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On February 14,
2000, the NEAR Shoemaker spacecraft began its year-long orbit of asteroid
Eros determine its mass, structure, geology, composition, gravity, and
magnetic field. Eros is the largest of the so-called near-Earth asteroids
whose orbits cross that of Earth's. These bodies are of interest because
of their potential for collision with Earth, as well as for the clues
they hold about the nature of how small bodies, including the Earth,
were formed.
EARLY MISSION RESULTS
During its year-long
orbit, NEAR Shoemaker flew past Eros at altitudes from 3 to 35 miles
(5 to 56 km), producing thousands of spectacular images and returning
data that will be analyzed for years to come.
 Combining digital images and data from the laser rangefinder, scientists
have built the first detailed map and three-dimensional model of an
asteroid.
Previously scientists had theorized that asteroids were either solid
iron or cosmic rubble piles-Eros is neither. Data suggests that Eros
is a cracked but solid rock, possibly a fractured chip off a larger
body, made of some of the most primitive materials in the solar system.
The regolith on Eros is nearly 300 feet (91 meters) deep in places.
Data indicate the regolith has moved downhill, smoothing over rough
areas and spilling into craters.
The cratering on Eros has surprised scientists, with intriguing square
ones and many fewer small craters than expected. More than 100,000 craters
wider than 50 feet (15 meters) have been counted. Also, the large number
of boulders was unexpected, with about one million house-sized or larger
boulders.
The last images returned showed clusters of boulders, a mysterious area
where the surface appears to have collapsed, and extremely flat, sharply
delineated areas in the bottoms of some craters, indicating the story
of Eros's composition is still emerging.
LANDING ON EROS
After a journey of
more than two billion miles, NEAR Shoemaker gently landed on the tips
of two solar panels and its bottom edge on February 12, 2001, at 3:01
p.m. (EST). The spacecraft snapped 69 detailed pictures during the final
three miles (five km) of its descent, the highest resolution images
ever obtained of an asteroid, showing features as small as one centimeter
across.
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(Click image for full size view)
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The slow touchdown speed left the spacecraft intact and still sending
a signal back to Earth. NASA decided to extend the mission to February
28th, to get "bonus science" from the spacecraft, which had already
collected 10 times more data than originally planned. This allowed the
gamma-ray spectrometer to collect data from an ideal vantage point about
four inches (10 cm) from the surface, in the first gamma-ray experiment
that has ever been done on the surface of a body other than Earth.
The NEAR mission returned more 160,000 detailed images that solved some
mysteries and unveiled new ones. The amazing amount of data collected
will be shared with scientists all over the world, to reveal facts about
Eros and our solar system that no one knows today.
MISSION MANAGEMENT
The NEAR mission was managed for NASA by the Johns Hopkins University
Applied Physics Laboratory, in Laurel, MD. The Program Scientist was
Andrew Cheng.
For complete information, including the full archive of images, science
updates, news releases and a flyby movie, visit the Near
Earth Asteroid Rendezvous mission home page.
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