But the researchers still couldn’t explain how Enceladus had such high concentrations of phosphates in its ocean. Some of the study’s researchers investigated this at the Tokyo Institute of Technology by simulating the geochemical interactions between the ocean’s water and its rocky floor.

They found answers in the alkaline waters of Enceladus, which are rich in carbonates. “You could call it a ‘soda ocean,’” Dr. Postberg said.

Phosphorus naturally occurs most often in solid minerals, such as those found inside asteroids and comets. “And if it’s locked up in a rock, it’s hard to harvest for life,” Dr. Postberg said, because it needs to be soluble to be used biologically. “But we find that this soda water can dissolve phosphates really well.”

Mikhail Zolotov, a planetary geochemist at Arizona State University who wrote a perspective article on the study for Nature, was unsurprised by this explanation. “It was clear before, by studies of soda lakes on Earth, that we would expect high amounts of phosphorus in any natural soda lakes,” he said.

Beyond Enceladus, Dr. Postberg says, this discovery may indicate that other ocean worlds in the outer solar system, like Jupiter’s moon Europa or the dwarf planet Pluto, are rich in phosphates — and thus potentially habitable.