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17/06/2015 11:37 BST | Updated 17/06/2015 11:59 BST

Former NASA Astronaut Say 'Aliens Probably Know We Exist'

Great news everyone if there is extraterrestrial life out there, it probably knows we exist.

John Grunsfeld, a former NASA astronaut told the Astrobiology Science Conference in Chicago U.S., that changes that life on earth has created in the environment might be a dead give away to aliens.

john grunsfeld

However, Grunsfeld is not talking about Hollywood's green Martians that we're so used to seeing on our screens.

To the wider scientific community, alien life means tiny single celled microbes that most of us would never see with the naked eye.

Grunsfeld, who is now an associate administrator for NASA’s Science Mission Directorate said:

“If there is life out there, intelligent life, they’ll know we’re here.

"We put atmospheric signatures that guarantee someone with a large telescope 20 light years away could detect us.”

His comments come as a team of Scottish scientists find evidence of methane gas on Mars, an indication of life existing on the red planet.

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The research led by Aberdeen University said the gaseous substance could be a food source for organisms inhabiting Mars.

If you're itching to know more about our potential neighbours, the wait is not that long.

In April, NASA's chief scientist Ellen Stofan predicted that the search for alien life should only take us 20 to 30 years. Plenty of time to get ready for company then.