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(meteorobs) [ASTRO] NEAR Begins Looking Closely At Eros


------- Forwarded Message

From: Ron Baalke <BAALKE@KELVIN.JPL.NASAdot gov>
Date: Thu, 17 Feb 2000 18:41:28 GMT
Subject: [ASTRO] NEAR Begins Looking Closely At Eros

Don Savage
Headquarters, Washington, DC                 February 17, 2000
(Phone:  202/358-1547) 

Mike Buckley 
Johns Hopkins University Applied Physics Laboratory, Laurel, MD 
(Phone:  240/228-7536)

RELEASE:  00-28

NEAR BEGINS LOOKING CLOSELY AT EROS

     Only a few days into the first close-up study of an asteroid, 
data from NASA's Near Earth Asteroid Rendezvous (NEAR) mission 
indicate 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 in Laurel, MD, 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 bulk 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 radio science team leader Dr. Donald Yeomans of 
NASA's Jet Propulsion Laboratory in Pasadena, CA.  "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' age and 
geography.  The large number and concentration of craters points 
to an older asteroid, uniform grooves across its craters and 
ridges hint at a global fabric and, perhaps, underground layers.  
In addition to numerous boulders, the digital camera has also 
captured brighter spots on the surface that NEAR scientists are 
anxious to study.

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

     A low-phase flyby during last weekend's final approach put 
NEAR directly between the sun and Eros, allowing the 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 potato-shaped asteroid's chemistry, geology, and 
evolutionary history.  The mission also includes a radio science 
experiment to 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. 

                              - end -

Images and information about the NEAR mission are available at:

                       http://near.jhuapldot edu

------- End of Forwarded Message


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