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Posted by: alan Mar 28 2007, 04:28 AM

I've been noticing that the images of Spirit's sundial have been appearing mottled lately.

http://qt.exploratorium.edu/mars/spirit/pancam/2007-03-25/2P228098425ESFAS4JP2122L7M1.JPG
http://qt.exploratorium.edu/mars/spirit/pancam/2007-03-25/2P228098462ESFAS4JP2122R1M1.JPG

The pattern looks the same in both left and right pancam images so I believe this is not dust on the lens nor a compression artifact. I think Spirit's driving, and particularlly dragging the stuck wheel, has produced enough vibration to cause the dust on the sundial to clump. This may be happening on the solar panels too. Has anyone noticed this in images of the solar panels or heard if the power levels have been climbing faster than expected?

Posted by: alan Mar 28 2007, 04:36 AM

OK answering my own question. this image from the pancam site appears to have some clumping although it could just noise.

http://marswatch.astro.cornell.edu/pancam_instrument/images/False/Sol1113A_P2560_1_False_L257.jpg

Posted by: jaredGalen Mar 28 2007, 01:50 PM

So, would clumping be a good thing or a bad thing? Or would there be any noticeable difference in Watt hours.....?

Posted by: fredk Mar 28 2007, 02:55 PM

It's definitely real structure - it persists in detail on different sols and under different lighting:

http://marsrovers.jpl.nasa.gov/gallery/all/2/p/1143/2P227839385ESFAS4JP2838L7M1.JPG

And back on sol 1139 some of the detailed structure we see today was present, and some isn't:

http://marsrovers.jpl.nasa.gov/gallery/all/2/p/1139/2P227477179ESFASZWP2111L7M1.JPG

Posted by: Jeff7 Mar 28 2007, 08:55 PM

The result of extremely slight condensation, perhaps? If it's getting warmer, maybe the humidity is increasing to whatever miniscule amount it gets to on Mars.

Posted by: djellison Mar 28 2007, 09:18 PM

I'm going to try a little experiment on this - icing sugar and a flat surface...then tap the surface for a while ( like driving over rough terrain ) - see what happens

OK - cocoa powder dusted onto a piece of carbon fibre. Then - all I did - was shake the thing for a few seconds - not much - just a little shake for a few seconds, perhaps 5mm amplitude, 5hz for 2 seconds....and I get 'clumping' of sorts.

That dial is on the edge of an array that is going to bounce and wobble a little bit as the vehicle drives - I can well imagine the same thing happening on the dial.

Doug

Posted by: CosmicRocker Mar 29 2007, 05:19 AM

This is interesting, but also odd. These rovers have been vibrating all over the place as they have bounded over the surface of this planet and have gotten dusty and cleaned off several times. I don't think we've seen anything quite like this before. I've tried my bag of tricks on the images and thought I "might" have seen clumping on vertical surfaces, though they are nothing I would post. It sure looks "real," though.

Posted by: nprev Mar 29 2007, 06:14 AM

On the other hand, what if this is flour-fine material is sticking to the sundial via purely electrostatic means? We haven't had a cleaning event in quite some time, so it seems possible that wind-borne dust may be accumulating on this elevated area which has a slightly different charge than the terrain...just a thought.

Wonder if maybe MSL should drag a grounding strip behind it as many cars do in the Southwest US desert.

Posted by: djellison Mar 29 2007, 07:07 AM

....doesn't need to keep solar panels clean

Doug

Posted by: fredk Mar 29 2007, 02:20 PM

One more point - the dust layer looks the thickest it's ever been now - it's almost impossible to make out the concentric rings on the sundial! Maybe this is some clumping behaviour that only happens after some critical thickness is reached.

Posted by: atomoid Mar 29 2007, 09:34 PM

too bad there's no humidity instrument on spirit...

..if even a little humidity (and since were in this valley might humidity tend to concentrate here more?) were to assist in an otherwise humidity-free clumping process, it might indicate why we havent seen it until this season in this place.
..or maybe its the composition of the dust, being that were in a relatively saltier place, and maybe that helps too.

Posted by: nprev Mar 30 2007, 01:57 AM

Snap!!! Actually, I was thinking more about dust accumulation in mechanical joints or on antennas, sensors, etc. Any of that can't be good in the long term, and the longevity of the MERs has provided some invaluable data on this process, at least qualitatively. I'd like to see MSL fully functional until the last possible useable erg has been extracted from the RTG(s?)...

Posted by: alan Apr 1 2007, 04:38 PM

From the Planetary Society's MER update:

This is about 20 watt-hours ( ~5 % )over Helvick's last projection:
http://www.unmannedspaceflight.com/index.php?s=&showtopic=2195&view=findpost&p=79094

No way to tell if this is because of the clumping or if dust levels are lower than last year though.