Sulfur was the key to Earth’s first water.

“These two papers reinforce each other enormously, and I think their story is becoming more and more compelling,” said Alessandro Morbidelli, a planetary scientist at the Côte d’Azur Observatory in Nice, France, who was not part of either research team.

The four planets closest to the Sun, Mercury, Venus, Earth, and Mars, all formed inside the solar nebula, a disk of gas and dust that orbits the newborn Sun. The inner region of the solar nebula is so dense that friction heats it so much that it dries it out. Many researchers have therefore proposed that Earth only acquired its water after icy asteroids and comets formed far from the Sun struck the Earth.

But in 2020, researchers reported a surprising finding: Hydrogen is present in rare meteorites known as enstatite chondrites, which are similar to the components of our own Earth.Serial Number: 8/27/20) Astrochemist Laurette Piani and her colleagues at the University of Lorraine in Vendeau-les-Nancy, France, have discovered that the Earth’s composition contained a large amount of hydrogen from the beginning.

But some scientists were skeptical of the results. They feared that Earth’s water today could have contaminated the meteorite with hydrogen.

Last year, French researchers reported: The hydrogen in enstatite chondrite is combined with sulfur.. Now another team has discovered it. Most of the hydrogen is trapped inside the pyrite.Thomas Barrett and colleagues at the University of Oxford report on the bronze-colored iron sulfide mineral in a paper submitted to arXiv.org on June 19.

“Their claim of spectroscopic signatures of where the hydrogen lives in the rock is valid,” UCLA cosmochemist Edward Young said of the latest study, meaning the hydrogen came from meteorites and was not the result of terrestrial contamination.

Morbidelli agrees. “This explains why enstatite chondrites have hydrogen,” he says, calling the discoveries of the past four years a paradigm shift. “They don’t collect water. They collect hydrogen and oxygen separately in different minerals, and then they combine with each other.”

This is easy to do because the early Earth was hot and molten and covered with a magma ocean. “You can think of the magma ocean as a big ball of hot oxygen,” says Young. Oxygen is more abundant in the Earth’s crust than all the other elements combined. Add hydrogen to the Earth’s composition and you get H.₂o.

But Young questions whether Earth’s components actually provide most of the hydrogen in our planet’s water. He thinks: Hydrogen also came directly from the solar nebula.Composed primarily of molecular hydrogen or H₂Gas. And more hydrogen arrived in the form of water when the icy object hit Earth.

“From an exobiological perspective, this study of the origin of water in enstatite chondrites is really important,” Morbidelli says. Sulfur is common. It’s the tenth most abundant element in the universe. So even in solar systems without icy asteroids and comets, rocky planets should be able to acquire hydrogen and convert it to water, creating a foundation for life to develop on these worlds.