The Earth may be crawling with undiscovered creatures with a different biochemistry to life as we know it.
"'Are we alone?' is one of the biggest unanswered questions," said study first author Howard Chen.
Human's evolved through a series of highly unlikely events—so finding another intelligence like us would be like winning the lottery many times over.
"In the search for life beyond our solar system, the most promising planets might not be Earth twins," says geochemist Stephanie Olson.
Nieves penitentes on Earth's second highest volcano could offer insight in the search for extraterrestrial life.
Breakthrough Listen is a program designed to search for evidence of alien life by scouring the the skies for distant radio signals.
Build-ups of toxic gases in the atmospheres of many exoplanets in the "habitable zone" could limit the "safe zone" in which life outside our solar system could actually exist.
NASA's James Webb Telescope will open up an entirely new avenue for searching for extraterrestrial life.
The exoplanet orbits a star that sits just six light-years away from Earth.
"Our work is calling for a complete revision for how we think about the potential for life on Mars."
Scientists think life might survive on Proxima b, in spite of powerful lashings from its host star.
The planets could have similar light and temperature conditions to those that may have existed when life first emerged on Earth.
If it's anything like the lake beneath the ice of Antarctica, it might just harbor life.
UFO skepticism has become something of a religion with an agenda.
A stable climate could be key to hosting life.
The moon contains the key requirements for life.
There are about 400 subglacial lakes around the world, but these are the first scientists believe to be salty.
"I think that in this century we are going to be finding life beyond Earth," said Jill Tarter, a scientist at the SETI Institute research center in California.
"We have no idea what's behind these weird incidents because we're not investigating," Christopher Mellon said.