Phoenix on Mars

Hi Brian et al

Just saw this report here

Seems like the TECP instrument has found no liquid or vapour water at the surface despite the layer of ice at about 3 cms and diurnal significant changes in humidity in the atmosphere around the lander.

It seems to be a most perplexing result.

Could it be that the surface cohesivity factor (whatever it is) strongly and quickly binds any moisture coming from the atmosphere or from the subsurface? COuld the fluffy surface layers that we see in the OMs be binding water that isn't released when the TECP detector pins enter the soil? If there is a difference in structure of the subsurface layers above the ice, might scrapings from that layer contain water?

I must admit I am very disappointed at the results, so far, of the TECP investigations.

Winston

LWS,

When I was reading the report, it did not make sense to me: why had they expected water to be in a not ice fashion in soil and on surfaces?

It is very easy to test on Earth, and I believe that at -17C, there will be no conductivity here too.

The humidity is less than 100%, since it looks like the stuff is drying through
sublimation when exposed to air.

es

well they seem to be puzzled by the parodox.

"Three other sets of observations by Phoenix, in addition to the terrestrial permafrost analogy, give reasons for expecting to find thin-film moisture in the soil.

One is the conductivity probe's own measurements of relative humidity when the probe is held up in the air. "The relative humidity transitions from near zero to near 100 PERCENT with every day-night cycle, which suggests there's a lot of moisture moving in and out of the soil," Zent said.

Another is Phoenix's confirmation of a hard layer containing water-ice about 5 centimeters (2 inches) or so beneath the surface.

Also, handling the site's soil with the scoop on Phoenix's robotic arm and observing the disturbed soil show that it has clumping cohesiveness when first scooped up and that this cohesiveness decreases after the scooped soil sits exposed to air for a day or two. One possible explanation for those observations could be thin-film moisture in the ground."

Possibilities... its all on the lander leg...

another.. the probes sensitive nature is fooled by the static soils

or moisture sinks as in Under rocks, or shade, not in the sun.

as a whole it seems very positive, they expect to find microbes using the vapor trails.

As I understand it the probe can only establish if there is any unfrozen water in the soil (down to incredibly small amounts). But what we seem to have is frozen ground where all pore water (if indeed there is any) has turned to ice. Any exchange of H20 between air and ground and back again is limited to sublimation - no liquid phase. That would fit with the apparent lack of hydration shattering in the rocks around Phoenix.

But it is also a thermal probe? So do they use heat transfer to determine the thermal conductivity of the regolith and does this enable them to measure any liquid water film resulting in the frozen ground? I mean, does the result also indicate that there is no ice content in the regolith? More information please Leslie; what is the thermal inertia characteristic of the regolith, is it possibly hydrophobic? It must be a superb insulator.

I mentioned before Winston that I put my hopes on the ice/regolith boundary layer, but from the probe results I'm not holding my breath. I don't know what the sub surface temperature is, but it must be very low since we have well bonded permafrost that slowly sublimates when exposed, despite the fact that it is expected to be salty with significant freezing point suppression.

Hmm an exposed water ice source next to the lander. I wonder if that is the source of the humidity changes? Is it a local effect - did we have the same effect during the few windy days?

Brian, what you say about ice sublimating rather than melting under these conditions is true, but not at all scales.

At the surface of a forming ice crystal/layer there is a layer of water molecules one or two molecules thick, kept 'liquid' by the pressure of the van der waals forces between them (I've probably spelt that wrong).

This layer ought to be there even at much lower temperatures than occur at the phoenix site. But it's not, almost as though the water vapour in the air can't touch the soil...

It might be a bit of blow for those hoping for present day life, but we really don't know whats going on here, so at the end of the day it might not be after all.

We'll just have to hope we get enough clues from phoenix to figure it out.

assumptions, assumptions, assumptions...

I say, why not experiment, this is something that can be checked on Earth.

Permafrost might be a candidate for the model, but apparently it is not good one.

Humidity change is due to temperature change, it might be not associated with any movement of water in and out of the ground.

e s

Humidity is the water content of the air right? If i'm wrong on that or there's some subtle point about it I've missed feel free to correct me.

If the humidity goes up then water must have been put into the air from somewhere.

So the water must have moved from somewhere else. What have I missed here?

folks>>>

As any Doctor will tell you, foreign objects in a foreign place may give one a rash, fever, headache or just a plain old allergic reaction.

Perhaps Mars is rejecting the metallic substances of landing pads and shovels with their pointed probes and this is the first time we can examine such contact and we are now 'perplexed'?

The OM is a powerful scope for such minute examinations. NASA/JPL/UA may have 'overstepped' the requirement for data interpretation.

yt
dx

Mother Nature may NOT always do what we think it should do just because we are on Mars with our probing instruments.

Who knows what that Titan Lander looks like today or any of our 'other' landers. This is NOT the Moon either.

yt
dx

Hi Marsbug.
In the report they talk about relative humidity which is the partial pressure of the water vapour divided by the saturation vapour pressure of water in the Martian atmosphere at the reading air temperature. But Relative Humidity is temperature dependent and would be expected to vary significantly as a function of the daily temperature swings at the Phoenix site. Zent was reported as saying that the variation in relative humidity ‘suggests there's a lot of moisture moving in and out of the soil’ so I guess we have to assume that the relative humidity change is greater than what would be expected for stable water content. It would have made more sense if they had used Absolute Humidity being the quantity of water in a unit volume of air.

From the article they seem to be expecting H2O molecules adhering to the surface of soil particles as is the case with permafrost on Earth. They are not there so perhaps the regolith really is hydrophobic. Or maybe only the grains right at the surface are affected.

Thanks for the guidance on the liquid film at the ice/vapour interface at depressed temperatures. I had thought that such would only exist when the kinetic energy of translation was effectively equal to the Van der Walls forces. Live and learn.

