The situation with Oppy is known to be more benign because she is closer to the equator, not by much but enough to make a difference. Mid winter is on the way but she'll bottom out on power before things get critical unless there is a major additional dust complication. Given that the SH winter season is a lower dust period (in general) the dust problem is not a major concern. That's not to say things aren't tight but that's how things have played out over the past few winters. If there is a positive dust cleaning event or two, then all the better.

I wouldn't necessarily disagree with fredk's assessment that the 250watt hour number is just a blip in tau but it's a pretty big jump from 227, it could well be an indication of a small dust cleaning event. We'll know soon enough in any case.

Bill/Helvick,

Thank you for your replies - a lot of good information for me there.

Sometime ago I stated my big fear was Oppy expiring 5 metres from the rim of Endeavour Crater - but now I feel a lot more confident and optimistic... I think we'll get within a metre now!

Thanks again, and as ever Go Oppy!

Neil

Short drive on sol 2220, aborted due to excess slip?
http://207.7.139.5/mars/opportunity/forwar...00P1211L0M1.JPG

That's was my thought too when I saw the picture. She moved "only" 10m.

Looking at the "right front" wheel in the FHazcam image, the first thought is "whoa, that's starting to dig", but looking at the (stretched, to see shadow detail) RHazcam image the corresponding wheel (on the left) isn't starting to dig in. Yet. So I don't think she's getting into trouble. From the virews from the Navcam and FHazcam, the soil has been quite firm and good to drive on since leaving San Antonio.

--Bill



Added: The Navcam of that track behind the "right front" wheel looks grim...

http://qt.exploratorium.edu/mars/opportuni...00P1992L0M1.JPG

Could it be that the RM slipped first then the RF slipped on the newly loosened stuff..?

The dunes are not very large here, so it's surprizing that she seems to've gotten bogged down a bit. And there was the episode soon after leaving San Antonio. It makes me wonder if the dune material (or crust on top) is getting softer as we head south.

If you look at one of the recent RL track images (will post a link in a sec after I find it), you'll see that all of a sudden the wheel starts sinking a bit in a low spot after hopping a dune.

It looks the the soil surface strength changed very abruptly; perhaps Oppy just drove off the edge of an evaporite crust? If so, doesn't appear to be any good way to discern those before actually driving over them since the dust covers everything.

EDIT: Found it.

We can just ask Opportunity's sister about that.

Based on this image, I would guess the observed difference in the surface strength is pretty local. (granted of course the tracks are being seen at different angles, that might throw off this interpretation)

The dunes in the area are dynamic and have become somewhat mobile. You can see more deflation with the formation of transverse dunes (ripples) and very well-defined laminations on the windward (eastern) slope of the ripples where there is more erosion. There is net deposition on the lee (western) slope and you'd expect the younger material to be, well, "fluffier" than the older, more consolidated material. You would expect to see this looser material to the west (left, in our direction of travel) of the ripple crest. As we run south and east, I'd expect to run into little "surprises" like this until the surface stabilizes.

It's rather like back when we were accustomed to the good traction of the mature surface around Endurance and ran into Purgatory when we got into the longitudinal ripple regime on the way to Erebus.

--Bill

I'm trying to see what's at the open space behind the RF wheel, i.e. between that wheel and the RM wheel on this fhazcam picture downlinked a few hours ago: http://qt.exploratorium.edu/mars/opportuni...00P1214R0M1.JPG
I can't see any cleat marks but possibly a "trench", is that right? Would it be an indication that the RM wheel stopped and was dragging the soil and so increasing the resistance to the movement?

Edited: Here's a crop of the area of interest.

If a wheel stops wouldn't the drive be aborted instantly?

No. IIRC a drive is aborted "instantly" if the motor current goes above a defined threshold.

I think you may be right

I really hope you're wrong, Tesheiner.

The left frame shows a bit more detail in the "trench":

There clearly is a trench, but it's not clear to me if there are cleats in it or not. There is a hint of a cleat in this left frame. At least the trench isn't perfectly smooth.

If the RM is still turning, but just digging in, then we wouldn't expect clean, well defined cleats like on a normal drive. Notice how the track behind the RF is much more chaotic and jumbled than a couple of metres farther back.

If the RM has stalled, then I'd think the trench would be very smooth. But maybe there would be some structure in it.

Basically, it's wait for more information...