1. You can colonize Mars. I'm staying here. Mars has such a weak magnetic field that its surface is bombarded by high-energy ions (cosmic rays, solar wind). As long as you lived 10 meters underground you'd be fine, until you realized you were in a prison of your own making.
2. Now both NASA AND ESA have reliable connections to Mars. Ground-based antennae are adequate for the vast majority of the time. It's not like you're going to use a data connection to Mars like you use the Internet. Can you imagine playing Quake 15 with your Martian buddies and getting 10 minute lag?
3. Ok, so maybe eventually there will be a fleet of communication satellites around Mars just like there is around Earth. Then GPS, some secret military satellites, and it would be just like home...
Hmmmm... magnetic fields generated by liquid core dymanos are generally dipoles (except when they are flipping over). Mars' magnetic field is extremely weak in the northern hemisphere (blasted off by an enormous collision). In the south it is patchy: in some areas it comes in stripes of opposing polarity. This suggests it is remanent magnetism frozen in place when the rocks first formed. There must have been a reversing dipole field at one time, and each stripe of rock formed between field reversals.
The set of equations used in magnetohydrodynamics is so complicated we don't even understand the Earth's magnetic field very well. Rotation, turbulence, magnetism frozen in to the solid core, the chemical evolution of the liquid iron (sulphur or no sulphur?) and a myriad other factors all play a part.
My personal guess is that Mars' core doesn't generate much of a field because it is small and so doesn't have a large moment of inertia. But ha! What do I know?
The satellite's orbit is what is used to measure tidal bulges. Here's how it works, in layman's terms:
A satellite orbiting Mars will describe a roughly ellipsoidal shape. One can draw a straight line through the point where the satellite is closest to Mars and the point where it is farthest (a.k.a. major axis). In the absence of tidal bulges, orbit after orbit, this line will remain pointed in the same direction in space. This works even if Mars's mass is not arranged in a perfectly spherical manner (caverns, dense mineral deposits, huge volcanoes, etc.).
The important thing to note is that a tidal bulge is actually a wave that displaces any given point on Mars twice a day. As the satellite is orbiting, it gets a little extra gravitational nudge from the tidal bulges roughly twice each orbit. The overall effect is to cause the major axis of its orbit to drift a little bit, or precess. It is cumulative over time, so even if the major axis drift per orbit is small, after hundreds of orbits it will be quite noticeable. So that is how a bulge can be measured without actually measuring actual ground displacement.
The Earth's outer core is liquid, but the inner core is solid. A solid inner core will naturally be crystalline. The real question is whether it is one giant crystal or many interlocked crystalline domains of random orientation.
Note that the liquid core is exterior to the solid core. It's the high pressures at the center that cause it to be solid. Mars, with a much lower mass, would have a lower central pressure, so it's not surprising that it is liquid (ignoring differences in temperature, of course).
The first of the ESA missions, Mars Express, will launch in June 2003 carrying an orbital craft and the British lander Beagle 2.
There are several problems with turning a Mars probe into a "repeater." Firstly, it's weight would be increased significantly by the extra antennae ('cause one would need to be pointed at Earth, each of the others pointed at the target missions), the extra power source (solar panels?), and computing hardware. The other problem is more significant. Mars and Earth have different orbital periods. Once every 2.1 years or so the Sun will lie between the two planets. Also, probes further out will not have the same period as Mars. There will be points in time during missions when the probe and the Earth are on one side of the solar system and Mars on the other, so the probe and Earth will be closer to each other than the probe is to Mars. An entire fleet of repeaters would be necessary to provide continuous coverage.
its ion cloud today seems to spell doom for what Sir Arthur C. Clarke indicated, is another reason to avoid probing life on Europa
ceejayoz writes "A newly discovered gas cloud around Jupiter, created by ion radiation hitting the surface of Europa, has cast doubt on possible life on the moon.
The ion cloud is completely irrelevant to the chances of finding life deep in the oceans of Europa. The Earth itself is surrounded by belts of ionized radiation. Ions bombard the atmosphere hard enough for it to visibly glow near the magnetic poles. And yet life thrives in just about every Earth environment that isn't molten rock. And the original posted link about the Jovian ion torus never mentioned any hazards to Europan life.
Galaxy collisions are not nearly so violent as you make them out to be. Galaxies are mostly empty space, so while orbital chaos may ensue, rarely will you find stars actually running into each other.
We have no way of knowing whether the radiation is just inherent to our solar system, galaxy, or even planet. In fact, it is most likely that the instruments themselves are the problem.
