Post by Chicago Astronomer - Astro Joe on Feb 8, 2006 15:24:03 GMT -6
The Growing Habitable Zone: Locations for Life Abound
In a galaxy filled with billions of stars, scientists searching for alien life need some way to pick out those which are most likely to harbor habitable planets and moons. For more than 150 years, an important tool in this screening process has been the concept of a "circumstellar habitable zone."
Traditionally, this zone has been defined as a narrow disk around a star where temperatures are moderate enough that water on the surface of a planet can exist in a liquid form. The idea is that where liquid water exists, life might arise.
Beginning in the latter half of the 20th century, new information began to emerge that challenged the traditional view. Scientists on Earth began finding rugged organisms thriving in harsh conditions that were off-limits to most other creatures. Meanwhile, images beamed back by robotic probes in space revealed that other moons within our solar system were much more interesting geologically—and perhaps biologically—than our own.
However, beginning a decade ago, planets discovered around other stars began to reveal a diversity of planetary systems that was beyond expectations.
More recently, scientists have gone back and reexamined their ideas about the possibility of habitable planet forming around red dwarf stars. Despite being the most abundant stars in the galaxy, red dwarfs have traditionally been shunned by scientists as being too small and too dim to support life. Those prejudices are beginning to fade and the recent discovery of a small, rocky world in orbit around a red dwarf 28,000 light-years from our corner of the solar system has refueled speculations that these stars might harbor planets with life.
Extremophiles are a diverse group of organisms that thrive in harsh environments intolerable to virtually all other creatures. Since the late 1960s, scientists have discovered hundreds of different extremophile species, most of them bacteria.
This hardy group includes members that can survive scalding waters, subzero temperatures, bone-crushing pressures, corrosive acid, extreme salt and arid conditions. Extremophiles have been found that can withstand massive doses of radiation, breath rust, eat sulfur, belch methane and live without oxygen or sunlight.
"Finding extremophiles on Earth has just been mind-blowing," said Carol Tang, a researcher from the California Academy of Sciences who studies extremophiles. "If you think about how there's very few places on Earth where there isn't life, you can't think about the solar system and the universe in a very limited way anymore."
Full Space.com story here: www.space.com/scienceastronomy/060207_habitable_zone.html
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It will all a matter time in where there will be so many damned life forms out there, we will need a flyswatter!..
