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Artist concept of original Stardust spacecraft showing sample return capsule

NASA Researchers Make First Discovery of Life’s Building Block in Comet

NASA Goddard Space Flight Center–By Bill Steigerwald

NASA scientists have discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by NASA’s Stardust spacecraft.

“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 Dr. 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.”

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Example of one of the many organic particles collected and recovered by the Stardust mission. 

Elsila is the lead author of a paper on this research accepted for publication in the journal Meteoritics and Planetary Science. The research was presented during the meeting of the American Chemical Society at the Marriott Metro Center in Washington, DC..

“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 Dr. 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 nucleus of Wild 2 (pronounced “Vilt-2”) on January 2, 2004. As the spacecraft flew through this material, a special collection grid filled with aerogel – a novel 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 on January 15, 2006. 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.” 

Earlier, preliminary analysis in the Goddard labs detected glycine in both the foil and a sample of the aerogel. However, since glycine is used by terrestrial life, at first the team was unable to rule out contamination from sources on Earth. “It was possible that the glycine we found originated from handling or manufacture of the Stardust spacecraft itself,” said Elsila. The new research used isotopic analysis of the foil to rule out that possibility.

Isotopes are versions of an element with different weights or masses; for example, the most common carbon atom, Carbon 12, has six protons and six neutrons in its center (nucleus). However, the Carbon 13 isotope is heavier because it has an extra neutron in its nucleus. A glycine molecule from space will tend to have more of the heavier Carbon 13 atoms in it than glycine that’s from Earth. That is what the team found. “We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet,” said Elsila.

The team includes Dr. Daniel Glavin and Dr. Jason Dworkin of NASA Goddard. “Based on the foil and aerogel results it is highly probable that the entire comet-exposed side of the Stardust sample collection grid is coated with glycine that formed in space,” adds Glavin.

“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.”

The research was funded by the NASA Stardust Sample Analysis program and the NASA Astrobiology Institute. NASA’s Jet Propulsion Laboratory, Pasadena, Calif., manages the Stardust mission for NASA’s Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, developed and operated the spacecraft.

To learn more about the mission, visit http://stardustnext.jpl.nasa.gov/ <http://stardustnext.jpl.nasa.gov/>  .

For more about the NASA Goddard astrobiology team, visit http://astrobiology.gsfc.nasa.gov/analytical <http://astrobiology.gsfc.nasa.gov/analytical> .

…………………………………………………………………………………………….. 

Mission Overview

Comets preserve important clues to the early history of the solar system, and may have also contributed some of the volatiles that make up our oceans and atmosphere. Comets may even have brought to Earth the complex molecules from which life arose.

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Woodcut showing destructive influence of a fourth century comet from Stanilaus Lubienietski’s Theatrum Cometicum (Amsterdam, 1668) Don Yeomans’ Comets: A Chronological History of Observation, Science, Myth and Folklore. Used with permission.

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Artist concept of original Stardust spacecraft showing sample return capsule  

About Stardust-NExT:

Stardust-New Exploration of Tempel is a low-cost, low-risk mission that reuses the Stardust spacecraft, launched in February 1999, to flyby Comet Tempel 1 at a distance of 200 km on February 14, 2011 (39 days post perihelion) and obtain high-resolution images of the coma and nucleus, as well as measurements of the composition, size distribution and flux of dust emitted into the coma. The mission plans to expand the investigation of Comet Tempel 1 initiated by the Deep Impact spacecraft in July 2004, and for the first time assess the
changes in the surface of a comet between two successive perihelion passages providing important new information on how Jupiter family (JF) comets evolve and how they were put together at their formation 4.6 billion years ago.

Our major aims are:

  • To extend our understanding of the processes that affects the surfaces of comet nuclei by documenting the changes that have occurred on comet Tempel 1 between two successive perihelion passages.
  • To characterize the crater produced by Deep Impact in July 2005 to better understand the structure and mechanical properties of cometary nuclei and elucidate crater formation processes in them.

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This image shows the composite ITS image of the nucleus with a grid or coordinate system laid over it. The grid helps the science team reference features on the surface. The positive pole is over the horizon at upper right and the longitudes increase according to the right hand rule as defined by the IAU convention. The prime meridian was defined to go through the center of the well-defined crater above the impact site.
CREDIT: NASA/UM/Cornell/Peter Thomas and Tony Farnham
 

Image the nucleus (and jets) at resolutions as high as 12m/pixel

Measure the flux, size distribution, and composition of dust surrounding the nucleus.

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First of NASA…
Stardust-NExT will be the first mission to document the surface changes of a comet nucleus between successive perihelion passages.  as well as measure a specific comet with identical instruments the dust properties of two comets (Wild 2 and Tempel 1).

The mission will determine how the Deep Impact experiment modified the surface of Tempel 1 (e.g., crater size) and provide additional information on enigmatic layering and flow features discovered by Deep Impact.

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A molecule associated with life on Earth originated in space, perhaps in the halo of comet Wild 2 (above) where it was collected.

Credit: JPL/NASA

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This is an 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

PhysOrg.com — NASA scientists have discovered glycine, a fundamental building block of life, in samples of comet Wild 2 returned by NASA’s Stardust spacecraft.

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 Dr. 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 will be presented during the meeting of the American Chemical Society at the Marriott Metro Center in Washington, August 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 Dr. 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.

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This is an artist’s concept of particle hits on the aerogel collection grid. The greenish areas represent the aerogel. Hits are the light green teardrop-shaped areas. Particles are represented by dots at the tips of the teardrops. Credit: NASA/JPL 

Stardust passed through dense gas and dust surrounding the icy nucleus of Wild 2 (pronounced “Vilt-2”) on January 2, 2004. As the spacecraft flew through this material, a special collection grid filled with aerogel – a novel 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 on January 15, 2006. 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.”

Earlier, preliminary analysis in the Goddard labs detected glycine in both the foil and a sample of the aerogel. However, since glycine is used by terrestrial life, at first the team was unable to rule out contamination from sources on Earth. “It was possible that the glycine we found originated from handling or manufacture of the Stardust spacecraft itself,” said Elsila. The new research used isotopic analysis of the foil to rule out that possibility.

Isotopes are versions of an element with different weights or masses; for example, the most common carbon atom, Carbon 12, has six protons and six neutrons in its center (nucleus). However, the Carbon 13 isotope is heavier because it has an extra neutron in its nucleus. A glycine molecule from space will tend to have more of the heavier Carbon 13 atoms in it than glycine that’s from Earth. That is what the team found. “We discovered that the Stardust-returned glycine has an extraterrestrial carbon isotope signature, indicating that it originated on the comet,” said Elsila.

The team includes Dr. Daniel Glavin and Dr. Jason Dworkin of NASA Goddard. “Based on the foil and aerogel results it is highly probable that the entire comet-exposed side of the Stardust sample collection grid is coated with glycine that formed in space,” adds Glavin.

“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.”

More information: To learn more about the mission, visit http://stardustnext.jpl.nasa.gov/ .

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