Small Asteroid to Give Earth a Close Shave

This story was updated at 4:32 p.m. ET.

A tiny asteroid will zip close by Earth tonight (Nov. 16) at a range much closer than the moon, but poses no threat of striking our planet or even entering the atmosphere, NASA has announced.

The asteroid 2010 WA will pass Earth at 10:44 p.m. EST (0344 GMT), missing the planet by about 24,000 miles (38,000 kilometers), NASA's asteroid-watching team wrote on Twitter. It is nearly 10 feet (3 meters wide), so small it would simply break apart if it encountered Earth's atmosphere.

NASA officials said the asteroid is a "very small space rock" that will pass the Earth at roughly one-tenth the distance between our planet and the moon, according to NASA's AsteroidWatch Twitter feed. [5 Reasons to Care About Asteroids]

On average, the moon is about roughly 238,900 miles (384,402 km) from Earth. Some of the highest satellites above Earth fly in geostationary positions about 22,370 miles (36,000 km) up. The International Space Station sails through space about 220 miles (354 km) above Earth.

Asteroid 2010 WA is the fourth space rock in as many months to buzz harmlessly by the Earth within the moon's orbit. The asteroid 2010 TD54 passed the planet at nearly the same miss distance on Oct. 12. In September, a rare sighting of two asteroids ? called 2010 RX30 and 2010 RF12 ? was spotted when they both passed within the moon's orbit on the same day (Sept. 8).

Like 2010 WA, those earlier asteroid flybys posed no threat to Earth and most were small enough that they would burn up in the atmosphere if they hit it.

"Still, a good practice in detection," NASA's asteroid-tracking team wrote of 2010 WA on Twitter.

An asteroid about 16.5 feet (5 meters) across can be expected to pass Earth inside the orbit of the moon about once a day, NASA scientists have said. They typically enter Earth's atmosphere about once every two years, they added.

Bigger asteroids of about 460 feet (140 meters) wide can cause widespread damage around their impact sites. But much larger space rocks would have to strike Earth to cause global devastation.

There are an estimated 30 million unknown asteroids in our solar system, NASA has said.

Asteroid 2010 WA is not even the first space rock to slip by the Earth-moon system this month.

On Nov. 9, the small asteroid 2010 VL65 passed the Earth at a range of 610,000 miles (980,000 km) ? about 2 1/2 times the distance between our planet and moon, NASA officials said. That asteroid was only 23 feet (7 meters) across ? small enough to burn up completely in the atmosphere ? and was only visible to seasoned skywatchers with telescopes.

NASA routinely tracks asteroids and comets that fly near Earth as part of its Near-Earth Object Observations program, which uses a network of ground and space telescopes to monitor the space rock environment around the planet. To date, the program has tracked about 85 percent of the largest asteroids that fly near Earth and 15 percent of asteroids in the 460-foot class, according to the latest report.

The U.S. space agency also plans to send astronauts to an asteroid by 2025 under a space plan ordered by President Obama. The mission could help scientists better understand the composition of asteroids, as well as develop better methods of deflecting them before they pose a threat to Earth, agency officials have said.

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Asteroid Dust Successfully Returned by Japanese Space Probe

A Japanese spacecraft that touched down on a space rock during a billion-mile mission successfully returned the first ever samples from the surface of an asteroid, Japan's space agency said today (Nov. 16).

The samples are in the form of tiny dust grains collected directly from the asteroid Itokawa in 2005 by Japan's Hayabusa spacecraft, which returned to Earth in June. It was a 1.25 billion-mile (2 billion-kilometer) trip that took seven years to complete. [Photo of the asteroid samples]

The dust was found inside a sample return capsule that landed in Australia and was flown back to Japan for analysis.

"About 1,500 grains were identified as rocky particles, and most of them were judged to be of extraterrestrial origin, and definitely from Asteroid Itokawa," the Japan Aerospace Exploration Agency said in a statement.

JAXA scientists have known there were particles of material in the Hayabusa sample return capsule since July. But they were unsure if those particles were actually pieces of an asteroid, cosmic dust or contamination from Earth.

Now, they said, it is clear. The Hayabusa spacecraft collected samples of an asteroid.

"Being able to retrieve material from a celestial body beyond Earth was more than we had hoped for," Hayabusa project manager Junichiro Kawaguchi told Japan's Mainichi Daily News. "When the capsule returned, I said, 'Just having it return is like a dream,' so I don't know how to express this, which was beyond my dreams."

This graphic shows how the Hayabusa asteroid mission worked. Itokawa is a silicon-rich asteroid about 1,755 feet (535 meters) long at its longest side. It takes about 556 days to complete one orbit around the sun.

JAXA scientists used a scanning electron microscope to study the asteroid samples collected by Hayabusa. They found signs of minerals such as olivine, pyroxene and others, which matched remote-sensing observations taken by Hayabusa when it visited asteroid Itokawa.

Most of the particles are about 10 micrometers in size, roughly 1/10th the width of a human hair. They were found in one of two compartments inside the Hayabusa sample return capsule and must be handled delicately, JAXA officials said.

"JAXA is developing the necessary handling techniques and preparing the associated equipment for the initial (but more detailed) analyses of these ultra-minute particles," they added.

The fact that the Hayabusa spacecraft returned asteroid samples is the ultimate vindication for Japan's mission team.

JAXA launched Hayabusa (Japanese for "Falcon") in 2003. The spacecraft arrived at the asteroid Itokawa in 2005 while the asteroid was 180 million miles (nearly 290 million km) from Earth ? almost twice the distance between our planet and the sun.

But Hayabusa experienced several crippling problems during the mission, including a fuel leak, communications breakdowns and malfunctions with its ion engines. The setbacks added an extra three years to Hayabusa's mission.

The probe was supposed to drop a lander on Itokawa, but the lander missed the asteroid's surface. Attempts to fire a projectile at the asteroid to kick up dust to be collected also failed.

Ultimately, JAXA directed Hayabusa to directly land twice on asteroid Itokawa in attempts to force some samples into its return capsule.  

The Hayabusa spacecraft returned to Earth on June 13. Most of the craft burned up in Earth's atmosphere as planned during re-entry. Its sample return capsule, which was equipped with a heat shield and parachute, was ejected to make its own successful landing in the Australian outback and was later recovered.

"I'm filled with emotion and I can't believe it," Kawaguchi said. "A long period of hard work has paid off."

With the mission's success, JAXA has already begun planning a follow-up mission ? called Hayabusa 2 ? which would send a $200 million spacecraft to visit a carbon-rich asteroid. That mission is slated to launch in 2014, arrive at the asteroid in 2018 and return samples to Earth by 2020, JAXA officials have said.

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