National Geographic Daily News
A diagram shows the orbits of two small asteroids.
Asteroids 2010 RF12 and 2010 RX30 are passing between Earth and the moon's orbit Wednesday.

Image courtesy NASA

Eros, an asteroid.

The asteroid Eros in 2000, as pictured by NASA's Near Earth Asteroid Rendezvous mission. Photograph courtesy NASA/JHUAPL.

Ker Than

for National Geographic News

Published September 8, 2010

The second small asteroid to pass near Earth in a single day will make its closest approach later today, scientists say.

(Related: "NASA to Visit Asteroid Predicted to Hit Earth?")

The approximately 30-foot (10-meter) asteroid, dubbed 2010 RF12, will pass within about 50,000 miles (80,000 kilometers) of Earth at 5:12 p.m. ET.

About 12 hours earlier, at 5:51 a.m. ET, a 50-foot (15-meter) asteroid called 2010 RX30 passed within about 154,000 miles (248,000 kilometers) of our planet—roughly halfway between Earth and the moon.

Both asteroids' paths are too far away to endanger Earth or any satellites, said Lindley Johnson, program executive for the Near-Earth Object Program at NASA headquarters in Washington, D.C.

"Even if they were to hit Earth, these two asteroids would disintegrate in the atmosphere," he said. "We'd get a few meteorites out of them, but there wouldn't be any damage to the ground."

(See "'Killer Asteroid' Debate Pits Gravity Tractors Against Bombs, Projectiles.")

Asteroids Found Only Sunday

Both asteroids were discovered on Sunday by the Catalina Sky Survey near Tucson, Arizona.

Astronomers estimate that a small asteroid like 2010 RF12 and 2010 RF30 passes between Earth and the moon every day. (Read about an asteroid that unexpectedly buzzed Earth last year.)

Most of these space rocks are never seen, because instruments scanning the skies for dangerous near-Earth asteroids aren't designed to notice rocks smaller than about a hundred feet (30 meters).

"The Catalina Sky Survey just happened to be looking at the right part of the sky at the right time to pick them up Sunday morning," Johnson said.

2010 RX30 was not visible to the naked eye when it made its closest approach to Earth, and 2010 RF12 isn't expected be discernible either.

"You'd need a fairly sophisticated amateur telescope, something on the order of 20 inches [50 centimeters] or so, to be able to see these asteroids," Johnson said.

For an insider's take on space news, check National Geographic's Breaking Orbit blog >>

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