Polar Storms

sol 101 sundog?:

er, zvezdichko, what science do you know makes you feel that every posting in this thread is not only pseudoscience ( false-truth ) but utter pseudoscience?

Be specific.

Please cite observations, theories, papers, experiments, web links, etc. which support your argument that every post, including this reply, is false.

As it stands your remark is baseless.

Hi zvezdichko,
Hort's got a real point there though I feel he is being a bit rough on you. I don't blame you one bit for being offended at the reply 74 response to your questions, which indeed has definite elements of both pseudoscience and disrespect. But your all inclusive reaction is not a scientific approach either. I think you are in the last year of a science degree? You are therefore probably more up to date in many things than dinosaurs like me, but you will find that practice it is all shades of grey rather than the black and white your classes probably infer. Reject what you see as rubbish by all means, but at leat analyse it before you do - sometimes there is a grain of truth in there.

And keep posting

I don't blame you one bit for being offended at the reply 74 response to your questions, which indeed has definite elements of both pseudoscience and disrespect.

That's right. I was offended

But your all inclusive reaction is not a scientific approach either

Yeah, that was silly. I'll try to be more specific...

He can't ignore the pressure completely. It's an important factor. Remember Phoenix latest results - we have water in the air, but it doesn't absorb on the surface.

Morning Has Broken:

I was pleasantly surprised how well my new imagej macro ( named clouds ) was able to extract some useful information from the "raw" ( yuk ) super-duper stretched JPGs.

Be warned that the last frame was pointed 3 degrees to the left of the others.

( BTW, the song is one of my favorite hymns.)

Sorry guys had to go and do the Hurricane thang.

Now lets see what has transpired.

Brian said:

“Fred,
Pressure is a key variable. Because of the low atmospheric pressure the Martian atmospheric column can only hold less than 100 precipitable microns of H20 with the amount dependent on the temperature. This will of course freeze out over the polar winter but the main source of snow is carbon dioxide snow as the atmosphere freezes.”

Well, The triple point of water is 6.7 MB. Water can exist as a solid at 0MB. I doubt the pressure gets that low on Mars. The moisture capability of the Martian atmosphere is totally dependent on temperature. You got that right, yea.

The main source of snow on Mars is CO2. The amount of water snow is unknown but we do have surface storms and mid and upper level storms. That means we have moisture advection into the storms. This is a variable we are just starting to understand. How much will we get? Grab some pop-corn and hope the wind blows it off the solar panels and we will see.

“Pseudoscience?” To me it is High School science.

Nice images Hort, I will check them out and let you know what I see.

Fred

Fred.
The moisture content of the atmosphere is a function of both pressure and temperature. At 0 mB the moisture content of the atmosphere is zero because there isn't any atmosphere.

I'm not sure you really appreciate what a moisture content of near zero to a max around 100 precipitable microns means. There was a Cornell comment that put it in perspective. If all the water vapour in the atmosphere could instantaneously deposit on the ground as water, we would have a layer about one third the width of a human hair.

When the atmospheric temperature drops sufficiently this trace moisture can form tiny ice crystals and fall out (rather than deposit direct on the surface). The 'diamond dust' effect. If the crystals are small enough then they can be lofted in the same manner as the dust, forming a fog. I guess under some circumstances they could also sublimate as they fall resulting in a cyclical sublimation process, again forming a fog. Given the size of the ice crystals and the amount I am not really sure that we could even really call it snow.

Moisture advection? Moisture by definition being diffuse wetness or water (or other liquid) causing a slight wetness or dampness? I really don't think so.

To me ther seem sto be something odd about the pressure on mars Brian. How can there be so little pressure,,But stong enough wind to shake the lander?

no pressure but stong enough winds to blow things under Opp.?

Is there large pressure variations in the wind gusts themselves?

I heard the atmosphere of mars actually extends farther from the surface than our own.

That our feet could be quite warm, but our head would freeze and fall off to the ground.

that the place right where phoenix sets gets up to 68 F, in mid summer.

If the soil is bone dry, and it never so far been above the temp vapor point for the ice, how could the soil be clumpy and sticky one day, then shrink and crumble to dust the next day?

What is precipitable microns? I think Robert Clark summed it up pretty well.

“The term "precipitable microns" means the thickness of liquid water you would have if the entire water vapor content in a column were condensed to liquid.”

[link]

Brian said

“I'm not sure you really appreciate what a moisture content of near zero to a max around 100 precipitable microns means. There was a Cornell comment that put it in perspective. If all the water vapor in the atmosphere could instantaneously deposit on the ground as water, we would have a layer about one third the width of a human hair.”

This may be true based on the standard Atmospheric construct. If we have sub-surface venting of water vapor, rapid sublimation or subsurface eruption of water then this would not be applicable. We have satellite data that shows this does occur.

