Scientists get one step closer to finding out how Earth got its water

• Published date: 17 March 2023
• Publication title: Jerusalem Post, The: Web Edition Articles (Israel)

Water covers 71% of Earth's surface, but it is unknown when or how all this water arrived on Earth

The study, which was published in the scientific journal Nature on Wednesday, helps scientists get closer to understanding these questions.

"We 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."

Megan Newcombe, Assistant Professor of Geology at the University of Maryland

The scientists, led by Megan Newcombe, an Assistant Professor of Geology at the University of Maryland, analyzed melted meteorites that had been floating in space since the formation of the solar system. The team found that the meteorites were extremely low in water content. In fact, they were among the driest extraterrestrial materials ever measured.

"We wanted to understand how our planet managed to get water because it's not completely obvious," said Newcombe. "Getting water and having surface oceans on a planet that is small and relatively near the sun is a challenge."

The scientists analyzed seven melted, or achondrite, meteorites that broke off of at least five planetesimals - objects that collided to form planets - billions of years ago. Many of the planetesimals were heated up by the decay of radioactive elements that were present in the early solar system, causing them to separate into layers with a crust, mantle and core in a process called melting.

The experiment marked the first time anyone had ever measured the volatiles of these extremely old meteorites as they fell to Earth just recently.

Because these meteorites fell to Earth only recently, this experiment was the first time anyone had ever measured their volatiles. Liam Peterson, a geology graduate student at UMD who was part of the study, measured the levels of magnesium, silicon, iron and calcium in the samples using an electron microprobe before assisting Newcombe with measuring their water contents using a secondary ion mass spectrometry instrument at the Carnegie Institution for Science's Earth and Planets Laboratory.

"The challenge of analyzing water in extremely dry materials is that any terrestrial water on the sample's surface or inside the measuring instrument can easily be detected, tainting the results," said Conel Alexander of the Carnegie Institution for Science, who co-authored the study.

In order to reduce contamination, the researchers put the samples in a...