Posted on 02/07/2006 1:59:24 PM PST by tricky_k_1972
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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
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."
Habitable moons
In 1979, NASA's two Voyager spacecrafts shocked scientists with images they beamed back of Jupiter's moon Europa. The images showed a shiny world covered in water ice, but what was really remarkable was how smooth its surface was.
Unlike our own moon, Europa has relatively few impact craters. Because it doesn't have an atmosphere to burn up incoming objects like asteroids, scientists concluded that Europa had an internal heat source that kept its waters fluid, allowing the moon to periodically repave its icy shell and erase away the craters that must routinely be carved.
"Before the Voyager missions, scientists used to think that the moons of the other planets were old, rocky, battered bodies like our moons," said Cynthia Phillips, a SETI planetary scientist.
Scientists think Europa stays warm by a process called tidal heating. All moons, including our own, are stretched and pulled by the planet they orbit. Jupiter is so massive and its gravity so strong that it actually causes Europa’s surface to bulge and shrink as it circles around in its orbit. This constant motion generates friction and heat.
Saturn's cloud-covered moon, Titan, is thought to be warmed by the same process. Other moons generate heat through different means. Scientists recently discovered that Saturn's moon Enceladus, for example, contains a mysterious hot spot in its southern hemisphere that might be caused by radioactive material left over from the moon's formation billions of years ago.
Widening zone
This revelation, that not all the moons in our solar system are as dead and barren as our own, meant that places outside the traditional habitable zone might sustain liquid water and support life.
"If you have a fairly sizable planet with plenty of internal energy to keep warm it might not need to be close to the Sun," said biologist Ken Nealson from NASA's Jet Propulsion Laboratory in California."It might have plenty of energy to support a perfectly good biomass without having a lighted surface."
Scientists believe that beneath Europa’s icy shell lies an ocean vaster than Earth’s. For this reason, many scientists figure the Jovian moon may be a better bet for finding alien life than Mars.
"There might have been liquid water on Mars in the past and there could have been life then, but it's pretty unlikely that we'll find life living there today," Phillips said. "But on places like Europa, there could be and probably is water there today. Instead of looking at an extinct biosphere, we could be looking at a currently active one." Red dwarfs
Last fall, a group of about 30 scientists from different fields got together in Mountain View, California for a workshop sponsored by the SETI Institute. The workshop was convened to answer a single question: are the planets orbiting red dwarfs habitable?
SETI scientists will soon begin looking for radio signals from intelligent extraterrestrial life using the Allen Telescope Array and they wanted to know whether red dwarfs should be included in the list of stars to search.
Red dwarfs are believed to make up about 85 percent of the stars in the universe, but they are so small and so dim that scientists have traditionally ignored them as possible havens for habitable planets.
One of the main objections was that the habitable zones of red dwarfs would be very narrow and very close to the stars. For a planet orbiting a red dwarf to be warm enough to have liquid water, it would need to be located closer to the star than Mercury is to our own Sun. At such a close distance, the planet would become tidally locked to the red dwarf the way our Moon is to Earth. Any water existing on such a planet would be boiled away on the side facing the star and frozen solid on the other.
In recent years, however, new computer models have suggested that the situation isn’t as impossible as it might seem. The models predict that if an orbiting planet had a thick enough atmosphere, heat could be redistributed from the lit side of the planet to the side that was dark.
As for the criticism that a red dwarf’s habitable zone is very narrow, Todd Henry, an astronomer at Georgia State University, has an interesting view. Because there are so many more red dwarfs than stars like our Sun, Henry has performed calculations suggesting that if the narrow habitable zones of all the red dwarfs in our galaxy were combined, they would equal the habitable zone of the all the Milky Way’s Sun-like stars.
"You open up a lot more territories if you put [red dwarfs] back on the table," Henry said.
Ever see the Outer Limits episode "Cry of Silence"? The alien was so different, contact was impossible.
Scariest Outer Limits ever IMHO.
