a: There's a big difference betwen the detonation of a nuke and a melt down in a reactor. Case in point: Chernobyl was worse in terms of radiation than Hiroshima or Nagasaki.

b: One nuke isn't going to make an entire planetoid radioactive. Sometimes it's hard to realize just how big a moon is. And the site wouldn't be radioactive for as long as you seem to think either. In case you didn't know, people live in Hiroshima and Nagasaki. By your logic, those two bombs should have made all of Japan "another Chernobyl" and they should be uninhabitable even today. The fact that those sites are inhabited cities seems to prove that you're objection is unfounded.

c: quite obviously the probe would still be in orbit when the bomb is dropped. There is no danger of damaging the probe.

You appear to have some odd misconceptions. That's why I say, and I'm sorry to offend you, but you are overly emotional about this. I feel that you are just reacting rather than giving my suggestion serious consideration. When someone says "nuclear" you are immediately opposed. I really hate to be so blunt but it's thinking like yours that nearly cost humanity the Cassini project. Everything that we are going to learn about Saturn and Titan was very nearly lost because people heard the word nuclear and had a negative reaction. The potential benefits didn't matter them – they were against it because it used plutonium.

A nuclear reaction is just a tool that an intelligent species can use to accomplish a task. They aren't "bad" or good. They are just tools. A lot of people have been killed with knives throughout history. But you would certainly think I was being silly if I stood next to you while you sliced an apple and said "I don't think I want an apple covered in blood!"

Oh. I apologize then.

What I was thinking was, you create a hole in the ice by detonating a nuclear bomb. Then your probe make a nice, soft water landing inside that hole. The probe swims around for a while and then returns to the surface to radio its findings with a high gain antenna.

Since people are so opposed to nukes, consider this. What if there was an asteroid on a collision course with Europa? Assuming the asteroid would break through the ice – leaving a hole – would you then object to landing a probe on the water in the hole and accessing the oceans that way?

If it's ok to use the breach created by an asteroid, why is it not ok to create your own breach in the ice?

The problem is *not* radiation. Hiroshima and Nakasaki are quite livable today. At any rate, even if there was a radiation problem, Europa is a big place. We wouldn't spoil the whole thing.

Going back to the war and Hiroshima, it was a horrible thing. I'm not saying who was right or wrong. The bombing of Hiroshima was a terrible event, but there were reasons for it and there were other bad events during war. Japanese attacking villagers Asia, working british and American prisoners to death in their worker camps, Imperial attack on peral habor, kamikaze attacks.
Hiroshima may be livable, like other cities are livable.... but there are problems, cancer clusters, they test the soil and water, and the people of the city are sometimes neglected and isolated by others..people from Tokyo sometimes are afraid to date or marry such a person in case their future offspring get sickness or deform. The A bomb was very weak ( one today are thousands of times more powerful ), it was weak yet it caused much destruction and killed so many thousands. Can you imagine what are weapons could do to a delicate life-form on anther body in space, it is not a good idea.
If we are considering that life exists elsewhere and we cosider looking for life on Europa I think it best Not to irradiate the place into another Chernobyl before we get there. There might be benefits with nukes in Space, like blowing up Asteroids and other things but when it comes to looking for alien microbes I think we should leave our nuclear explosions out of it.

I'm not going to argue the merits of the approach because I think it's irrelevant: there's no way that NASA is going to get permission to nuke what may be the only other life-bearing body in the solar system. The protests would make the anti-Cassini RTG movement look like a flyspeck.

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I'm not sure how reasonable that is, though. You're talking about a crater 30 km deep, probably hundreds of km wide. That's a lot of ice to vaporize.

Would it be possible to not have to drill/melt all the way through the ice to find evidence of life? What about taking samples several meters down? If there was life on Europa, couldn't some of the remains of the lifeforms be frozen in the ice?

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Keep in mind that it's not quite as bad as that, since due to the lower surface gravity (I'm assuming the density is about the same as Earth ocean water here), the pressure at 50 km would be about like a depth of 7 km here on Earth. Also, you get a minor reduction since surface pressure is essentially 0 there, but that only gives you an extra 220 feet or so, rather insignificant overall.
I'm not saying that makes it easy, but it's nowhere near as bad as 50 km on Earth would be.

