[X] My Assistant

[Steve G]

Tricky to line up the two RAC images but here is my attempt.

[gallen_53]

Occam's Razor says it is ice.

Maybe. It could be any of the following:

1) water ice
2) dry ice
3) salt
4) pure silica such as observed by MER
5) something unexpected

Occam's Razor fails on Mars because our simplist explanations are based upon terrestrial experience.

[foxfire]

Has anybody commented on what appears to be the obvious strata in the rear (distal) wall of of Dodo Trench? [For reference, a good example (among many) appears in the June 3 blog by AJS Rayl in the Planetary News: Phoenix (2008) Phoenix Scoops Mars and Digs It--in this instance the site is called the Knave of Hearts; I surmise to distinguish it from the trench itself.] I've searched in vain for comments on the strata. If these are "Mars-annual", it is hard to understand how the "varves" can form underneath the apparent topsoil/dust layer.

[JRehling]

Occam's Razor fails on Mars because our simplist explanations are based upon terrestrial experience.

But Odyssey data indicates a major source of hydrogen in the immediate subsurface. And CO2 (which doesn't have hydrogen anyway) is a gas at this pressure/temperature. So even operating on martian data, I'd agree that Occam's Razor falls hard on the side of this being (largely) water ice. We don't yet have absolute proof, but I'd say we're well in excess of 90% confidence that this is water ice at some significant degree of concentration. (Perhaps salty or acidic.)

[brianc]

Well, speaking as an amateur myself, I've always wondered about the electrostatic properties of Martian dust. Are the clods sticking together because of this?

On this subject of electrostatic process - not sure if arm can reach but would be interesting to see if particles ended up being stuck to any underside flat surfaces
underneath the lander and see if over a period of time any such particles drop off the underneath - might give some insite into electrostatic properties or other 'sticking' mechanisms (so far the under-lander images have only shown ground underneath lander and the underside itself is tantalisingly out of view at the top of image apart from the descent thrusters)

Also switching to Mars Rovers - can the rover's robotic arm look on any underside surfaces of the rover with the MI - to get close-up of any dust sticking to under surface of lander or lander solar arrays ???

[imipak]

But Odyssey data indicates a major source of hydrogen in the immediate subsurface.

...but the Odyssey GRS apparently has a resolution of 300km, so presumably localised concentrations of "other stuff" (e.g. kieserite) aren't ruled out. My uninformed personal opinion was that the scoop's hitting small patches of salts, but that Holy Cow is ice, based purely on visual appearance... and then DnD 2 changed my mind. Er, I think. (Who knows? It's just nice to know that TEGA will give us an answer in a few sols' time )

That said, I suppose if TEGA sees both ice and salts, we could be debating what this or that particular whitish patch is for a long time to come.

[ahecht]

would be interesting to see if particles ended up being stuck to any underside flat surfaces underneath the lander and see if over a period of time any such particles drop off the underneath - might give some insite into electrostatic properties or other 'sticking' mechanisms

The MECA microscope will actually be doing a bit of this. In addition to the "sticky" silicone substrate that we've seen so far, there are sixty-nine different substrates on the wheel. By seeing how much the dirt sticks to the various substrates as it is rotated from horizontal to vertical, a lot can be learned about the electrostatic (and magnetic) properties of the soil.

[fredk]

On this subject of electrostatic process - not sure if arm can reach but would be interesting to see if particles ended up being stuck to any underside flat surfaces underneath the lander

I don't think this is what you had in mind, but we can see what I think are some essentially vertical surfaces that were coated with light-coloured splotches during landing (see white arrows in image below). Most of those splotches are on upwards-facing surfaces, but if I've got my geometry right the arrowed ones are on vertical or even slightly downwards-facing surfaces.

[teck]

Is this a Philips screw?

Nasa just released some info on this: it is part of a spring.

[As old as Voyage...]

Glad the location from which the spring fell has been identified.

It would've only been a matter of time before Hoaxland declared it as 'evidence'

[dburt]

...Occam's Razor fails on Mars because our simplest explanations are based upon terrestrial experience.

I suspect that what you have in mind is not Occam's Razor, but what is sometimes called the "Rosenthal effect" (or experimenter expectancy effect) named for psychology Prof. Robert Rosenthal, recently honored for "groundbreaking research into experimenter bias and self-fulfilling prophecy": that is, for proving that most people see only what they expect to see, and that their expectations influence the outcome of supposedly unbiased experiments and trials (in the social sciences and in jury trials, at least). Based on personal experience, when it comes to data-deficient Mars this effect is hardly restricted to the social sciences, natural scientists being people too, and that's what you seem to be saying also (i.e., if we expect Mars to be analogous to Earth, then we will interpret it using terrestrial experience). See, e.g.,
http://www.newsroom.ucr.edu/cgi-bin/display.cgi?id=1752
or http://www.encyclopedia.com/doc/1O87-exper...ectncyffct.html

Still, ice seems the most likely explanation for that patch, with salts a close second, and silica or some other substance way down there, at least for the moment (keeping in mind that combinations are permitted too). Getting the data could end that argument!

-- HDP Don

[Guest_Oersted_*]

Well, what result did Dr. Rosenthal expect?

[nprev]

"Rosenthal Effect"...thanks, Don! I've long suspected that such a thing might exist, and our experience in planetary exploration seems to prove it in spades. We are often surprised that the Solar System isn't what we expected it to be, and we shouldn't be.

Suggest a new mantra to be chanted everytime we see a new piece of data from UMSF: "It's an alien world, it's an alien world..."

[ElkGroveDan]

"Rosenthal Effect"...thanks, Don! I've long suspected that such a thing might exist,

Don's post is only proof that you wanted and expected such an effect to exist all along.

[nprev]

...great...NOW my CPU has overloaded in a death-spiral of recursive logic which only massive amounts of alcohol can cool to the point of safe rebooting...thanks, Dan, love ya, man!

[dburt]

Well, what result did Dr. Rosenthal expect?

Congratulations, Oersted and EGD and nprev, for spotting that recursive paradox, one that was considered early on (and that Dr. Rosenthal apparently tried to alleviate by effectively isolating himself from the actual experiments). So, is Dr. Rosenthal telling us that the canals on Mars are really there after all, and that it's simply our modern expectations that aren't up to snuff?? Or was it simply that additional data became available? In any case, as I stated above, additional data (and an absolutely open mind, free of expectations) are commonly required to do good science.

-- HDP Don