Alien life may already exist on Earth -- us.
There's an idea -- common, but not popular in scientific circles -- that all life on Earth was seeded from comets, asteroids or meteors which struck the planet and contained the building blocks necessary to kickstart the evolutionary process.
It's a theory called "panspermia," and it caused a tremendous debate some 15 years ago when several scientists backed claims that there was evidence of life in a Martian meteorite found in the Allan Hills in Antarctica.
It's been proven that life can survive in space, just as it's been proven that the interior of that Martian meteorite never rose above 50C during its journey to Earth. Unfortunately for alien-spotters, the cells from the meteor can also be found on Earth, so the argument remained unsettled.
Then in July 2001, the rain turned red in India.
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