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(meteorobs) Excerpts from "CCNet, 15 March 2000"
------- Forwarded Message
From: Benny J Peiser <b.j.peiser@livjm.acdot uk>
To: cambridge-conference@livjm.acdot uk
Subject: CCNet, 15 March 2000
Date: Wed, 15 Mar 2000 09:12:05 -0500 (EST)
CCNet, 33/2000 - 15 March 2000
------------------------------
QUOTE OF THE DAY
"The NASA satellite conducting the first-ever close-up study of an
asteroid will be renamed to honor Dr. Eugene M. Shoemaker, a
legendary geologist who influenced decades of research on the role
of asteroids and comets in shaping the planets. The Near Earth
Asteroid Rendezvous (NEAR) spacecraft, currently orbiting asteroid
433 Eros more than 145 million miles from Earth, will now be known
as NEAR Shoemaker."
-- NASA, press release 14 March 2000
(1) NEAR SHOEMAKER: NASA RENAMES NEAR SPACECRAFT IN HONOUR OF
GENE SHOEMAKER
NASANews@hq.nasadot gov
(2) GLIMPSES INTO EROS' SHADOWS
Ron Baalke <baalke@jpl.nasadot gov>
[...]
(5) ANGULAR MOMENTUM TRANSFER IN OBLIQUE IMPACTS
M. Yanagisawa*) & S. Hasegawa, UNIVERSITY OF ELECTROCOMMUNICATION
[...]
(8) FASTEST SPINNING ASTEROID?
Charles F. Peterson <cfp@mcn.org>
[...]
=================================================================
(1) NEAR SHOEMAKER: NASA RENAMES NEAR SPACECRAFT IN HONOUR OF
GENE SHOEMAKER
>From NASANews@hq.nasadot gov
Donald Savage
Headquarters, Washington, DC March 14, 2000
(Phone: 202/358-1547)
Mike Buckley
Johns Hopkins University Applied Physics Laboratory, Laurel, MD
(Phone: 240/ 228-7536)
RELEASE: 00-38
NASA RENAMES NEAR SPACECRAFT FOR
PLANETARY SCIENCE PIONEER GENE SHOEMAKER
The NASA satellite conducting the first-ever close-up study of an
asteroid will be renamed to honor Dr. Eugene M. Shoemaker, a legendary
geologist who influenced decades of research on the role of asteroids
and comets in shaping the planets. The Near Earth Asteroid Rendezvous
(NEAR) spacecraft, currently orbiting asteroid 433 Eros more than 145
million miles from Earth, will now be known as NEAR Shoemaker.
"Gene Shoemaker was an inspirational, charismatic pioneer in the field
of interplanetary science," said Dr. Carl B. Pilcher, Director of Solar
System Exploration at NASA Headquarters, Washington, DC. Pilcher
announced the new name today during the Lunar and Planetary Science
Conference in Houston. "It is a fitting tribute that we place his name
on the spacecraft whose mission will expand on all he taught us about
asteroids, comets and the origins of our solar system. "
Shoemaker died in a 1997 car accident in the Australian outback while
on an annual study of asteroid impact craters. With his wife and
research partner, Carolyn, Shoemaker was part of the leading comet
discovery team of the past century, perhaps most famous for finding the
comet (Shoemaker-Levy 9) that broke up and collided with Jupiter in
1994.
He was an expert on craters and the impacts that caused them.
Shoemaker's work on the nature and origin of Meteor Crater in Arizona
in the 1960s laid the foundation for research on craters throughout the
solar system. He also established the lunar geological time scale that
allowed researchers to date the features on the moon's surface.
Though he never realized his dream of tapping a rock hammer on the
moon, Shoemaker taught Apollo astronauts about craters and lunar
geology before they left Earth. Last year, when NASA's Lunar Prospector
spacecraft crashed on the Moon in an experiment at the end of its
mission, a small vial of Shoemaker's ashes, carried aboard the
spacecraft, was scattered on the lunar surface.
Shoemaker was a key member of the 1985 working group that first studied
the NEAR mission, defining its science objectives and designing a
conceptual payload. Many of the group's recommended instruments were
included in the actual spacecraft, which only a month into its yearlong
orbit of Eros is already returning fascinating data on the asteroid's
surface and geology.
