06-05-2003 07:16									#61
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quote: Originally posted by Ned Yeah, maybe it collapsing for its last time and we will share the fate of Mars. I think science needs to take a hard look at what's going on to happen and see whether we can do anything about it. BTW, I liked the movie Core. But I don't see how we could send a craft to the center of the earth.

We will have a magnetic field as long as we have a liquid outer core. Living things have gone through reversals THOUSANDS of times over the past 3.9 billion years with no ill effects, why start worrying now.

	06-05-2003 07:17									#62
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Heres more on an upcoming Odyssey mission. It includes package called Marie that will measure harmful radiation at the surface. Here is quote from Nasa's site.

"Mars is substantially exposed to the harshest elements of space weather. Unlike Earth, which sits inside a protective magnetic field called the magnetosphere, Mars does not have a global magnetic field to shield it from solar flares and cosmic rays. Another factor is the lack of atmosphere. Mars’ atmosphere is less than 1% as thick as Earth. These two factors make Mars vulnerable to space radiation. The Marie instrument was designed to measure the amount of harmful radiation in the Mars environment.

The radiation particles which are harmful to humans falls mostly in the energy range of 15 Me V to 500 MeV per nucleon. These are the particles with enough energy to damage human DNA. Some of the particles with 500 MeV/n and above pass through the human body so quickly there is not enough time to transfer their energy into the surrounding tissue. The Marie instrument is designed to measure particles in the range of 15 MeV to 500 MeV/n. The data gathered is combined into an energy spectrum which tells the story of how many particles at what energy level were present."

http://marie.jsc.nasa.gov/main.html

	06-05-2003 07:20									#63
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Sure, but I'm sure spacesuits have sufficient protection. There's no doubt that a naked Sava in space would get cancer. But I'd probably die from decompression or get frozen solid before that.

	06-05-2003 07:23									#64
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quote: Originally posted by Odin We will have a magnetic field as long as we have a liquid outer core. Living things have gone through reversals THOUSANDS of times over the past 3.9 billion years with no ill effects, why start worrying now.

Really? We survived, but the field reversals were short - a matter of weeks. What happens when they last 1,000 years? Who knows what happens then. Perhaps the only things that survived were fish living in the protected ocean and animals that lived in caves. Who knows. I haven't seen any studies on this.

The data from Mars suggests that even there that 1.5 years is tolerable, assuming the data pans out as expected. But longer?

	06-05-2003 07:25									#65
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quote: Originally posted by Sava Sure, but I'm sure spacesuits have sufficient protection. There's no doubt that a naked Sava in space would get cancer. But I'd probably die from decompression or get frozen solid before that.

Sava, NASA is planning, I believe, to generate powerful local magnetic fields using nuclear reactors. I can see these protecting the spacecraft on the way to Mars, and a base. But what about exploring vehicles on the surface?

Man, we are really going to have to come up with some neat inventions to put nuclear reactors on Mars cars.

	06-05-2003 07:25									#66
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Data from Mars? There were humans on Mars?

	06-05-2003 07:26									#67
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quote: Man, we are really going to have to come up with some neat inventions to put nuclear reactors on Mars cars.

I want a Nukemobile!

	06-05-2003 07:32									#68
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Here is a summary from the Mar. 13 Odyssey report:

"Odyssey has measured radiation levels at Mars that are substantially higher than in low-Earth orbit. "The martian radiation environment experiment has confirmed expectations that future human explorers of Mars will face significant long-term health risks from space radiation," said Dr. Cary Zeitlin, principal investigator for the martian radiation environment experiment, National Space Biomedical Research Institute, Houston. "We've also observed solar particle events not seen by near-Earth radiation detectors."
http://mars.jpl.nasa.gov/odyssey/ne.../20030313a.html

	06-05-2003 07:32									#69
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I highly dought the reversal will take 1000 years. I tust Discovery Mag with my science news thank you.

	06-05-2003 07:34									#70
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I don't see NASA allowing astronauts to go to Mars only to be killed or worse from the radiation, even if some think that 1.5 years can be "tolerated."

	06-05-2003 07:35									#71
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quote: Originally posted by Odin I highly dought the reversal will take 1000 years. I tust Discovery Mag with my science news thank you.

What did Discovery Mag. have to say?

	06-05-2003 07:57									#72
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quote: Originally posted by Ned What did Discovery Mag. have to say?

I was just questioning the credibility of your sorce.

	06-05-2003 08:36									#73
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Lunar space suits are bulky gadgets designed to provide radiation protection. Astronauts were able to move easily in Lunar .16 gee gravity. The current design is lighter, but spacewalks are conducted in LEO well below the Van Allen Belts providing the bulk of protection against solar wind and flares.

