in December 2013 astronomers reported
that the Hubble Space Telescope had
detected water vapor in the atmospheres
of five planets outside of our solar
system before you get too excited these
are not really candidates for life they
are all hot Jupiters gas giants that
orbit very close to their stars but you
should be excited that we now have proof
that water exists in atmospheres outside
of our solar system and that we have a
method of detecting it here's how it
works when a planet's orbit takes it
between us and its star that star's
light passes through the halo of the
planet's atmosphere using an instrument
called a spectrograph scientists can
split that light into a spectrum this is
the same electromagnetic spectrum you
seen your whole life it goes from
infrared light through the colors of
visible light up through ultraviolet etc
now when nothing is between us and a
star we can see the whole spectrum as
the star emits it and when something is
blocking that light we can't see any of
it but when a planet's atmosphere is
transparent it lets some light through
but not all of it so the spectrum
created by the spectrograph has these
dark bands running through it from where
different gases in the planet's
atmosphere block or absorb different
frequencies of light
they're called absorption lines a really
amazing thing is different chemicals
create different patterns of absorption
lines so a scientist can look at the
information from the spectrograph and
figure out which gases the light has
passed through at the moment we don't
have a telescope powerful enough to read
the atmospheres of anything smaller or
darker than those hot Jupiters but in
the future we will probably as soon as
2018 when NASA launches the James Webb
Space Telescope once we can read the
atmospheres of terrestrial planets like
Earth made of metal and rock instead of
gas we could start looking for signs of
life outside our solar system what will
we be looking for will definitely water
vapor water in the air means there might
be water on the ground especially if the
planet is the right distance from the
Sun life as we know it couldn't happen
without liquid water we'll also be
looking for free or molecular oxygen
molecules of oxygen o2 oxygen atoms are
relatively abundant in the universe in
fact the
earth is 45% oxygen by weight and about
85% oxygen by volume but almost all of
it is bound up in molecules with silicon
magnesium and iron making up the rocks
under our feet it's really friendly Adam
always looking to pick up an electron
from any other atom that can spare one
but when it bonds with itself to form Oh
two molecules it's not particularly
stable so it tends to get converted into
other molecules but our atmosphere is
more than twenty percent o2 because it's
always being made by living things
particularly plants and other
photosynthetic organisms which use
sunlight water and carbon dioxide to
create massive amounts of atmospheric
oxygen so Vanilli astronomer will
looking at our atmosphere they would see
something was chemically out of balance
the planet has too much free oxygen
something is alive down there and once
you have water and oxygen the way is
open for the development of cellular
respiration which is how aerobic
organisms use oxygen to fuel their
metabolic processes anaerobic metabolism
is much more efficient than anaerobic
metabolism the kind of doesn't use
oxygen something with anaerobic
metabolism can extract up to sixteen
times more energy out of the same amount
of fuel you need that kind of energy to
support multicellular creatures animals
and plants and eventually people type
things
so finding water vapor in the atmosphere
of these hot Jupiters is just the next
step toward finding habitable and
potentially inhabited planets
identifying planets like ours isn't just
the stuff of science fiction anymore
sometime in the next ten years we're
going to be able to point a telescope
into deep space look at a faraway planet
and know if there's any chance that
there might be someone out there looking
back thanks for watching and an extra
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