July 13, 1998 NEW YORK, N.Y., and HAIFA, Israel, July 9, 1998 -- Jets of cosmic rays from colliding stars can produce lethal amounts of muons in the earth's atmosphere, destroy the ozone layer and radioactivate the environment. The three astrophysicists who first proposed that some of the earth's great extinctions were caused by such events -- Arnon Dar, Ari Laor, and Nir Shaviv from the Technion-Israel Institute of Technology -- now propose that the radiation produced would also cause mutations that create new species in surviving life. Their doom and creation theory is published in the June 29 Physical Review Letters.
Other causes proposed to explain past extinctions include asteroids or comets hitting the earth, volcanoes, nearby supernovae, and rising sea levels. Cosmic ray jets, however, explain key characteristics of the most massive extinctions, the authors maintain.
One feature explained by cosmic ray jets is the abrupt repopulation of the earth with completely new species that occurred after some extinctions. New species would be created through rapid mutations caused by radiation. Thus, these cosmic events could radically change the nature of existence on earth by both destroying and creating life. Furthermore, the extinction by cosmic ray jet theory explains why radiation resistant species, including many insects and plants, survived through all but the greatest extinctions. It also explains why species sheltered from the mouns in canyons, caves and underground habitats were not destroyed. Sea life in deep water also survived, while life in shallow waters and on the surface was wiped out. For example, tiny marine creatures called foraminafera displayed this selective survival; one type that lived in shallow waters disappeared, while most species of a type dwelling deep in the ocean survived.
Dar, Laor, and Shaviv suggest ways to gather more substantial evidence for their doom and creation theory. Energetic particles would have left tracks in earth and moon rocks, and left behind particular forms of some chemical elements in rocks. Sensitive instruments can be used to search for these traces of past catastrophes.
Neutron stars whose collisions create cosmic rays are the extremely massive and dense remnants of some supernova explosions. They contain several times the mass of the sun crammed into a space only about 12 miles across (compared to 864,000 miles for the sun). Some neutron stars come in pairs; these stars circle each other at closer and closer range until they spiral into each other. In an earlier paper, Dar and Shaviv suggested that when they collide, a brilliant disk forms briefly and spews enormous jets of high-energy particles known as cosmic rays.
If the earth were in the path of a jet and less than 3,000 light years away, it would experience an intense bombardment, up to a month long, of fast-moving muons. Muons would flood the earth, penetrating hundreds of yards underwater or underground, destroying an organism's central nervous system and causing death within days. Chemical compounds that form would deplete the earth's ozone layer, increasing the amount of ultraviolet light that reaches the surface, which together with the radioactivity produced would be deadly to many plants, disrupting the food chain.
Astronomers have identified five pairs of neutron stars in our galaxy, two of which are within 3,000 light years of earth. They calculate that it will be several hundred million years before any of them collide. But they estimate that there are hundreds more pairs in the Milky Way. As these pairs are discovered, their orbits can be measured to determine when they can be expected to collide. The stars approach each other slowly enough that humankind will probably have time, possibly hundreds of thousands of years, to prepare for such events.
The Technion-Israel Institute of Technology is the country's premier scientific and technological center for applied research and education. It commands a worldwide reputation for its pioneering work in communications, electronics, computer science, biotechnology, water-resource management, materials engineering, aerospace and medicine, among others. The majority of Israel's engineers are Technion graduates, as are most of the founders and managers of its high-tech industries. The university's 11,000 students and 700 faculty study and work in the Technion's 19 faculties and 30 research centers and institutes in Haifa.
The American Technion Society (ATS) is the university's support organization in the United States. Based in New York City, it is the leading American organization supporting higher education in Israel. The ATS has raised $650 million since its inception in 1940, half of that during the last six years. Technion societies are located in 24 countries around the world.
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