TRAPPIST-1 Planets Might Actually Have Too Much Water to be Habitable

“[T]he TRAPPIST-1 planets are too small in mass to hold onto enough gas to make up the density deficit. Even if they were able to hold onto the gas, the amount needed to make up the density deficit would make the planet much puffier than we see.”

“We typically think having liquid water on a planet as a way to start life, since life, as we know it on Earth, is composed mostly of water and requires it to live. However, a planet that is a water world, or one that doesn't have any surface above the water, does not have the important geochemical or elemental cycles that are absolutely necessary for life.”