A ring of temperate climate may offer a habitable haven

Halfway house? Some planets may have habitable zones midway between their day and night

Extra-terrestrial life could find a haven in an unexpected place – the narrow band between day and night on planets where one side is tidally locked facing their star.

“This is a planet where the dayside can be scorching hot, well beyond habitability, and the night side is going to be freezing, potentially covered in ice. You could have large glaciers on the night side,” says Ana Lobo from the University of California, Irvine.

Such worlds have been found around many M-dwarf stars, which make up 70 percent of the stars in the night sky. To see if these common worlds could be habitable, Lobo used computer simulations to reveal that the light–dark boundary region (ironically known as the Terminator Zone) can have temperatures in the ‘sweet spot’ where water can remain liquid. Liquid water is a key component of life on Earth, so its presence is considered a vital marker of potential habitability. www.uci.edu