The microwave radiation is blueshifted in the direction our galaxy appears to be moving in relation to points at the edge of the visible universe, after correcting for blueshifts from our motion around the sun and the sun's course through the galaxy. This rather handily shows the source of the microwave radiation to be outside our galaxy. If you blame it on the instruments themselves, then you have to come up with a theory that explains how the instruments produce anomolous readings that correspond exactly with the extra-galactic point they happen to be aimed at at the moment (versus what planet, local star, geomagnetic longitude, etc. they are pointed at). And the source of the microwaves isn't claimed by astrophysicists to be "distant stars everywhere." It is obvious that you don't know enough about the theories or the instruments and observations that stimulated them to discount them. Part of science is to come up with theories that explain observations. No where is it implied that the theories have to be whole and perfect or even correct, just that they explain all the evidence gathered so far. If we could send probes to distant galaxies and they showed that the Milky Way was responsible for all the microwave radiation, then the theories would be rewritten and/. user Angram crowned as a visionary. But don't hold your breath.
[T]he "Roche limit".... is the closest a object can come to another object without being torn apart.... The larger the satellite, the larger the difference in force and therefore the larger this limit.
The Roche limit for non-rotating spherical icy bodies >40 km in diameter approaching the sun is ~1.1 billion meters, and does NOT depend on size. NEAT never got closer than 15 billion meters (according to this article). Even if NEAT was much larger than it actually is, it was immune to tidal breakup.
Mirror matter .....not that I believe it
on
Do Comets go Poof?
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Some theorists have speculated about mirror matter. This hypothetical stuff is exactly like ordinary matter but only interacts with ordinary matter gravitationally. They theorize that comets disappear because they are a thin matrix of ordinary molecules gravitationally bound to a large mirror object (perhaps a mirror asteroid in the mirror universe). The sun drives off the ordinary stuff, but the mirror object goes unchecked. I'm not making it up!
The triple-point (temperature and pressure at which it exists as gas, liquid, and solid simultaneously) of carbon dioxide is 216.55 deg K, 517,000 Pa. So apparently its state depends greatly on where it is. Alpha-Centauri, for example, would destroy carbon dioxide by ionizing it.
I doubt that "[t]he issue [of killer asteroid censorship] may be making its rounds because an asteroid was discovered orbiting the sun between Venus and Earth earlier this week." As was made quite clear in the link, this asteroid will remain harmless for the rest of its life, unless aliens strap a nuclear rocket to it, or space-monkeys attach a 1000 km solar sail to it, and heave it out of its low energy orbit.
The kind of information they are likely come up is not "a 10 km. asteroid is definitely going to hit New York next week." More likely it will be "a.5 km asteroid has a 1:300 chance of hitting the earth in the year 2080." Then they will track it for a few more months (or find it in archival photos), and recalculate its orbit. "Upon further analysis, we don't think it has a snowball's chance in hell of coming within the moon's orbit in the year 2080."
These upper atmosphere electrical phenomena are associated with thunderstorms, and there weren't any in the area, especially over San Francisco where the "purple corkscrew" was photographed. Scientists are frantically searching for infrasound signature (think 'spriteclap' instead of 'thunderclap') of this event.
The ionosphere itself wasn't very active either. First, the pre-dawn ionosphere tends to be weaker than after the sun heats things up. Also, the sun's xrays were not strong, and geomagnetic storm activity was subdued.
"NASA did not attempt to examine Columbia's left wing with high-powered telescopes on the ground, 180 miles below, or with spy satellites. The last time NASA tried that, to check Discovery's drag-chute compartment during John Glenn's shuttle flight in 1998, the pictures were of little use, [shuttle program manager Ron] Dittemore said. Besides, he said, `'there was zero we could have done about it.' "
The article discusses other options and why they wouldn't have worked. Recommended reading....
A NASA engineering analysis discounted the possibility of significant damage from foam insulation striking the left wing during launch. In the analysis an estimate of the mass and velocity of the chunk would have been necessary, amongst other variables. It is possible that they underestimated the mass of the insulation. What follows is a wild and perhaps misinformed theory.
Poorly bonded insulation allows air to infiltrate between the insulation and the tank. Water ice is deposited. If liquid water condenses as well, an insulation-prying process develops: freezing water expands, widening the gap and thus increasing the volume of airspace for additional liquid and ice to form. Eventually the heavy load of ice, vibations, g-force, and severely weakened area of bonding cause the tank to shed the chunk of insulation with its heavy load of ice. The ice would be denser than the foam insulation. Ignoring its buildup could cause serious under-estimation of the chunk's mass and mechanical strength.
Helioseismology has matured to the point that it can be used to image the far side of the sun", which is impressive, considering the sun is 1.4 million kilometers in diameter. SOHO strikes again.
I might have jumped the gun. The pressure would remain the same at sea level but there would be a redistribution in atmosperic density vs. altitude. On a mountain, with some of the atmosphere having moved from below one's feet to over one's head, the pressure would be higher, but not enough to notice.
