Water on Mars - Page 9

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Posts: 3062

Reply: 161

PostPosted: February 4, 2012 8:06 PM 

And Serpens. It is passing strange that you would accept as being supposedly good science, the obvious guesstimate that the NASA people would have made in guesstimating the Viking frost covers on the ground and dissing Barsoomers attempt to provide a much more elegant and potentially accurate estimate of frost cover on the gnomon.

The bias is apparent.



Posts: xxx

Reply: 162

PostPosted: February 4, 2012 9:42 PM 

LWS. The reason I have not stated a measurement is that it is absolutely impossible to identify the edge of the out of focus gnomen. Regardless of whether you use a ruler like Barsoomer or try pixel count, the definition you are purporting to achieve is wishful thinking. Yet you spout definitive figures without even error bars . But you are right, let others expand the image until individual pixels loom large and try and do their own measurement.

Yes I do have a bias. It is towards hard data, the laws of science and logic. I appreciate that that does not sit well with you. Nor could it given your fantasy world of a Meridiani awash with water and bursting with life to the extent that spores are swept into windrows and drifts.

John Henry Dough

Posts: xxx

Reply: 163

PostPosted: February 4, 2012 10:30 PM 

The benefit of such a marriage as proposed above make MRB the winner.

The fact that it is allowed to live and yes,,Flourish here is a Winner.

The only thing lacking is the first revolution of
a single wheel on the Mars Science Laboratory.

As the well qualified make arguments the UN-schooled benefit by it.

God Willing ,,,we will all be here in August to see.


Posts: 3062

Reply: 164

PostPosted: February 5, 2012 5:23 AM 

Serpens; re. your reply 162; Error bars for one measurement?? The best that could be done in that regard are maximum and minimum values. I'll do that later if that would make you less unhappy.

But back to the Viking frost measurement, Where did you critique the science in those measurements?

Ben; re the microchannels; Could you explain why these cracks have all been filled in by fine dust that coincidentally all exhibit a bluish colour in false colour images and totally distinguishable from the nearby sand in colour? and that they also all seem to flow downhill, apeing fluid flow downhill? Surely normal cracks won't do that?



Posts: xxx

Reply: 165

PostPosted: February 5, 2012 7:09 AM 

LWS. What? You only did one measurement? Barsoomer - are you in that boat too? Why not 50 or so at different angles for the diameter. I tried to differentiate around the entire cirumference with wildly different results. The gnomen is out of focus!

And Barsoomer. Look up the definition of channel (noun). Channel equates to water...bit of a pre-judgement wouldn't you say, and a new approach to the term neutral. Crack on the other hand describes it perfectly. But there is a water connection, almost certainly they are dessication cracks caused by dewatering - a long long time ago.

The cracks would have formed immediately subsequent to the drying out. Subsequently active basaltic dunes have crossed Meridiani (now frozen) so don't yopu think basaltic sand rather than current dust would be the fill? You know, like the dark streaks from Victoria?

Finaly, why would I citique the viking statement? It correlates to the known. minimal atmospheric water content which we now know is concentrated mainly above 20m km height.


Posts: 344

Reply: 166

PostPosted: February 5, 2012 1:41 PM 

Regarding the gnomon, it is true that I got different results depending on which angle I used to measure the diameter.

It is conceivable that the frost cover varies at different locations, which might explain varied results. I don't recall any angle where the frosty gnomon measured less than the dry one.

I do have other concerns about the difficulty of making the measurement, which I am pondering as time permits. The work involved in doing these comparisons is painstaking with the tools I have at my disposal.


Posts: 2270

Reply: 167

PostPosted: February 5, 2012 1:42 PM 

Serpens explained the channel -crack situation well and I would add that a function of density causes the (air-transported) heavier basaltic grains to be trapped in the cracks.

And, all of the cracks don't slope downhill; only those specifically modified by wind erosion.


Posts: xxx

Reply: 168

PostPosted: February 5, 2012 5:28 PM 

The pixel count would be more accurate than a ruler on a hard copy print Barsoomer. But the minimum focal length of the pancam is 1.5 m and the distance to the gnomen in 1.33. Not a problem when using the sundial color chips because they were deliberately made large to compensate but the edges of the gnomen are not sufficiently defined to measure.


Posts: 3062

Reply: 169

PostPosted: February 5, 2012 5:49 PM 

Serpens / Barsoomer;

The images of the gnomon for which we have to determine the diameter is 2 dimensional.

The image of the gnomon is expected to be circular (Barsoomer's info posted earlier) with a large knob at its base.

The diameter of a circle passes through its centre.

The diameter of a circle is the length of the straight line originating on the circumference, passing from there through the centre of the circle and ending on the point of the circumference exactly opposite to the point where it started.

The diameter of a circle is the length of longest arc passing through the centre?

The diameter of what should have been a perfectly machined gnomon (given its likely cost and specs) should not deviate from the length given in Barsoomer's link.

If one determines the longest horizontal line through the circle it should be the diameter. Any other horizontal lines must by definition be shorter than the diameter.
The Gnomon, with its cylindrical base, would not allow vertical measurements.

ImageJ allows easy determination of the lengths (in pixels) of horizontal lines cutting the gnomon into segments.

