Scientists at NASA's Lunar Science Institute (NLSI) near San Jose, Calif., announced this week that our Moon and large asteroids have more in common that was previously thought. Those similarities help support theories about what our solar system was like billions of years ago.
Today we think of the orbits of the planets as being reliable and unchanged. However, millions of years ago the gas giants Jupiter, Saturn, Uranus and Neptune tended to wander. Jupiter moved closer to the sun while Saturn moved away, creating significant gravitational pushing and pulling of all the leftover bits of planet formation in the asteroid belt between Jupiter and Mars. This triggered lunar cataclysm, a high-speed bombardment of the inner solar system.
Researchers studied moon rocks returned by the Apollo astronauts along with meteorite samples originating from the large asteroid Vesta.
Radiometric aging of both found impacts occurred around the same time, between 3.4 and 4.1 billion years ago. The impacts themselves were also unique, occurring at over 22,000 miles per hour, double the typical speed of impacts from main belt asteroids.
"Although the moon is located far from Vesta ... they seem to share some of the same bombardment history." said Yvonne Pendleton, NLSI director.
Simone Marchi of the Lunar and Planetary Institute in Houston pointed to "signs of the asteroid belt losing a lot of mass, ... beating up on both the surviving main-belt asteroids and the moon at high speeds. Our research not only supports the current theory, but it takes it to the next level of understanding."
You can see a Vesta meteorite as well as a moon rock in the Postcards from Space exhibit at the North Carolina Museum of Natural Sciences Nature Research Center in Raleigh. You can also see moon rocks in the permanent collection of the Museum of Life and Science in Durham as well as a temporary exhibit running through April at the North Carolina Museum of History in Raleigh.
Tony Rice is a volunteer in the NASA/JPL Solar System Ambassador program and software engineer at Cisco Systems. You can follow him on twitter @rtphokie.