While most depictions of extraterrestrials are confined to science fiction, nearly two-thirds of Americans believe that some form of alien life exists somewhere in the universe, according to a new survey.

The telephone poll, which questioned 1,000 Americans, found that 60 percent of those surveyed believe extraterrestrial life exists on other planets.

Of those who believed, most agreed that they would be "excited and hopeful" upon learning of the discovery of extraterrestrial life while 90 percent of them said Earth should reply to any message from another planet, the poll reported. At least two-thirds of those polled who said they did not believe in extraterrestrial life also stated that Earth should respond to an alien signal if the situation arose, the survey reported.

Conducted by the Center for Survey and Research Analysis at the University of Connecticut, the telephone poll surveyed 523 women and 477 men above the age of 18 between April 20 and May 2. The survey was commissioned by the National Geographic Channel, which debuted its television special 'Extraterrestrial' on May 30, in association with the Search for Extraterrestrial Intelligence (SETI) Institute.

"It is quite likely that there is life elsewhere in our galaxy, and there's a real possibility that we will find evidence of intelligent extraterrestrial life by the year 2025," said Seth Shostak, senior astronomer for SETI, who appeared in 'Extraterrestrial.'

Shostak, a SPACE.com contributor, said that the public's interest in the possibility of alien life can be seen in instances such as the 1996 announcement by researchers claiming to find evidence of ancient microbes inside a Martian meteorite, which sent shockwaves through media and scientific circles at the time. The find has remained controversial.

"But it indicates how important it would be to find life, even dead microbial life," said Shostak of the meteorite debate in a telephone interview. "Because it [would] tell you it is very common."

Of those polled who believed in the possibility of extraterrestrial life, 77 percent thought alien lifeforms could develop on planets very different from Earth. About eight of 10 Americans believe it is likely that intelligent aliens on other planets are more advanced than humans, the poll found.

The poll also reported that belief in alien life did not split across political lines, but did vary depending on religious practices. Democrats and Republicans were equally likely to believe in life on other planets, while regular churchgoers were less likely to believe in extraterrestrial life (about 46 percent) than non-churchgoers (about 70 percent), the poll stated.

"One never knows what we'll find, but...we'd like to have a very long list of planets that are suspected of having biology," Shostak said, adding that future space observatories like the Terrestrial Planet Finder would be vital. "If you have thousands and thousands of those [planets], then you'll have a very good direction for the SETI experiment."