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Water makes up 71% of the Earth’s surface, but no one knows how or when such massive quantities of water arrived on the Earth. A new study published in the journal Nature brings scientists one step closer to answering that question.

Led by University of Maryland Assistant Professor of Geology Megan Newcombe, researchers analyzed melted meteorites (熔化的陨石) that had been floating around in space since the solar system’s formation 4.5 billion years ago. They found that these meteorites had extremely low water content — in fact, they were among the driest materials ever measured outside the Earth.

These results, which let researchers rule them out as the primary source of the Earth’s water, could have important information for the search for water — and life — on other planets. It also helps researchers understand the unlikely conditions making the Earth a livable planet.

Researchers wanted to understand how our planet managed to get water because it’s not completely obvious. Getting water and having surface oceans on a planet that is small and relatively near the sun is a challenge.

“We knew that plenty of outer solar system objects were differentiated, but it was sort of secretively assumed that because they were from the outer solar system, they must also contain a lot of water,” said Sune Nielsen, a study co-author and geologist at the Woods Hole Oceanographic Institution. “Our paper shows this is definitely not the case. As soon as meteorites melt, there is no remaining water.”

The findings have applications beyond geology. Scientists of many fields — and especially exoplanet (系外行星) researchers — are interested in the origin of the Earth’s water because of its deep connections with life.

“Water is considered to be a must for life to be able to exist, so as we’re looking out into the universe and finding all of these exoplanets, we’re starting to work out which of those planetary systems could be potential hosts for life,” said Newcombe. “In order to be able to understand these other solar systems, we want to understand our own.”