Huge Space Clouds May Have Caused Mass ExtinctionsThe idea that we pass through clouds of galactic debris is not new. In fact, a 2003 study found that we're traveling through a mild one right now... The dust layer would hover around Earth, reducing the amount of sunlight reaching the planet while letting terrestrial heat escape into space, creating a snowballing chill. "There are indications from 600 to 800 million years ago that at least two of four glaciations were snowball glaciations," Pavlov said. "The big mystery revolves around how they are triggered." Moderately dense space clouds, the sort that might destroy the ozone layer, are huge, Pavlov points out, and the solar system could take up to 500,000 years pass through one. Extra cosmic rays produced during such an event, owing to interactions of the interstellar dust with the Sun, would break up nitrogen molecules in Earth's atmosphere, leading to ozone destruction... Geologists could look for higher amounts of uranium 235 in soil layers corresponding to the time of known glaciations. Uranium 235 can't be produced naturally in the solar system.
by Robert Roy Britt
March 4, 2005
(beryllium "clouds" would be from impact events)Dodge that Hydrogen Oh, No! Killer Cosmic Clouds!Now along comes Gary P. Zank, a theoretical physicist with the Bartol Research Institute at the University of Delaware... Ice cores from the South Pole contain higher levels of a form of beryllium, a rare metal, which is created when cosmic rays strike Earth. "We find beryllium enhancements at 35,000 years ago, and possibly at 60,000 years ago," he says. "Nobody can explain why." He sees one possible explanation. If a cosmic cloud passed by Earth then, it could have weakened Earths cocoon enough to allow much higher levels of cosmic rays to reach the ground, producing the layers of beryllium.
Special to ABCNEWS.com
June 17, 1999
Rosetta Stone Decodes Gamma-ray Burst MysteryThis telling March 29 burst in the constellation Leo, one of the brightest and closest on record, reveals for the first time that a gamma-ray burst and a supernova -- the two most energetic explosions known in the Universe -- occur simultaneously, a quick and powerful one-two punch... The team said that the "Rosetta stone" burst also provides a lower limit on how energetic gamma-ray bursts truly are and rules out most theories concerning the origin of "long bursts," lasting longer than two seconds. Gamma-ray bursts temporarily outshine the entire Universe in gamma-ray light, packing the energy of over a million billion suns. Yet these explosions are fleeting -- lasting only seconds to minutes -- and occur randomly from all directions on the sky, making them difficult to study... GRB 030329, named after its detection date, occurred relatively close, approximately 2 billion light years away (at redshift 0.1685). The burst lasted over 30 seconds. ("Short bursts" are less than 2 seconds long.) GRB 030329 is among the 0.2% brightest bursts ever recorded. Its afterglow lingered for weeks in lower-energy X-ray and visible light.
by Bill Steigerwald
NASA Goddard Space Flight Center