SETI [ASTRO] Scientists Calculate Odd Of Doomday Scenarios For Solar System


Larry Klaes (lklaes@bbn.com)
Wed, 02 Jun 1999 14:44:35 -0400


>X-Authentication-Warning: brickbat12.mindspring.com: majordom set sender to owner-astro using -f >Date: Tue, 1 Jun 1999 16:24:02 GMT >From: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov> >To: astro@lists.mindspring.com >Subject: [ASTRO] Scientists Calculate Odd Of Doomday Scenarios For Solar System >Sender: owner-astro@brickbat12.mindspring.com >Reply-To: Ron Baalke <BAALKE@kelvin.jpl.nasa.gov> > >The University of Michigan >News and Information Services >412 Maynard >Ann Arbor, Michigan 48109-1399 > >Contact: Sally Pobojewski >Phone: (734) 647-1844 >E-mail: pobo@umich.edu >Web: http://www.umich.edu/~newsinfo/ > >News Release: May 27, 1999 (15) > >Scientists calculate odds of doomsday scenarios for solar system > >"Some say the world will end in fire. Some say in ice." -- Robert Frost > >CHICAGO -- For a poet, Robert Frost was a pretty good scientist, say >astrophysicists Fred Adams and Greg Laughlin. Frost's fire-or-ice scenario >neatly sums up two outcomes from their new study of possible future >encounters between our solar system and passing stars. > >While other astrophysicists study how the universe began, Adams and >Laughlin are fascinated by how it will end. In a presentation at the American >Astronomical Society meeting held here May 31-June 3, Adams presented >their apocalyptic visions of what could happen to our solar system in the >next 3.5 billion years. > >Laughlin and Adams used a computer and statistical processing calculations >to model more than 200,000 interactions between binary stars passing by >our solar system and orbits of the Earth, sun, and four outer planets, >especially Jupiter. > >"Jupiter is vulnerable to gravitational interactions with a passing star," >said Adams, an associate professor of physics at the University of Michigan. >"Because of its large mass, even a modest disruption of Jupiter's orbit could >have a catastrophic effect on Earth. The chances of such an encounter either >hurling the Earth out into space or plunging it into the sun during the next 3.5 >billion years are about one in 100,000 -- much greater than your chances of >winning the Michigan lottery." > >Other possibilities and their estimated odds of occurrence include: Doubling >of the eccentricities of Neptune's orbit (one in 400), Earth being directly >ejected from the solar system by a passing star (one in 2.2 million), Earth >being captured by a passing star (one in 3.6 million), and the solar system >capturing another star (one in 300,000). > >Without one of the escape scenarios modeled in the Adams-Laughlin study, >the Earth's long-term future is grim. During the next 3.5 billion years, our >aging sun will increase in size and grow more than twice as bright as it >is today. When this happens, "the Earth's fragile biosphere will become >seriously compromised," Adams said. > >The alternative to eventual incineration is being thrown out of the solar >system into deep space. "The surface biosphere would rapidly shut down >and oceans would freeze solid within one 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," said Laughlin, >a postdoctoral fellow at the University of California-Berkeley. > >Adams and Laughlin's detailed models for a frozen Earth have interesting >implications for extra-terrestrial life. Adams maintains that liquid >oceans could exist beneath thick ice sheets on many planets or moons >of giant planets in the galaxy, especially planets that develop past the >"snowline" in the planetary formation disk. "The snowline indicates the >temperature where water ice can form in disk material," Adams said. >"The easiest places to get a large volume of water onto a rocky planet >or moon are places where it's cold enough to form ice. > >"Since water is vital to the existence of life as we understand it, many >people have suggested Jupiter's moon, Europa, as a good candidate for >supporting life," Adams added. "Our work suggests that the most likely >places for extra-terrestrial life to develop would be in liquid oceans >under ice. In other words, life on frozen icy bodies like Europa may be >much more common in the galaxy than life on planets with liquid water >on the surface like Earth. If true, this shift would greatly affect the >possible branches of biological evolution in these extra-terrestrial >environments." > >"Even though our solar system has never been disrupted by a passing star, >these results imply that interactions between binaries and planets may >be more common than has been believed," Laughlin said. "It's possible that >millions of planetary systems throughout the galaxy have been affected >by these binary scattering events, especially in the dense clusters where >stars often form." > >Noting that many of the recently discovered planets in other solar systems >have unusual elliptical orbits, Adams and Laughlin have also suggested >that some of these orbits could be the result of a close encounter with a >passing star or pair of stars. > >The research project is supported by NASA and the U-M. > >



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