h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

>>"I think we are referring to a simultaneous process of cooling and volcanism."

Logically, there must be *some* molten material around right up to the point the a volcano finishes being built, which does seem to contradict your idea it couldn't possibly be supported by a solid outer over a fluid inner. At some point, it presumably must have been supported in that way, even if it isn't any longer, and even if the solid part was absolutely or relatively thicker than the Earth's crust.

When we say that it's bigger than any volcano on Earth are we including those rising from under the sea such as Hawaii and Bermuda? Could it be the biggest volcano in the solar system?

LL,

Yup, Olympus Mons is the largest volcano discovered in the solar system. It's a proper big bugger!

Arnie,

"In travelling between earth and Mars, a photon of gamma radiation and/or ionized particle will travel across the entire length of every cell in your body. This is extremely likely to induce cancer, rapidly."

Not really, Gamma ratiation is pure energy, so while it has extreme penetration possibility, also has a low interaction percentage with what it passes through, so while it is the most difficult to shield against, it is also the least dangerous (in relative terms) to your body.

Arnie,
Are you sure? Cosmonauts, astronauts, Moon walkers and spacemen working out of doors on the ISS seem to be perfectly healthy.

Arnie did mention charged particles as well as gamma rays.
Are such particles lower in number around the ISS than in interplanetary space?

Gamma rays are energetic enough to knock electrons out of atoms and break atomic bonds; that makes them dangerous. Even if a single gamma ray photon is less harmful than a helium nucleus travelling at high speed, the sun emits an awful lot of them, and as you say they are difficult to shield against.

Everything in low earth orbit is protected by the earth's magnetic field. The Apollo astronauts did venture outside this, but only for a few days. I think Arnie is right - I read somewhere that if you sent two people to Mars, statistically only one of them would survive the journey.

Isn't gamma radiation electrically charged? In that case, wouldn't it be fairly easy to deflect it with an electrical charge on the ship's hull?

Gamma radiation is not electrically charged, it is basically radiation of frequency higher than x-rays.

Yes, you are probably right about the low interaction between gamma ray photons and cells, but still, there are a huge number of cells presenting a "cross section"/target, and I wonder how many have to get damaged to cause a serious/fatal illness.

Yes, I believe the charged particles are probably the real problem. I read a book by Bob Park (physics professor http://www.bobpark.org/) which describes the problems with manned space flight to mars, however it's several hundred miles away from me right now.

"Gamma radiation is not electrically charged, it is basically radiation of frequency higher than x-rays."



Of course it isn't... My excuse is I was mixing gamma up with alpha and beta particles.

OK, then your question becomes can we deflect alpha and beta particles using strong electric/magnetic fields. This seems to be the proposed method for the moon base. I'm not sure how effective this will be for a moving spaceship. These particles have (I think) around millions of electron-volts (eV) of energy - meaning you'd need electric fields near the order of millions of volts in order to deflect them. Generating and maintaining those fields might be a problem.

>>"Everything in low earth orbit is protected by the earth's magnetic field."

Even from Gamma rays?

Probably not. But it does protect you from kryptonite.

Isn't there a manned trip to Mars in the NASA planning? Year 2025 or something like that. They must be aware of space-raditaion and such things and are developing systems to take care of it. So that aspect wouldn't be a problem.

Actually, that's the whole point of the massive opposition to the planned manned trip. That developping it will be a complete waste of time and money, and actualy, real information could be gained by using that time and money to send robotic missions.

NASA has yet to answer what a manned mission will actually do that a robotic mission couldn't.

A scientist on the radio this morning reckoned that there was a good chance of finding alien life on Europa, the largest moon of Jupiter. He said the solar system's largest ocean under a sheet of ice could be home to various life forms.
I think a couple of human beings might be able to explore Mars better than a robot which might easily get bogged down in a ditch or topple over on a steep bank.

Well, you can make robots that won´t do those things. Insect-like robots for example.
Yes Europa has long been mentioned as a likely place to find life. They want to test some probes in Lake Vostok which should be able to melt down into the ice, and swim around without infecting anything.

None of the robots deployed to Mars have done any of those things Lucky.

Anything got to be better than humans with all their soft fleshy bits, right? I mean spacesuits don't exactly make for manual dexterity. Probes can see and hear better than us, and there's less negative publicity if they break down.

Exactly! The extra equipment required to maintain human presence can be completely done away with, the money, time, effort saved or used for more robotic missions.

Maybe in some far distant future (assuming that robotic advancement comes to a halt) we will have exhausted everything robots can learn from planets. *But we are not there yet*! not by a long shot.

But sending people into space and onto other planets is **cool**. It gets people **excited**.

The value of that should not be underestimated.

Ste