouds then exposed them to ultraviolet radiation. When analyzed, the resulting material contained glycine, alanine, and serine, amino acids that play central roles in all living organisms on Earth. The team reported its results in the March 28 issue of the journal Nature.

"We had previously shown that the chemistry that occurs under these conditions makes a number of different types of organic compounds of biological interest," said Dr. Max Bernstein, first author and chemist at the Center for the Study of Life in the Universe at the SETI Institute and NASA Ames, "but because of their critical role in life on Earth, we really wanted to see if amino acids were in the mix."

"A variety of amino acids have previously been detected in certain kinds of primitive meteorites," noted Dr. George Cooper of Ames. "Their presence in meteorites proves that amino acids are, in fact, made in space. However, it has generally been thought that they were produced in the solar system within asteroids, the sources of most meteorites. Our latest work suggests that at least some of the amino acids found in meteorites may predate our solar system."

"Indeed," noted Dr. Scott Sandford of Ames, "these findings are particularly intriguing because the amino acids found in meteorites do show some signatures that suggest an interstellar connection. This connection, combined with our finding that amino acids can be made in interstellar clouds suggests that the Earth may have been seeded with amino acids from space in its earliest days."

"The infall of these materials on the early Earth may have facilitated the origin of life on our planet," said Dr. Jason Dworkin of the SETI Institute and Ames. "Furthermore, since new stars and planets are formed within the same clouds in which new amino acids are being created, this probably increases the odds that life has evolved elsewhere."

"It now seems possible that at least some of the amino acids found in meteorites predate the formation of our solar system and were in fact synthesized in interstellar space. If they were incorporated into meteorites, it's natural to ask if they would have been incorporated into comets as well. Since recent work [e.g. Amino acid survival in large cometary impacts (E. Pierazzo and C.F. Chyba). 1999. Meteoritics and Planetary Science 32, 909-918. ] suggests that some amino acids should survive cometary impacts with Earth, there may be a direct link between prebiotic organic molecules on early Earth and interstellar space," says Dr. Christopher Chyba, a recent MacArthur Award winner who holds the Carl Sagan Chair and heads the Center for the Study of Life in the Universe (LITU) at the SETI Institute.

Previously, members of this team had demonstrated that irradiation of interstellar ice analogs results in the production of other compounds that are also of potential biological interest. These include a class of compounds called amphiphiles that can self-organize to form membranes and a class of compounds called quinones, aromatic ketones that play important roles in the metabolisms of living organisms on the modern Earth. "Taken in combination, these results suggest that interstellar chemistry may have played a significant part in supplying the Earth with some of the organic materials needed to get life started," Sandford concluded.

The mission of the SETI Institute is to explore, understand and explain the origin, nature, prevalence and distribution of life in the universe.

• astrochem.org

• Center for the Study of Life in the Universe

SETI Institute Contacts

• Karen Randall
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• Taylor Bucci
  Center for the Study of Life in the Universe
  (650) 960-4519

Vacuum system and cryostat

Above is a picture of the vacuum system and cryostat in the astrochemistry lab that is fit with the manual liquid Helium transfer line. With this set-up it is possible to go as cold as 4 K, just four degrees above absolute zero! (that is almost - 270 C or -450 F) Drs. Salama and Halasinksi use it to take UV spectra of PAHs and PAH ions in solid Ne, and these are compared to astronomical data.

Window at the center of the vacuum system

Above is a closer look at the window at the center of one of these vacuum systems. You are looking in the side of the vacuum system, through an outer window where a laser, IR, or UV light would shine. Inside the vacuum system is another window in a black frame (illuminated by blue light) and it is on this smaller innner window that the sample is prepared. Off to the right the thing that looks like its wrapped in gauze is a pyrex tube containing a sample of PAH. The wrap is heat tape, heating is needed to sublime the sample.

More equipment images