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Astrobiology
The cosmic chemistry of life (the molecular basis)
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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.
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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.
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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.
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Setting the Stage
• These were, at the time, momentous discoveries (what was happening at this time?)
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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?
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The Periodic Table as We Know It
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An Astrochemist’s Periodic Table
Size of the element’s symbol is proportional to how much of each element is out there.
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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.
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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.
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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.
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Studying the Cosmic Soup
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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.
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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.
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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.
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Studying the Cosmic Soup
The red coloration is indicative of organic compounds
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Studying the Cosmic Soup
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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).
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The Scope of Molecular Complexity
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Ex. Carbon Monoxide and UV
All of these molecules are found in the interstellar medium
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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.
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Ices
Ices form in space just as snow flakes form here on Earth
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Occurrence of Ices
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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?