While there are those that believe aliens exist, some people believe that they are already here – and living among us.
According to a YouGov survey of 1,619 adults, nearly one in five Brits (19%) believe it is either somewhat or very likely that extraterrestrial beings are living on Earth.
This figure compares to two-thirds (66%) who believe it is not very likely or not likely at all.
The results of the survey come after British astronaut Dr Helen Sharman said that aliens do exist and that they are already living on the planet.
Speaking to the Observer Magazine, Dr Sharman said: "Aliens exist, there's no two ways about it.
“There are so many billions of stars out there in the universe that there must be all sorts of different forms of life.”
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She added that although they may not be made up of carbon and nitrogen like humans, "it's possible they're here right now and we simply can't see them”.
Dr Sharman, 56, made history by becoming the first Briton in space when she participated in a mission to the Soviet modular space station Mir in May 1991.