Quarter-mile wide asteroid passes Earth

An asteroid as big as an aircraft carrier has passed by Earth in the closest encounter by such a massive space rock in more than three decades.

Scientists ruled out any chance of a collision but turned their telescopes skyward to learn more about the object known as 2005 YU55.

Its closest approach to Earth was pegged at a distance of 202,000 miles at 11.28pm GMT. That is just inside the moon's orbit; the average distance between Earth and the moon is 239,000 miles.

The last time a large cosmic interloper came that close to Earth was in 1976, and it will not happen again until 2028.

Scientists at Nasa's Deep Space Network in the California desert have tracked the quarter-mile-wide asteroid since last week as it approached from the direction of the sun at 29,000mph.

NASA OSIRIS-REx Satellite to Visit Near Earth Asteroid

In a few years a NASA spacecraft will seek the building blocks of life in a shovelful of asteroid dirt. The OSIRIS-REx1 spacecraft, targeted for launch in September 2016, will intercept asteroid 1999 RQ36, orbit it for a year, and then reach out a robotic arm to touch its surface.

"We call it 'touch and go,'" explains principal investigator Michael Drake of the University of Arizona. "OSIRIS-REx will approach the surface at 0.1 m/sec (only 0.2 mph, less than a tenth of walking pace) and, without landing, stretch out its arm equipped with a sample collector. We'll simply agitate the asteroid's surface with ultra-pure nitrogen to stir up material for capture."

Asteroids appear to be as lifeless as Yorick's skull, yet material captured from 1999 RQ36 could hold clues to life's origin on Earth.

Some scientists believe Earth's surface was sterilised soon after the planet was formed some 4.5 billion years ago. Planetoids and other debris left over from the genesis of planets pummeled Earth, turning it into a cratered wasteland. The tremendous kinetic energy from the collisions heated Earth to the boiling point.

"Earth at 'time zero' had a steam atmosphere that was wrung out to make a boiling hot ocean," says Drake.

"Imagine standing on a lava lake in Hawaii, but it's a planet-wide, 600 mile deep lake. You and everything else, including any organics and any one-celled organisms, would be instantly converted to carbon dioxide and water."

In this scenario, an infusion of organics from elsewhere might be required to ignite life here. The building blocks for life on our planet may have come, at least in part, from asteroids.

"Observations by ground-based telescopes suggest that asteroid 1999 RQ36 has a wealth of carbon-based compounds, but we don't know exactly what is there. Are there amino acids?

To find out, we need to bring a sample home where we have sophisticated, exquisitely precise instruments, plus the ability to react to new discoveries."

Radar Clicks Asteroid Images

Radar Clicks Asteroid Pic

Near-Earth asteroid 2005 YU55 was "imaged" by the Arecibo Radar Telescope in Puerto Rico on April 19. Data collected during Arecibo's observation of 2005 YU55 allowed the Near-Earth Object Program Office at NASA's Jet Propulsion Laboratory to refine the space rock's orbit, allowing scientists to rule out any possibility of an Earth impact for the next 100 years.

The space rock was about 2.3 million kilometers (1.5 million miles) from Earth at the time this image of the radar echo was generated.

The ghostly image has a resolution of 7.5 meters (25 feet) per pixel. It reveals 2005 YU55 as a spherical object about 400 meters (1,300 feet) in size.

Not only can the radar provide data on an asteroid's dimensions, but also on its exact location in space. Using Arecibo's high-precision radar astrometry capability, scientists were able to reduce orbit uncertainties for YU55 by 50 percent.

NASA: WISE Telescope Detecting Near Earth Asteroids

NASA's Wide-field Infrared Survey Explorer, or WISE, has spotted its first never-before-seen near-Earth asteroid, the first of hundreds it is expected to find during its mission to map the whole sky in infrared light.

The near-Earth object, designated 2010 AB78, was discovered by WISE Jan. 12. After the mission's sophisticated software picked out the moving object against a background of stationary stars, researchers followed up and confirmed the discovery with the University of Hawaii's 2.2-meter (88-inch) visible-light telescope near the summit of Mauna Kea.

The asteroid is currently about 158 million kilometers (98 million miles) from Earth. It is estimated to be roughly 1 kilometer (0.6 miles) in diameter and circles the sun in an elliptical orbit tilted to the plane of our solar system. The object comes as close to the sun as Earth, but because of its tilted orbit, it is not thought to pass near our planet. This asteroid does not pose any foreseeable impact threat to Earth, but scientists will continue to monitor it.

WISE, which began its all-sky survey on Jan. 14, is expected to find about 100-thousand previously undiscovered asteroids in the Main Belt between Mars and Jupiter, and hundreds of new near-Earth asteroids. It will also spot millions of new stars and galaxies.