Research by Rice University Earth scientists suggests that virtually all of Earth's life-giving carbon could have come from a collision about 4.4 billion years ago between Earth and an embryonic planet similar to Mercury.
In a new study this week in Nature Geoscience, Rice petrologist Rajdeep Dasgupta and colleagues offer a new answer to a long-debated geological question: How did carbon-based life develop on Earth, given that most of the planet's carbon should have either boiled away in the planet's earliest days or become locked in Earth's core?
"The challenge is to explain the origin of the volatile elements like carbon that remain outside the core in the mantle portion of our planet," said Dasgupta, who co-authored the study with lead author and Rice postdoctoral researcher Yuan Li, Rice research scientist Kyusei Tsuno and Woods Hole Oceanographic Institute colleagues Brian Monteleone and Nobumichi Shimizu.
Around 3.8 billion years ago, an asteroid more than 150 miles across, roughly equal to the length of New Jersey, slammed into the Moon and created the Imbrium Basin -- the right eye of the fabled Man in the Moon. This new size estimate, published in the journal Nature, suggests an Imbrium impactor that was two times larger in diameter and 10 times more massive than previous estimates.
"We show that Imbrium was likely formed by an absolutely enormous object, large enough to be classified as a protoplanet," said Pete Schultz, professor of earth, environmental and planetary sciences at Brown University. "This is the first estimate for the Imbrium impactor's size that is based largely on the geological features we see on the Moon."
Previous estimates, Schultz said, were based solely on computer models and yielded a size estimate of only about 50 miles in diameter.
These new findings help to explain some of the puzzling geological features that surround the Imbrium Basin. The work also suggests -- based on the sizes of other impact basins in the Moon, Mars and Mercury -- that the early solar system was likely well stocked with protoplanet-sized asteroids.
