Comet

Are Asteroids History’s Greatest Killers?

Publication: National Geographic News   Date: November 20, 2003   View Article

Catastrophic asteroid impacts are gaining a credible edge over violent volcanic eruptions as the greatest killers Earth has ever seen, according to two pieces of scientific detective work reported in tomorrow’s issue of the journal Science.

The first cataclysm in question occurred about 250 million years ago, when according to the fossil record more than 90 percent of Earth’s marine species and 70 percent of life on land perished. The event is known as the Permian-Triassic (P-T for short) mass extinction, named because it falls on the boundary between the two geological eras.

Space Dust Flooding Our Solar System

Publication: National Geographic News   Date: August 27, 2003   View Article

A flood of interstellar dust is breaching the sun’s weakened magnetic shield and drifting into the solar system, according to European astronomers.

The interstellar dust particles measure about one-hundredth the diameter of a human hair. The bits are thought to supply the building blocks of all solid bodies in the galaxy, including the planets and humans.

Killer Asteroids: A Real But Remote Risk?

Publication: National Geographic News   Date: June 19, 2003   View Article

It is almost certain that Earth will be hit by an asteroid large enough to exterminate a large percentage of our planet’s life, including possibly over a billion people, according to researchers. But as such cataclysmic collisions occur on average only once in a million years or so, are they really worth worrying about?

At some point in the geological future a large chunk of rock and ice will smack into Earth and destroy life as we know it. This is a cold, sober, scientific fact, according to Andrea Milani, a researcher at the University of Pisa in Italy.

Comets: How Big A Threat To Earth?

Publication: National Geographic News   Date: January 28, 2003   View Article

Earth-bound asteroids grab newspaper headlines for good reason. Scientists say the fallout of an asteroid several city blocks wide smacking into the planet would be catastrophic. Mass extinctions, runaway infernos, erratic climate fluctuations, and devastating impacts on human civilization are just some of the scenarios imagined.

Why, then, does the threat of a comet impact with Earth—potentially as dire if not worse than an asteroid—rarely leak onto the pages of the popular press?

NASA Practices Satellite Flyby of Asteroid

Publication: National Geographic News   Date: November 1, 2002   View Article

Practice makes perfect, or so the thinking goes at mission control for the Stardust spacecraft. The satellite, launched in 1999 to collect samples from a comet, planned to run through a full dress rehearsal today in preparation for its one-shot encounter 14 months from now.

“As we know from vast experience, spacecraft do not necessarily respond exactly as predicted the first time we try things,” said Thomas Duxbury, project manager for the mission at NASA’s Jet Propulsion Laboratory in Pasadena, California.

© 2008-2010 Collected Writings By John Roach