Meteorite Analysis Shows Earth’s Building Blocks Contained Water

When our Sun was a young star, 4.56 billion years ago, what is now our solar system was just a disk of rocky dust and gas. Over tens of millions of years, tiny pebbles of dust coalesced, like a snowball rolling larger and larger, to become kilometer-sized "planetesimals"-the building blocks of Earth and the other inner planets. Researchers have long tried to understand the ancient environments in which these planetesimals formed. For example, water is now abundant on Earth, but has it always been? In other words, did the planetesimals that accreted into our planet contain water? Now, a new study combines meteorite data with thermodynamic modeling and determines that the earliest inner solar system planetesimals must have formed in the presence of water, challenging current astrophysical models of the early solar system. The research was conducted in the laboratory of Paul Asimow (MS '93, PhD '97), Eleanor and John R. McMillan Professor of Geology and Geochemistry and appears in the journal Nature Astronomy on January 9. Researchers have samples of the earliest years of the solar system in the form of iron meteorites. These meteorites are the remnants of the metallic cores of the earliest planetesimals in our solar system that avoided accretion into a forming planet and instead orbited around the solar system before ultimately falling onto our planet.