The first in NASA's Discovery Program of low-cost planetary missions,
NEAR launched from Cape Canaveral Air Station, FL, on Feb. 17, 1996.
After a four-year journey that included flybys of Earth (Jan. 1998) and
asteroids Mathilde (June 1997) and Eros (Dec. 1998), NEAR began
orbiting Eros on Feb. 14, 2000. The car-sized spacecraft will observe
the asteroid from various distances -- coming within several miles of
the surface -- before the mission ends in February 2001. The Johns
Hopkins University Applied Physics Laboratory in Laurel, MD, designed
and built the NEAR spacecraft and manages the mission for NASA's Office
of Space Science.
EDITORS NOTE: Images and information on the NEAR mission are
available at: http://near.jhuapldot edu
Information on Eugene Shoemaker is available at:
http://wwwflag.wr.usgsdot gov/USGSFlag/Space/Shoemaker/GeneObit.html
=================================================================
(2) GLIMPSES INTO EROS' SHADOWS
>From Ron Baalke <baalke@jpl.nasadot gov>
NEAR image of the day for 2000 Mar 14
http://near.jhuapldot edu/iod/20000314/index.html
Glimpses into Eros' shadows
This image mosaic, showing Eros' saddle and a shadowed feature to its
left, was taken from a distance of 204 km (127 miles). In this picture
features as small as 20 meters (65 feet) are visible. This is the best
view to date of this area. The sun is coming from the northeast
illuminating a shadowed feature that consists of three large craters
situated adjacent to each other. The two largest are each about 4-5 km
(2-3 miles) across. Because the sun is very low with respect to these
craters, even small topographic features cast long shadows, making them
easier to see. As a result, several boulders can be distinguished,
ranging from about 50 to 100 meters in diameter, on the crater walls.
The saddle, on the right of the mosaic, is relatively smooth, with
few impact craters, and has several grooves running across it. At the
top of the saddle are several curved grooves that are brighter than the
surrounding surface. Unusual brightness patterns are also visible in
the crater at the top left of the mosaic. The walls of the crater
appear to be more reflective and its floor less reflective than nearby
parts of the asteroid.
- --------------------------------------------------------
Built and managed by The Johns Hopkins University Applied Physics
Laboratory, Laurel, Maryland, NEAR was the first spacecraft launched in
NASA's Discovery Program of low-cost, small-scale planetary missions.
See the NEAR web page at http://near.jhuapldot edu for more details.
=================================================================
(5) ANGULAR MOMENTUM TRANSFER IN OBLIQUE IMPACTS
M. Yanagisawa*) & S. Hasegawa: Angular momentum transfer in oblique
impacts: Implications for 1989ML. EARTH PLANETS AND SPACE, 1999,
Vol.51, No.11, pp.1163-1171
*) UNIVERSITY OF ELECTROCOMMUN,1-5-1 CHOFUGAOKA,CHOFU,TOKYO
1828585,JAPAN
We conducted 10 shots of high-velocity oblique impact experiments
(1.95-3.52 km/s) using nylon projectiles and spherical mortar targets.
Large craters were formed, but these targets were not disrupted by the
impacts. We then calculated the efficiencies of momentum transfer from
the projectile to the post-impact target for each experiment. The
efficiencies of angular momentum transfer from the translational motion
of the projectiles to the rotation of the post-impact targets were also
derived. A representative efficiency of angular momentum transfer was
calculated to be 0.17 for random successive collisions. The efficiency
was applied to an equation expressing the precession angle of
asteroids. It is shown that 1989ML, target of Japan-US
asteroid-sample-return-mission (MUSES-C) would be tumbling. Copyright
2000, Institute for Scientific Information Inc.
=============================
* LETTERS TO THE MODERATOR *
=============================
(8) FASTEST SPINNING ASTEROID?
>From Charles F. Peterson <cfp@mcn.org>
In terms of useful information about NEAs, it would seem that the
velocity of the surface of the asteroid tells more than the rotational
period. Am I correct?
The surface of a 100 meter asteroid with a rotational (day/night)
period of 10 minutes is not moving as fast at its equator as the
surface of a one kilometer asteroid with a much longer rotational
period. Surface velocity would tell something about origin and impact
history, right? Day/night period seems to be an interesting but
inconsequential artifact of the relationship of diameter to surface
speed.
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