Scientists say they've detected a gas in the clouds of Venus that, on Earth, is produced by microbial life.
The researchers have racked their brains trying to understand why this toxic gas, phosphine, is there in such quantities, but they can't think of any geologic or chemical explanation.
The mystery raises the astonishing possibility that Venus, the planet that comes closest to Earth as it whizzes around the sun, might have some kind of life flourishing more than 30 miles up in its yellow, hazy clouds.