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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 5 Feb 2014 10:24:45 -0800 (PST)
Message-ID: <201402051824.s15IOjC9019375_at_zagami.jpl.nasa.gov>


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.

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."

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
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.
Received on Wed 05 Feb 2014 01:24:45 PM PST

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