|Public domain image. SOURCE.|
Despite its name, a good part of exobiology is concerned with the origins of life on Earth itself. Earth is currently thought to be around 4.55 billion years old, with the first evidence of life occurring on the record at 3.5 billion years; however, the state of life up until relatively recently in the planet's history is unknown. Harold Urey (famous for the Miller-Urey Experiment) proposed that Earth had an atmosphere containing methane, ammonia, hydrogen, and water--a "reducing" atmosphere--which would be the right conditions for organic chemistry to exist. Another theory is panspermia, or that life arrived from another planet via an object such as an asteroid.
|An asteroid. Public domain image. SOURCE.|
David Harry Grinspoon
David Grinspoon is the current Curator of Astrobiology at the Denver Museum of Nature and Science's Department of Space Science; he is also Adjunct Professor of Astrophysical and Planetary Science at the University of Colorado. He is an advisor to NASA on space exploration, an Interdisciplinary Scientist on Venus Express (a satellite studying the atmosphere of Venus led by the European Space Agency), and has published books including Venus Revealed and Lonely Planets: The Natural History of Alien Life. He was awarded the Carl Sagan Medal for public communication of planetary science in 2006.
What do you think the chances are that significant signs of life will be found on another, non-Earth planet? And if you think it's possible, how advanced do you think it could be?
-----The Golden Eagle