From where did earth get its water?


2020-08-29 16:30:50



A new study finds that Earth's water may have come from materials that were present in the inner solar system at the time the planet formed  instead of far-reaching comets or asteroids delivering such water. The findings published in Science suggest that Earth may have always been wet.

Researchers from the Centre de Recherches Petrographiques et Geochimiques (CRPG, CNRS/Universite de Lorraine) in Nancy, France, including one who is now a postdoctoral fellow at Washington University in St. Louis, determined that a type of meteorite called an enstatite chondrite contains sufficient hydrogen to deliver at least three times the amount of water contained in the Earth's oceans, and probably much more.

Enstatite chondrites are entirely composed of material from the inner solar system -- essentially the same stuff that made up the Earth originally.

The findings from this study are surprising because the Earth's building blocks are often presumed to be dry. They come from inner zones of the solar system where temperatures would have been too high for water to condense and come together with other solids during planet formation.

The meteorites provide a clue that water didn't have to come from far away.

The most interesting part of the study  is that enstatite chondrites, which were believed to be almost 'dry,' contain an unexpectedly high abundance of water.

This study showed that their hydrogen and nitrogen isotopes are similar to Earth's, too. In the study of extraterrestrial materials, the abundances of an element's isotopes are used as a distinctive signature to identify where that element originated.

If enstatite chondrites were effectively the building blocks of our planet  as strongly suggested by their similar isotopic compositions  this result implies that these types of chondrites supplied enough water to Earth to explain the origin of Earth's water, which is amazing.

The paper also proposes that a large amount of the atmospheric nitrogen  the most abundant component of the Earth's atmosphere  could have come from the enstatite chondrites. Coupling two analytical techniques  conventional mass spectrometry and secondary ion mass spectrometry (SIMS)  allowed researchers to precisely measure the content and composition of the small amounts of water in the meteorites.