Posted on 11/21/2006 8:42:28 PM PST by SunkenCiv
Before the dust even settled after the Great Pluto War at the International Astronomical Union (IAU)'s General Assembly in Prague, one thing became clear: There will never be an accepted scientific definition for the term "planet." Rather than crafting an acceptable definition, the IAU alienated members, put the group's authority in jeopardy and fueled schisms among astronomers on theoretical grounds and even nationality. And the whole affair was scientifically pointless, many astronomers say..."It is a little-known fact that nearly 25 percent of the known extrasolar planets are in binary- or multiple-star systems," said Stephen Kortenkamp , a research associate at the University of Maryland. "That further complicates the notion of creating a universal definition of planet." ...The known setups are a tiny sample of what's out there. There are perhaps 250 billion planets in our galaxy, says Gregory Laughlin, an exoplanet hunter and planetary system theorist at the University of California, Santa Cruz. Eventually, astronomers could find two Earth-size objects orbiting each other around a center of gravity in the space between them, Laughlin said. Other worlds might be accompanied by planet-size "Trojans" that move with them in a horseshoe-shaped pattern. The present IAU definition, requiring a planet to clear out the path of its orbit, is not set up to handle such offbeat configurations. It's also possible two planet-mass objects could be found orbiting each other with no star involved.
(Excerpt) Read more at space.com ...
Yeah. I've heard astronomers also say comets are giant snow balls. However, NASA's has taken some close ups of some famous ones and they look to have a silicate nucleus.
I agree that Pluto is probably rocky just like all the moons out there. I even think the gas giants have a lot of rock (certainly more than the Earth) but that they just have so much gas that the mass of the gas causes gravity to keep the rock liquid. The gas giants most certainly have HUGE solid cores. The magnetosphere of Jupiter is WICKEDLY powerful and I doubt humans will ever be able to venture anywhere near it because of the ions.
How cool would it be (literally) to stand on Pluto though. First off, it would be pitch black except for the stars. No day whatsoever. The sun would simply appear to be the brightest star in the sky. You would have to bring lots of floodlights or night vision helmets. With night vision you would be able to see Charon, Pluto's moon easily. If you were on the Charon side it would never move.
Just this year we launched a probe to Pluto. It will get there in 10 years. Imagine being on that little world...ten full years away from Earth. You better have something faster.
Good idea. There are three candidates for human exploration that come to mind as being pretty easy because they have very little atmosphere -- the Moon, Mars, and Mercury. Human landings on Pluto might be possible, depending on how the surface looks when the New Horizons probe gets there. Ceres, Vesta, and Pallas are also possibilities. The larger moons of Jupiter and Saturn appear to have atmospheres and nasty ones at that. The difficulty of landing and taking off has that added to it.
http://www.freerepublic.com/focus/f-chat/1294934/posts?page=12#12
http://www.freerepublic.com/focus/f-chat/1447339/posts?page=4#4
O lord, I wasn't referring to actually landing on the gas giants, I was referring to getting near them period! We can't even put probes on the gas giants without them liquefying in minutes.
Planets with solid spinning cores, like the Earth, create a magnetosphere that acts as a shield against radiation. This is cool. Where these field lines are strongest particles in the field are ionized, or given an electric charge. When we look at the Aurora Borealis the lights we see are these ionized particles.
HOWEVER, when you have something the size of Jupiter with a spinning solid core, the ionization is much more severe and very deadly. These ions could kill you by frying cells in your brain. You would never see them or feel them, you would just drop dead. The gas giants have an invisible field of these ions whipping around. These things are not just deadly to humans, they're dangerous to probes and we've had to toughen the probes we've sent out there to account for this. They can fry circuits and cause all kinds hardware failures.
I believe Mercury and Venus are out of the question. Mercury is too close to the massively radioactive sun and Venues has a greenhouse gas effect that melted a Soviet probe in about two minutes. It's pretty much Mars, Pluto, and the asteroids and moons in between in terms of actually visiting and staying alive.
