Bowser
09-23-00, 08:21 PM
Bill Steigerwald Embargoed for Sept. 21, 2000
Goddard Space Flight Center, Greenbelt, Md. 2:00 p.m. EDT
Release No. 00-118
EROS ASTEROID MAY HAVE BEEN PRESENT
AT THE BIRTH OF THE SOLAR SYSTEM
The Eros asteroid could have witnessed the formation of the Earth,
according to a preliminary analysis of its surface composition using
NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft. Analysis of
solar X-rays from Eros' surface indicate that it has a composition
similar to the chondrite meteorites found on Earth, which are
believed to be primordial agglomerations of dust grains from the
nebula that became the Sun and planets.
"It looks like Eros is one of the most ancient rocks in the solar
system, according to the initial data from NEAR," said Dr. Jacob
Trombka, NEAR X-ray Gamma-Ray Spectrometer (XGRS) Science Team
Leader at NASA's Goddard Space Flight Center, Greenbelt, Md.
"Exploring Eros will help us understand how the rocky planets like
Earth formed, so we can learn more about how we came to be."
The result will be published in the September 22 issue of the journal
Science, as part of a special edition describing the latest results
from the NEAR-Shoemaker mission.
X-rays from the Sun strike Eros' surface and cause elements to
fluoresce (to be stimulated, then glow) in specific X-ray "colors,"
invisible to the human eye but detectable by XGRS. This is similar to
the way a black light uses ultraviolet light to make pop-art posters
glow in various garish colors. Each element on Eros glows in unique
X-ray colors, allowing XGRS to build a map of the element
distribution at and just beneath the surface of Eros.
Discovering the composition of Eros is the key to unlocking the
mystery of its origin. When a forming planet reaches a certain size,
its heat and gravity become sufficient to cause differentiation of
its elements - the planet becomes molten, and heavy elements, like
nickel and iron, tend to sink to the center, while light elements,
like silicon and carbon, rise to the surface. If Eros was composed
mostly of light elements, this would indicate that it was a fragment
from near the surface of a larger body. If it was rich in heavy
elements, it would likely have been from the center of a larger
object. However, instead Eros appears to be undifferentiated, like
the chondrite meteorites found on Earth, so it probably never was
exposed to much heat. This implies that it is a very primitive,
unprocessed object, probably an aggregate of smaller objects from the
early solar system nebula.
"The result is preliminary, because we have only mapped about 20
percent of Eros' surface so far," said Trombka. "Also, the X-ray
spectrometer only reveals composition right at the surface, in a
layer about the thickness of a human hair. Bombardment by cosmic rays
or micrometeorites could have altered the surface composition."
"However, we made the same X-ray measurements of the Moon during the
Apollo missions," added Trombka. "The Apollo astronauts took core
samples, and the composition of the samples agreed with our surface
map. This gives us confidence that our surface map of Eros reflects
its true composition. Also, later in the mission, when NEAR makes its
closest approach to Eros, our Gamma-ray spectrometer will reveal the
composition down to about five inches beneath the surface. This will
let us see if the composition right at the surface is the same as the
interior."
The NEAR mission is managed for NASA's Office of Space by the Johns
Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
For images and more information, refer to: http://www.gsfc.nasa.gov/GSFC/SpaceSci/solarexp/NEARXGRS1.htm
-end-
------------------
It's all very large.
Goddard Space Flight Center, Greenbelt, Md. 2:00 p.m. EDT
Release No. 00-118
EROS ASTEROID MAY HAVE BEEN PRESENT
AT THE BIRTH OF THE SOLAR SYSTEM
The Eros asteroid could have witnessed the formation of the Earth,
according to a preliminary analysis of its surface composition using
NASA's Near Earth Asteroid Rendezvous (NEAR) spacecraft. Analysis of
solar X-rays from Eros' surface indicate that it has a composition
similar to the chondrite meteorites found on Earth, which are
believed to be primordial agglomerations of dust grains from the
nebula that became the Sun and planets.
"It looks like Eros is one of the most ancient rocks in the solar
system, according to the initial data from NEAR," said Dr. Jacob
Trombka, NEAR X-ray Gamma-Ray Spectrometer (XGRS) Science Team
Leader at NASA's Goddard Space Flight Center, Greenbelt, Md.
"Exploring Eros will help us understand how the rocky planets like
Earth formed, so we can learn more about how we came to be."
The result will be published in the September 22 issue of the journal
Science, as part of a special edition describing the latest results
from the NEAR-Shoemaker mission.
X-rays from the Sun strike Eros' surface and cause elements to
fluoresce (to be stimulated, then glow) in specific X-ray "colors,"
invisible to the human eye but detectable by XGRS. This is similar to
the way a black light uses ultraviolet light to make pop-art posters
glow in various garish colors. Each element on Eros glows in unique
X-ray colors, allowing XGRS to build a map of the element
distribution at and just beneath the surface of Eros.
Discovering the composition of Eros is the key to unlocking the
mystery of its origin. When a forming planet reaches a certain size,
its heat and gravity become sufficient to cause differentiation of
its elements - the planet becomes molten, and heavy elements, like
nickel and iron, tend to sink to the center, while light elements,
like silicon and carbon, rise to the surface. If Eros was composed
mostly of light elements, this would indicate that it was a fragment
from near the surface of a larger body. If it was rich in heavy
elements, it would likely have been from the center of a larger
object. However, instead Eros appears to be undifferentiated, like
the chondrite meteorites found on Earth, so it probably never was
exposed to much heat. This implies that it is a very primitive,
unprocessed object, probably an aggregate of smaller objects from the
early solar system nebula.
"The result is preliminary, because we have only mapped about 20
percent of Eros' surface so far," said Trombka. "Also, the X-ray
spectrometer only reveals composition right at the surface, in a
layer about the thickness of a human hair. Bombardment by cosmic rays
or micrometeorites could have altered the surface composition."
"However, we made the same X-ray measurements of the Moon during the
Apollo missions," added Trombka. "The Apollo astronauts took core
samples, and the composition of the samples agreed with our surface
map. This gives us confidence that our surface map of Eros reflects
its true composition. Also, later in the mission, when NEAR makes its
closest approach to Eros, our Gamma-ray spectrometer will reveal the
composition down to about five inches beneath the surface. This will
let us see if the composition right at the surface is the same as the
interior."
The NEAR mission is managed for NASA's Office of Space by the Johns
Hopkins University Applied Physics Laboratory (APL) in Laurel, Md.
For images and more information, refer to: http://www.gsfc.nasa.gov/GSFC/SpaceSci/solarexp/NEARXGRS1.htm
-end-
------------------
It's all very large.