As for reversals, these processes aren't as "clockwork" as some suggest. The statistical distribution is almost certainly a c² or similar weighting that isn't intuitively assessed as easily as a Gaussian. A 250k average could easily allow a 1000k interval around 2s (the upper 10% probability).

If Earth did enter a reversal transition we'd get nifty aurorae at all lattitudes. Other than that, duration and effects are a big unknown.

	06-05-2003 08:48									#74
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why is it almost certainly x^2? and I dont remember it being a 250k avg. I remember being "every 250k years"

certainly if there is valid sources for this its all good. but if its just conjecture then why bother?

	06-05-2003 08:51									#75
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quote: Originally posted by Straybow Lunar space suits are bulky gadgets designed to provide radiation protection. Astronauts were able to move easily in Lunar .16 gee gravity. The current design is lighter, but spacewalks are conducted in LEO well below the Van Allen Belts providing the bulk of protection against solar wind and flares. As for reversals, these processes aren't as "clockwork" as some suggest. The statistical distribution is almost certainly a c² or similar weighting that isn't intuitively assessed as easily as a Gaussian. A 250k average could easily allow a 1000k interval around 2s (the upper 10% probability). If Earth did enter a reversal transition we'd get nifty aurorae at all lattitudes. Other than that, duration and effects are a big unknown.

Since it is not whether there will be a reversal, the question is how soon. It could happen "anytime" in the next 1000 years. The idea that the process is gradual is belied by the examples of weeks for a reversal to complete.

The next question, is what will be the effects on earth.

Since no one really knows the answer, we need someone to start finding out now.

	06-05-2003 10:57									#76
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They ought to nuke the polar ice caps in mars, to institute super-greenhouse-effect. Worked in Total Recall (I think)....

Would it work?

	06-05-2003 12:00									#77
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If you take a statistics course you'll find out that most natural processes subject to decay or dissipation have c² or log-normal distributions. Let's say the average is 250ky. It cannot be less than 0ky, yet it could be almost any length greater than 250ky. The assymetric boundary conditions are part of what defines the distribution.

Typically, the curve rises sharply to an early peak, and the trailing slope is gentle. The average will be near the peak, but the trailing slope means that the standard deviations s aren't going to be linearly spaced. The +1s interval will be 250ky + nky, but the +2s interval will not be 250ky + 2nky but farther out. Can you visualize what I mean?

I don't trust the scientists who say a field reversal could happen "anytime in the next 1000 years." The next 1000 years is way outside our ability to predict, especially for processes we know squat about. The only thing we can do is measure the field in many locations and model it as a series of dipole moments in 3D, each decaying at different rates.

The last I saw there were a dozen dipoles in the model, and much uncertainty about decay rates (or growth rates in some cases) for the minor ones. The predominant dipole has been decaying with a half-life of 1400 years for the last 400 years. They guess at what threshhold the reversal might come, based on relative strengths of induced magnetism in igneous rocks.

Since that decay rate cannot be extended backwards more than 2-3 half-lives before the magnetic moment becomes too large to fit with observed induced magnetism the model can't be predictive of a process that extends for hundreds of half-lives (250ky+).

Hence I say with absolute confidence that the eggheads who make predictions on this are full of…

themselves.

	06-05-2003 12:25									#78
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Straybow, all we really know is that a statistically overdue reversal is in process. We have no idea what the threshold is for a reversal or what causes the different rates of reversal. Probably, the worst thing for the world is a slow reversal, one that take years, decades, millenia during which time the ionic winds from the Sun blast our atmosphere, stripping it away and heating it at the same time, perhaps killing the ozone layer, and inundating the world in harsh ultraviolet light and much higher radiation levels.

But a slow decay that is what seems to be happening now.

	06-05-2003 16:57									#79
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quote: Originally posted by Ned Straybow, all we really know is that a statistically overdue reversal is in process. We have no idea what the threshold is for a reversal or what causes the different rates of reversal. Probably, the worst thing for the world is a slow reversal, one that take years, decades, millenia during which time the ionic winds from the Sun blast our atmosphere, stripping it away and heating it at the same time, perhaps killing the ozone layer, and inundating the world in harsh ultraviolet light and much higher radiation levels. But a slow decay that is what seems to be happening now.

Are you sure that magnetic field reversals ocur every 250,000 years? If magnetic field reversals were slow wouldn't you expect mass extinctions coinciding with field reversals?

	06-05-2003 18:54									#80
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quote: Originally posted by Lord Merciless Magnetic field has no effect on gamma rays.

hmmm... i kinda thought this was the case also. what are all you rocket scientists talking about?? it's the atmosphere that blocks stuff like this... i thought. spacecraft need to be launched to view gamma rays from space as they dont reach the surface. but the spacecraft do not orbit high enough to be outside earths magnetic field. i could be wrong.

as far as warming up mars. maybe in a billion years when the sun is a bit brighter it will warm up on its own. a long time to wait i guess. perhaps get a big rock and orbit it around mars in a way to drag the planet in a bit.

