When scientists get together to talk about extraterrestrial life, they certainly don’t imagine little green men. In fact, our first contact with life beyond our planet probably will involve a microbe. Although it doesn’t hold the Hollywood appeal of coming face to face with an alien biped, the search for signs of microbial life in the universe is generating a lot of excitement these days. “Any discovery of extraterrestrial life — even if it’s microbial life — would be among the most significant scientific discoveries ever,” said Chris Chyba, who holds the Carl Sagan chair at the SETI (Search for Extraterrestrial Intelligence) Institute in Mountain View, Calif. Chyba is among the scientists gathered at Crystal Mountain this week for the first astrobiology conference held by the University of Washington.