Astrobiology
The cosmic chemistry of life (the
molecular basis)
Chemistry to Biology
• The history of the cosmos has been one of
increasing complexity (from astrochemistry to
astrobiology).
– Chemical – nucleosynthesis and the formation of
more complex molecules.
• This is the cosmic soup (formally called the Interstellar
Medium).
– Biological - evolving molecules capable of
autocatalysis giving rise to “living” organisms.
Setting the Stage
• Going back to the 1960s, it was believed that
space was a void.
– That there was no chemistry, no nothing,
whatsoever in the space between stars, planets,
and other bodies.
– Temperatures were thought to be too low and
radiation too high – any chemical molecule (like
water, methane, ammonia, etc.) would be ripped
apart.
Setting the Stage
• In 1969, astronomers made the momentous
discovery of molecules of ammonia and
formaldehyde in space.
• That discovery was followed up by the
discovery of carbon monoxide in 1970.
Setting the Stage
• These were, at the time, momentous discoveries
(what was happening at this time?)
The Beginning of Astrochemistry
• The discovery of those molecules showed us
that chemistry was possible in the “interstellar
medium.”
• So we asked the question: “Could there exist,
out there, molecules that have function?”
– What might those functions be?
The Periodic Table as We Know It
An Astrochemist’s Periodic Table
Size of the
element’s
symbol is
proportional
to how much
of each
element is
out there.
The Elements of Life
• Thinking about that periodic table, what do
those elements have to do with life?
– All life on Earth is made predominately of carbon,
oxygen, nitrogen, and hydrogen.
– Interestingly enough, even though Earth is a
silicate rock, silicon does not figure into our
biology.
The Chemistry Was in Plain Sight (Sort of)
• Our sight is restricted to only the visible
spectrum – there is a lot out there we couldn’t
see (and did not realize it).
• When we started to use other instruments like
infrared light detectors and mass
spectroscopy, we began to see space for what
it is – anything but a void.
– There is a lot more happening than we realized –
like giant molecular clouds.
The Chemistry Was in Plain Sight (Sort of)
After our
discovery
of
chemistry,
we began
to look for
it in our
system
and other
systems.
Infrared
was the
key.
Studying the Cosmic Soup
Studying the Cosmic Soup
• Once we started to look at the universe with
the right set of tools, we began to see all sorts
of surprising things.
• We discovered lots of organic compounds and
ices.
– We learned that water is an extremely common
compound.
Studying the Cosmic Soup
An
example of
what we
discovered
comes
from this
comparison
of a
spectrum
taken from
the Orion
Nebula and
one taken
from diesel
fumes.
Studying the Cosmic Soup
• We have discovered that the powerful UV-rays
found in space (the same ones that give you
skin cancer) drive all sorts of chemical
reactions.
• The “skin” of every interstellar cloud we see is
made up of what we call PAHs (Polycyclic
Aromatic Hydrocarbons).
– In other words, they are loaded with organic
compounds.
Studying the Cosmic Soup
The red coloration is indicative of organic compounds
Studying the Cosmic Soup
What Do We Know (Summary)
• We know there is a lot of freely accessible
carbon in forming solar systems (and,
therefore, presumably there was in ours).
• We know hydrocarbons are found in
meteorites, comets, and interplanetary dust
particles.
• We know the amount of available carbon has
been around for a long time (within 2 billion
years of the Big Bang).
The Scope of Molecular Complexity
Ex. Carbon Monoxide and UV
All of these
molecules
are found
in the
interstellar
medium
Interstellar Ices
• We find all of the organic molecules we have
been talking about in ices.
– There are ices that contain compounds made from
hydrogen, oxygen, nitrogen, helium, carbon –
silicon serves as a core or nucleus.
– Ice forms in space the same way it forms here on
Earth – beginning with a speck of dust as a core.
– Water is the number one molecule found in ices.
Ices
Ices form
in space
just as
snow
flakes
form
here on
Earth
Occurrence of Ices
Questions
• Why were the interstellar ices so important to
the formation of the solar systems?
• Why were they so important to the formation
of Earth?