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Early this Saturday (July 17) morning EDT, NASA's Dawn spacecraft will rendezvous with the asteroid Vesta. This will be our best look yet at an asteroid, and what the probe digs up could help scientists answer several questions about this and the hundreds of thousands of asteroids that populate the solar system.
Most asteroids, including Vesta, reside in the doughnutlike ring of the main asteroid belt that peppers the space between Mars and Jupiter. Other asteroids whirl in tight circles closer to the sun than the Earth, while a large number of them share planets' orbits. Not all asteroids are so happy to stay put, though: Some asteroids' orbits take them on planet-crossing swings through the inner solar system.
Given this variety of asteroids, some notably strange ones have popped up over our two centuries-plus of observations since the first asteroid, Ceres, was spotted in 1801.
In honor of Dawn's historic mission, here are seven of the solar system's strangest asteroids. (Note that space rocks out beyond the orbit of Jupiter, although somewhat asteroidal in nature, are classified as different bodies, and so we'll leave those alone for now.)
Ceres: A water-logged sphere?Slide 2 of 15
Ceres: A water-logged sphere?
The biggest asteroid by far is Ceres which explains why it was discovered first and it makes up about a third of the asteroid belt's mass. The object is so hefty that it's the only asteroid that has the gravitational strength to pull itself into a sphere.
On account of this roundness, Ceres is also considered a "dwarf planet," a designation it shares with four other objects in the solar system, including Pluto.
After scoping out Vesta, the Dawn spacecraft will journey on to Ceres, arriving in 2015. Once there, the spacecraft will gather data to help scientists learn more about Ceres' composition. The object is probably the "wettest" asteroid, with large stores of water in its interior as ice, though also possibly as a liquid layer beneath the surface.Slide 3 of 15
Baptistina: The mother of the dinosaur killerSlide 4 of 15
Baptistina: The mother of the dinosaur killer
It's a name that, had they survived into modern day, dinosaurs (intelligent ones with language, at least) would curse: Baptistina.
Baptistina is the name of one of the youngest families of asteroids in the asteroid belt.
(Families of asteroids are swarms of objects that share orbital characteristics, and are often named after their most prominent member.)
According to computer models, Baptistina and its swarm were spawned some 160 million years ago by a smashup between a 37-mile-wide body (60 kilometer) body and another object about 106 miles (170 kilometers) in diameter. That cataclysm created hundreds of large objects, some of which then drifted into a collision course with Earth.
One or several of these rocky shards of shrapnel then plowed into our planet 65 million years ago and helped doom the dinosaurs. The impact gouged out the Chicxulub crater, now buried by the Yucatan peninsula and the Gulf of Mexico. [Read: What If a Giant Asteroid Had Not Wiped Out the Dinosaurs? ]
The 100-million-year Baptistina barrage did not spare the Moon, either. A meteorite scooped out the giant Tycho crater about 109 million years ago.Slide 5 of 15
Kleopatra: A metal dog bone with moons!Slide 6 of 15
Kleopatra: A metal dog bone with moons!
Many asteroids, believe it or not, have a moon, and some even sport two satellites. Kleopatra has two moons, which were named Alexhelios and Cleoselene earlier this year. To boot, the metallic asteroid has an unusual dog-bone shape.
The asteroid is roughly 135 by 58 by 50 miles (217 by 94 by 81 kilometers) in length, height and width. Its moons Alexhelios and Cleoselene are, respectively, about 3 miles (5 kilometers) and 1.9 miles (3 kilometers) in diameter.Slide 7 of 15
Hektor, the biggest TrojanSlide 8 of 15