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Did you know the smallest form of life can\h
travel enormous distances? How do they do that?\h\h

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How do microbes fly in the upper atmosphere? Hi,\h
I'm Jim Green, Chief Scientist at NASA, and this\h\h

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is Gravity Assist. On this season of Gravity\h
Assist, we're looking for life beyond Earth.\h\h

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I'm here with Dr. David J. Smith\h
from the NASA Ames Research Center\h\h

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and David is an astrobiologist. Welcome\h
to Gravity Assist. Thank you so much,\h\h

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Jim. I'm happy to be here. Let's start out\h
with- what are we talking about? What do we mean\h\h

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when we're talking about microorganisms and why\h
are they so important in the search for life?\h\h

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When we talk about microorganisms or microbes,\h
we're really talking about small life\h\h

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life's so small that you can't see it\h
with your own eyeball. You know when,\h\h

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uh, our Earth had microbes for four billion years\h
or so and and survived many mass extinctions that\h\h

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went on you know, perhaps that's what happened on\h
other planets and this is why we're looking for\h\h

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microbial life on those planets. I remember\h
when the discovery of microbes were found\h\h

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at high altitudes. What type of microbes have\h
we found? We see same kinds of microbes in the\h\h

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atmosphere that you would see if you went outside\h
and scooped up some soil, a representative sample.\h\h

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The reason for that is maybe easier to understand\h
if we just talk about how microbes move in air,\h\h

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right. So if you were to sneeze and I were\h
to microbiologically sample what's coming\h\h

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out of your sneeze, more or less, it would\h
be representative of the microorganisms\h\h

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in your mouth. Now in the atmosphere, you could\h
think of geological and meteorological processes\h\h

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in effect causing the earth's surface to sneeze,\h
and therefore the same signal we get in the\h\h

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atmosphere is representative of what was on the\h
surface. We see fragments of pollen and other\h\h

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pieces of biological debris in the atmosphere\h
as well too. And you know, speaking of sneezing,\h\h

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anybody that suffers from seasonal allergies is\h
acutely aware of pollen in the earth's atmosphere.\h\h

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You may not know that if you suffer from\h
seasonal allergies, you too are an aerobiologist\h\h

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but that's just to say that you know we we have\h
been impacted in a lot of ways by the movement\h\h

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of airborne microbes. You've done a lot of\h
experiments not only from aircraft but from\h\h

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balloons too, can you give us a little overview\h
about what you've been doing with those platforms?\h\h

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Yeah, so we used large NASA scientific balloons\h
to get to even higher altitudes into the middle\h\h

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stratosphere, around 120,000 feet, where we can\h
linger for days if not weeks depending on where\h\h

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and when we launch, which is just so exciting\h
because of the kinds of science that we can do.\h\h

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And in most cases, we'll take the same types of\h
resilient microorganisms that we've collected\h\h

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using NASA aircraft to those middle regions\h
of the stratosphere and large NASA balloons\h\h

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to expose them to the environment and all those\h
stressful conditions in a way that after the\h\h