Search

The article focuses on the debate over whether a comet impact triggered the extinction of huge mammals in North America 12,900 years ago, and put Earth into deep freeze for 1,400 years. It notes that the confidence of geologist Allen West on the theory that blames the mass extinction on a comet impact rests on an overabundance of small diamond grains he and others have discovered in ice and sediments laid down around the period of the extinction of the mammoth. Also mentioned is the theory that climate change is the cause of the mass extinction.

Discusses the ecological implications an impact from asteroids and comets with Earth may result in. Description of the Meteor Crater at Colorado Plateau in northern Arizona; Velocity of the meteorite; Shock; Impact on Earth; Threat of future collisions.

Focuses on studies on the possible collisions of asteroids and comets with the Earth. Computation of the likelihood of such collisions and estimates of possible damages; Description of the types of global destructions that a collision might bring; Consequences to face when reporting an imminent asteroid or comet collision with the planet. INSET: The most dangerous rocks in space. by Stuart J. Goldman.

Focuses on the realism of comet or asteroid collisions with Earth portrayed in science fiction movies. Astronomical and austrautical elements of the movies' plots consulted with science advisors; Balance of truth and art essential in making science fiction films.

Discusses scientific ideas about the possible collision of a wayward comet or asteroid with the earth, presented by planetary scientist Richard Binzel at a dinner hosted by the Planetary Society. Origin of the issue of near-earth objects; Explanation of the Torino Impact Hazard Scale, in which an object is assigned a value based in its collision probability; Career background of Binzel.

Focuses on the development of numerical yardsticks to improve public communication surrounding the increasingly high-profile impact-prediction of comets or asteroids. Nature of the Torino Scale; Details of the Palermo Scale; Investigation of hazard scales.

Focuses on the recommendations made by Great Britain's Task Force on Potentially Hazardous Near Earth Objects regarding the monitoring of asteroids and comets which might collide with the planet Earth.

Focuses on the scientific community's success at accurately defining the size and structure of Chicxulub, the crater discovered in Mexico supposedly formed when a comet or asteroid slammed into Earth 65 million years ago. Description of the crater located in the Yucatan Peninsula's northern shoreline; Seismic-reflection data used by scientists to revise previous size estimates; Theories about impact effects.

Reports on a statistical theory examining the correlation between mass extinctions of species and impacts of comets and asteroids. Impact-crater formation; Allowances for differences of crater sizes.

Focuses on the observations done on comets and warnings of their possible collision with earth. How dynamicist Paul W. Chodas has tested hypothetically comets Hyakutake and Hale-Bopp on a collision course with earth; Dangers of long-period comets; What should be undertaken to lengthen warning time and lessen observation errors.