Bill Bottke
Department of Space Studies
Southwest Research Institute

Note: The site you are looking at has not been seriously updated since 1998. To find my recent publications, go here.

Introduction:

• To see an image of myself, my wife, and my family, go here.
  
• To see an image of my daughter Laura, go here.
  
• To see more images of Laura and family, go here.
  
• To see an image of my newest daughter Julie, go here.

This is an exciting time to be involved in asteroid research. Not only do we have recent images of main belt asteroids Gaspra and Ida (and its moon Dactyl) (seen above) from the Galileo spacecraft, but we also have delay-Doppler radar images of near-Earth asteroids Castalia, Toutatis, and Geographos (also, see the information below). We even have a mission (called NEAR) which is is in orbit around near-Earth asteroid Eros. It has already imaged the large main-belt asteroid Mathilda.

Some Science Questions About Asteroids:

• Are any asteroids related to a known meteorite type?
• How exactly do meteorites get to Earth, and what does that tell us about the evolution of asteroids in general?
• Could asteroids be rubble-piles?
• Is there evidence that certain asteroids are fragments of larger bodies?
• Are many asteroids related to comets?
• Are most asteroids chemically primitive or differentiated?
• What were/are the dominant geological processes in an asteroid's evolution?
• What specific morphology and surface properties do asteroids of different sizes have, and what does their morphology tell us about their evolution?
• How often do asteroids impact the Earth and other terrestrial planets?
• Are asteroid impacts a threat to life on Earth?
• How do planetary tidal forces affect asteroids?

Other interesting asteroid links

Links to observatories, institutions, societies, and journals

FAQs: Ten Frequently Asked Questions about NEO Impacts

Are Asteroids Rubble Piles?

Selected Publications and Preprints

Crater Chains on the Earth and Moon?

This is a SAR ("radar") image taken from the shuttle Endeavour of a known impact crater in an area called Aorounga, in northern Chad. A. Ocampo and K. Pope of JPL suggest that the two circular marks near the known crater may be additional impact craters, each about 10 miles in diameter. Could this be evidence of a crater chain on Earth similar to those formed on the Galilean satellites? How would such a chain form in the first place?

My other publications and my curriculum vitae

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Current Research Topics:

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Tidal Disruption of Rubble-Pile Asteroids:

This image shows what happens when a rubble-pile asteroid with a moderately fast prograde rotation rate makes a close approach to the Earth. You can see that several large clumps are thrown off the primary, while many more smaller fragments are scattered off the ends. At the moment, I can only provide a teaser, but suffice to say that this work (completed in collaboration with Derek Richardson at the University of Washington) may shed some light on several questions related to near-Earth asteroid evolution.

	Can Tidal Disruption of Asteroids Make Crater Chains on the Earth and Moon? Bottke, W. F., D. C. Richardson, S. G. Love (1997) Icarus 126, 470-474.

	Production of Tunguska-sized bodies by Earth's tidal forces Bottke, W. F., D. C. Richardson, S. G. Love (1997) Planetary and Space Science, in press.

1620 Geographos: A Tidally Distorted Asteroid?

1620 Geographos is a unusually shaped asteroid whose orbit crosses the Earth's orbital path around the Sun. Delay-doppler radar images from Steve Ostro (and others) at JPL show that this asteroid is nearly 3 times as long as it is wide (5.1 x 1.8 km, or 2.8 x 1.0 normalized). In addition, these images show the Geographos has an "S" or a "pinwheel" shaped structure. We believe this shape could have been produced during a close encounter with Earth sometime in the past, where Earth's tidal forces stretched the object into a new highly-elongated and irregular configuration.

1620 Geographos and 433 Eros: Shaped by Planetary Tides?

Binary Asteroids and the Formation of Doublet Craters:

I am currently trying to understand the formation of doublet craters on the Earth and the other terrestrial planets. Nearly 10% of the largest craters on Earth (including East and West Clearwater Lake in Canada, shown above) are doublets, formed by the nearly simultaneous impact of objects of comparable size. My results suggest that these objects can only be formed by a population of binary asteroids (asteroids with satellites) among the near-Earth asteroid population. Moreover, that Earth's tidal forces are the source for most of the binaries in the near-Earth asteroid population. I suggest that rubble-pile asteroids, after experiencing a close approach with Earth, are frequently split into multiple fragments which can begin to orbit one another. These objects can reencounter the Earth at a later time and impact while separated.

	(Press Release) The formation of asteroid satellites and doublet craters by planetary tidal forces Bottke, W. F., & H. J. Melosh (1996) Nature 381, 51-53.
	Binary asteroids and the formation of doublet craters Bottke, W. F., & H. J. Melosh (1996) Icarus 124, 372-391

Images of Interesting Large Elliptical Craters

Other Links:

Bill Bottke
Department of Space Studies
Southwest Research Institute
1050 Walnut St, Suite 400
Boulder, CO 80302

Tel: (303) 546-9670
Fax: (303) 546-9687
E-mail:bottke[at]boulder.swri.edu

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