There’s another problem with voyages to Europa — it’s right smack in the middle of Jupiter’s radiation belts.

Contaminating the ocean is probably not an immediate issue, since the ocean, if present (and it probably is), would be about 50 km beneath the ice. Humanity has never dug a hole that deep and may never do so.

But that’s just me …

Cheers.

Paul

The Meridiani Journal
a chronicle of planetary exploration
http://web.mac.com/meridianijournal

I know that Mars has large areas of Olivine on the surface. From what I understand this mineral readily weathers in water. I don’t know how quickly it weathers. In decades, millenia, or millions of years? I don’t know when it formed before or after a supposed Mars wet period. Does this put an upper limit on how much water Mars has or had? http://www.psrd.hawaii.edu/Nov03/olivine.html

I think we should explore Mars just for the sake of exploring Mars, not to look specifically for water (and life). Because if it’s hyped that Mars was very wet (and by implication could have harbored life), and it turns out that Mars was never very wet nor very hospitable for life then I think we lose public interest and support. We can learn as much about the Earth by contrast in studying Mars as by what the two worlds have in common. Discovering liquid water and life on Mars would be icing on the cake.

I’m more inclined to accept that Mars was damp but not wet. Any pointers to more info would be appreciated.

Why the New Gully Deposits Are Not Dry Dust Slope Streaks
MGS MOC Release No. MOC2-1621, 6 December 2006

There are many excellent images on this page which compare the gully deposits versus slope streaks which are common on Mars.

“In developing geologic interpretations from inspection of images, many factors are considered: size, relief, shape and pattern, color or brightness, texture, and association (context). Context is often the final discriminator between features that look similar. It is undeniable that the gully deposits resemble slope streaks, but they do not share the same context. If they are slopes streaks formed by downslope movement of dry, unconsolidated dust, then they are extremely rare features, because the new gully deposits (a) do not occur in regions where slope streaks occur, (b) are not found near any dark slope streaks, while typical light slope streaks have dark ones nearby, and (c) formed during the MGS MOC mission, while no new light slope streaks were observed to have formed anywhere else on the planet during the mission. Conversely, their presence within craters with gullies and the existence of similar light-toned features on other gullied (and in some cases on adjacent) slopes, with which they share geomorphic attributes, may be coincidental but is probably not. The gullies themselves provide the context for the gully deposits, and argue for a genetic relationship.”

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“It rules out pure liquid water,” said lead author Jon D. Pelletier of The University of Arizona in Tucson
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They added that their research does not rule out the possibility that the images show flows of very thick mud containing about 50 percent to 60 percent sediment. Such mud would have a consistency similar to molasses or hot lava. From orbit, the resulting deposit would look similar to that from a dry avalanche.
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So the Pelletier study is not ruling out liquid water at all, just pure liquid water. Well, duh. I doubt pure liquid water could even travel 100 meters without evaporating first in a 0.006 atm atmosphere. Who claimed that it was pure water? Certainly not Malin.

I agree that it’s best to check these things out up close and personal. Your automated rover factory stationed on Phobos sounds suspiciously similar to a Von Neumann probe or a Bracewell probe. I’m not sure our present technology is up to building one of these things yet. Maybe in the future we will be able to do this but at the moment each rover mission is $200 million apiece.

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“The shapes of these deposits are what you would expect to see if the material were carried by flowing water,” said Michael Malin of Malin Space Science Systems, San Diego. “They have finger-like branches at the downhill end and easily diverted around small obstacles.” Malin is principal investigator for the camera and lead author of a report about the findings published in the journal Science.

The atmosphere of Mars is so thin and the temperature so cold that liquid water cannot persist at the surface. It would rapidly evaporate or freeze. Researchers propose that water could remain liquid long enough, after breaking out from an underground source, to carry debris downslope before totally freezing. The two fresh deposits are each several hundred meters or yards long.

The light tone of the deposits could be from surface frost continuously replenished by ice within the body of the deposit. Another possibility is a salty crust, which would be a sign of water’s effects in concentrating the salts. If the deposits had resulted from dry dust slipping down the slope, they would likely be dark, based on the dark tones of dust freshly disturbed by rover tracks, dust devils and fresh craters on Mars.

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I’m not sure what is being claimed in the new report. Is it claiming that the plume is really subsurface material that is lighter in color and we can see it due to the overlying darker material being blown away or falling down the hill? If so then there are several questions we might want to ask such as is the direction of the plume in the same direction as the prevailing winds? Or can we see where the darker material fell to down the wall of the crater? It’s been a while since I read the article about the original discovery but as I recall they had several reasons to believe the plume was deposited by running liquid.

