Potentially Threatening Space Rock Rediscovered

A recently discovered space rock that could one day threaten Earth turns out to be an object found seen more than four decades ago but lost in space ever since.

The object, thought to be a burned out comet that now resembles an asteroid, was catalogued as 2007 RR9 this year when found. When it was last seen, in 1960, it carried the designation 6344 P-L. It's considered a "potentially hazardous asteroid" because part of its orbit is near the path our planet takes around the sun.

2007 RR9 is one of 886 (not 887) known asteroids bigger than 500 feet (150 meters) that pass within 4.6 million miles (7.5 million kilometers) of Earth. Astronomers did not give an exact diameter for this one. The object poses no specific threat to the planet any time in the foreseeable future. Over time, however, the orbit of a space rock will shift and could cause it to hit the planet.

"The object was long recognized to be dangerous, but we didn't know where it was," said SETI Institute astronomer Peter Jenniskens. "Now it is no longer just out there."

2007 RR9 goes around the sun once every 4.7 years in an elongated orbit that carries it nearly to Jupiter. Technically, it is now called a Jupiter Family Comet.

"This is a now-dormant comet nucleus, a fragment of a bigger object that, after breaking up in the not-so-distant past," Jenniskens said.

The rock is too dim to be seen by the naked eye from Earth.

Strange Asteroids Baffle Scientists

Images depicting how scientists think large asteroids form. If massive enough, an asteroid will undergo internal heating, which will create layers with different compositions. The core will consist primarily of iron and nickel, while the crust and mantle will be made up of basalt and olivine, respectively. Credit: Ruth Zlethe

Two space rocks in our solar system's outer asteroid belt might contain mineral evidence for a new class of asteroids or long eroded mini-worlds.

The asteroids, (7472) Kumakiri and (10537) 1991 RY16, were found to contain basalt, a grey-black mineral that forms much of the crust on Earth and the other inner planets.

Basalt has also been found in space rocks shed by Vesta, the third largest object in the asteroid belt, located between the orbits of Jupiter and Mars. The presence of basalt is evidence that an object was once large enough to sustain internal heating.

"We need now to observe both objects in the near-infrared range to confirm whether they have a basaltic surface," said study leader Rene Duffard of the Institute of Astrophysics of Andalusia in Grenada, Spain. "If they do, we will need to try to work out where they came from and the fate of their parent objects. If they do not, we will have to come up with a new class of asteroid."

The finding, made using photometric data from the Sloan Digital Sky Survey (SDSS), was presented at annual European Planetary Science Congress in Potsdam, Germany.

Until recently, all basalt-containing asteroids were thought to be fragments of Vesta. In 2001, scientists discovered (1459) Magnya, an object in the outer asteroid belt that contained basalt of a slightly different chemical composition, suggesting it did not belong to the Vesta family.

The lack of basalt and another mineral, olivine, in asteroid belt objects has long puzzled scientists. These two minerals would have formed the crust and mantle, respectively, of belt objects the size of Vesta or larger; theory predicts that more than half of all asteroids should be composed of one or the other of these substances.

"Finding either one is significant because both are quite rare, much rarer than they should be," said Michael Gaffey, a geologist at the University of North Dakota who was not involved in the study. "Roughly 99 percent of the stuff we expect to see [in the asteroid belt] is missing."

One possibility, Gaffey told SPACE.com, is that the parent bodies of Kumakiri and 1991 RY16 were long ago worn down by repeated collisions into smaller and smaller pieces, which have since been whisked out of our solar system.

Asteroid flyby

Well, lucky us then! Below a picture of Tunguska as it looked after the blast.

"On April 16th, asteroid 2007 GU1 will fly past Earth. There's no danger of a collision. The 50 meter-wide space rock will be 500,000 miles away at closest approach, about twice the distance to the Moon. Interestingly, an asteroid about this size may have caused the Tunguska explosion of 1908. Such an impact occurs every thousand years or so, researchers believe. This time, no Tunguska!"

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3D Flyby

"Get ready to cross your eyes. On March 28th, when asteroid 2006 VV2 flew past spiral galaxy M81, two photographers on opposite sides of the USA photographed the encounter. A cross-eyed view of their photos makes the asteroid pop out in startling 3D:

(Hint: Stare at the middle of this image and cross your eyes until the two galaxies overlap. Focus on the asteroid. The longer you stare, the more pronounced the 3D sensation becomes.)

"I produced this stereogram by combining the images of William Keel in Tuscaloosa, AL, and Robert Long in Vado, NM," explains Colorado astronomer Chris Peterson. "Because the asteroid was so close (4.6 million km), and the baseline between the images so long (1780 km), the parallax between the asteroid and the background stars is significant, and the stereo effect is quite real." [more]

Another must-see image is Robert Long's motion picture of the asteroid-galaxy flyby. Click here to play the 1.6 MB movie."

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Asteroid to Pass Near Earth Friday Night

"An asteroid will fly past Earth tonight (March 30) about 2 million miles away. That's about nine times farther away than the Moon.

There is no danger of collision. And that's a really good thing. This space rock, named 2006 VV2, is more than a mile wide (about 2 kilometers), according to the web site Spaceweather.com. If one that big did hit Earth, it'd destroy everything for hundreds of miles around and likely upset global commerce and create climate change unlike anything seen in modern history.

The rock will be far too dim to see with the naked eye. Seasoned backyard astronomers will try to spot it with good-sized telescopes and CCD cameras, however.

The best viewing locations will be in the Americas, according to Spaceweather.com. The rock will pass directly over southern California at about 11 p.m. local time.

Astronomers have catalogued hundreds of asteroids larger than a half-mile that sometimes pass in the vicinity of Earth's orbit. None are known to be on a collision course, but more remain to be found. One asteroid, called Apophis, will pass very close to Earth in the year 2029 and has a minor chance of hitting the planet in 2036. Some have called for a mission to track Apophis more closely by attaching a device to it."

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