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---
title: Building Blocks of DNA Found in Meteorites From Space | Biological Molecules on Meteorites
date: 2011-08-09T18:58:58Z
source: http://www.space.com/12569-meteorites-dna-building-blocks-discovery.html
tags: science
---
The components of DNA have now been confirmed to exist in
extraterrestrial meteorites, researchers announced.
A different team of scientists also discovered a number of molecules
linked with a vital ancient biological process, adding weight to the
idea that the earliest forms of life on Earth may have been made up in
part from [materials delivered to Earth the planet by from
space](http://www.space.com/10498-life-building-blocks-surprising-meteorite.html).
Past research had revealed a range of building blocks of life in
meteorites, such as the amino acids that make up proteins. Space rocks
just like these may have been a vital source of the organic compounds
that [gave rise to life on
Earth](http://www.livescience.com/10668-thick-haze-protected-life-earth.html).
Investigators have also found nucleobases, key ingredients of DNA, in
meteorites before. However, it has been very difficult to prove that
these molecules are not contamination from sources on Earth. [[5 Bold
Claims of Alien
Life](http://www.space.com/11057-science-claims-alien-life.html)]
"People have been finding nucleobases in meteorites for about 50 years
now, and have been trying to figure out if they are of biological origin
or not," study co-author Jim Cleaves, a chemist at the Carnegie
Institution of Washington, told SPACE.com.
To help confirm if any [nucleobases seen in
meteorites](http://www.space.com/9366-meteorite-based-debate-martian-life.html)were
of extraterrestrial origin, scientists used the latest scientific
analysis techniques on samples from a dozen meteorites — 11 organic-rich
meteorites called carbonaceous chondrites and one ureilite, a very rare
type of meteorite with a different chemical composition. This was the
first time all but two of these meteorites had been analyzed for
nucleobases.
The analytical techniques probed the mass and other features of the
molecules to identify the presence of extraterrestrial nucleobases and
see that they apparently did not come from the surrounding area.
Two of the carbonaceous chondrites contained a diverse array of
nucleobases and structurally similar compounds known as nucleobase
analogs. Intriguingly, three of these nucleobase analogs are very rare
in Earth biology, and were not found in soil and ice samples from the
areas near where the meteorites were collected at the parts-per-billion
limits of their detection techniques.
"Finding nucleobase compounds not typically found in Earth's
biochemistry strongly supports an extraterrestrial origin," Cleaves
said.
"At the start of this project, it looked like the nucleobases in these
meteorites were terrestrial contamination — these results were a very
big surprise for me," study lead author Michael Callahan, an analytical
chemist and astrobiologist at NASA Goddard Space Flight Center, told
SPACE.com.
Lab experiments showed that chemical reactions of ammonia and cyanide,
compounds that are common in space, could generate nucleobases and
nucleobase analogs very similar to those found in the carbonaceous
chondrites. However, the relative abundances of these molecules between
the experiments and the meteorites differed, which might be due to
further chemical and thermal influences from space.
This findings reveal that meteorites may have been molecular tool kits,
providing the essential building blocks for life on Earth, Cleaves said.
[[7 Theories on the Origin of
Life](http://www.livescience.com/13363-7-theories-origin-life.html)]
"All this has implications for the origins of life on Earth and
potentially elsewhere," Callahan said. "Are these building blocks of
life transferred to other places where they might be useful? Can
alternative building blocks be used to build other things?"
In a different study, researchers discovered molecules that make up key
parts of a vital biological pathway, the citric acid cycle, in a number
of carbonaceous chondrites.
The citric acid cycle is "thought by many experts to be among the most
ancient of biological processes," study co-author George Cooper, a
chemist at NASA Ames Research Center, told SPACE.com. "One function of
this cycle is respiration, when organisms give off carbon dioxide."
"It is always exciting to find extraterrestrial and ancient 4.6
billion-year-old organic compounds that might have had a role in early
life," Cooper added.
Cleaves, Cooper and their colleagues detailed their findings in two
studies online Aug. 8 in the Proceedings of the National Academy of
Sciences.
*Follow SPACE.com contributor Charles Q. Choi on
Twitter*[@cqchoi](http://twitter.com/cqchoi).
|
