astrobiology talk

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DEFINITIONS OF LIFE

  1. / 7. “matter that can reproduce itself and evolve as survival dictates”

  2. “THERMODYNAMIC systems with an organized MOLECULAR structure that can reproduce itself and evolve as survival dictates”

  • no good reason why it has to be chemical

  • robots might outlive organisms

  • don’t know chemistry at high pressure

  • entropy gradients -> Jupiter-sized planets

  1. biological definitions

example of respiration

slides

DIVERSITY OF LIFE ON EARTH

  • We have very little idea about prehistoric life except for the types that have fossilised.

  • Almost all species go extinct without leaving any noticeable trace at all.

  • The details of large parts of the evolutionary tree of life are largely guesswork. (Although not as much as Christian fundamentalists would like us to think!)

  • We haven’t studied all the environments that could support life on earth.

  • We haven’t studied any environment completely - gene mush

  • We haven’t studied rainforests thoroughly, although they contain the most large-animal diversity.

  • We’ve barely studied the upper atmosphere.

  • We’ve barely studied the oceans, except for a few commercially important parts.

  • We’ve barely studied the soil, except for the top couple of hundred metres.

slide

prokaryotes

bdelloid rotifers

Last year, “restoration of bdelloid rotifers after being frozen for 24,000 years in the Siberian permafrost.”

Desulfurodis audaxviator

  • discovered down a mineshaft in 2006

  • one-organism ecosystem

  • doesn’t use sunlight, even indirectly

Deinoncoccus radiodurans

Mammals are notably:

  • well understood (biologically!)

  • oxygen-breathing (aerobic)

  • sexual

  • non-parasitic

  • enormous

  • slow to evolve

  • recent

  • rare, both measured in numbers measured by weight (``biomass’’)

slide

Conclusions - So what can we look for?

  • any kind of chemistry/atmosphere might be interesting, not just oxygen atmospheres

  • lone Jupiters are at least as likely to have life as Earths in a Goldilocks zone

  • SETI