Kind: captions
Language: en
finding an Earth-like planet in the far
reaches of the cosmos is a difficult
task
but once we've actually found one how
can we tell if there's life on it
luckily scientists like Lisa carltonager
have ways of gauging the life potential
of a distant planet while staying right
here on Earth
they do it by analyzing the planet's
atmosphere
and they do that using light and heat
a star is the only thing that actually
shines itself
so it emits life
a planet usually reflects the light from
the star
the light gets reflected and comes to
you
the star also heats the planet
and the planet then emits this heat as
infrared light
scientists capture this infrared and
visible light from the Spectrum
split it into separate wavelengths and
chart it on a graph like this one called
a spectrum
they use the Spectrum to figure out what
the planet's atmosphere is made of
if there are chemicals in the
atmospheres the planet
they absorb part of that light
add light from the planet
and at a certain point there's something
missing there's an absorption feature
this is how you know what's in the
atmosphere of that planet
we know that particular chemicals absorb
certain wavelengths of light
carbon dioxide for example absorbs
specific wavelengths in the infrared
Spectrum
as does water methane ozone and so on
by collecting light from a planet and
analyzing its Spectrum from missing
wavelengths
we can deduce what chemicals are in the
atmosphere
which is the first step to detecting
life
detecting the types of chemicals in the
atmosphere is the first step to finding
life
but making sense of what the chemicals
mean is a different ball game
if you have a look at our own Earth you
actually have CO2
you have water methane and you have
ozone or oxygen
so if we are searching for a planet like
Earth that's the golden fingerprint
you're looking for
in the right combination these golden
fingerprint chemicals can indicate
Earth-like biological activity
if we can find all of them in the
atmosphere of a temperate rocky planet
we have hit the jackpot
but a planet doesn't have to have all of
these chemicals for life to exist there
life here on Earth has changed over
billions of years and the chemicals in
our atmosphere have changed with it if
you have a look at our own Earth you
have six different kind of fingerprints
from when the Earth was really very
young to where we are right now
the different chemical fingerprints the
Earth has had over time as life has
evolved and changed can guide us in our
search for life on other planets
but what if life on the distant planet
is completely different from anything
Earth has ever harbored
can only go and look for something that
we know how to find as weird as that
sounds there could be a lot of life
that's different from ours and we
wouldn't necessarily find it
but if we do find a planet that has an
Earth-like fingerprint
being a scientist I'm not going to say
there's life but being a scientist I'm
going to say this all the indication
that there's life and we have to
investigate more