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Moon and asteroids share a common history

Jenny Winder, News Writer
Mar 27, 2013, 7:00 UTC

Sen—Our Moon has more in common than previously thought with the large asteroids that roam our Solar System.

NASA's Lunar Science Institute (NLSI) has discovered that the same population of high-speed projectiles that impacted the moon four billion years ago also hit the giant asteroid Vesta and perhaps other large asteroids.

This unexpected link between Vesta and the Moon provides new means for studying the early bombardment history of terrestrial planets.

"It's always intriguing when interdisciplinary research changes the way we understand the history of our solar system," said Yvonne Pendleton, NLSI director. " Although the Moon is located far from Vesta, which is in the main asteroid belt between the orbits of Mars and Jupiter, they seem to share some of the same bombardment history."

The research supports the theory that the migration of gas giant planets like Jupiter and Saturn from their original orbits to their current location destabilized portions of the asteroid belt and triggered a Solar System-wide bombardment of asteroids, called the lunar cataclysm. It also provides new constraints on the start and duration of the lunar cataclysm, and demonstrates that the cataclysm was an event that affected not just the inner Solar System planets, but the asteroid belt as well.

Scientists have now discovered that studying meteorites from the giant asteroid Vesta helps them understand the event known as the "lunar cataclysm"

Scientists have now discovered that studying meteorites from the giant asteroid Vesta helps them understand the event known as the "lunar cataclysm," when a repositioning of the gas giant planets destabilized a portion of the asteroid belt and triggered a solar-system-wide bombardment. Image credit: NASA/GSFC/ASU/JPL-Caltech/UCLA/MPS/DLR/IDA

Ages derived from meteorite samples have been used to study the collisional history of main belt asteroids. In particular, howardite and eucrite meteorites, found on Earth, have been used to study asteroid Vesta, their parent body. With the aid of computer simulations, researchers determined that meteorites from Vesta recorded high-speed impacts which are now long gone.

By linking the two datasets, researchers found that the same population of projectiles responsible for making craters and basins on the Moon were also hitting Vesta at very high velocities, enough to leave behind a number of telltale, impact-related ages.

Their interpretation of the howardites and eucrites was augmented by recent observations of Vesta's surface by NASA's Dawn spacecraft. The team also used the latest models of early main belt evolution to discover the likely source of these high velocity impactors. They determined that the population of projectiles that hit Vesta had orbits that also allowed some objects to strike the Moon at high speeds.

"It appears that the asteroidal meteorites show signs of the asteroid belt losing a lot of mass four billion years ago, with the escaped mass beating up on both the surviving main belt asteroids and the Moon at high speeds" says lead author Simone Marchi, who has a joint appointment between two of NASA's Lunar Science Institutes, one at the Southwest Research Institute in Boulder, Colorado, and another at the Lunar and Planetary Institute in Houston. "Our research not only supports the current theory, but it takes it to the next level of understanding."