Aliens certainly "exist" and we are likely to find the "truth out there" within two decades, two astronomers from the Search for Extraterrestrial Intelligence (SETI) Institute have claimed.

During a hearing with the US House Committee on Science, Space and Technology in an appeal for continued funding to research life beyond Earth, SETI's senior astronomer Seth Shostak said, "It's unproven whether there is any life beyond Earth. I think that situation is going to change within everyone's lifetime in this room."

Shostak has said the scientists are searching for life around the universe using three different methods and they are "hopeful" of finding aliens in next 20 years, reported.

Although one such method included searching for microbial extraterrestrials or their remains beyond the solar system, the hunt was mostly limited to Mars. However, scientists are now considering other areas too.

"At least a half-dozen other worlds (besides Earth) that might have life are in our solar system. The chances of finding it, I think, are good, and if that happens, it'll happen in the next 20 years, depending on the financing," Shostak said during the hearing.

The second method would use a scanner to search for any signs of oxygen or methane in the atmosphere beyond earth, as these gases are mainly associated with the creation and existence of life, reported.

The third technique would involve searching for technologically advanced aliens, who send radio signals to outer space.

"That makes sense because in fact even we, only 100 years after the invention of practical radio, already have the technology that would allow us to send bits of information across light years of distance to putative extraterrestrials," Shostak told the committee.

Alien hunter and director of the SETI Research Center, Berkeley, Dan Werthimer, too supports Shostak's claims.

"I suspect that the universe is teeming with microbial life," Werthimer told the committee. "I think there are going to be some planets in the universe where it's advantageous to be smart," he said.

The alien search operations hold strong ground after NASA's Kepler telescope released pictures of possible habitable planets in the galaxy, projected as Earth's siblings.

"If this is the only planet on which not only life, but intelligent life, has arisen, that would be very unusual," Shostak argued.