The longest horizontal line bisecting a circle is the diameter.

There is only one such line.

I determined the longest horizontal line through the gnomon using imageJ.

Trying to measure the diameter at various angles to the horizontal did not seem to be of significant value in an exercise such as this one where the assumption is that the gnomon is evenly covered in frost (It looks like it is).

If one were doing a study for a peer reviewed scientific paper to determine the actual volume of the frost cover then such might be required but for this exercise I didn't consider it necessary.

Serpens; Give us the 50 or so angular measurements you made of the gnomon.



Posts: xxx

Reply: 170

PostPosted: February 5, 2012 6:19 PM 

LWS. I didn't even bother to keep them given the inaccuracies inherent in this rather futile exercise.

The longest horizontal line bisecting a circle is the diameter. agreed

There is only one such line rubbish. Rotate the measurement, there are multiple lines. Forget the frost gnomen, do the exercise for a frost free image and the same variation due to inability fto identify he actual edge of the out of focus gnomen exists.


Posts: 3062

Reply: 171

PostPosted: February 5, 2012 7:20 PM 

Serpens; If you rotate the gnoman, or the measurement, the gnoman would no longer be horizontal. There is only one such line if one leaves the gnoman in its original orientation.

But, I agree that one could rotate the image by various degrees and measure the resulting new horizontal diameter lines that are not actually THE original horizontal diameter line. but why would I go to so much trouble to see if I got a similar diameter measurement to Barsoomer's?. This isn't rocket science being done here. I measured the horizontal diameter line and got a figure similar to barsoomer's. If Barsoomer is going to write a paper on frosty the gnoman then he would have to measure several diameters and make several of the normal assumptions that are very standard in modern science.

As you've indicated the Focal length of the pancam lens is 1.5 m and the distance to the gnoman is 1.33 m. The diameter of the gnoman is 2 cm. I suspect that, using the Oppy frosty the gnomon images, inter alia, an optics person could develop a model to determine a max and min figure for the frost cover from these data. But of course, the frost cover really could not be important as we know all there is to know about moisture, or lack thereof, on Mars.



Posts: xxx

Reply: 172

PostPosted: February 5, 2012 7:59 PM 

Winston. The diameter of a circle has nothing to do with the horizontal which after all is an arbitrary orientation to an external reference. The horizontal measurement is but one of a set.

If it were possible to measure the depth of frost I have no doubt that JPL, Cornell or some other institution would have done so.


Posts: 3062

Reply: 173

PostPosted: February 5, 2012 9:23 PM 

Serpens; If it were possible to measure the depth of frost I have no doubt that JPL, Cornell or some other institution would have done so.

Of course you would think so. But if it was possible for them to provide a guesstimate with the perhaps fuzzier, images of very uneven and disparate frost covered objects in the viking frost images it should have been a piece of cake for them to provide another similar guesstimate with the frost on one gnomon image, fuzzy or not.



Posts: xxx

Reply: 174

PostPosted: February 5, 2012 10:17 PM 

Winston. The thickness of frost has been the subject of a number of papers over the years. One analysis that impressed (me) was by Hart and Jakosky in Icarus 1986 on the VL2 condensates. They calculated that the photemetric properties wee consistent with around 10 microns of frost. This correlates to the fact that when the frost sublimated the increase in atmospheric water vapour content was only a few precipitable microns.

John Henry Dough

Posts: xxx

Reply: 175

PostPosted: February 6, 2012 4:10 PM 

Couldn't the '''fuzziness''' of the gnome be dust? Or more Stain?

John Henry Dough

Posts: xxx

Reply: 176

PostPosted: February 6, 2012 4:12 PM 

Or for now just''''unknown?'''',,naw,,forgit it.no-way (totally against human nature)


Posts: 3062

Reply: 177

PostPosted: February 6, 2012 4:38 PM 

Barsoomer; I went back to the original Gnomon images. I measured Frosty the Gnomon's diameter as compared with a non frosty image of the same day from the same series using Gimp and rotating the images by 30 degrees. There were no differences between the images where it was possible to measure the dark non frosty image. That image was badly out of focus on one side while Frosty the gnomon was fairly well focused throughout.

Serpens; I think you were substantially correct on this occasion.



Posts: 344

Reply: 178

PostPosted: February 6, 2012 5:00 PM 

Winston, I agree, Serpens may well be correct on this one. I went back to Sol 8 to try to get a well-defined image of the dry gnomon. I'm not entirely sure if the scale is the same, but the measurement along the horizontal diameter seemed to be about the same as Frosty.

Oddly, a similar measurement from Sol 9 seemed less than Frosty. Even on Sol 9, there seems to be some discoloration on the side of the gnomon that influences the measurement attempt.


Posts: 344

Reply: 179

PostPosted: February 15, 2012 12:45 PM 


This seems to confirm fog, as distinct from dust, in Valles Marineris.


Posts: xxx

Reply: 180

PostPosted: February 15, 2012 10:32 PM 

Barsoomer. Valles Marineris is a big long deep hole in the ground. Remember why in cold area you should never campo in a valley? clod air settles, warmer air rises overnightt, The result is water ice fog. A miniscule level of water content as measured repeatedly from orbit. No liquid water.

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