And as far as the nukes are concerned, keep in mind that the main thing that spreads the radiation here on Earth is the atmosphere. On Europa, you won't have any wind to carry little radioactive bits around. On the other hand, I was guessing that escape velocity for Europa would be low enough that any debris wouldn't be carried back, but after doing the calculation, it's about 2.0 km/s to get off, and I don't know anything about the initial velocity of radioactive debris in a nuclear detonation.

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I agree with ToSeek on the politics. But I will also comment on the ethics. I think the proposal is repugnant. I think the idea that nuclear bombs are tools to be used like any other tool is just wrong. We are trying to find life on Europa, not kill it off. And yes, I know one bomb won't kill off all life on Europa (if there is any). That doesn't make it right. This is like doing a census by killing everyone and counting the bodies. And no, I can't support this opinion with facts, this is a emotional/moral feeling.

If you want to dismiss me as some sort of left-wing, knee-jerk, tree-hugger fine. I'm not a brain-dead anti-nuke, anti-technology. I have no problem with a nuclear powered probe or an RTG melter. But this is different.

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So, would you object to any plan that has the possibility of killing the life you're looking for? What if we didn't use nukes but still knew that what we were doing was going to kill some of the life we were looking for. Would you still be opposed?

Here's why I ask:
Actually it's much closer to studying life in Earth's oceans by deploying dredges. In case you didn't already know, many if not most of the species of deep-water organisms known to science were discovered by the Challenger expedition. They dredged the ocean floor and cataloged the marine life that they pulled up. All of the creatures they caught died in the process but as I said, much of what we know about the ocean floor we know because of that expedition.

Would you call their methods repugnant? Would you call them unethical? If so, you must resign yourself to eternal ignorance of a good portion of nature. Because in a lot of cases, you can't study it without killing something. As the saying goes, if you want to make an omelet, you have to break a few eggs.

Or how about this example. One of the experiments that the Viking probes used to detect Martian life involved super heating the soil in order to study the gases that were released. Oh no! We are boiling the precious Martian bacteria!

Surely you don't have a blanket objection to any scientific study that might kill something. So what specifically is the problem with a nuclear bomb? How is it conceptually any different than dredging the ocean floor? Both actions affect the environment. Both run the risk of killing something. But how else are the different?

Nukes are bright and scary. So maybe there is some subconsciouses instinctive fear you have of them. They have been used to murder hundreds of thousands of our fellow humans, so there is an understandable societal stigma attached to them. But both of these reasons are irrelevant to a hypothetical discussion of science. Are there any other reasons?

Some people think using nuclear bombs to go into Europea Moon of Jupiter is a good idea, but I can tell you what we know about nukes. They are used to power reactors, they are used as weaponary, but they are used by humans. People who make mistakes, don't understand enough, cause accidents. ..like Three mile island water reactor leaks into water supply, Tomsk Siberia clouds of uranium particles cause toxic damage, Tepco Japan reactor leakage and frightens locals, Church Rock USA uranium pollutant caused water to become 6,500 times more radiated polluted as saftery standards allow. In the past some people used to cure illness in strange ways. Some doctors didn't understand science or biology. If a man had an infection in his foot we might cut off his entire leg, now days we have great things like keyhole surgery. Using nukes to check for life is a rather crude and careless method, especially now with our record of mistakes in human history, wars, destruction of artifacts. I think this nuclear bombing of europa Moon would be another that we would regret in the future for mankinds understanding of science and space.

No I would not (as long you are not talking about killing all the life, which even I admitted your bomb probably wouldn't do). I don't equate your proposed technique to dredging or heating soil up as was done on Viking. I have no general problems with either.

I think the last sentence I've quoted is probably closest to my feeling. I'm going to guess you'll say that this is unscientific (and here I am, a professional scientist being unscientific). You are probably right. I suspect many ethical judgements are completely unscientific.

The other problem I have is that this seems like a crude and even disrepectful way of doing things. Its like studying a Ming vase by taking a rock and smashing it up into little pieces. Manchurian Taikonaut is saying the same thing at the end of his last post.

