I love this !

Yeah...objectivity, what a concept. Give 'em hell, HDP!

Yeah, yeah, yeah...but sometimes the two geologists, the committee, the jury, and congress will all come to the same conclusion. Sometimes the conclusion is obvious to the most casual observer.

CR - I don't want to touch that one with a 50 foot pole, unless you provide some concrete examples. Mars examples would be especially helpful, and might even keep us on track. Of course, I'm tempted to say, "like the perfectly obvious conclusion that a dropped boulder on Mars will fall appreciably faster than dropped pebble?" A majority in Congress and on most U.S. juries might agree on that one (not to mention a few geologists I know ).

-- HDP Don

This link may help convince those geologists:

http://nssdc.gsfc.nasa.gov/planetary/lunar...ather_drop.html

I'm not sure why you wouldn't. I wasn't suggesting anything controversial, political, or otherwise inappropriate for discussion here. I think I can provide some concrete examples, and Mars has some good ones. Your example of a "perfectly obvious conlusion" might fool many of our politicians, but it doesn't work in a debate among scientists familiar with the basic laws of physics. My favorite question along those lines is, "Which weighs more, a pound of feathers, or a pound of lead."

Of course any two geologists might disagree on the interpretation of a particular geological environment, but if you ask 100 geologists, most likely a majority of them will settle around one or two (or a few) favored interpretations. I'm not suggesting that the majority is always correct, but the majority often is. When people discuss scientific interpretations, Occam's razor is often quoted. But one version of Occam's razor; the one that I favor, is, "Everything should be explained as simply as possible, but not more simply."

The unmanned/robotic exploration of Mars can offer some examples, because the orbiting spacecrafts, landers, and rovers each have a limited number of analytical instuments. Id est, the information they can send back to us for interpretation is limited, and usually less than ideal. A rock formation on earth can be mapped and sampled in detail, and analyzed by a full array of techniques here on Earth, but that's not an option on Mars, yet. That is why many scientists favor sample-return missions and the manned exploration of Mars.

For example, I understand that the early remote sensing orbiter exploration of Mars detected very similar spectral signatures all across the planet. The simplest version of Occam's razor would dictate that scientists should have concluded that the entire surface of the planet was of the same composition. We now know that is not the case, and that the globally distributed dust coating the entire surface is biasing the remotely sensed data.

The rovers on the ground have helped us study and understand that phenomenon, and have raised other questions. In another example, we have all seen pictures of spherical features in rocks on opposite sides of the planet through the eyes of Opportunity and Spirit. What if the rovers only had simple cameras, and no other analytical tools? As geologists, we know that spherical structures of various origins are common in terrestrial rocks. But now we are on Mars, so the most simplistic interpretation of Occam's razor might require us to assume that spherical structures in thinly layered rocks were created by the same processes across the planet. Fortunately for us, the rovers do have some additional analytical instruments that have demonstrated that the spherical objects have different compositions and microscopic features.

I am only saying that robotic, planetary exploration is more challenging than many would suspect.

CR - I certainly agree with your final statement! My main point was to disagree with your earlier implication that having one or a bunch of scientist-astronauts jostling each other on the Mars outcrops (with all anxious to show off their erudition in front of the cameras) would necessarily eliminate most scientific controversy. Also, inasmuch as you brought it up, I feel obligated to point out that if different spherules have different compositions or appearances on different sides of Mars, this doesn't necessarily indicate different origins. That is, concretions alone have hugely varying compositions and appearances (e.g., silica, carbonate, oxide, hydroxide) and sizes and shapes (only rarely are they perfectly spherical; most commonly they are nodular and clumped together), and impact-related spherules, etc. likewise have many different (generally small) sizes and compositions (e.g., glassy tektite "splash droplets" vs. spherical glassy condensates vs. spherical accretionary lapilli formed as a result of sticky steam condensation on various particles).

I generally prefer Einstein's formulation of Occam's razor (the simplest hypothesis that accounts for ALL of the observations - equivalent to your "and no simpler"). For that reason about a year ago I asked anyone on this site to suggest Meridiani features NOT explained by the impact hypothesis - given that the extant highly complex watery scheme actually fails to account for many features, including many features of the spherules themselves (e.g., the gray or specular hematite, size limitation, shape limitation, general clumping failure, and distribution in the rock). FWIW, that original request remains unfulfilled. (Note: I respect Doug's eventual decision to cut off the pointlessly repetitive and emotional discussion that followed, and don't wish to restart it now). Thanks for your intelligent input.

-- HDP Don

Not wishing too hard eh? It restarted. Three posts deleted.

Seriously - not again.

On a number of occasions Steve Squyers has expressed an interest in looking at cobbles on the plains after Oppy is finished with Victoria. I guess that his reason is that there is not much variety in the rocks of Meridiani and so the opportunity for Oppy to look at more meteorites and rocks from elsewhere on Mars (such as "Bounce") is attractive.

I think that Oppy's first scientific target after it has left Victoria will be a rock close to Beagle crater described in the following Opportunity Update:

"Sol 875: On this sol, the rover successfully backed away from the ripple that saw 80 percent slip on sol 873. Opportunity used its panoramic camera and miniature thermal emission spectrometer on a distant potential meteorite; those instruments also completed an observation of the sky and ground."

There are nice color and false color photos of this rock in the following post:

http://www.unmannedspaceflight.com/index.p...ost&p=61844

The following map shows the general area that Oppy was in in SOL 875:

http://www.unmannedspaceflight.com/index.p...ost&id=7283

At that time I saw this extensive area of pavement just to the North West of Victoria's ejecta blanket as possibly of interest. An unwillingness to drive Oppy too far with its arm extended might add to the attractiveness of this area.

Reading Stu's lovely epitaph for the exploration of Victoria, I started wondering what benefit there might be to retracing most of Oppy's path thus far. There must be plenty of known targets bypassed in favor of proceeding to Victoria. And how cool would it be to get back close to square one several years after landing? How do the tracks from the early sols look after a global dust storm and several martian years of wind?

Is that what mission planners favor at this point?

No doubt, there were many, many such targets. Retracing most of the path seems unlikely to me, unless they passed by a particularly juicy target early on the trek to Endurance, and then to Victoria.

In all honesty, it would make me feel like continued mission funding would have been better diverted to MSL. Does anyone else feel that, cobbles aside, that any major science was bypassed on the way to Victoria? As much as people refer to it as the rush to get there, I found the journey maddeningly methodical from a purely "tourist" perspective. They stopped and did a LOT of science, even if it wasn't always by choice.

They left Victoria because they felt there was nothing to find there that would be of Mars-shaking significance. I have to think that's how they feel about retracing their journey. Just a lot of work for little added science. I just don't see the need to backtrack any further than to squint at a few tempting cobbles.
Any long term study of track alterations can wait for the day when the rover is hobbled and has all the time in the world to sit and study the changes to the world around her. Preferably, somewhere in the vicinity of Ithaca.

I've seen mention of a return to Erebus / Terra Nova before. Probably 1/4 of the distance back to Endurance. It looking interesting - but they wanted to get a move on.

Doug

Regarding track alteration, they couldn't find a better spot to study it than where they are right now. At this very spot they have tracks from where they first arrived and peeked into Duck Bay, 2 years ago (before the dust storm) and where they came back to enter Duck Bay 1 year ago, plus tracks made in the last few days.

I don't really think there's much to be learned from it anyway, that we haven't seen before. New territory has to be the best bet.

Phil

Yeah - they had 6 month old tracks as a comparison when they left Endurance.