The pressure will remain the same (on average). The ideal gas law: PV=nRT. T going up causes V to go up, P remains the same (as it is related to the weight of the air column over the area where the pressure is being measured). So the breathable atmosphere won't be taller.
The amount of energy needed to create enough ozone would make it prohibitively expensive. Luckily the offending ozone-destroying molecules have been largely phased out and the ozone layer will start to recover within our lifetime.
It is incorrect to assume "that asbestos problems had been mostly solved by removing it from all buildings, etc." Unfortunately, asbestos will be around for a long time. Consider the case of Libby, MT. For years this town's residents mined vermiculite contaminated with tremolite, a very hazardous form of asbestos. This vermiculite was used as insulation, potting soil, came home to families on miners' clothing, etc., and so almost the entire town is now contaminated. Rates of rare cancers have sky-rocketed. Also consider the World Trade Center's asbestos. Luckily it was only used on the first 40 floors of the North tower and half of it was later removed, but still the dust that coated lower Manhattan was contaminated with the stuff. Controversy still swirls around issues of the cleanup and its costs.
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1. You can colonize Mars. I'm staying here. Mars has such a weak magnetic field that its surface is bombarded by high-energy ions (cosmic rays, solar wind). As long as you lived 10 meters underground you'd be fine, until you realized you were in a prison of your own making.
2. Now both NASA AND ESA have reliable connections to Mars. Ground-based antennae are adequate for the vast majority of the time. It's not like you're going to use a data connection to Mars like you use the Internet. Can you imagine playing Quake 15 with your Martian buddies and getting 10 minute lag?
3. Ok, so maybe eventually there will be a fleet of communication satellites around Mars just like there is around Earth. Then GPS, some secret military satellites, and it would be just like home...
The set of equations used in magnetohydrodynamics is so complicated we don't even understand the Earth's magnetic field very well. Rotation, turbulence, magnetism frozen in to the solid core, the chemical evolution of the liquid iron (sulphur or no sulphur?) and a myriad other factors all play a part.
My personal guess is that Mars' core doesn't generate much of a field because it is small and so doesn't have a large moment of inertia. But ha! What do I know?
The important thing to note is that a tidal bulge is actually a wave that displaces any given point on Mars twice a day. As the satellite is orbiting, it gets a little extra gravitational nudge from the tidal bulges roughly twice each orbit. The overall effect is to cause the major axis of its orbit to drift a little bit, or precess. It is cumulative over time, so even if the major axis drift per orbit is small, after hundreds of orbits it will be quite noticeable. So that is how a bulge can be measured without actually measuring actual ground displacement.
Note that the liquid core is exterior to the solid core. It's the high pressures at the center that cause it to be solid. Mars, with a much lower mass, would have a lower central pressure, so it's not surprising that it is liquid (ignoring differences in temperature, of course).
The first of the ESA missions, Mars Express, will launch in June 2003 carrying an orbital craft and the British lander Beagle 2.
There are several problems with turning a Mars probe into a "repeater." Firstly, it's weight would be increased significantly by the extra antennae ('cause one would need to be pointed at Earth, each of the others pointed at the target missions), the extra power source (solar panels?), and computing hardware. The other problem is more significant. Mars and Earth have different orbital periods. Once every 2.1 years or so the Sun will lie between the two planets. Also, probes further out will not have the same period as Mars. There will be points in time during missions when the probe and the Earth are on one side of the solar system and Mars on the other, so the probe and Earth will be closer to each other than the probe is to Mars. An entire fleet of repeaters would be necessary to provide continuous coverage.ceejayoz writes "A newly discovered gas cloud around Jupiter, created by ion radiation hitting the surface of Europa, has cast doubt on possible life on the moon.
The ion cloud is completely irrelevant to the chances of finding life deep in the oceans of Europa. The Earth itself is surrounded by belts of ionized radiation. Ions bombard the atmosphere hard enough for it to visibly glow near the magnetic poles. And yet life thrives in just about every Earth environment that isn't molten rock. And the original posted link about the Jovian ion torus never mentioned any hazards to Europan life.
Galaxy collisions are not nearly so violent as you make them out to be. Galaxies are mostly empty space, so while orbital chaos may ensue, rarely will you find stars actually running into each other.
You obviously didn't read the article....
It seems more like spectroscopy to me anyway.
The microwave radiation is blueshifted in the direction our galaxy appears to be moving in relation to points at the edge of the visible universe, after correcting for blueshifts from our motion around the sun and the sun's course through the galaxy. This rather handily shows the source of the microwave radiation to be outside our galaxy. If you blame it on the instruments themselves, then you have to come up with a theory that explains how the instruments produce anomolous readings that correspond exactly with the extra-galactic point they happen to be aimed at at the moment (versus what planet, local star, geomagnetic longitude, etc. they are pointed at). And the source of the microwaves isn't claimed by astrophysicists to be "distant stars everywhere." It is obvious that you don't know enough about the theories or the instruments and observations that stimulated them to discount them. Part of science is to come up with theories that explain observations. No where is it implied that the theories have to be whole and perfect or even correct, just that they explain all the evidence gathered so far. If we could send probes to distant galaxies and they showed that the Milky Way was responsible for all the microwave radiation, then the theories would be rewritten and /. user Angram crowned as a visionary. But don't hold your breath.
