Last week, Seth Shostak and Dan Werthimer of the Search for Extra-Terrestrial Intelligence (SETI) Institute told the U.S. House Science and Technology Committee that they expect solid evidence of life beyond Earth in the next two decades. Given what is currently known about our solar system and galaxy it would certainly be a bad sign if no life is found in the near future.

There are several places in our own solar system, including some of the moons of Saturn and Jupiter, where scientists believe that some form of life is possible. Though conditions in some of these places may be harsh, researchers have found complex living organisms in some of the most extreme environments Earth has to offer.

Beyond our solar system, new planets are being discovered on an almost daily basis. It is currently estimated that the majority of the 200 to 400 billion stars in the Milky Way galaxy have planets of their own.

“In our own galaxy there are tens of billions of other planets that are the kind you might want to build condos on. And if that isn’t adequate for your requirements, let me point out there are 150 other galaxies we can see with our telescopes, each with a similar complement of Earth-like worlds.What that means is that the numbers are so astounding that if this is the only planet in which not only life, but intelligent life, has arisen, then we are extraordinarily exceptional. It’s like buying trillions of lottery tickets and none of them is a winner. That would be very, very unusual. The history of astronomy shows that every time we thought we were special we were wrong,” said Shostak, according to Discovery News.

Currently, in addition to physical exploration of the solar system by NASA and other space agencies, distant exoplanets are being analyzed for signs of gasses like oxygen and methane which could indicate habitable worlds. The SETI Institute, and others, are also monitoring space for anything that could be a deliberate signal such as a radio wave.

For those who are interested in the possibility of intelligent, extraterrestrial life and what might happen when we meet them, SETI’s Director of Interstellar Message Composition Douglas Vakoch, has written a book titled “Anthropology, Anthropology and Interstellar Communication.” The book has been made available for free by NASA.