Asteroids were once the forgotten lesser members of the Solar System, far behind planets, moons, comets and meteorites. That changed as telescopes, especially orbiting ones, became stronger and space probes began visiting the asteroid belt instead of just passing through on their way to Jupiter and beyond. Now we’re suddenly finding out intimate details about the behavior of these space rocks and learning we’re much closer relatives that once thought. This past week brought the news that the asteroid Bennu has a weird and possibly disgusting habit of spitting out smaller rocks, while a piece of a meteorite found in Turkey has been identified as a chunk of the asteroid Vesta.
Asteroid 101955 Bennu was discovered on September 11, 1999, during a Near-Earth asteroid survey by the Lincoln Near-Earth Asteroid Research (LINEAR). It’s roughly a smoothish sphere with a mean diameter of 492 m (1,614 ft; 0.306 mi). Because of its size and close proximity to Earth, Bennu was chosen as the destination for NASA’s OSIRIS-REx mission to acquire and return samples from an asteroid. OSIRIS-Rex has been orbiting Bennu since December 3, 2018, and once it’s done mapping the surface it will land in July 2020, scoop up some material and return it to Earth in September 2023. Unless it gets hit by spitting rocks.
“(This) is probably the biggest surprise of the early stages of the OSIRIS-REx mission and, I would say, one of the biggest surprises of my scientific career."
OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, announced the discovery at a news conference on March 19. It turns out Bennu is a rare ‘active’ asteroid that has been observed at least 11 times spewing bursts of surface particles numbering up to 100 per spit, with some measuring 10 cm (4 inches) or larger and traveling at a rate of 11 km/h or 7 mph. That could sting, although Lauretta, being your typical space scientist, thinks it’s cool.
"Basically, it looks like Bennu has a continuous population of particles raining down on it from discrete ejection events across its surface. This is incredibly exciting."
And incredibly puzzling, since they’re not sure what is causing the spewing. While it doesn’t appear to be a danger to Bennu, it could be to Earth. The asteroid-lets may be causing an annual meteor shower in September in the Southern Hemisphere, which Lauretta says astronomers are now searching for.
Speaking of meteor showers, that takes us to Turkey, where in 2015 a three-foot meteor burst into pieces near Sariçiçek. An amazing 343 chunks were recovered and researchers identified them as Howardites, an unusual type of meteorite believed to have come from the asteroid Vesta. Why Vesta? The brightest asteroid visible from Earth was hit by something 22 million years ago, creating a massive crater and knocking a huge amount of Vesta particles into space. When NASA's Dawn spacecraft entered orbit around Vesta in July 2011 for a year, it studied what the 10 mile (17 km) wide Antonia crater and determined it was 22 million years old.
Still with me?
The Turkish researchers determined that the Howardite meteorite pieces were also 22 million years old. However, that wasn’t enough to connect the dots. That’s when they looked at the videos. Believe it or not, security cameras in Sariçiçek picked up the incoming meteor and gave them enough information to determine its trajectory, which they traced back to … get your eureka ready … the area in the sky where Vesta is located! Put it all together and they’re confident they’re holding a piece of the asteroid Vesta. All of this is published in the current edition of Meteoritics & Planetary Science.
That sound you hear is Turkish scientists yelling, "Eat our asteroid dust, OSIRIS-REx!"