Imagine a planet twice as wide as Earth, covered in an ocean that smells like sweet cabbage.
Every day, a faint red star warms this ocean world and the uncountable masses of hungry, plankton-like creatures that inhabit it. They rise to the surface by the billions, joining together in a living, floating continent larger than Australia — spewing out a pungent gas as they knit sunlight into food.
The sulfurous gas steams out of the alien bloom, filling the air so fully that a lone telescope floating 700 trillion miles (over a quadrillion kilometers) away can sense it — faintly, for just a few hours every month, when the watery planet glides in front of its small, red star. For those few hours, the alien algae of the pungent planet make themselves known to Earth.
It sounds like science fiction ... but is it?
For the past two years, this question has been the subject of intense debate among alien-hunting scientists, with the James Webb Space Telescope (JWST) at its center. Captured in the powerful telescope's crosshairs is the planet K2-18b, located around 120 light-years from Earth. There's no question that the planet itself is real. But its surface conditions, as well as its likelihood of harboring life, remain contested.
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