With all the special effects that are put into sci fi these days, it's amazing how scary the old Outer Limits were. I still think about those shows to this day. Still give me the creeps. Ha ha
How about the one where the guy was changed into an alien? Or the alien that could make a force field by pushing a button in his hand? Or the one where the scientist's assistant evolves into the genius with 6 fingers? What great writing. The sets probably cost $40, but what entertainment.
The problem is not just whether life can in fact live in hostile conditions; the problem is where are they?
If you look at the age of life existence on our planet and the time it took for that life to develop into intelligent life it is very small compared to the age of the universe or even other solar systems.
If life on Earth is not an aberration, and I don't think that it is, then let suppose a similar developmental process for life and it's eventual "evolution" into intelligence.
John von Neumann was a scientist and most notably a theorist who presupposed an intelligent race that created machines that could recreate themselves, probably not too far advanced from where we are today, he went onto propose that these machines even without the benefit of faster than light travel could eventually travel the entire galaxy in relatively (compared to the age of the Universe) short period of time and leave their mark.
The question is, if life can be and is numerous, and if life will eventually evolve into intelligence (given eneough time), where are they?
I loved them. Have all of them on DVD. :-)
When younger I had the fortune to work at a research company (in a lowly technician position), and also to meet an academic physicist who had an improvemnt for optical telescopes.
At the company an idea or discovery was greeted with "so-and-so will want this, it'll put 'em two years ahead of the competition". Basic research arose out of the need for the clients to keep ahead in the market.
The academic, however, spent years getting his idea funded because of poitics- basically because funding would go to another department.
Intelligence- that's a different matter. Are there intelligent life forms out there? You've got me. BUT, you can't tell me that somewhere, on some planet out in the middle of nowhere, there isn't some "stuff on a rock." An ocean planet with a rock sticking out of the waves, with crud on it. Gloopy self-replicating crud. ha
Fermi's paradox: If intelligent life is common in the galaxy, where is it?
Many, many explanations of this.
My personal thoughts: We are a spontaneous, inevitable product of carbon chemistry in a infinite, evolving universe. The problem is that this evolution is taking place all across the universe at essentially the same time. The other civilizations are all rising contemporaneously.
qUITE A HALF-LIFE!
Speaking of lenses- off topic :) A few years ago, I remember reading about a scientist who had made a few atoms of transparent gold in the lab. Ive used "gold" lenses from time to time (lenses with a thin layer a few atoms thick of gold) and they have great optical properties. But for the life of me, I can find nothing regarding his research on the web. Familiar with that?
Looks like a pinger!
What odds?
Until the powers that be can figure out a way to retain control over people out there, we're not getting off.
America was a big lesson in what happens when pissed off indivdualists get away from the elite.
I got out just in time: '95 Navy Dept.
Kinda like a C vs E thread?? ;^)
The scientific theories of life- as we know it- depend on as miraculous gestation of intelligent species as religious ones. There are so many requirements and pitfalls.
Consider such postulates as Neumann's and Ferni's for humanity though. Once nuclear power is as under our control as electicity is now- something we can at least reasonably assume will happen- there will be few limits to our growth. We'll be everywhere- or dead.
Ah, but life is about competition, even among single species.
Competition will eventually bring about specialization and specialization will bring about instinct.
Instinct will eventually bring you to the top of the food chain and from there tool development.
Tool development will bring about modification of your environment to a point where basic survival is no longer a concern leading to social competition.
Social competition will lead "eventually" to intelligence.
Ok now everybody, that was a high school (maybe a little more) evolutionary progress sheet. I know it might be wrong in it's development, but it is essentially what is proposed by evolutionists.
My former post was not suppose to be about evolution, but it does concern it strictly scientifically speaking. I DO NOT WANT TO ARGUE EVOLUTION VS. CREATIONISM
(Just as a guess) putting "plasma deposition" gold lenses transparent in Google got results that may be on what you're thinking of.
NO, no, no, no, NO!
E VS.C has been argued, reargued, hashed and rehashed to death around here.
We don't need it and I don't want it.
I am a preachers son, so I have had these arguments myself, and believe it or not, with myself.
I am simply looking for ideas on arguments within the realm of "science" on this topic
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