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I can't let you get away with continually mischaracterizing the argument. First you said:
Now you're saying:
Neither one of those are good analogies. We are talking about punching a tiny hole in a chunk of ice. You wont be able to see it from orbit and it will freeze right back. It *may* kill a couple of fish. More likely though, there are no fish to kill.

That's it.

Please stop making up doom and gloom comparisons. That doesn't add anything to the conversation.

I, for one, think that yes nukes are tools, just like any other tool. That does not mean that I think that blowing holes in the crust of Europa is a proper use of them. One interesting use of nukes was proposed by Arthur C. Clarke in his Novel Hammer of God. Set off a Gigaton device at the Earth-Sun L3 point (other side of the Sun in Earth orbit). Use the EMP to radar-map every object in the Solar System. Do it three times and you have the position and trajectory of every comet, asteroid, and KBO in the system. No more ambiguity as to potential Earth impacts.

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I have no problem with nukes--as a matter of fact, i like nukes. Unfortunately, I don't think you're going to be able to do this with a conventional nuclear device--i don't think they'd make a hole of the right size or shape. Maybe you could toss a small bomb down a hole, wait for the debris to clear, and toss another. Repeat a few hundred times until you get a shaft. There are some obvious problems with that approach, one of which is that the ice around the shaft will start flowing into it.

JohnOwens wrote:

1 atm gives about 32 ft head of water on Earth (= about 4.32 ft on Europa at a figure of 0.135 that of Earth's surface g!) but the rest I agree with. Hadn't considered g in my original scenario.

Interestingly though, supposing the temperature under the surface was at 273.15K (tripple point) then the depth of ice required to keep it liquid would only be 32/(0.92 for the densty of ice x 0.135 for local g) = aprox 250 ft or, for the purists 1bar equates to a water head of 10.19m => 82m depth of ice (assuming pure water - a pretty big assumption)

To be really acurate we would also need to know what type of ice it is (No jokes from the UK about the wrong kind of snow please!) This was something I hadn't considered in the rough calculation above but depending on the crystal structure of the ice it can have very different densities. Heavier ice SG>1 would presumably form on the colder surface but would attempt to sink through plastic "ordinary ice" until it phase changed as it warmed up. Could this give a mechanisim for the striations seen on Europa's surface as ice plates become unstable, tilt and dip on a liquid sub-layer? If this is so, could we land a probe at the ege of a tilting plate and simply wait for it to pitched overboard?

Ref http://www.lsbu.ac.uk/water/phase.html

Edit:
Note: Looking at the phase diagram I think I have answered my own question. Heavy ice XI doesn't form at low pressure.

Thinking in different gravities, temperatures, pressures and phases hurts my head lol!

I know the 32 ft figure pretty nearly (I rounded it off to 30 ft in my calculation, from my memory), but on Europa that would give you 7 times as much, not 7 times less, depth you can go to. Think of it this way: say you go to a depth where total pressure is 2 atm. On Earth, you'll be 32 ft deep, of course. On Europa, since surface pressure is negligible, and you get about 240 ft/atm due to the lesser gravity, you'd need to go down about 470 ft from the surface to reach 2 atm.

Added: After all, the weight of the water column is what's being reduced by the lower gravity. A 240 ft water column on Europa would weigh about the same as a 32 ft column on Earth, not the other way around.

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JohnOwens wrote:

Muddled thinking on my part, it really is a long time since I did any elementary hydrostatics. Thanks for your tollerance and insight.

Pop quiz, hot shot: When you vaporize water and send it hurling into space, the water molecules are dispersed to a density of approximately 1 per cubic meter of space. How then are they supposed to refreeze?

My earlier post went on to say that some of the water vapor would undoubtedly fall back onto the moon, but that it would settle all over the surface, not just back in the hole from whence it came.

The whole point of this BB is to rationally discuss these things based on the merits of each other's ideas. If someone has a problem with something I say - object to it. I'll either clarify my point or take it back. But it's irrational and unscientific to just 'discount your objection altogether' just because you don't agree with me.