	06-05-2003 19:24									#81
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Yes, whatever effort done will require many many years for it to have an overall effect. So it would make sense to take any possible initial steps while we wait for the technology and desire to catch up.

RAH

	06-05-2003 19:56									#82
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quote: Originally posted by Dr Strangelove Are you sure that magnetic field reversals ocur every 250,000 years? If magnetic field reversals were slow wouldn't you expect mass extinctions coinciding with field reversals?

Dr. Strangelove, yes. Apparently the last one occurred 1 million years ago.

As to the mass extinctions - and the emergence of new species - I would think so if the reversals lasted a long time. I haven't even heard of any studies on this, though. From the article I quoted, it appears that we really do not understand what will happen if we lose our magnetic field. But there is a lot of speculation about dramatic effects in the upper atmosphere.

	06-05-2003 21:34									#83
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quote: Originally posted by Kamrat X How? It´s not like the wealth of Mars will be equally distributed among people on Earth. It will go into the pockets of big business, just like it does on this planet.

The capital\labor ratio would create higher wages.

	07-05-2003 01:31									#84
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I suspect the only thing that operates on Mars in the future will be machines. I do not see colonization if the radiation problem is as bad as it seems.

	07-05-2003 01:37									#85
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at the very least Ned we could live in radiation sealed areas and develop plants that could withstand it. I guess thats not the very least. but its certainly a skeptics compromise.

	07-05-2003 02:13									#86
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quote: Originally posted by Sava I think it will be more than that. If the US gets to be as dense as China or Europe, you are looking at more than 10b.

But one of the main reasons the US is growing is because of immigration. First generation immigrants generally have larger families than long term residents. In a generation or two, their offspring will cotinue the trend of industrialized nations and produce less children than is required for population growth.

	07-05-2003 02:23									#87
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quote: Originally posted by Ned Paramount's latest sci-fi thriller, The Core - directed by Englishman Jon Amiel, and starring Hilary S**** and Aaron Eckhart - depicts a world beset by just such a polar reversal, with radiation sweeping the planet. The solution, according to the film, to be released next year, involves scientists drilling into Earth's mantle to set off a nuclear blast that will halt the reversal.

It doesn't strike you as suspicious that this article promotes a movie that's in development? I've read other articles, one over at BBC online, that have pointed to this one and debunked it entirely, claiming it's simply a PR piece.

PS Here's a quote from one article on the BBC web site.

quote: Whatever happens will not happen quickly. It will take thousands of years and there is no evidence that when it has happened in the past it has seriously affected life on Earth.

	07-05-2003 02:51									#88
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quote: Originally posted by yavoon at the very least Ned we could live in radiation sealed areas and develop plants that could withstand it. I guess thats not the very least. but its certainly a skeptics compromise.

Agreed. But terraforming will not work so long as the basic cause of the loss of atmosphere still exists: no magnetic field.

We are going to have to figure on how to restart that before we can do anything else. On possiblity would be to maneuver a bunch of large asteroids into striking the planet to heat it up again. But I am sure that such actions would also leave the planet surface unihabitable for upwards of several million years.

	07-05-2003 03:06									#89
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quote: Originally posted by Ned Agreed. But terraforming will not work so long as the basic cause of the loss of atmosphere still exists: no magnetic field.

The Earth's magnetic field wards off ionized radiation, but does it have any effect on the retention of atmospheric gases? Either way, large amounts of an inert gas would also be needed because a pure oxygen atmosphere would be unstable (and toxic).

quote: We are going to have to figure on how to restart that before we can do anything else. On possiblity would be to maneuver a bunch of large asteroids into striking the planet to heat it up again. But I am sure that such actions would also leave the planet surface unihabitable for upwards of several million years.

Hey, here's an idea: instead of slamming the asteroids into the surface of Mars, how about slamming them into Demos and Phobos? Perhaps if the moons were sufficiently large the tidal forces exerted on Mars would be enough to heat up the core of the planet sufficiently to liquify it, and hence form the convection currents of liquid magnetic metals that generate the Earth's magnetic field.

	07-05-2003 03:30									#90
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quote: Originally posted by Dr Strangelove The Earth's magnetic field wards off ionized radiation, but does it have any effect on the retention of atmospheric gases? Either way, large amounts of an inert gas would also be needed because a pure oxygen atmosphere would be unstable (and toxic).

AFAIK, the solar wind would blow and broil away our atmosphere just as it did Mars'. I suspect the phenomenon takes hundreds of thousands of years, at a minimum. But who knows?