Skip to main content

Scientific American

Stories by Walter Alvarez

Space & PhysicsOctober 1, 1990

An Extraterrestrial Impact

Accumulating evidence suggests an asteroid or comet caused the Cretaceous extinction

Frank Asaro, Walter Alvarez

Subscribe to Scientific American to learn and share the most exciting discoveries, innovations and ideas shaping our world today.

Subscription Plans Give a Gift Subscription

Explore SciAm
Latest Issue
News
Opinion
Newsletters
Podcasts
Games
Travel

Company
About
Press Room
FAQs
Contact Us
Standards & Ethics
International Editions
Advertise

More
Accessibility
Terms of Use
Privacy Policy
US State Privacy Rights
Use of cookies/Do not sell my data
Return & Refund Policy

Scientific American is part of Springer Nature, which owns or has commercial relations with thousands of scientific publications (many of them can be found at www.springernature.com/us). Scientific American maintains a strict policy of editorial independence in reporting developments in science to our readers.

© 2026 SCIENTIFIC AMERICAN, A DIVISION OF SPRINGER NATURE AMERICA, INC.
ALL RIGHTS RESERVED.