Astrobiology is very interested in what is necessary for life - what chemical constituents, temperatures, mixing mechanisms, etc. might allow life to get started.
The diagram to the left illustrates the Miller experiment. This experiment was first performed in 1952 by Stanley Miller and Harold Urey and sought to reproduce the conditions under which life began on the earth. In the experiment gases are passed through water in the presence of an electric arc. This produces amino acids which are the building blocks of proteins.
What was the environment like on the earth when life first formed? Do similar conditions exist anywhere else in the solar system right now?
Saturn's moon Titan and Jupiter's Moon Europa are very interesting places!
What types of stars would have regions surrounding them where the temperature is right for life? What shape of planetary orbits would be needed for these conditions to be stable?
The green regions in the diagram to the right illustrates where a plnet would have a moderate temperature. The F0 star is hotter than the sun, the G2 is the same temperature as the sun, and the K0 and M0 stars are cooler.
Do planets exist around other stars? If yes, how common are they? What are some of the techniques that are used to search for planets around other stars and what have we learned?
What efforts are underway to listen for signals from "ETs" and what have they found? Should we really expect there to be other intelligent civilizations in the universe?
The Drake Equation allows one to estimate the number of intelligent civilizations that exist in the universe -- however different astronomers get very different results when making this calculation.
What messages have we sent to other worlds? When might we reasonably expect an answer?