Comets, other solar systems, origins of life, our grand conclusion

In our last installment, we turn to "everything else that we haven't already discussed." Basically, comets are the moles of the solar system: they can turn up anywhere, from near the atmosphere of the sun to the farthest regions. Knowledge of comets will complete our "inventory" & then we will turn to the synthesis of it all and go for the "big picture". Already, more than 30 other stars are known to have planets in orbit about them, and so far our system is still unique. How does life form and what allows it to "stick" on a particular planet?

Let's start with


Cometary Orbits

"Anatomy" of a comet -- the nucleus is the heart of it all

Composition in the context of formation: Volatile & Refractory

Viewing comets is tricky business

What have we learned?

Now to spring from there to

Life as we know it...

    requires energy
    is comprised of organic material -- H, C, O, and N (most abundant)
    probably needs water
    needs other elements, too -- probably N, P, S

    is all the same & all different
    20 amino acids, 5 nucleotides
    RNA, then DNA

    reproduces itself in some way
    can evolve by mutation or selection

Earth and life are inseparable, life alters the environment

What factors influence the existence of life? (create a list)

    source of organic material
    presence of atmosphere
    moderate temperatures
    presence of liquid water
    stable conditions
    time to develop
    catastrophic events
    life in extremes -- bottom of ocean, km's under surface
    to wipe it ALL out, have to go deep
An outline of life origin on Earth:

Life was established within 1 billion years of Earth's formation.

Ok, fine, but where/how did it start in the first place:

Unlikely scenarios:

More likely is a terrestrial organic origin:

At the end, we look back:

  1. Energy is clearly available & sufficient in lots of places
  2. Carbon is in lots of places, and in many forms (comets & ISM)
  3. Other elements are also there (comets & ISM, asteroids, meteorites)
  4. Water is the "waterloo"?

Extrasolar planetary systems

Initial results: see also: Mass Radius Plot