Impacts with Space Debris

William P. Leeman
Keith-Wiess Geological Laboratories
Rice University

From'Asteroid & Comet Impact Hazards' webpage from NASA-Ames

The following document summarizes information and sources of information used in our Geology 108 module on extraterrestrial impacts.

"The Aztecs had believed the world would end in one of four ways: earthquake, fire, flood, or jaguars falling from the sky. Here there would be no fire. Nor earthquake nor flood, now that he thought of it. Leaving only the jaguars ... " - Kim Stanley Robinson, Red Mars, p. 14

Review Questions - examples of what to expect on the exam...

  1. Why are impact scars so well preserved on the Moon (and other rocky planets such as Mercury or Venus), whereas they are rather inconspicuous and seemingly rare on the Earth? You might want to know some basic facts about the Moon...

  2. How would you distinguish craters formed by meteorite impact from those that are volcanic in origin? See comparison of these types of features on Venus or use what you have learned about Earth.

  3. Roughly, how many impact sites currently are recognized on the Earth's surface? Where are they concentrated, and why?

  4. What are the differences between meteorites, asteroids, and comets? Why do comets have tails, and why do they always point directly away from the Sun?

  5. Assuming they have the same diameter, what are the relative impact hazards posed by impacts of these types of objects.

  6. Where do each of these types of objects likely originate? (multiple possibilities for some)

  7. Is there any economic value to meteorites?

  8. How much space debris is added to the Earth each day? How is it distributed and is it economic or dangerous?

  9. How large must a meteoroid be (give diameter in metric units) for it to pass effectively through the atmosphere without burning up?

  10. Draw a cross section of an impact crater produced by a 10 km-diameter asteroid that hits the Earth's surface with a velocity of 20,000 mph (12,000 kph).

  11. Make a comprehensive list of evidence that would convince scientists that a specific area (e.g., Chicxulub) was the site of an ancient asteroid impact. Also see discussion.

  12. What is the so-called "iridium anomaly" and what is its significance at the 'K-T boundary'?

  13. Describe a reasonable sequence of life-threatening events that might accompany the collision of a 10 km-diameter asteroid with the Earth (what would the last dinosaurs have experienced)?

  14. There are many large impact craters on Earth whose formation apparently did not coincide with mass extinctions. Explain why this may be.

  15. Some of the largest impact craters (multi-ring basins) on the Moon are nearly 1000 km in diameter. If similar features formed on the Earth at comparable ages, would there have been accompanying mass extinctions? (think carefully about this...)

  16. What are the odds that such a large event (previous question) might occur today (i.e., how frequent is such an event in recent geologic time)? Ditto for a 10 km-diameter impactor? Ditto for a person being struck (killed) by a meteoroid? See Table of Terrors, Table of Fatalities, Figure of expected fatalities vs. impactor size, and discussions of probabilities and scenarios.

  17. A comet recently collided with a planet in our solar system. What was the name of the comet and the planet it struck? What was the extent of damage that occurred? How would such and event affect the Earth today?

  18. From the perspective of loss of human life, where on Earth would be the 'safest' impact site to park a 1 km-diameter asteroid? For your chosen site, what kinds of global effects would you expect? Explain your reasoning.

  19. What should society as a whole do about impact hazards?

  20. If impact by a large asteroid was inevitable in the US, what would you advise our government to do about it? Would your advice differ if we had an advance warning of five years, one year, one month? Explain.
    The following resources provide clues, clues, and more clues. the asteroid game - brought to you by National Geographic - good Impact Animation!!!

Further information resources are provided below.....

Space Objects - Asteroids, Comets, Meteorites, Astronomy

Hale-Bopp home page/JPL
Shoemaker-Levy 9 home page - Comet impacts Jupiter (July 1994)
Shoemaker-Levy 9 home page - Table of contents
Shoemaker-Levy 9 comet - Space Telescope Science Institute - images & animation!
Shoemaker-Levy 9 comet - NASA/JPL
Hyakutake comet - animation
Tunguska 1908 impact - includes Table of Terrors (impact facts)
Asteroid research page - Bill Bottke/CIT

