February 4, 2014
New Techniques Tease Out Building Blocks Of Life In Meteorites
[ Watch the Video: New Technique For Studying Out-Of-This-World Particles ]
Lawrence LeBlond for redOrbit.com - Your Universe OnlineScientists have long delved into the mysteries of the origins of life here on Earth and more recently have found evidence pointing to the skies above us. Some evidence has been found in material created in space and delivered to Earth via comets and meteors, containing the building blocks for life.
Callahan and colleagues have analyzed carbon-rich meteorites, known as carbonaceous chondrites, and found amino acids within. These amino acids, which make proteins, are the building blocks critical for life to begin. Proteins are among the most important molecules in life, needed for the creation of structures such as hair and skin. The meteorite analyses have also turned up evidence of components responsible for creating DNA, as well as other important life-based molecules.
Despite a wealth of discoveries, Callahan admits that such carbon-rich meteorites are relatively rare, with less than five percent of those recovered containing the building blocks of life. Also, the team claim that the building-block molecules found in these impactors have been at low concentrations, somewhere on the lines of parts-per-million or parts-per-billion.
Due to the relative rareness of such impacts and low concentrations of material, some critics question the validity and significance of meteors supplying the Earth with the building blocks of life. However, meteors are only one of many extraterrestrial forms that regularly bombard the Earth with material – most others being in the form of cosmic dust from comets and asteroids.
"Despite their small size, these interplanetary dust particles may have provided higher quantities and a steadier supply of extraterrestrial organic material to early Earth," said Callahan in a statement. "Unfortunately, there have been limited studies examining their organic composition, especially with regards to biologically relevant molecules that may have been important for the origin of life, due to the miniscule size of these samples."
Callahan and his team have more recently applied a new technique to inspect the small meteorite samples even more closely to tease out the components of life therein.
"We found amino acids in a 360 microgram sample of the Murchison meteorite," he said. "This sample size is 1,000 times smaller than the typical sample size used." One microgram equals one-millionth of a gram. Comparatively, 360 micrograms is equivalent in weight to that of a few eyebrow hairs.
"Our study was for proof-of-concept," adds Callahan. "Murchison is a well-studied meteorite. We got the same results looking at a very small fragment as we did a much larger fragment from the same meteorite. These techniques will allow us to investigate other small-scale extraterrestrial materials such as micrometeorites, interplanetary dust particles, and cometary particles in future studies."
Callahan noted that analyzing such miniscule samples is a big challenge.
"Extracting much less meteorite powder translates into having much lower amino acid concentration for analyses," he said. "Therefore we need the most sensitive techniques available. Also, since meteorite samples can be highly complex, techniques that are highly specific for these compounds are necessary too."
Nanoflow liquid chromatography was the new technique implemented by the team to sort out the molecules in the sample. Once the molecules were sorted, the team then used a nanoelectrospray ionization to give them an electric charge and then used a high-resolution mass spectrometer instrument to identify the molecules based on their mass.
"We are pioneering the application of these techniques for the study of meteoritic organics," said Callahan. "These techniques can be highly finicky, so just getting results was the first challenge."
"I'm particularly interested in analyzing cometary particles from the Stardust mission," adds Callahan. "It's one of the reasons why I came to NASA. When I first saw a photo of the aerogel used to capture particles for the Stardust mission, I was hooked."
"This technology will also be extremely useful to search for amino acids and other potential chemical biosignatures in samples returned from Mars and eventually plume materials from the outer planet icy moons Enceladus and Europa," Daniel Glavin, of the Astrobiology lab at Goddard, said in a statement.
The team expresses that the technology and techniques employed at the Goddard lab will be of huge significance in the future analytics of meteorites from sample-return missions, especially since any material from space will likely have limited quantities of the building blocks of life.
"Missions involving the collection of extraterrestrial material for sample return to Earth usually collect only a very small amount and the samples themselves can be extremely small as well," said Callahan. "The traditional techniques used to study these materials usually involve inorganic or elemental composition. Targeting biologically relevant molecules in these samples is not routine yet. We are not there either, but we are getting there."
Callahan was the lead author of a paper on the findings, published online in the Journal of Chromatography A; Glavin was a coauthor.
The research was funded by the NASA Astrobiology Institute, the Goddard Center for Astrobiology and the NASA Cosmochemistry Program.
Image Below: This photo compares the sample size typically used in meteorite studies (yellow oval) to the sample size used with the new equipment (blue circle) in Goddard's Astrobiology Analytical Laboratory. Credit: Michael Callahan