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Spirit Parachute Nov '06 to Sept '07, Anim from HiRISE
djellison
post Nov 21 2007, 09:18 PM
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Saw a new HiRISE image up of Gusev earlier and wondered if the 'chute had moved given the strong winds.

The top of the 'chute moved between Nov-22 and Dec-12 '06, and then back again May-10 '07. I'm not sure how much is lighting and brightness/contrast within photoshop - but I think the last image, the chute is possibly dirtier than the other.

Off to hunt at Meridiani now smile.gif

Doug
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CosmicRocker
post Nov 23 2007, 04:03 AM
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That is really interesting to see. Thanks for putting that together. Considering all the wind activity we have observed through Spirit's eyes, I'm surprised the parachute seems to have moved so little over such a large time interval. All I can guess is that the wind is consistently unidirectional, or that the 'chute is snagged on rocks. Did you find anything interesting at Meridiani?


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Phil Stooke
post Nov 23 2007, 04:19 AM
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That is brilliant!

Phil


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Guest_Sunspot_*
post Nov 23 2007, 08:08 AM
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There is a rather dramatic deterioration in image quality as time passes - is that due to the problems they have had with the camera, or atmospheric/distance to the target etc?
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djellison
post Nov 23 2007, 08:20 AM
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There's only two of BS+HS at Meridiani and nothing's happened up there at all. Couldn't really see any changes at the HS either. I might see if the lander's deflated or had dust built up or something as well - but that's for another day smile.gif

Not sure on the loss of quality - I agree it's not all as good as that first shot. It's all 1x1 binning - all the same product for each observation ( JP2 Grey scale map projected quicklook for IAS ).

Doug
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AndyG
post Nov 23 2007, 08:34 AM
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While it certainly looks like the 'chute has moved, I suppose there's a chance that there's a process of deposition and uncovering by dust, too.

Andy
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djellison
post Nov 23 2007, 08:37 AM
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The chance of one single patch of 'chute being covered to exactly the same shade and texture as the underlying soil, then being perfectly cleared again seems a bit of a long shot smile.gif

Doug
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Juramike
post Nov 23 2007, 02:36 PM
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That sequence brings Mars even closer to the imagination....

Would the "flap" sound of the parachute moving be at a higher pitch or lower pitch than here on Earth?


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nprev
post Nov 23 2007, 03:45 PM
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Not sure if the freq would shift at all, Mike; can't see any obvious reason why it would. However, the volume of the sound would be MUCH lower because of the low density of the atmosphere (each flap slaps far fewer air molecules than a flap on Earth= less kinetic energy transmitted).


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kenny
post Nov 23 2007, 11:46 PM
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We hear higher frequency "Donald Duck" speech from someone who has breathed Helium at normal atmospheric pressure - e.g. my daughter does it for a laugh out of those toy Helium balloons you can buy at the fair. That pitch change has nothing to do with pressure, which is constant, but with the composition of the gas mixture. Since the Martian atmosphere is different in composition as well as pressure from Earth's, might we also expect a different frequency and well as the lower sound volume which nprev mentions ?

Kenny
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nprev
post Nov 24 2007, 12:05 AM
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That's a good point. Given that the Martian atmosphere is something like 95% CO2 (atomic weight around 44), 3% O2 (atomic weight 32) and ours is 78% N2 (atomic weight around 28) + 21% O2, there ought to be a difference, but I can't pin down the critical factor(s). The differences in the average atomic weight of the atmospheric mixtures should have an effect on amplitude (though not as much as the differential densities), but is there also a resonant component? Dunno.

EDIT: Aha! All hail Google; found this right away. Looks like pitch is a function of atomic weight, so my best guess is that sounds on Mars will actually have a lower pitch than their terrestrial equivalents, but of course not nearly as loud for the reason I cited earlier.

EDIT2: This is a more interesting question the more I think about it. As anybody who's ever traveled by air knows, things still sound the same when you're at cruising altitude, omitting the white noise from the engines & air friction, although the air density is a lot lower than normal (airliners are usually pressurized at the 10,000 ft equivalent level, or something like 75% of sea-level pressure). Therefore, pitch differences do seem to be almost completely dependent on gas mixtures...so, things are likely going to sound a bit different to us on every world, and also would have during some of Earth's previous geological eras when the O2 ratio was much higher...the dinosaurs probably had some pretty deep roars...neat! smile.gif


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kenny
post Nov 24 2007, 09:37 AM
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Interesting! I've been to 18,000 ft climbing and never noticed voice pitch changes, but volume certainly gets weaker. Incidentally I've always thought aircraft are pressurised to 8000 ft equivalent, but the precise figure doesn't much matter, your point is valid.
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Reckless
post Nov 24 2007, 09:53 AM
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Very interesting comments, we really must have a microphone on Mars soon to hear the flapping of parachutes etc.
And of course the sound of dinosaurs on Mars would be super neat.

Roy
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ngunn
post Nov 24 2007, 03:04 PM
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The molecular weight (and temperature) affect the speed of sound, and therefore the resonant frequencies in a cavity such as the human voice box or a tin whistle. This is what makes the helium-breather's voice go high. However there is no change in frequency of the sound once emitted, as a result of travel through the atmosphere - any atmosphere. The same number of wave-fronts must pass each observer in a given time interval, therefore sounds that are emitted by mechanical vibration such as a tuning fork will be heard at the same pitch on any airy planet. The only way to change the perceived frequency is via the doppler effect when relative motion is involved.

However it is the case that different atmospheres could attenuate different frequencies differently. That could affect the 'colour' of white noise such as might be produced by a rustling fabric. Any difference would be minimal at close range, increasing with distance. I have no details on this.
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fredk
post Nov 24 2007, 05:41 PM
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I think you've nailed it there, ngunn. Given a source of some frequency, it must be heard at the same frequency barring Doppler shifts.

But it's still an open question what effects the different Martian air might have on the generation of sound to begin with. I'd expect that the dynamics of a large piece of flapping fabric would be quite different in Martian air than on earth, but it's a messy problem. Could there be resonances involved? Since there's less air resistance and the wind speeds are higher on Mars, I'd guess the generated pitches would tend to be higher. Just a guess.
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