ABCs of Near Earth Objects
Near Earth Objects - overview
NEO number vs. size - Figure from Spaceguard report
NEO impact frequency vs. energy - Figure from Spaceguard report
NEO expected fatalities vs. diameter - Figure from Spaceguard report
Danger in space - Near Earth Objects
Comets, culture, currency
Near hits - contemporary risk assessment
Comets and the Bronze age collapse
Sky survey coordinates - Astronomy views
Astronomy & miscellany - how's your Finnish?
Asteroid links

Lunar near side - shows mare basins and cratered terranes
Terrestrial impact sites - locator map (Geol/ Soc. Canada)
Terrestrial impact craters - examples of terrestrial impact structures
Venus impact craters - see crater classification, distinction from volcanic structures
Comet crashes - a watered down explanation from the Why? Files
Chicxulub crater - K-T boundary impact site
Impact structures - examples from Canada
Meteor Crater, AZ - large photograph

More Solar System Views & Reviews

Views of the Solar System - comprehensive description of the Solar System
The Nine Planets - excellent multimedia tour
Welcome to the Planets - selected NASA images
Planetary images - Good pics! (compiled by G. Byerly)
the Moon - Lunar views and information
Moon/Clementine/GOOD images! - may not always be available
Lunar 'top 10' - most important things we have learned about Luna
NASA - information - NASA subject index
Mars geology - shows major volcanoes
Age of Mars' surface

Space Catastrophes and Disasters

Asteroid impact simulation - interesting animation
Deep Impact - the movie WWW page
Asteroid-ocean impact simulation - from the movie
Asteroid & comet impact hazards - good links on the subject (NASA/Ames)
Meteorites, impacts, etc - excellent survey of meteorite types and impact hazards
Spaceguard survey - reaction to terrestrial impact threat
Planetary defense - a military solution
Meteor defense
Comet busters - a review of what to do...
MIAC - Meteorite Impacts Advisory Committee/GSC
Iridium anomaly - evidence for role of meteorites in mass extinctions
Impact products in the sedimentary record
Mass extinction @ K/T boundary - outcrops of the K-T boundary (incl. Brazos River section, TX)
Probability of impacts
Doomsday asteroids/comets - a short discussion of impact hazards
Impacts & extinctions - hypercard animations
Impacts & dead dinosaurs - outline of key points
Geological time scale - stratigraphic column, punctuated by extinction events
Catastrophism 1 - diverse notes
Catastrophism 2 - frequently asked questions
What killed the dinosaurs - U.C. Berkeley Museum of Paleontology
Volcano theory of dinosaur extinction - Earth System & Biosphere Evolution Research report
Extinction pages on WWW - Links to extinks
Life over time - Field Museum

Meteorites & Extraterrestrial Life

Life on Mars? - McKay et al. (1996) Science Online article
Martian meteorite - Is there life on Mars?
X-Files - Official page
X-Files home page
Mars life - meteorite
Meteorites, impactites, etc. - samples for sale

Related Organizations, Courses

Earth catastrophes course - UC Santa Cruz/check out the cool logo
Catastrophes course - U Puget Sound w/ group projects
Astronomy - Ohio State Univ.
Another X-files - The truth is in here...realm of the 'parabelievable'
Astronomy tutorial - Search for Extraterrestrial Intelligence
Center Adv Space Studies - affiliate of the Lunar Planetary Inst., Houston
Galileo Project - NASA - bringing Jupiter to Earth (visually)
JPL new products
Lunar & Planetary Institute
NASA educational resources
NASA info by subject
NASA Mission to Planet Earth
NASA Observatorium
Space Telescope Institute - Hubble space telescope images
IPCC - International Panel on Climate Change

Remote Sensing

An astronauts's view of Earth - the ultimate field trip (by Kathy Sullivan)
JPL 3-D Images - 3-dimensional image exhibit
JPL Imaging Radar home page
JPL photos of Earth - SIR-C/X-SAR radar images
JPL radar images of Earth - SIR-C/X-SAR radar images
JPL clickable world map - select radar images of your favorite areas on Earth
JPL volcanoes from space - SIR-C/X-SAR radar images of famous volcanoes
Declassified EROS satellite photos - Spy satellite photos of Earth
Topographic images - digital elevation models
USGS EROS data center - Earth Resources Observation Systems imagery
EROS - Ames - national mapping information
Earth RISE images - photographs from space
JPL image archive - space photos

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-----LAST MODIFIED: 3/20/97
-----BY: Bill Leeman