While we tend to think that Earth’s oceans make it a watery planet, it’s actually only a tiny fraction of a percent of water by mass. Looking out into the universe, it’s clear water is more common than our own planet implies. Some exoplanets can have half their mass as water. So, what causes some planetary systems to stay wet, while others dry out? The answer might be aluminum.

Tim Lichtenberg is the lead author of a new study published Feb. 11, in Nature Astronomy. He says that large amo