New Mars

Spiky Probe on NASA Mars Lander Raises Vapor Quandary

TUCSON, Ariz. -- A fork-like conductivity probe has sensed humidity rising and falling beside NASA's Phoenix Mars Lander, but when stuck into the ground, its measurements so far indicate soil that is thoroughly and perplexingly dry.

"If you have water vapor in the air, every surface exposed to that air will have water molecules adhere to it that are somewhat mobile, even at temperatures well below freezing," said Aaron Zent of NASA Ames Research Center, Moffett Field, Calif., lead scientist for Phoenix's thermal and electroconductivity probe.

In below-freezing permafrost terrains on Earth, that thin layer of unfrozen water molecules on soil particles can grow thick enough to support microbial life. One goal for building the conductivity probe and sending it to Mars has been to see whether the permafrost terrain of the Martian arctic has detectable thin films of unfrozen water on soil particles. By gauging how electricity moves through the soil from one prong to another, the probe can detect films of water barely more than one molecule thick.

"Phoenix has other tools to find clues about whether water ice at the site has melted in the past, such as identifying minerals in the soil and observing soil particles with microscopes. The conductivity probe is our main tool for checking for present-day soil moisture," said Phoenix Project Scientist Leslie Tamppari of NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Preliminary results from the latest insertion of the probe's four needles into the ground, on Wednesday and Thursday, match results from the three similar insertions in the three months since landing.

"All the measurements we've made so far are consistent with extremely dry soil," Zent said. "There are no indications of thin films of moisture, and this is puzzling."

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.

The Phoenix team is laying plans for a variation on the experiment of inserting the conductivity probe into the soil. The four successful insertions so far have all been into an undisturbed soil surface. The planned variation is to scoop away some soil first, so the inserted needles will reach closer to the subsurface ice layer.

"There should be some amount of unfrozen water attached to the surface of soil particles above the ice," Zent said. "It may be too little to detect, but we haven't inished looking yet."

The thermal and electroconductivity probe, built by Decagon Devices Inc., Pullman, Wash., is mounted on Phoenix's robotic arm. The probe is part of the lander's Microscopy, Electrochemistry and Conductivity instrument suite.

The Phoenix mission is led by Peter Smith at the University of Arizona with project management at NASA's Jet Propulsion Laboratory in Pasadena, Calif., and development partnership at Lockheed Martin in Denver. International contributions come from the Canadian Space Agency; the University of Neuchatel, Switzerland; the universities of Copenhagen and Aarhus in Denmark; the Max Planck Institute in Germany; and the Finnish Meteorological Institute.

For more about Phoenix, visit: http://www.nasa.gov/phoenix or http://phoenix.lpl.arizona.edu.

This does not surprise me. The surface layer has a very high porosity. Could be instrumentation, maybe they should stick it in the ice and see if it works,

Regolith is such a dead term I believe it is a surface layer with no organics. Sense they can not get most of the dirt in the oven that too is speculation.

Vincent

Nice try, Vincent, but no cigar for you. The martian regolith has been proven to be utterly bone-dry. A little while a go you were claiming to see mud on the surface. This latest piece of scientific evidence should put such silly notions to rest.

And, naturally, you completely missed the significant of this latest finding. Given the measured diurnal exchange of vapor between the atmosphere and surface, we should be able to detect at least a handful of molecules of liquid water adhering to particles in the regolith. Guess what? That's not happening. This stuff is drier than anything we might ever find on earth.

And I suspect that we won't find organics either, just as we haven't yet detected a single drop of liquid water on Mars.

Now Now, Algorithms

Don’t get your panties in a wad. Lets look at what they are saying.

"If you have water vapor in the air, every surface exposed to that air will have water molecules adhere to it that are somewhat mobile, even at temperatures well below freezing," said Aaron Zent of NASA Ames Research Center, Moffett Field, Calif., lead scientist for Phoenix's thermal and electroconductivity probe.

That means at 100 percent relative humidity it, “Should,” happen.

"All the measurements we've made so far are consistent with extremely dry soil," Zent said. "There are no indications of thin films of moisture, and this is puzzling."

This means they do not understand why.

“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.”

This means they are missing it.

"There should be some amount of unfrozen water attached to the surface of soil particles above the ice," Zent said. "It may be too little to detect, but we haven't finished looking yet."

This means they will keep on looking.

So tell me brother, why are you so quick to reach conclusion? Now you seem like a knowledgeable chap. Why you want to let an old drunk weatherman spank you?

Vincent

Vincent,

You are truly exasperating. Here we have a direct measurement of the moisture content on the martian regolith and, guess what? Not a single molecule of liquid water to be found! They have measured water vapor exchanging between the subsurface ice and the atmosphere, but no liquid water whatsoever. This is actually quite remarkable and is a testament to just how incredibly dry Mars truly is. What it suggests is that there is something about the soil chemistry that prevents water molecules from adhering to the soil particles. There is no place on planet earth quite this dry.

Algorithms

Is it not just sublimation at work?

