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Building block of life reported found in comet

Aug. 18, 2009
Courtesy NASA
and World Science staff

Sci­en­tists have re­ported find­ing a fun­da­men­tal build­ing block of life in sam­ples of com­et Wild 2 brought to Earth by NASA’s Star­dust space­craft.

The chem­i­cal, gly­cine, “is an ami­no ac­id used by liv­ing or­gan­isms to make pro­teins, and this is the first time an ami­no ac­id has been found in a com­et,” said Ja­mie El­sila of NASA’s God­dard Space Flight Cen­ter in Green­belt, Md. “Our dis­cov­ery sup­ports the the­o­ry that some of life’s in­gre­di­ents formed in space and were de­liv­ered to Earth long ago by me­te­or­ite and com­et im­pacts.” 

Artist's con­cept of the Star­dust space­craft be­gin­ning its flight through gas and dust around com­et Wild 2. The white ar­ea rep­re­sents the com­et. The col­lec­tion grid is the ten­nis-rack­et-shaped ob­ject ex­tend­ing out from the back of the space­craft. (Cred­it: NA­SA/JPL )


El­sila is the lead au­thor of a pa­per on this re­search ac­cept­ed for pub­lica­t­ion in the jour­nal Me­te­or­it­ic and Plan­e­tary Sci­ence. The re­search was also pre­sented at an Amer­i­can Chem­i­cal So­ci­e­ty meet­ing in Wash­ing­ton, D.C. on Aug. 16. 

The dis­cov­ery “sup­ports the idea that the fun­da­men­tal build­ing blocks of life are prev­a­lent in space, and... that life in the un­iverse may be com­mon,” added Carl Pil­cher, Di­rec­tor of the NASA As­tro­bi­ol­o­gy In­sti­tute which co-funded the re­search. 

Pro­teins are the work­horse mo­le­cules of life, used in eve­ry­thing from struc­tures like hair to en­zymes, the cat­a­lysts that speed up or reg­u­late chem­i­cal re­ac­tions. Just as the 26 let­ters of the al­pha­bet are ar­ranged in lim­it­less com­bina­t­ions to make words, life uses 20 dif­fer­ent ami­no ac­ids in a huge va­ri­e­ty of ar­range­ments to build mil­lions of dif­fer­ent pro­teins. 

Star­dust passed through dense gas and dust sur­round­ing the icy co­re of Wild 2 (pro­nounced “Vilt-2”) on Jan. 2, 2004. As the space­craft flew through this ma­te­ri­al, a spe­cial col­lec­tion grid filled with aer­o­gel – a sponge-like ma­te­ri­al that’s more than 99 per­cent emp­ty space – gently cap­tured sam­ples of the com­et’s gas and dust. 

The grid was stowed in a cap­sule which de­tached from the space­craft and par­a­chut­ed to Earth two years lat­er. Since then, sci­en­tists around the world have been busy an­a­lyz­ing the sam­ples to learn the se­crets of com­et forma­t­ion and our so­lar sys­tem’s his­to­ry. 

“We ac­tu­ally an­a­lyzed alu­mi­num foil from the sides of ti­ny cham­bers that hold the aer­o­gel in the col­lec­tion grid,” said El­sila. “As gas mo­le­cules passed through the aer­o­gel, some stuck to the foil. We spent two years test­ing and de­vel­op­ing our equip­ment to make it ac­cu­rate and sen­si­tive enough to an­a­lyze such in­credibly ti­ny sam­ples.” 

“The dis­cov­ery of ami­no ac­ids in the re­turned com­et sam­ple is very ex­cit­ing and pro­found,” said Star­dust Prin­ci­pal In­ves­ti­ga­tor Pro­fes­sor Don­ald E. Brown­lee of the Un­ivers­ity of Wash­ing­ton, Se­at­tle, Wash. “It is al­so a re­mark­a­ble tri­umph that high­lights the ad­vanc­ing ca­pa­bil­i­ties of lab­o­r­a­to­ry stud­ies of prim­i­tive ex­tra­ter­res­tri­al ma­te­ri­als.” 


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Scientists have reported finding a fundamental building block of life in samples of comet Wild 2 brought to Earth by NASA’s Stardust spacecraft. The chemical, glycine, “is an amino acid used by living organisms to make proteins, and this is the first time an amino acid has been found in a comet,” said Jamie Elsila of NASA’s Goddard Space Flight Center in Greenbelt, Md. “Our discovery supports the theory that some of life’s ingredients formed in space and were delivered to Earth long ago by meteorite and comet impacts.” Elsila is the lead author of a paper on this research accepted for publication in the journal Meteoritics and Planetary Science. The research was be presented during the meeting of the American Chemical Society in Washington, D.C. on Aug. 16. “The discovery of glycine in a comet supports the idea that the fundamental building blocks of life are prevalent in space, and strengthens the argument that life in the universe may be common rather than rare,” said Carl Pilcher, Director of the NASA Astrobiology Institute which co-funded the research. Proteins are the workhorse molecules of life, used in everything from structures like hair to enzymes, the catalysts that speed up or regulate chemical reactions. Just as the 26 letters of the alphabet are arranged in limitless combinations to make words, life uses 20 different amino acids in a huge variety of arrangements to build millions of different proteins. Stardust passed through dense gas and dust surrounding the icy core of Wild 2 (pronounced “Vilt-2”) on Jan. 2, 2004. As the spacecraft flew through this material, a special collection grid filled with aerogel – a sponge-like material that’s more than 99 percent empty space – gently captured samples of the comet’s gas and dust. The grid was stowed in a capsule which detached from the spacecraft and parachuted to Earth two years later. Since then, scientists around the world have been busy analyzing the samples to learn the secrets of comet formation and our solar system’s history. “We actually analyzed aluminum foil from the sides of tiny chambers that hold the aerogel in the collection grid,” said Elsila. “As gas molecules passed through the aerogel, some stuck to the foil. We spent two years testing and developing our equipment to make it accurate and sensitive enough to analyze such incredibly tiny samples.” “The discovery of amino acids in the returned comet sample is very exciting and profound,” said Stardust Principal Investigator Professor Donald E. Brownlee of the University of Washington, Seattle, Wash. “It is also a remarkable triumph that highlights the advancing capabilities of laboratory studies of primitive extraterrestrial materials.”