Little green men? Or something else? Here’s how to spot alien life forms

The thought of extraterrestrial life — usually imagined as some form of green Martians — has captured our imaginations for years. And as we discover more about the universe around us, the possibility of finding those other life forms seems closer than ever before.

A few likely contenders: NASA has found evidence of ice on Mars, which could be promising. Earlier this month scientists studying Saturn’s moon Enceladus reported a chemical reaction under ice on the moon’s surface that could provide the ingredients for life. And on Thursday scientists found another possible site: a “rocky super-Earth” orbiting a nearby star.

But how do we find our fellow beings? Axios has helpfully prepared a guide.

Digging through the data: It’s a numbers game, says astrophysicist Paul Sutter, which means finding out how many planets are out there, and how many have water and other good conditions for life.

“It’s only by obsessive, detailed observations will we crack it,” he wrote.

Spot the first signs: We’re looking for gases like carbon dioxide and methane in a planet’s atmosphere, says planetary geologist Ellen Stofan.

A big telescope: “To confirm life, we need to build large enough space-based telescopes to image extrasolar planets, hopefully only a few decades from now,” Stofan wrote.

And big antennas: We generally use large antennas to hunt for “faint, deliberately produced radio signals from other worlds,” wrote astronomer Seth Shostak.

Be open-minded: Real aliens probably will bear no resemblance to the Martians of sci-fi movies. We are hard at work on artificial intelligence here on Earth, so wouldn’t advanced aliens have done this long ago? Maybe we should be looking for thinking machines, not biological beings, Shostak says.

“The most impressive intellects of the universe won’t need the life-friendly environments of planets, and could be spread throughout space,” he wrote. “The real extraterrestrials may not be little gray men, but little gray boxes.”

Photo: A handout photo released by the European Space Agency on April 20, 2017 shows an image displaying the galaxies NGC 4302 seen edge-on and NGC 4298, both located 55 million light-years away. They were observed by Hubble to celebrate its 27th year in orbit. (AFP Photo/NASA/ESA/Hubble/M. Mutchler) (STScl)


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