The big question: Did they leave artifacts behind for us to find?
He started writing it just weeks after Britain entered WWII.
"We really do know that pretty much every star in the sky hosts at least one planet," says astronomer Adam Frank.
"A fundamental approach in astrobiology is to use terrestrial sites as analogs, where we look for insight into the possibilities
Columbia University astronomers say their laser plan would work, but others aren't so sure.
It will be able to detect and receive signals from outer space and help search for extraterrestrial intelligence.
"Life could spread from host star to host star in a pattern similar to the outbreak of an epidemic."
Just last month astrophysicist Stephen Hawking announced that he was supporting a $100 million program to investigate extraterrestrial
"Billions of years ago, when microbial life may have littered the Red Planet, the occasional meteor impact could accidentally
Finding life elsewhere would end our cosmic isolation: if there is life in our own planetary backyard, then life is probably common throughout the universe. These enticing possibilities are why my colleagues and I have spent 17 years developing a spacecraft mission dedicated to understanding Europa.
"When our planet was frozen over during an episode known as 'snowball Earth,' the effect on the biota seems to have been
The research was presented in Pasadena, Calif. on April 23 at the annual meeting of the Seismological Society of America