Getting NEAR Eros!

Excerpted Highlights of the NEAR mission: the first Earth ship to orbit an asteroid!
Go to the Official NEAR Site

Fabulous data are streaming in, and Eros is turning out to be as geologically diverse and fascinating as anyone could have hoped. The new images have once again driven home a lesson that scientists have learned many times before - whenever we obtain new observations at a significantly higher resolution, we learn something new. We have an excellent example in the region of Eros discussed in the updates for February 14 and February 8, 2000. The crater discussed on February 8, seen in the image-of the-day for February 7, frame 11:09:45, is the very same crater that appears at the center of the image for February 14. In the earlier image, taken at a distance of 7700 km, the crater appeared to be perfect, in the sense of having an (apparently) perfect bowl shape with a prominent rim. In the later image, taken at 330 km distance giving 23 times higher resolution, we can see that the crater is decidedly imperfect. It is all the more beautiful for its blemishes - the boulder lying in the bowl, the evidence for underlying layered structure, the grooves crosscutting the rim.

It is also evident in the February 14 image-of-the-day, as well as that for February 15, that there are bright patches on the surface at scales of a kilometer or smaller. I have yet to hear anyone on the team hazard a guess as to what these are.

Andy Cheng
NEAR Project Scientist

NEAR Team Digs into Data from Eros

Laurel, MD,Feb 17 (JHU Applied Physics Laboratory) - Only a few days into the first close-up study of an asteroid, data from NASA's Near Earth Asteroid Rendezvous (NEAR) mission indicates that 433 Eros is no ordinary space rock.

Since the NEAR spacecraft met up with and began its historic orbit of Eros on Feb. 14, NEAR team members at the Johns Hopkins University Applied Physics Laboratory, which manages the mission for NASA, have pored over images and other early scientific returns. It will take months to unravel the deeper mysteries of Eros, but data from NEAR's final approach and first days of orbit offer tantalizing glimpses of an ancient surface covered with craters, grooves, layers, house-sized boulders and other complex features.

"Work is just starting, but it's already clear that Eros is much more exciting and geologically diverse than we had expected," says Dr. Andrew Cheng, of the Applied Physics Laboratory, who serves as the NEAR mission's lead scientist.

Scientists now know that Eros' mass is 2.4 grams per cubic centimeter - about the same density of Earth's crust and a near match of the estimates derived from NEAR's flyby of Eros in December 1998.

"With this new data, it now looks like we have a fairly solid object," says NEAR radio science team leader Dr. Donald Yeomans of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "There is no strong evidence that it's a rubble pile like Mathilde," the large asteroid NEAR passed and photographed in 1997.

Even without in-depth analysis, pictures snapped with NEAR's Multispectral Imager offer several clues about Eros' origin, age and geography. The large number and concentration of craters point to an older asteroid. Uniform grooves across its craters and ridges hint at a global fabric of underground layers, which Cheng says could indicate Eros was once part of a larger body.

The digital camera has also captured brighter spots on the surface that NEAR scientists are anxious to study.

"One patch is about 25 percent brighter than the rest of the asteroid, and that's a very large difference from the materials you expect to find on the surface," says Dr. Mark Robinson, a NEAR imaging team member from Northwestern University. "That's a really neat feature to keep our eyes on."

The spacecraft's Near Infrared Spectrometer has picked up variations in the asteroid's mineral composition, possibly proportions of pyroxene and olivine, iron-bearing minerals commonly found on Earth, the moon, Mars and in meteorites.

A low-phase flyby during last weekend's final approach put NEAR directly between the sun and Eros, allowing the infrared instrument to gather unique data on the asteroid's mineral makeup under optimal lighting. Combined with multispectral images, this information will help form the first mineral map ever made of an asteroid.

"We want to correlate the changes in color with the geologic features," says Dr. Scott Murchie, a science team member from the Applied Physics Laboratory. "If we see a crater, for example, is it different on the outside than on the inside? Is the face of a cliff different than the ridge? This data will eventually tell us about the asteroid's history."

For the next year, NEAR's instruments will continue to examine the 21-mile-long, potato-shaped asteroid's chemistry, geology, and evolutionary history. The mission's radio science experiment will more precisely calculate Eros' density and mass distribution - clues critical to determining the asteroid's gravity and refining NEAR's orbit.

NEAR's scientific capabilities expand soon, when its X-ray/Gamma-Ray Spectrometer and Laser Rangefinder are turned on within the next two weeks. The spectrometer will measure important chemical elements such as silicon, magnesium, iron, uranium, thorium and potassium; the laser scans will determine Eros' precise shape.

NASA's NEAR sees craters, boulders,'noses' on Eros

WASHINGTON, Feb 17 (Reuters) - Three days after NASA's NEAR probe went into orbit around the asteroid Eros, scientists on Thursday unveiled images of mansion-size boulders, massive craters and two "noses" on the peanut-shaped space rock.

The so-called noses are the bulges at either end of the lumpy oval asteroid, named for the Greek god of erotic love. It is huge as asteroids go, about 21 miles (33.6 km) long or nearly twice the length of Manhattan island.

The Near Earth Asteroid Rendezvous, or NEAR, spacecraft began orbiting the monster asteroid on Monday, the first time a craft has ever orbited an asteroid.

The light beige asteroid has a vast saddle that may have been scoured smooth as the result of a rock slide on one side of its midsection, and a crater about 3 miles (5 km) across on the other side.

There are mysterious bright patches, and even visible boulders that may be 50 yards (meters) in diameter.

But to project scientist Andrew Cheng, the most exciting aspect of the new images is the hint of a layered structure, which means that it might have been a chip off an old planet.

If so, this would give scientists clues to the early solar system that contains Earth.

At a briefing at NASA headquarters, scientists told of the early data returned from the orbiting craft, which showed Eros to have a surface about as dense as Earth's crust, far more solid than some asteroids that are little more than piles of loosely bound rubble.

It also showed clear signs of the minerals olivine and pyroxene, which have been found on Earth, Mars and the Moon, and are commonly present in meteorites.

POSSIBLE LANDING ON ASTEROID?

NEAR is orbiting Eros for a leisurely year-long look. But Cheng said scientists at Johns Hopkins University's Applied Physics Laboratory and others working on the project are considering an even closer observation.

"A landing is a possibility that has been discussed," Cheng said. "Certainly there are good science reasons ... we want to get data from as close as we can."

Jet Propulsion Laboratory scientist Donald Yeomans agreed that a landing on an asteroid would be useful.

"Depending on how the mission's going, certainly landing and possibly lifting off again if there's enough fuel, to take a look at the divot that we made, would certainly be interesting but that hasn't been decided," Yeomans said.

One fanciful-sounding reason space scientists are studying asteroids is their possible use as a training ground for human exploration, Yeomans said.

"Some asteroids are far easier to land on than the Moon itself of course and many of them have hydrated minerals, certainly some of them are ex-comets," Yeomans said, inferring that they may contain water, bound up in minerals.

"So if you're going to have a human presence in space, particularly Mars, it might make sense to try out some of these technologies to turn water into usable hydrogen fuel and oxygen on asteroids and comets before you try the much more difficult task of trying to terraform Mars and using the resources there to make rocket fuel and supporting life," Yeomans said.

The new images of Eros and more information is available on Web site http://near.jhuapl.edu


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