Honestly, when I look at Phobos and Deimos, I just see raw material, and considering the relative cost of flying out a single rover vs. a rover factory…

However years later when the first hi-res images came back from Mars showing the potential water caused landforms I remembered that cave on the Nullarbor. Sure the scale was different however it basically looked the same. Someone should do the experiment with a sealed stable box and really, really fine dust, just out of interest.

I don’t see this as a significant problem. By far the greatest danger with nuclear-powered spacecraft is the possibility of them exploding during launch or re-entry (or entry, in the case of Europa), and spreading hundreds of kilos of highly radioactive matter across territory visited by living things.

In the case of Europa, the greatest danger will take place outside the thick ice-shell protecting the possible ocean(s). If the craft explodes and sprays ultra-toxic nuclear material across kilometers of frozen surface, any critters living in the liquid far, far beneath the surface will never know it. It’s only once the spacecraft has landed and is in good condition that its probe will begin to melt its way through the thick ice. Travel through the ice and into any liquid under the ice is very, very safe compared to the journey the craft had to endure to even land on the surface.
My concern is the inadvertent survival of a few Earth-microbes in small crevices in the spacecraft. Hopefully, the heat of the entry shock-wave should sterilize any Earth-critters not human-sterilized before launch that manage to survive the very long journey through the vacuum and solar radiation. It’s barely, just barely, possible that one or more micro-spores could make it that far and then proceed to colonize the under-ice ocean to the possible detriment of Europan life.
A sub-ice nuclear accident involving the Earth robot…vanishingly unlikely.

“I was surprised. I started off thinking we were going to prove it’s liquid water.”

I often see scientists making this sort of statement, which is essentially “If I’m right, we should see A, and not B. We found B. I was wrong, and I’m glad to be corrected.”

When’s the last time a priest or theologian made a similar statement, or was even surprised at their conclusion?

There is something I’ve been curious about since the initial report – has anyone figured out how liquid water would react under those conditions? I was a little skeptical (though hopeful) about the liquid water report because it seems to me that water would sublimate or freeze almost instantly under these conditions. Has anyone actually tried simulating a large mass of water running down the side of a hill at temperatures and pressures present at these crater locations? I would think this could be done fairly easily with a computer model.

On the issue of Europa, my understanding is that it isn’t so much a funding issue holding up a Europa mission as it is that we don’t yet know what we want to do or how to go about doing it. Keep in mind that we have drilled to within a few meters of Lake Vostok in Antarctica and have refrained from drilling the rest of the way for fear of contaminating the lake. How would we drill through the ice of Europa, which is over a hundred kilometers thick and harder than steel at those temperatures, without contaminating the ocean below it? This is both an ethical question and a scientific one. We must, on one hand, take into consideration the possibility of permanently changing an alien environment that has an excellent chance, in my opinion, of having life. Also, if we do find life, we need to be totally sure that anything we find didn’t come in on the spacecraft. The power source needed for this task must also be considered. The only power source I can think of that could do this job is nuclear. I don’t have any issues with putting nuclear reactors in space, or even orbit. But, if you start talking about putting one on the surface of the ice or into the under-ice ocean, this is a whole new game and we need to think long and hard about that one. These kinds of issues have to be resolved before we can go to Europa.

“…Then again, maybe they’re afraid of what we’ll find at Europa, or at least the consequences of such a discovery.”

Such as an abandoned Earth vessel with skeletons in the cryo-pods and two EVA pods waiting for what’s left of HAL to activate them?

Absolutely. This calculation greatly weakens earlier (water-gushers on Mars!) speculation that was very emotionally appealing. This news in no way shows that there was never life on Mars or that simple Mars-life may not still exist under the best conditions that Mars still offers. It just means that the observations in question probably were not of recently flowing liquid water.

Brando:
“…In this case, we really WANTED to find evidence for water on Mars, but thanks to intellectual honesty and the scientific method, we get an answer we’re not exactly too thrilled about but is more likely the truth. …Oh and CFD does too”

So true. I read blog after blog from conspiracy-sayers shouting that scientists are marching shoulder-to-shoulder fighting against anything that doesn’t agree with their “dogma”. This report is a prime example of scientists heaving a sigh for the loss of a very emotionally appealing possibility and then continuing their pursuit of figuring out the universe with clear eyes.
I’ve tried to argue on woo-woo sites that many scientists would sell their first-borns for the chance to disprove a well-accepted theory and thereby become centuries-famous and fabulously wealthy. No woo-woo artist has bothered to respond to that argument…

By the way, what is “CFD”?

Maybe somewhere, beneath all that ice, we can find something…

‘Course, I’d love to see a similar search take place at Europa.

Someone must yell to Congress “Hey! We’ve got this great place that has a chance for life! Approve a mission to go there, okay?”

Then again, maybe they’re afraid of what we’ll find at Europa, or at least the consequences of such a discovery.