If you could hop in a time-travelling spacecraft, go back three billion years and land any place in our solar system, where would you want to end up? Earth, with its barren continents and unbreathable atmosphere? Or Mars, a chillier version its big brother? Wait, what about Venus?
Researchers at the University of Washington’s Virtual Planetary Laboratory have devised a new habitability index for judging how suitable alien planets might be for life. The point of the exercise is to help scientists prioritise future targets for close-ups from NASA’s yet-to-be-launched James Webb Space Telescope and other instruments.