The Roche limit for non-rotating spherical icy bodies >40 km in diameter approaching the sun is ~1.1 billion meters, and does NOT depend on size. NEAT never got closer than 15 billion meters (according to this article). Even if NEAT was much larger than it actually is, it was immune to tidal breakup.
Some theorists have speculated about mirror matter. This hypothetical stuff is exactly like ordinary matter but only interacts with ordinary matter gravitationally. They theorize that comets disappear because they are a thin matrix of ordinary molecules gravitationally bound to a large mirror object (perhaps a mirror asteroid in the mirror universe). The sun drives off the ordinary stuff, but the mirror object goes unchecked. I'm not making it up!
The triple-point (temperature and pressure at which it exists as gas, liquid, and solid simultaneously) of carbon dioxide is 216.55 deg K, 517,000 Pa. So apparently its state depends greatly on where it is. Alpha-Centauri, for example, would destroy carbon dioxide by ionizing it.
I doubt that "[t]he issue [of killer asteroid censorship] may be making its rounds because an asteroid was discovered orbiting the sun between Venus and Earth earlier this week." As was made quite clear in the link, this asteroid will remain harmless for the rest of its life, unless aliens strap a nuclear rocket to it, or space-monkeys attach a 1000 km solar sail to it, and heave it out of its low energy orbit.
The kind of information they are likely come up is not "a 10 km. asteroid is definitely going to hit New York next week." More likely it will be "a .5 km asteroid has a 1:300 chance of hitting the earth in the year 2080." Then they will track it for a few more months (or find it in archival photos), and recalculate its orbit. "Upon further analysis, we don't think it has a snowball's chance in hell of coming within the moon's orbit in the year 2080."
The ionosphere itself wasn't very active either. First, the pre-dawn ionosphere tends to be weaker than after the sun heats things up. Also, the sun's xrays were not strong, and geomagnetic storm activity was subdued.
"NASA did not attempt to examine Columbia's left wing with high-powered telescopes on the ground, 180 miles below, or with spy satellites. The last time NASA tried that, to check Discovery's drag-chute compartment during John Glenn's shuttle flight in 1998, the pictures were of little use, [shuttle program manager Ron] Dittemore said. Besides, he said, `'there was zero we could have done about it.' "
The article discusses other options and why they wouldn't have worked. Recommended reading....
Poorly bonded insulation allows air to infiltrate between the insulation and the tank. Water ice is deposited. If liquid water condenses as well, an insulation-prying process develops: freezing water expands, widening the gap and thus increasing the volume of airspace for additional liquid and ice to form. Eventually the heavy load of ice, vibations, g-force, and severely weakened area of bonding cause the tank to shed the chunk of insulation with its heavy load of ice. The ice would be denser than the foam insulation. Ignoring its buildup could cause serious under-estimation of the chunk's mass and mechanical strength.
Helioseismology has matured to the point that it can be used to image the far side of the sun", which is impressive, considering the sun is 1.4 million kilometers in diameter. SOHO strikes again.
No.
Is the whole atmosphere being pushed out?
The outer atmosphere rises and falls in tune with the day night cycle and the 11 year solar cycle.
I might have jumped the gun. The pressure would remain the same at sea level but there would be a redistribution in atmosperic density vs. altitude. On a mountain, with some of the atmosphere having moved from below one's feet to over one's head, the pressure would be higher, but not enough to notice.
The amount of energy needed to create enough ozone would make it prohibitively expensive. Luckily the offending ozone-destroying molecules have been largely phased out and the ozone layer will start to recover within our lifetime.
I just fired up the ol ' iMac and clicked away.
INTELSAT launched the first commercial communications satellite in 1965. Perhaps what was meant was that IKONOS was the first commercial satellite with 1 meter resolution.
It is incorrect to assume "that asbestos problems had been mostly solved by removing it from all buildings, etc." Unfortunately, asbestos will be around for a long time. Consider the case of Libby, MT. For years this town's residents mined vermiculite contaminated with tremolite, a very hazardous form of asbestos. This vermiculite was used as insulation, potting soil, came home to families on miners' clothing, etc., and so almost the entire town is now contaminated. Rates of rare cancers have sky-rocketed. Also consider the World Trade Center's asbestos. Luckily it was only used on the first 40 floors of the North tower and half of it was later removed, but still the dust that coated lower Manhattan was contaminated with the stuff. Controversy still swirls around issues of the cleanup and its costs.