Space rock, or space rocks? A new study of asteroid 4179 Toutatis suggests the large asteroid that zips past Earth every four years is actually a collection of rocky fragments held together by gravity.
"We may conclude that Toutatis is not a monolith, but most likely a coalescence of shattered fragments," the researchers wrote in a paper in Scientific Reports.
The study, published Thursday, is based on images of the asteroid collected by the Chinese space probe Chang'e-2 (see above).
After completing its primary mission to study the moon in 2011, Chang'e-2 was positioned to take images of Toutatis just after the asteroid made a much-hyped close approach to Earth last December.
On Dec. 13, 2012, Chang'e-2 flew within half a mile of the tumbling Toutatis, collecting one image every 0.2 seconds. The photo shoot lasted just 25 minutes. By the end, the spacecraft was able to send 400 of the most detailed images ever collected of the asteroid back to Earth.
Chang'e-2's images show that Toutatis is shaped like a ginger root and consists mainly of a head (the small lobe) and a body (the larger lobe). The researchers counted 50 craters on both sections of the asteroid ranging from 118 feet to 1,700 feet in diameter, and at least 30 boulders scattered across its surface.
They also found evidence that the asteroid is covered with a layer of loose material called regolith, not unlike the powder on the moon.
But there is more work to be done. In the paper, the researchers note that Toutatis is probably a type of asteroid known as "contact binary," but they still do not know how these asteroids form.
Lead author Jiangchuaan Huang of the China Academy of Space Technology and his colleagues wonder if asteroid Toutatis is made of two separate objects or if two pieces of the same object shattered.
The good news is that Toutatis flies by the Earth once every four years, so perhaps in 2016 we will learn more.
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