Brian said

When the atmospheric temperature drops sufficiently this trace moisture can form tiny ice crystals and fall out (rather than deposit direct on the surface). The 'diamond dust' effect. If the crystals are small enough then they can be lofted in the same manner as the dust, forming a fog. I guess under some circumstances they could also sublimate as they fall resulting in a cyclical sublimation process, again forming a fog. Given the size of the ice crystals and the amount I am not really sure that we could even really call it snow.

Now this sounds like a. “Rock guy,” theory. Now I know how you fill when armatures mislabel rocks. Mars has an active atmospheric structure with both thermal and water vapor advection. I will work up a nice post complete with definitions and pictures just for you later today Brian.

Fred

sol 104 dust devil!

I just happened to notice this one and then went looking for others. I am xurrently working on a 3 frame animation of a dust devil moving across the plains!

Er, was this expected?

And here is a beauty about 1/2 hour later:

It was captured in 4 frames. See Flickr comments for, er, comments.

Hort, nice images. If it is what we would call a dust devil it is unlike the ones at Gusev. I believe this would be formed more like a gustnato, they form along gust fronts. Will be interesting to see if we get any vertical development with this hybrid. If it is a thermal dust devil then that surface is cooking compared with the air temperature. I find that hard to wrap my mind around.

Your second image clearly shows a weak devil with little vertical development. NASA posted an image late spring with a dust devil. I was quick to disregard. I never seen any dust devil tracks at this site in the satellite images. If they get big enough to cut a stripe the wind quickly covers it.

I never thought the surface could get hot enough to create a great devil. I also did not think it would be this windy. They say the atmospheric dust is like smoke and the atmosphere is a good industrial vacuum. I need to quit listening to NASA.

Fred

Hort,

Sure was. http://www.planetary.org/blog/article/00001416/

Mann,
The atmospheric pressure has a huge effect on the dynamic pressure which is directly proportional to the density of the atmosphere and the square of the wind speed. As a rule of thumb, for a wind on Mars to provide the same dynamic pressure as a wind on Earth it must blow around 9 times the speed. So the 20 m/s wind at the Phoenic site would be the equivalent to a 2.2 m/s wind on earth. Enough to slightly vibrate the light solar panels.

I think the surface temp you quote is equatorial summer, but the temperature gradient with height is indeed extreme. I don’t have a clue if the surface at Phoenix gets above freezing - I wish they would publish the soil temps from the probe. Let’s not assume the stickiness of the soil and the crumbling after exposure is due to sublimation of ice. It may well be but Marsman made a good case in another area for the crumbling of the soil to be due to exposure of the ultra dry regolith to the miniscule atmospheric water vapour. The reverse process. Could well be.

Fred. I will work up a nice post complete with definitions and pictures just for you later today Brian.

Please don't bother.

Hey Man,
An addendum. The very impressive dust devils in the link at reply 92 are a great demonstrator of the temperature gradient effects that you advised.

Hort cloud image analysis,

How do you do it? Detail from an early morning Martian artic sunrise, we would have never seen. “Nice image.” See bottom right image.

Image 1

Area I- Cloud bands alto-cumulus type clouds.
Area II- breaks with Martian sky visible.
Area III- Cloud bands alto-cumulus type clouds receiving more light.
Area IV- Glare from morning Fog and/or dust. Could be overdone due to overexposure.

http://farm4.static.flickr.com/3054/2845673794_b8fb15075b_o.png

Image 2

Earth early morning cloud comparison. Alto-cumulus type clouds at sunrise over Australia. Warning, much sharper image above 5K

Fred

OOOPs.

This post was supposed to go here.

Good week for the weather types. New MRO release had lots of clouds and ice.

This image centered 83.8 north. High clouds in the west. Is a storm brewing? Last seasons water snow all 2.5 microns clearly visible.

Fred

Sol 109 dust devil.

There may be more in the full "dust devil movie" sequence, but this is the only one I spotted.

As an aside, it always astounds me how close to "real time" we are getting this information. This dust devil happened on Mars a little over 3 hours ago!

sol 109 5 frame tracking animation from 14:58:59 to 15:02:36.

I am sure the NASA movie will be mush better.

OK, that was too easy.

I estimate this guy was about 300 meters distant and about 4 meters wide at its closest.

Let the dust devils roam. Great work Hort. I can imagine what you could do if NASA gave you the good stuff. A mystery has been solved in the polar areas, the white dunes.

NASA says Clear Ice in the caption? This image is from 77 North and was part of the latest MRO release covering late April to mid July Earth Time. This would include the summer solstice on Mars.

I will put this in the avalanche category and another illustration of NASA’s confusion over the Mars environment. The clue to what is happening here is the white caped dunes. You would think that the dunes being darker would get warmer and be the first to defrost. They are in fact being deposited with ice by low level supper cooled water vapor. This also gives a sheen to the ground below on the satellite image creating the illusion of clear ice.

This is the moisture source for Phoenix low level clouds.

Fred