An astronomer has urged caution about sending messages into space.
Humans have to be careful in communication with extraterrestrials
Adam Frank has warned that humans "don't know what's out there" and compared trying to communicate with extraterrestrials to "sticking your head above the grass and saying we're tasty".
Frank told BBC Radio 5 Live's science podcast: "I'm not a big fan of METI - the messaging extraterrestrial intelligence because really we don't know what's out there, and it may be that the best decision is to kind of lay low.
"Don't stick your head above the grass and be like, 'Hey, we're here, we're tasty.'"
Meanwhile, the physicist suspects that humans will one day discover "microbial life" elsewhere in the universe.
He said: "I think it's going to be pretty hard to imagine that microbial life hasn't evolved elsewhere in the universe, probably quite often."