A planet needs to start with a lot of water to become like Earth

The sweet spot is somewhere between 3 and 8 times all the water in Earth’s oceans

An illustration of a planet with blue watery oceans, reddish land, and an atmosphere, seen from above

Not every planet will end up with the Earthlike combo of water and land seen in this illustration.

Mark Garlick/Science Photo Library/Getty Images Plus

In planet formation, as in poker, you have to play the hand you’re dealt. If an Earthlike planet is the goal, the best starting hand might contain three to eight times all the water in Earth’s oceans.