Some of the perchlorate salts are hygroscopic. In one sense, this is the opposite of hydrophobic in that it attracts moisture. But on the other hand, it binds the water in a way that might make it unavailable to a surface thin film.

Zent was reported as saying that the variation in relative humidity ‘suggests there's a lot of moisture moving in and out of the soil’ so I guess

Probably wrong guess, Brian: I would rather expect this "scientist" to be ignorant beyond believe.

Barsoomer

I think your suggestion of Perchlorate involvement in this great mystery might be on the right track. Perhaps the strange behaviour of the TEGA instrument is part of the enigma. Perhaps we are totally wrong in trying to interpret what we see on Mars as a subset ofn extreme environment on Earth and not seeing that we could actually be looking at a totally different microenvironment to any on Earth.

Suppose the SODs; the Perchlorate; the dryness of the surface in the presence of copious water both below and above the surface; the abnormal atmospheric pressure that just happens to allow liquid water presence under certain triple point conditions; the visual damp appearance of the surfaces at meridiani; gusev and even on the phoenix scoop and OM images; are all trying to tell us that there is an "unearthly" water balance system that will always confound us if we try to explain it totally in Earth terms, using Earth instrumentation and throwing out any suggestions of moisture that our eyes continually suggest has been there recently.

A planet that has evolved totally differently to Earth and has many features unlike Earth must have some differences in its micro-geology and dare I say, its Biology that do not mimic Earth.

I think the discussion here is finally getting to see the reality of Mars close up.

Winston

Hi Barsoomer,
Re 391. I follow your point. If there were anhydrous perchlorates (or other anhydrous salts) present then they could bound water molecules as hydrates. For example lithium perchlorate trihydrate - LiClO4.3H2O. But the regolith never gets the thermal energy necessary to remove the water of hydration so I can't see how the cycle Zent was referring to could be attributed to perchlorates.

My feeling is that the regolith has thermal inertia characteristics much greater than modelled. Even a few centimeters coverage is enough to protect the permafrost ice. Has anyone seen any results on the soil temperature or thermal properties of the probe?

Thanks Brian, I didn't realise the difference between relative and absolute humidity. Extrasense may have a point, I don't know anything about Zent but even experts aren't immune to making a basic mistake now and then!

brian, Thanks for helping me discover this part of the blog.

Here is one thing I don't understand about this "quandary" over the presence or absence of soil moisture. Isn't adsorbed water ALWAYS present in a mixture of ice and other minerals? See:

http://www.lpi.usra.edu/meetings/geomars2001/pdf/7057.pdf

Here's a quote:

"Another observation is that any ice that forms in the soil-water system is separated from the mineral surface of the soil by liquid water. Beskow [1] was one of the first to realize the existence and importance of the un-frozen film in groundfreezing mechanics. The origin of the unfrozen water is a combination of the adsorption force emanating from the mineral surface along with other physical properties of the ice surface that requires a liquid transition layer on the surface of the
ice."

Maybe the above is somehow not true for Mars. So far Phoenix hasn't imaged any ice but what looks like fairly pure ice. Maybe mixtures of ice and soil are much more unstable than ice and rapidly lose all their water, but that doesn't explain the sticky soil apparently getting less sticky after it is exposed unless there is adsorbed water present to begin with.

sol 101 RAC RGB of, er, grey-greenish soil:

I really, really would like to see the NASA "Earth color" picture of this soil!

Hi Kye,
On the Blue Forum Marsbug came up with an interesting concept to explain the clumping effect and reduced stickiness of the soil once exposed to the atmosphere. Well worth a read.

Marsbug,
I'm not sure that the liquid film at the ice/vapour interface at depressed temperatures holds true. For sublimation at these temperatures H dangling bonds would seem to be the formation mechanism.

At the risk of being banned ( no wait - that's the other forum! ) I will suggest that perhaps the reason the soil loses it's "stickyness" is that it "dies" - ie, loses it's "essence".

IF the soil is totally dry, then the essence is not water.

Perhaps it is something as simple a current of electrons that interact in a substrate of, er, circuits.

What the heck are all those rings in the soil?

Yes, it dies like a stromatolite would if you took it out of the water and dumped it further up the beach on the dunes.

A stromatolite can tolerate wave erosion, sunlight, and other potentially adverse conditions because it creates it's own substrate and environment. It does this by secreting a gel coating that protects and captures surrounding grains of material. These mixtures of gel and grains over time form layered dome-like structures.

Stromatolites use water, sunlight, surrounding grains of material, and their own glue to build domes that house aerobic bacteria as well as anaerobic bacteria in towards the core of the colony. They build their own city with all kinds of different microbe critters that come and go over the life of the colony.

At first glance a stromatolite looks like a roundish rock with layers, nothing special at all until you realize what it actually represents.

The "dying" of the soil when it is disturbed seems to correspond to loss of moisture/sublimation, maybe also due to loss of static charge or perhaps a change/reversal of static charge due to being exposed to the above surface environment and sunlight.

I would expect that somewhere on Mars (heck maybe right before our eyes) there are or have been pockets of microbe cities much like the stromatolite in concept. They will use sunlight, moisture, and the surrounding chemistry of the environment to build a protected environment. Bacteria could have an ability to keep moisture in the soil, maybe even help form duracrusts.
It would be interesting to find a Martian bacteria that utilizes chemistry and static charge to regulate subsurface pockets of ice/water/moisture.

I would love to see life doing this on Mars but I would have thought that we would have seen some kind of evidence on the micro-images. But there are probably some images that they won't release. Primitive bacteria might help to explain the water and "dying" issue of the soils but where are the bugs? I'm still very optimistic that they are there. Can you hear them Horton?