I wasn't suggesting a landing on the gas giants (which probably don't have a solid surface per se), just their moon systems. Since a signal can be received from within Jupiter's magnetosphere, there shouldn't be any problem shielding a crew, but the difficulty (mostly toting the fuel) remains. Io at least probably can't be landed on.
Scientist even doubt that a colony can be put on the Moon due to the onset of bone loss and the exposure to radiation.That's been a suspicion for a long while; Asimov included that in one of his short stories, prior to the lunar landings.
It will matter after the Treaty is repealed.
Stop Plutonian Discrimination Now!
Yep. It's looking way bad for Mars too, which has no rotating core like the Earth and therefore no magnetosphere to block incoming radiation.
When asked where he would choose to land on Mars, former astronaut and senator John Glenn replied "In the highlands where there are caves so I can get shelter from the radiation."
Dude knows the deal.
If we're ever going to set up a colony on the Moon or Mars, I'm convinced that we're going to have to build super-sophisticated robots that we can operate from earth in order to make subterranean shelters for us when we get there. I think whatever humans travel to Mars in (if we ever do) it's going to have to duplicate the effect of Earth's magnetosphere and do it for years albeit on a much smaller scale. Essentially, the ship will need what sci-fi mavens have come to refer to as "shields." I can't even begin to imagine the power necessary for that.
I always believed they could simply declare two criteria for a planet:
1.They must be at least Pluto-sized or larger
2.They must not orbit around a larger body.
UV radiation risk:
http://mars.jpl.nasa.gov/science/human/
http://library.thinkquest.org/03oct/01858/text-only/colonization.html
My point exactly. You just do not just send a team to Mars on some Edgar Rice Burroughs dream that it's your God-given right to do so. These individuals are not just in orbit for two years, they're in interplanetary space. No shield from Earth, no nothing.
I'm sorry folks. I do not mean to play the cynic. I'm the first who would want them to get their as ducky as could be. :-)
My point exactly. You just do not just send a team to Mars on some Edgar Rice Burroughs dream that it's your God-given right to do so.I made no such point.
These individuals are not just in orbit for two years, they're in interplanetary space. No shield from Earth, no nothing.Ah, but there would be a shield from Earth, it would be artificial. Humans are able to survive on the Moon thanks to good planning and engineering.
I'm sorry folks. I do not mean to play the cynic. I'm the first who would want them to get their as ducky as could be. :-)The only impediments to getting to Mars and back are technological (which can be overcome) and microgravity exposure (which will just have to be endured). My view about human missions to Mars is that remote robotic exploration are far cheaper, obviously less risky, and will be more autonomous in the future than they are now. Also I don't see any budget for that kind of mission, unless it's a one of a kind (land, plant the flag, grab some rocks, return home).
Going to the Moon is not the same as going to Mars. The Moon, 300,000 miles away though it may be, is still bathed in the Earth's magnetosphere. A trip to Mars requires a trip into the zone where the Sun's radiation is not held at bay by Earth's field lines and an arrival point with no magnetosphere.
Transporting the oxygen, the water, the food. Landing on a planet that has been notoriously hard to hit even with probes...
I think it's going to have to be a stunt, same as the Apollo Moon landings. A very, very expensive, very risky adventure.
I would rather have a human somewhere than a robot any day. But going to Mars - you would have to have a flying Holiday Inn of oxygen, water, and food. The crew would have a skeletal depletion beyond anything on record for the ISS record-setter for months in orbit. They will arrive to Mars, each of them, with weak frames. I think the trip itself is the killer. But Mars has proven tricky to hit even with the latest technology. We've crashed a lot of probes there. Russia has never even managed to hit it for the most part.
It's a big job, an expensive job, and the people footing the bill (US taxpayers) simply have interest because it's not a pissing contest with our worst enemy anymore.
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