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View Full Version : Venus's and Mars's magnetospheres.



Zero Signal
2004-Feb-20, 09:58 PM
I've been doing some reading on this lately. Quite interesting. Though these two planets don't have dipolar magnetic fields, I've read on how electromagnetic currents in their ionospheres generate a makeshift magnetosphere that just barely staves off the solar wind.

Hypothetical question: What if humans were actually able to terraform Mars, complete with an Earth-like atmosphere complete with an ozone layer. What would the lack of a magnetic field on Mars be like? Would an ionosphere and ozone layer be sufficient, or do you think assistance from a global magnetic field is necessary in assisting these layers in protecting organisms from dangerous solar radiation?

Another question: I was once told that there were long "stringy" structures in Venus's magnetotail that stretch a good bit of the way to Earth. I did a web search and mostly got links to sites by neo-Velikovskian catastrophists. Is there any truth to Venus having a long magnetotail?

Jigsaw
2004-Feb-21, 04:47 AM
Any of this help?

Link. (http://www-ssc.igpp.ucla.edu/personnel/russell/papers/venus_mag/)

Link. (http://www.es.ucl.ac.uk/research/planetaryweb/undergraduate/dom/magrev/venusmag.htm)

Emspak
2004-Feb-24, 07:12 PM
The Earth's magnetic field does protect people from the charged particles (protons, mostly) that would ordinarily hit it from both the Sun and cosmic sources, so that's a pretty big benefit.

To note: Near Jupiter where you have a heavy proton flux zooming through its magnetic field, human spacecraft would have to be shielded. The same is sort of true for people going into orbit, though you don't need a lot because people don't spend a lot of time in the Van Allen belts -- which are defined by the Earth's field.

So on a planet like Mars (where plate tectonics has basically stopped as the planet cooled) or Venus (where the slow rotation has made its own core, proabbly similar to Earth's, generate a smaller field) the charged particle flux is a lot higher. Ozone only stops UV rays, and not all of that. One issue in terraforming Venus is that the UV flux would be more intense -- it's closer to the sun. Same problem arises for Mars, but that's because while the amount of UV energy hitting the planet is less (it's almost twice as far from the sun) the amount that hits the ground is greater (no ozone layer).

So yes, if you terraformed Venus you'd need to find a way to deal with these things. Probably any terraforming project would involve "spinning up" Venus anyway. You could do this too ways. You could smack asteroids into the side of it in glancing trajectories -- some scientists think something like this slowed the planets rotation to begin with. Or you could wrap a big superconducting cable around it and couple it with another similar sized cable in orbit (lots of juice needed for that one tho).

Either way, spinning the planet up would likely start the dynamo process working in Venus' still-molten core, and decrease the amount of particles hitting the surface. I've left out the effects of the clouds of venus, by the way, as I am not sure what effect those clouds would have on surface levels of charged particles. My instincts tell me that with clouds in place, few of those particles hit the surface now, but obviously terraforming it would involve removing the sulfuric acid skies.

As they say, just a thuoght.

Kaptain K
2004-Feb-24, 07:28 PM
I think that, if you spin up Venus by smacking it with asteroids, most of the atmosphere will be blown of anyway. The problem will be waiting for it to cool of enough for the surface to solidify! :o

Emspak
2004-Feb-24, 09:35 PM
The solidifying suface might not take that long. Depends on how you smack it :-)

Remember you'd do it with sort of glancing blows. Might kick up a lot of dust and cool things down a bit if the dust could get above the cloud layer. And I bet the original event didn't liquefy the whole surface.

I haven't done the math. But Carl Sagan did a little calculation in Broca's Brain showing abou how long it would take a molten Venus to cool to ambient temperature (leaving out the effect of sunlight and greenhouse gas of course). I'll look it up and see what kind of timescale that was. You may be on to something pretty cool here...