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A NASA probe that ferried material from a comet to Earth appears to have brought back an amino acid from that encounter, bolstering a theory that life's precursors may have arrived on our planet from outer space.

The Stardust spacecraft, launched in 1999, passed through Comet Wild 2 in 2004, soaking up particulates and gas with a unique, lightweight capture material known as aerogel. The sample-return portion of the spacecraft dropped safely to Earth during a flyby of our planet two years later.

Early analysis of the samples revealed the presence of biological building blocks such as amino acids, but terrestrial contamination remained a possible explanation for their occurrence.

In research presented Sunday at the fall meeting of the American Chemical Society, NASA researchers announced that the simple amino acid glycine in Stardust's sample is enriched with carbon 13, a heavy isotope of the element that is relatively rare on Earth but more prevalent in space. (Isotopes of chemical elements have different numbers of neutrons in the nucleus and hence different masses—carbon 12 has six protons and six neutrons, whereas carbon 13 has six protons and seven neutrons.)

"We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet," Jamie Elsila, one of the NASA researchers, said in a statement. Elsila said that Wild 2's glycine is the first amino acid to be found in a comet.

Amino acids are critical to life and biochemistry; glycine is one of the so-called standard amino acids used to synthesize proteins.

As for Stardust, it is heading to a new cometary investigation under a secondary mission. In 2011 the probe will fly by Comet Tempel 1, which NASA blasted with part of a spacecraft called Deep Impact in 2005 to explore its composition. The cometary probe is now known as Stardust-NExT (New Exploration of Tempel) after its new target.

Photo of Wild 2 from the Stardust Navigation Camera: NASA/JPL-Caltech

5 Comments

1. 1. scientific earthling 06:17 PM 8/18/09

   Life seeds life elsewhere.
   
   Our planet too dumps microscopic life forms into space. They may remain frozen bits of dust till they encounter the right environment or eventually end up in a collapsing cloud to form a new star or planet, in which event they are lost.
   
   Why is it so surprising that life exists elsewhere?

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2. 2. slvrwraith in reply to scientific earthling 08:11 PM 8/18/09

   I think it is less "surprising" and more confirming than anything else... While it is easy to for one's beliefs (ahem... religion), it is altogether different to locate empirical evidence of one's beliefs.

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3. 3. kristi276 09:27 PM 8/18/09

   We are stardust. The fact that the finding of amino acid from a comet only confirms the fact that the thread of life transcends beyond our planet and that the solar system is, also, a thread in the fabric of life. If this amino acid is present in comets which brought the seeds of life on fertile ground, does this mean that there are many fertile lands that life could be? If the seeds of life were planted here by comets, why not the whole galaxy, or the whole universe?

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4. 4. Michael F in reply to kristi276 09:47 PM 8/18/09

   What do you mean, "why not the whole galaxy or the whole universe?" Unless I'm misreading your question, it sounds like you are assuming that there is no other life out there? I think there is life throughout the galaxy, and therefore also throughout the Universe.
   
   Personally, I think that anyone who attempts to comprehend the sheer enormity of the galaxy, and its 100 billion stars, would be unlikely to challenge the idea that life, even intelligent life, likely exists elsewhere.

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5. 5. Sez Me 10:05 PM 8/19/09

   And a galaxy of a hundred billion stars pales into insignificance in a universe of a hundred billion galaxies......

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