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.
And not just red -- The Hindu claimed witness reports of yellow, green and black rain in the months that followed.
The first theory to emerge was that it was simply sand or dust picked up from a desert, but a local physicist, Godfrey Louis, found that under a microscope, the water contained cells that looked like bugs.
Friday, after a further four years of studying the cells, joined by leading British panspermia theorist Chandra Wickramasinghe, Louis claimed that they are unlike anything found on Earth.
He said the cells -- inert at room temperature -- begin to reproduce at 121C.
Within two hours of being exposed to the heat, "daughter cells appear within the original mother cells and the number of cells in the samples increases with length of exposure," the scientists said in the new report.
While many spores on Earth can survive that kind of extreme heat, none have yet been discovered that can reproduce in those conditions, much less require it to begin reproducing.
The team also found an unusual pattern in the way the cells changed color under UV light, known as "fluorescence behavior."
They said it was "in remarkable correspondence" with red emissions from the Red Rectangle planetary nebula some 2,300 light years away, "suggesting, though not proving, an extraterrestrial origin."
While the panspermia angle is already being rejected by the scientific community at large, there's plenty of interest in the final finding of Louis's team -- the cells contain no DNA.
"As a biologist, let me assure you that a cell-sized and shaped organism that reproduces, lives off LB and doesn't appear to have any nucleic acid template (DNA or RNA) is a revolutionary discovery in and of itself," one commenter wrote at TechnologyReview.
The only lifeforms that occur on Earth without DNA, according to another commenter, are proteins known as "prions," best known on Earth as the cause of Mad Cow Disease. The team's findings are yet to be verified.