So where are the lakes, bogs, the mud, to put it bluntly - the evidence for it?

Because this isnt it - this is just dry dust being dragged through.

And why do all the leading authorities on Mars disagree with you? What astonishing revelation have you discovered which they have overlooked?

ODug

Yes we have seen frost at the Viking landing site, and its not at all unlikely that there have been some frost at the cryogenically cold nights the rovers might have experienced.
So far I am able to go with you RGClark, but that frost comes from the atmosphere in the first place.

The wheels might be a few degrees warmer than the environment, which means they still are somewhere 30-60 degrees colder than the melting point of water.

Secondly: Its one thing to feel frictional heat when you rub the palm of your hand against the textiles of your own pants for example, but it would take a calorimeter to even detect the extemely small fricitonal heat of wheels moving at centimeter speeds.

I'm referring to the micron scale ice/frost deposition that all the current Mars craft have shown exists even at near equatorial latitudes. The reports showing this are cited in the sci.astro posts I mentioned above.
Some of these reports show some of the deposition occurs during the local Summer season. Daytime temperatures are known to exceed the melting point of water near the equator during this season.
I would be interested to know what the authors of these reports say happens to this water during Summer daytime hours especially considering the presence salts/sulfates widespread on Mars.


Bob Clark

I never said that. I said practically no water will be freed this way. Some molecules maybe, but that's no water to me. It's nothing.

If it was enough to be visible on the MER rover as frost, it's more than nothing.
If this were liquified for example it would be enough to supply microbes with sufficient water to survive on.
I'm arguing that since the abundant salts known to be present lower both the temperature and pressure requirements for liquid water, it can and does become liquified seasonally on Mars.


Bob Clark

Bob: Just how was I not being civil when I posed that question to you? I thought I was simply asking an obvious question.

I think Bob just acknowledges that the subsequent use of bold capitals in his own reply is not civil

Let me summarise.

So far as I know, in the depths of Hellas there's enough atmospheric pressure to allow liquid water to briefly exist, though not to persist as it'd quickly evaporate; things are not so easy where the MERs are. Temperatures on Mars certainly *do* reach above the freezing point of pure water, and are often above that of salty water. Frost and snow were observed from the surface by Viking 2, and certain duricrust features observed by Viking implied the transport of water at least at molecular levels. Valles Marineris is often obscured by morning ground fogs made of water. Oh, and as for the polar caps and the sub arctic regions of Mars...

Any disagreements so far?

Now, add that catalogue of pretty well undisputed facts to the recent MER observations at Gusev. Frost *is* present; salty soils *are* present. There's the odd bit of cirrus in the sky.

We *have* seen strange flow features in numerous locations at Gusev, and they *could* be mediated by water. But, we can't tell much more than that at present, though there are certainly a few mechanisms which might make for some very interesting outcomes. And even if the mechanisms don't work today, they may have worked at some point in the past when the pressure of the atmosphere was not quite so low as we see today, and be preserved as a f*ssil record.

So where's the debate?

Well, we can argue about specifics, true. But the generalities? Nope!

Bob Shaw

As Chemist said, I wasn't saying you were being uncivil. On the internet putting something in bold caps is analogous to yelling. My apologies.
I was being rather annoyed that my repeated citations of the reports of deposited water/ice at near equatorial latitudes were being ignored. I am arguing that since daytime temperatures can exceed the melting point at these latitudes and the known presence of salts decreases the temperature and pressure requirements for liquid water, this overwhelmingly implies liquid water brines form seasonally on Mars.
Such liquid water even if at layers at the micron-scale is enough for microbes to survive on.
This would be consistent with the origin of the detected methane being at near equatorial latitudes.


Bob Clark

But not enough to make mud, which is where your argument begins, and I still don't buy, for one minute, that the drag of a wheel would cause an noticeable increase in temperature.


Doug

Mud or clays. Recall MER team members have argued APXS measurements of some Gusev rocks are best matched by clays.
Water vapor diffuses through porous soil. This subsurface water vapor may condense to ice. Being subsurface, it could be protected from subsequent evaporation/sublimation. Then over several days the amount of ice could be equivalent to millimeters of water.
The scraping away of the surface material by the wheels or by the airbags could expose this ice to the Sun. This with the additional heat produced by the dragging may have been enough to melt this ice.


Bob Clark

Ahh but what about pressure?

Skiiers/Snow Boarders/Skaters all ride on a layer of water even when the snow/ice temperature is a long way below zero C.
It is pressure that melts a very thin layer of ice/snow.

Not saying that I agree with the mud theory, but that is it more than temperature.

Nick

We've done this already

The rovers move very slowly, in 1/3 of our gravity. It isn't comparable to a dude on a snowboard.

For what its worth, I have always seen the "mud" as being very very fine dust.

Chris

I still maintain you're arguing a point that simply would not exist. At best, you would increase the temperature by an ammount significantly less than the day-night swing, and significantly less than seasonal swing. If mud like formations ( which is what you're saying this dragging has produces, soil with liquid water to produce that formation is your point ) can be triggered by the tiny tiny influence of a dragged wheel - then there should be HUGE ammounts of evidence of this all OVER the planet. Where is it?

Where's the pond in the bottom of the trenches that have been dug - you might get an increase in temperature there, of..ooo...a degree maybe? You're churning a lot of subsurface soil there, exposing it to the sun. Where are your mud and clays there? Where's the mud clinging to the wheels which have dragged their way thru km's of soil? Water vapour in the soil - that's great, but the total column volume of water in the atmosphere is about 20 microns.

Doug

Evidence, please. All sorts of things _could_ happen but on a science board we are interested in what _can_ happen. Water does exist on Mars and can condense as frost and water-related weathering _has_ occurred.

--Bill