Louis,

I think that the issue is that the TECP is documenting changes in humidity which are most likely explained by a diurnal sublimation/freezing cycle, but that as the water vapor moves between the regolith and atmosphere it should be creating microscopically thin films of liquid water as H2O molecules attach to soil particles. This apparently isn't happening. As a result, the regolith above the subsurface ice is thoroughly dessicated to an extent completely alien to what we can observe in permafrost environments here on earth.

Regards,
Algorithms

It would appear then that the upper regolith grains are either hydrophobic or contain a highly absorbant internal matrix, inhibiting surface adsorption (stuck the bolds in there for emphasis of the different processes). Assuming the data's good, of course.

Maybe it does adsorb, but something in the dust (like an iron and/or titanium oxide) acts as a photodissociative catalyst under Mars' intense UV conditions. Just throwing out random ideas from the peanut gallery. (:

Thanks for the clarifications!

Well Thankfully I know why. Could be solar radiation Vs. Surface or subsurface moisture.

Those boys at NASA should just drawn them a picture of the surface water exchange and the answer would be obvious. The short answer is any liquid film on the surface would be very transitory and of very very short duration under different conditions than they have had, such as the instant of frost or water snow phase change.

Image 1- This is a diagram of the surface make-up The blue line#1 is the permafrost layer. On Mars it is several centimeters below the surface and may be broken and a lot lower in other locations. The brown line#2 is the surface. In between we have a large area of porous dry surface material. The thin blue line#4 moisture exchange from the ice layer, “Temperature dependent.”

The Surface of Earth does not have this layer of dust like Mars. Trying to obtain the same results with different parameters is the definition of insanity. The sun does beat on the surface and would dry it out in a hurry. When they push the instrument in the ground we get a gas release and the natural state has already been changed. Hort showed us this in Image 2.

Vincent

Image 1


Image 2

Hard to say. It does seem odd that even liquid water in a very brief transient state as it interacts with particles in regolith should be possible, given the apparent movement of water vapor through the subsurface. But perhaps the chemistry of the regolith particles themselves prevents this from happening. Or perhaps this is simply what happens in environments characterized by such thin atmospheric densities and low temperatures. Maybe its a combination of all of these variables that has achieved a kind of equilibrium state that works against conditions that allow for even brief periods of thin liquid water films.

No matter what the cause, we are left with the astonishing result that Mars is far drier than than anyone ever imagined.

There must be some water. As you know, Phoenix have found it snowing some kilometers above. This water must first come from the ground somewhere and go up in gas form like here on Earth. Than of course form water drops a few kilometers up and frozen to snow.

In another place here, Vincent have found snowstorms and I think this confirmation of snowing indicate that Vincent is absolutely right in this case!

Sorry... ...i shall try to better my language.

I will thank you for many good and interesting messages here on this forum!

Bishop,

I think the point is that we haven't detected liquid water on Mars just yet. We know that there is vapor in the atmosphere, And we know that there is ice. But liquid water is ephemeral and probably quite rare on Mars.

The experiment may be flawed in that a set of probes in the air would need high voltage AC to show moisture between them conducting.

Placing a set of probes into mostly iron would look like they are electrically shorted when passing current through the soil. Of course passing DC current would also have a simular problem.

SpaceNut,

The TECP isn't flawed. It's performing precisely as intended. The "I-see-liquid-water-on-Mars" contingent can't wriggle out of this one. The TECP results found that the regolith at Phoenix is bone dry. The surface of Mars is incredibly dry. And here, near the north pole, where we might expect at least microscopically thin films of liquid water ephemerally adherring to soil particles, we've found none. The rest of Mars is drier still. Our remaining best hopes for detecting liquid water on Mars is in acquifers well beneath the surface or finding extant hydrothermal activity. Both of these elude us as well.

At the present moment in time, we have yet to detect a single drop of liquid water on Mars.

+1

seems like the lack of atmospheric pressure is eliminating any trace of liquid water at the surface of the red planet.

Yes, its very low but it is not constantly and can differ.

Mars Express har taken pictures from a crater there from where it is a solid ice clumb. Another picture from, I think it was Mars Global Surveyor, show that liquid water has flowed down a crater rim and has lengthen a white strim, I hope you know what I mean.
And in holes and caverns there can be water for short periods.
I will better my knowledge in Mars and the struggle with the language goes on....

Bishop----the right stuff?

In recent time? It is known that Mars had liquid water a very long time ago, but that was, I assume, before it lost most of its atmosphere. I would be very interested in any information indicating that water has flown on crater rims or in holes and caverns in recent time

Yes, two pictures in the last 10 years from I think it is Mars Global Surveyor. These pictures show that a white streak from a crater rim get longer and longer. I remember that there is also some V-shape in this.
Most scientist believe it must have been outburst of liquid water but a few scientist now think it is some sort of remnants.
I am not sure I can find this pictures but I will try....
The water and mud in holes and caverns are speculations from my side ...
I am not so good in searching in data and navigating and also the language is poor. But most importante is a brilliant brain... ...

Bishop----the right stuff?