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Large Asteroid to Scream Past Earth on Halloween

FILE - This is an artist's impression of a rocky and water-rich asteroid being torn apart by the strong gravity of a white dwarf star.

A large asteroid that scientists discovered just this month will make a relatively close approach to Earth on Saturday, astronomers say, providing one of the best opportunities in years to gather data about a passing space rock.

The asteroid, estimated to be about 1,300 feet (400 meters) in diameter, will shoot past the planet at 22 miles (35 kilometers) per second about 1 p.m. (1700 GMT). Known as 2015 TB145, it will come within about 300,000 miles (480,000 kilometers) of Earth, farther away than the moon but relatively close by cosmic measures.

Astronomers hope to capture radar images and measurements of the asteroid during the encounter, a rarity for scientists who typically rely on expensive robotic space probes to gather information about such rocky bodies. Scientists expect to learn about the asteroid's shape, dimensions, surface features and other characteristics.

The close approach and size of 2015 TB145 suggest that "it will be one of the best asteroids for radar imaging we'll see for several years," Lance Benner, an astronomer at NASA's Jet Propulsion Laboratory in Pasadena, California, said in an article posted on the U.S. space agency's website.

Aside from its pure scientific value, the encounter may help engineers develop better tracking techniques and countermeasures for asteroids that may be on a collision course with Earth. Small space rocks rain down on Earth constantly, with most disintegrating as they blaze through the atmosphere.

About 65 million years ago, an asteroid or comet roughly six miles (10 kilometers) in diameter crashed into what is now Mexico's Yucatan Peninsula, triggering global climate changes that killed off the dinosaurs, along with about 75 percent of life that existed at the time, scientists say.

More recently, a 65-foot-wide (20-meter-wide) asteroid broke apart over Chelyabinsk, Russia, in February 2013, shattering windows and damaging buildings. More than 1,000 people were injured by flying debris.

NASA is working to map potentially dangerous asteroids and comets that pass within 30 million miles (48 million kilometers) of Earth.

Asteroid 2015 TB145 was discovered less than three weeks ago.

"That such a large object, capable of doing significant damage if it were to strike our planet, was discovered only 21 days before closest approach demonstrates the necessity for keeping daily watch of the night sky," Detlef Koschny, an astronomer with the European Space Agency, said in a statement.