Doomsday a real possibility

Researchers present potential future scenarios for Earth -- none are too cheery.

Scripps Howard News Service

Even if no other catastrophe strikes, we are still toast in another 3 or 4 billion years, space scientists believe. As Earth's sun continues to grow larger, hotter and brighter, it will eventually become a red giant star, almost 200 million miles across, nearly reaching our planet's orbit. "The Earth's fragile biosphere will become seriously compromised," Fred Adams, a University of Michigan astrophysicist, said this week with a bit of understatement. Opinions vary as to whether our planet will be incinerated along with Mercury and Venus, the two planets nearest the sun. But the boiling oceans and immense doses of radiation make it unlikely that most life common on Earth today would survive. Adams and fellow researcher Greg Laughlin, a postdoctoral fellow at the University of California-Berkeley, are fond of considering the apocalyptic alternatives for our solar system. There are other things out there in space that could make for a different, if not necessarily better, destiny. In presentations before the summer meeting of the American Astronomical Society in Chicago this week, Adams and Laughlin describe various scenarios that could result from the disruptive pull of various binary stars passing by the solar system. Binary stars -- sets of two or more stars that orbit around each other -- are considered gravitational movers and shakers by many astronomers. And by some estimates, 60 percent or more of all stars the age of the sun or younger are part of such systems. Laughlin and Adams used a computer and statistical calculations to model more than 200,000 possible interactions between such stars and the orbit of the sun, the Earth and four outer planets, particularly Jupiter. "Jupiter is vulnerable to gravitational interactions with a passing star," Adams said. "Because of its large mass, even a modest disruption of Jupiter's orbit could have a catastrophic effect on Earth." The researchers calculate that the chances of Jupiter swinging about in a pattern that would either hurl Earth out into space or plunge us into the sun sometime in the next 3.5 billion years are 1 in 100,000. "Much greater than your chances of winning the Michigan lottery," Adams notes. Among the other possibilities:- Earth being directly ejected from the solar system by a passing star, odds: 1 in 2.2 million;- Earth being captured by a passing star, 1 in 3.6 million;- The solar system capturing another star, 1 in 300,000;Being thrown out of the solar system into deep space wouldn't be a particularly happy ending for Earth, either. "The surface biosphere would rapidly shut down, and oceans would freeze solid within 1 million years, but life could continue for some time near hydrothermal vents on the ocean floor, which are warmed by radioactive heat from deep within the Earth," Laughlin said.

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