[meteorite-list] New Technique Could Be Used to Search Space Dust for Life's Ingredients

[Ron Baalke]

http://www.nasa.gov/content/new-technique-could-be-used-to-search-space-dust-for-lifes-ingredients/

New Technique Could Be Used to Search Space Dust for Life's Ingredients
Bill Steigerwald
NASA's Goddard Space Flight Center, Greenbelt, Md.
william.a.steigerwald at nasa.gov
February 3, 2014

While the origin of life remains mysterious, scientists are finding more 
and more evidence that material created in space and delivered to Earth 
by comet and meteor impacts could have given a boost to the start of life. 
Some meteorites supply molecules that can be used as building blocks to 
make certain kinds of larger molecules that are critical for life.

Researchers have analyzed carbon-rich meteorites (carbonaceous chondrites) 
and found amino acids, which are used to make proteins. Proteins are among 
the most important molecules in life, used to make structures like hair 
and skin, and to speed up or regulate chemical reactions. They have also 
found components used to make DNA, the molecule that carries the instructions 
for how to build and regulate a living organism, as well as other biologically 
important molecules like nitrogen heterocycles, sugar-related organic 
compounds, and compounds found in modern metabolism.

However, these carbon-rich meteorites are relatively rare, comprising 
less than five percent of recovered meteorites, and meteorites make up 
just a portion of the extraterrestrial material that comes to Earth. Also, 
the building-block molecules found in them usually have been at low concentrations, 
typically parts-per-million or parts-per-billion. This raises the question 
of how significant their supply of raw material was. However, Earth constantly 
receives other extraterrestrial material - mostly in the form of 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 Michael Callahan of NASA's Goddard Space 
Flight Center in Greenbelt, Md. "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 at Goddard's Astrobiology Analytical Laboratory 
have recently applied advanced technology to inspect extremely small meteorite 
samples for the components of life. "We found amino acids in a 360 microgram 
sample of the Murchison meteorite," said Callahan. "This sample size is 
1,000 times smaller than the typical sample size used." A microgram is 
one-millionth of a gram; 360 micrograms is about the weight of a few eyebrow 
hairs. 28.35 grams equal an ounce.

[Image]
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.
Image Credit: Michael Callahan

"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 is lead author of a paper on this research 
available online in the Journal of Chromatography A.

Analyzing such tiny samples is extremely challenging. "Extracting much 
less meteorite powder translates into having much lower amino acid concentration 
for analyses," said Callahan. "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."

The team used a nanoflow liquid chromatography instrument to sort the 
molecules in the meteorite sample, then applied nanoelectrospray ionization 
to give the molecules an electric charge and deliver them to a high-resolution 
mass spectrometer instrument, which identified 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."

[Image]
This equipment is used by Goddard's Astrobiology Analytical Lab to analyze 
very small samples. On the right is the nanoelectrospray emitter, which 
gives sample molecules an electric charge and transfers them to the inlet 
of the mass spectrometer (left), which identifies the molecules by their 
mass.
Image Credit: Michael Callahan

"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," said Daniel Glavin of the Astrobiology lab at Goddard, a 
co-author on the paper.

This technology and the laboratory techniques that the Goddard lab develops 
to apply it to analyze meteorites will be valuable for future sample-return 
missions since the amount of sample likely will be limited. "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."

The research was funded by the NASA Astrobiology Institute, the Goddard 
Center for Astrobiology and the NASA Cosmochemistry Program.