[X] My Assistant

[Stu]

Some coloured-in bits n pieces...

[Astro0]

Let me be among the first to say HAPPY 4TH ANNIVERSARY SPIRIT!
May your winters be warm, the sunshine plentiful and the winds kind to you.


Astro0

[Doc]

Has anyone noticed that the tracks made the first time by Spirit(when she first arrived at Home plate) have disappeared?

Or maybe Im not looking hard enough! They said (MER landing team) that the winds at Gusev are particularly strong. Does this mean that the tracks can't survive for more then one martian year or less?

[Ant103]

Doc : remember the great summer storm. Around Spirit, fresh tracks have totaly disapear. Add to this some dust deposition after that, and it's as if there was no tracks.

[Doc]

Doc : remember the great summer storm.

I remember the storm very well.Its just that what amazes me is the rapidity and the efficiency of the wind and dust to wipe out any trace of the rover ever being there.

Even the erosion power at Meridiani (Oppy's old tracks) do not match those at Gusev.

[Cugel]

Even the erosion power at Meridiani (Oppy's old tracks) does not match those at Gusev.

I don't believe this is erosion. The tracks are actually still there, just covered up with dust. Mars seems to be pretty good at hiding stuff under a thick layer of dust (craters!), but these things don't really erode away. Some day the winds blow from another direction and the tracks might become (partially) visible again. I can remember reading an article in which the erosion rate on Mars was described in nanometers per year. For a piece of ordinary rock it takes around 3 billion years to erode 1 meter.

[djellison]

Well - we can see with the MI images taken of 1 year old tracks just outside Endurance crater that indeed, they were eroding away and were significantly eroded inside of a year. We've also seen, during the dust storm, motion of tiny ripple of dust along the ground in just a few days. And up near Larry's Lookout, significant softening of track details within a couple of days. In HiRISE imagery, you will struggle to find rover tracks before the north side of Home Plate. Mars is much more active that you presume.

Doug

[OWW]

I may be reading the data incorrectly, but according to the Pancam data tracking site all the "Tuskeegee-Pan" images from Sol 1412/1413/1414 are already down, but only the L2 images have shown up on Exploratorium. All the filters from Tuskeegee Sol 1417-1422 did show up however. Some sort of hiccup?

[alan]

Looking at the numbers and the stamps from 1413 its clear that only the thumbnail images have been downloaded for all filters.

[Phil Stooke]

Cugel said "I don't believe this is erosion. ...... I can remember reading an article in which the erosion rate on Mars was described in nanometers per year. For a piece of ordinary rock it takes around 3 billion years to erode 1 meter."

Right... but this area is loose dusty soil. The tracks might be covered with more dust, or they might have blown away. Back in Silica Valley, only about 40 m from here, time-lapse images showed 'ripples' moving across the surface during strong winds. If that happened here as well, that would probably remove tracks too.

Phil

[Cugel]

Mars is much more active that you presume.
Doug

Actually, I was of by a factor of 100. The correct erosion rate is 0.01 nm per year.
According to this paper that is: http://www.agu.org/pubs/crossref/2000/1999JE001043.shtml

Anyway, I'm not claiming that Mars is inactive or anything like that. Just that what we're seeing is not erosion but mainly dust blowing around. I don't think you can 'see' erosion on a timescale of a few months, not even on Earth.

[nprev]

Seems to me as if it would be very hard to assign a meaningful value for a global erosion rate , anyhow. There are too many variables: geographical location, terrain composition, microclimatology, local elevation, scale of putative erosional features, etc., etc.

For example, I'm sure that mountaintops and the southern highlands on Mars erode slowly indeed (esp. the basalts), but Oppy's area sure looks like it moves faster. Consider the fact that we've even seen blueberries blowing around a little, and that sedimentary rock is generally quite soft.

[OWW]

Looking at the numbers and the stamps from 1413 its clear that only the thumbnail images have been downloaded for all filters.

What are stamps and how do I view them?

[ElkGroveDan]

I don't think you can 'see' erosion on a timescale of a few months, not even on Earth.

Then you have a very atypical definition of "erosion" that you are using.

Erosion includes all of the macro-movement processes we are familiar with here on Earth including mass wasting, stream bed erosion, frost heaving as well as the aeolian processes you seem to be focusing on. On the scale of a few months it is actually quite easy to measure real and significant erosion on Earth, starting with entire mountainsides slumping into the ocean over minutes and hours. Spend a week camping in granite environs in late winter or spring such as Yosemite National Park and you can watch solid boulders shedding slabs over the course of a few days due to frost wedging. Finally, if you want to test for erosion by wind and sand, simply park an old car out on a playa in the desert near Palm Springs or Mojave for a few months from late summer to mid fall. You will come back to a vehicle with little or no paint and a nicely frosted windshield.

I could go on and on about all of the erosion processes on Earth that are real and observable on a timescale of a few months, but you get the idea.

[ngunn]

Cross purposes here I think. You might not be able to see hard rocks erode significantly over short timescales but structures formed in looser material erode much faster. Every time I walk on the beach after a high spring tide I notice new erosion at the base of the beach-head sand dunes. Likewise on a windy day it's not that hard to find examples of wind erosion features (perched pebbles and the like) that have formed in the period between one high tide and the next.

Edit - you got there before me EGD!