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InSight Surface Operations, 26 Nov 2018-
MahFL
post Dec 3 2018, 11:53 PM
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A new image is down.

https://mars.nasa.gov/insight/multimedia/ra...mission=insight
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PaulH51
post Dec 4 2018, 01:36 AM
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QUOTE (MahFL @ Dec 4 2018, 07:53 AM) *

Comparing the sol 5 ICC image with sol 4 (animated GIF) shows some dust reduction on the lens
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elakdawalla
post Dec 4 2018, 06:21 AM
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It's great that dust is flying off, but until the situation stabilizes, flat fielding will be impossible!

Complaints about dust on images aside, I'd like to point out that when it comes to the purpose for which this camera was put on the spacecraft -- imaging the foreground to guide placement of instruments -- the dust on the lens does not matter at all. The foreground is totally clear enough to guide instrument placement. "Pretty" is desirable for outreach but unnecessary to the accomplishment of mission goals.

Let's hope for some good wind puffs to make our view clearer, but there's zero problem here for the mission.


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elakdawalla
post Dec 4 2018, 06:22 AM
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I'm actually really intrigued by how deep the footpad has sunk. That's fascinating. I don't think any other footpad on any other mission has done that. Is the soil compressible? Was it blown away, undermined, during the final moments of landing? How did that happen?


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Paolo
post Dec 4 2018, 07:54 AM
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am I the only one who sees linear features (thruster-blown dust?) in the area between the leg and the big pebble?
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kenny
post Dec 4 2018, 09:09 AM
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I think that's correct about other lander footpads not sinking as deeply. But some Rover wheels did go deep, doubtless exacerbated by their rotation.
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HSchirmer
post Dec 4 2018, 10:00 AM
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QUOTE (elakdawalla @ Dec 4 2018, 07:22 AM) *
... Was it blown away, undermined, during the final moments of landing? How did that happen?


Found a graphic that suggests landing rockets create areas with up to 100k+ Pa of pressure,
that's about 14.6 psi overpressure, should be enough to blow small rocks and stones away.


Anybody know how much hydrazine propellant is left over?
It might be interesting to engage a 1-Newton attitude control thruster and see if that blows sand around.
Hmm, how about using more and more powerful rockets to characterize the range of surface dust-sand-pebble-rock sizes... Seems that the 3 types of thrusters are variable, ~.2 to 1 Newton, ~12-30 Newtons, and ~100-300 Newtons.

Heck, a scoop is nice for trenching, but you've potentially got a 10kPa hydrazine-powered leaf blower to remove the overburden (think Jacque Cousteau vacuuming away the sand to reveal the wreck, just done with rocket exhaust).
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vikingmars
post Dec 4 2018, 10:08 AM
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QUOTE (elakdawalla @ Dec 4 2018, 07:22 AM) *
I'm actually really intrigued by how deep the footpad has sunk. That's fascinating. I don't think any other footpad on any other mission has done that. Is the soil compressible? Was it blown away, undermined, during the final moments of landing? How did that happen?

Dear Emily, for your info, footpad #2 of Viking Lander 1 sunk at landing and was buried beneath a cover of loose Martian soil. It sunk about 12 cm, and fine-grained soil slumped into the depression of the footpad and over it
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elakdawalla
post Dec 4 2018, 04:15 PM
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Cool, thanks!


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pioneer
post Dec 4 2018, 06:00 PM
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QUOTE (elakdawalla @ Dec 4 2018, 07:22 AM) *
I'm actually really intrigued by how deep the footpad has sunk. That's fascinating. I don't think any other footpad on any other mission has done that. Is the soil compressible? Was it blown away, undermined, during the final moments of landing? How did that happen?


A scary thought just came to mind unsure.gif : what if the lander landed on quicksand? It's ridiculous, right?
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hendric
post Dec 4 2018, 06:04 PM
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Pretty much. "Real" quicksand requires liquid water to keep the sand in suspension. Not going to happen on Mars on the surface. I suppose super-fluffy dust or ash is possible, but hasn't been so far. Enough to get a rover caught, but not Neverending Story disappearing beneath the sands.


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HSchirmer
post Dec 4 2018, 08:15 PM
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QUOTE (pioneer @ Dec 4 2018, 06:00 PM) *
A scary thought just came to mind unsure.gif : what if the lander landed on quicksand? It's ridiculous, right?


Nope, not ridiculous at all. In hindsight, just unlikely.

The Surveyor landings on the Moon were (in part) to make sure the lunar seas were really cooled lava flows that you could land on, not tens of meters of uncompacted or electrostatically levitated dust that you'd sink into.
Turns out there ARE tens of meters of lunar dust, but it's compacted and mixed with larger grains so that it can support the weight.

There are some weird bodies that appear to have "quicksand" surfaces, i.e. just dust without a solid surface.
One is Saturn's egg-shaped moon Methone, which seems to be just dust.
Others are the "dust ponds on asteroids, which seem to accumulate dust in depressions,
https://www.sciencemag.org/news/2001/09/dusty-ponds-space
or at the low gravity point between contact binaries.

Now, for trying to answer the question- the problem wouldn't be "quicksand" but "deep loose dust"-
I think the answer would depend on what triggers the landing rockets to shut off.
If the landing rocket shutdown is triggered by foot-probes AND the dust has no bearing strength, (i.e. acts like a fluid) then the rockets don't get a shut-off signal and continue to fire as the lander approaches the dust.
I'll guess the lander has a fail-safe "when in doubt, hover, don't crash" routine so it should hover in place until it touches ground, that should be time enough to blow out the loose dust?
If the landing rocket shutoff is triggered by a proximity radar, then the loose dust probably reflects enough to fool the lander into thinking it's approaching solid ground, and the lander sinks into the dust.
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serpens
post Dec 4 2018, 09:51 PM
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Regardless of all the data from orbiters there is a degree of luck involved in landing. Curiosity did a hole in one in a small crater. Imagine if she had bounced to a stop in the middle of Endurance crater's central dune field.
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djellison
post Dec 4 2018, 09:57 PM
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That’s not how the landing works. At a certain altitude you’ll hear the EDL commentator say ‘constant velocity phase’’. At that altitude the radar starts to become unreliable and the spacecraft continues to descend at a constant velocity using the IMU. Once the three landing legs detect a touchdown the engines shut off.

The thermal inertia of this landing site precludes the sort of light fluffy dust that one might interpret as ‘quicksand’
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Phil Stooke
post Dec 4 2018, 10:00 PM
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"Curiosity did a hole in one in a small crater."

Opportunity! Curiosity landed in gigantic crater.

Phil


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