The Descent into Victoria, Possible and Actual Strategies Options

[glennwsmith]

Here's an obvious scenario that better minds can critique: we will descend hugging the clockwise cliff but also at some safe distance from it (lest a rock should become dislodged during the next wind event or daily thermal cycle and fall on the solar panels), occasionally turning to face it (but still at some safe distance) and using the full reach of the instrument arm to RAT and take micrographs and readings.

[Stu]

Think we're going to be seeing a LOT of this cliff face in the days ahead...

[BrianL]

Think we're going to be seeing a LOT of this cliff face in the days ahead...

Wrong cliff face, methinks. That's St Mary, not Verde. Unless I'm misinterpreting what you mean.

Brian

[Stu]

Sorry BrianL, should have been clearer... I know this isn't the bay she'll enter in, I meant that this looks like a good target for Oppy once she's down in the crater, cos of all the layering we can see.

Of course, this will be our first stopping point...

[abalone]

What impact is this going to have on the energy production due to excessive shading. Maybe we will go in a few metres parallel to the cliff and just "dash in" for a closer look once targets have been identified

[helvick]

There is a loss due to shading but it's less than you would think. At the moment 40-50% of the insolation is diffuse (and more if Tau is > 0.7) which is not affected by the shade so even if she parks right up against a wall she should not lose more than 20-25% of her potential power.

If she stands back a bit from a cliff so that it directly blocks, say, the rising sun for 3 hours past local dawn that would block approximately 10% of the daily total insolation. In addition there is a positive effect where a cliff that blocks direct morning sun will reflect evening sun so that effective insolation in the afternoon will rise slightly.

Since she is currently generating 800+whr/Sol she has plenty of power margin to do this sort of work right now.

[fredk]

It depends on what direction the cliff is facing, though. If we were parked right against a steep enough north facing cliff, we'd lose most of the direct sun and nearly half of the diffuse light, since the cliff would be in perpetual shadow now. Fortunately there are no directly north facing cliffs nearby!

The south-facing cliffs of Verde and St. Mary would be ideal for close visits now. I'd be interested in what being parked against a sunlit cliff does to local temperatures.

Still, we're not sure if they intend to inch up to cliffs or just sample the floor of Duck Bay. We've heard that they have a policy to avoid driving onto overhanging cliffs from above. Perhaps they'd be concerned as well about rockfall at the base, especially if they tried ratting the cliffface!

[Stu]

I'd be interested in what being parked against a sunlit cliff does to local temperatures.

Bad idea... just imagine all the damage that could be caused by puddle water dripping onto Oppy's sensitive electronics...

[As old as Voyage...]

I remember once reading that surface temperatures are far higher inside lunar craters than surrounding plains. I wonder if this holds true for Martian craters?

[dvandorn]

Yes, it generally is true. It's a matter of sunlight reflecting off the crater walls. If you look at THEMIS images from Mars Odyssey, you can see that craters tend to be warmer than the surrounding terrain, especially just after sunset.

-the other Doug

[AndyG]

...Hmmm. Then the focus of any near-parabolic craters must be an interesting place to be, with regards to the generation of thermals.

Andy

[dvandorn]

Most craters aren't parabolic, and thus don't have perfect heat-focusing characteristics. But they do, indeed, heat the air above them and create thermals. If you don't believe me, look at the dust devil tracks in Gusev -- they very frequently spin out of craters.

You have to wonder why you see dust devils forming at Gusev and not spinning out of Victoria, here. I imagine there are a lot of factors, but still -- it is odd that some craters spawn dust devils and others don't. None of the craters at Meridiani seem to be spawning DDs, and yet lots of them are formed at Gusev.

-the other Doug

[Guest_Edward Schmitz_*]

You do see DD's spinning off of craters but, from what I've read, they are more related to turbulance caused by air flowing over the crater. I've not heard anything about there being a heat differential over these crater causing the DD's.

[fredk]

Looking at wide angle orbital views, even at Gusev there are DDs only in a small region, which we happen to be sitting in the middle of. Why not elsewhere in Gusev? Is it the prevailing wind speeds? Is it that they do occur elsewhere, but the surface underneath the dust is lighter than it is here, so their tracks don't look dark? I seem to recall that we've discussed this before...

As far as crater shape goes, I would think even a somewhat not parabolic shape would still give a decent focus, if only the crater surface could reflect specularly, which unfortunately it can't.

[djellison]

1 p.m. EDT, Thursday, June 28

NASA will hold a media teleconference to discuss the scientific reasoning and risks related to the Mars rover Opportunity's planned descent into the massive "Victoria Crater."

Briefing participants are:
-- Alan Stern, NASA associate administrator, Science Mission Directorate, NASA Headquarters, Washington
-- Michael Meyer, lead Mars program scientist, Science Mission Directorate, NASA Headquarters, Washington
-- John Callas, Mars Exploration Rover project manager, NASA's Jet Propulsion Laboratory, Pasadena, Calif.
-- Steve Squyres, principal investigator, Mars Exploration Rover science instruments, Cornell University, Ithaca, N.Y.