NASA | DNA Building Blocks Can Be Made in Space

Uploaded by NASAexplorer on 08.08.2011

[music] Mike Callahan: My name is Mike Callahan. I'm a
research physical scientist in the Astrobiology Analytical Laboratory at NASA
Goddard Space Flight Center. We've discovered a variety of nucleobases and nucleobase
analogs in meteorites. Now what a nucleobase is, is it's a small molecule
that's found in DNA and RNA, and these molecules are essential
for all of life. And so our results show that these molecules are extraterrestrial
in origin, and they're products of a chemical reaction occuring on the meteorite.
We believe that these nucleobases in meteorites are extraterrestrial based on three
reasons, and the first is that we find nucleobase analogs in
meteorites. What a nucleobase analog is, is that, it is a molecule
that is structurally similar to the nucleobases you find in biology--
but it's different in that these structures are actually either rare
or even absent on Earth. The second reason is that
in addition to looking at meteorite samples, we also study terrestrial samples.
These meteorites are collected mostly in Antarctica, and one
that's very famous called Murchison was collected in Australia. So, we have
soil samples from that Murchison area in Australia, and we've also
had--we were lucky enough to get an ice sample from Antarctica, where
some of these meteorites were collected. And so when we look at these soil and ice samples in
the laboratory, we don't see the same distribution of nucleobases,
and with these nucleobase analogs, we don't see them at all in these
terrestrial samples. The third reason why we think these nucleobases are extraterrestrial in
meteorites is that in the laboratory, we study reactions of hydrogen cyanide,
and when we extract these products from these hydrogen cyanide
reactions, we also get nucleobases--and we actually get a similar
suite of nucleobases to what's found in the meteorite. And so
when we saw that, we were really excited, because we were thinking, well, hydrogen cyanide
is dispersed everywhere in the interstellar medium, and it's likely
to have some sort of chemical reaction on the meteorite. And so, when we saw that,
that really convinced us a lot that we're seeing something from
a chemical reaction rather than some sort of biological contamination coming
into the meteorite. So, this has implications for the origin of life on Earth.
We know that meteorites contain animo acids, which are the building blocks of your proteins,
and now from our research, we can show that nucleobases
--which are the building blocks of your genetic material, like DNA and RNA--
could be found in meteorites. And so these things together could have seeded an early
Earth with these really important molecules that could have built up to the larger molecules
you see today that are essential for biology.
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