[X] My Assistant

[dvandorn]

This event deserves its own thread.

To quote the illustrious Dr. King -- "Free at last, free at last, thank God Almighty, we're free at last!

So, how much y'all want to bet we'll stay here for a few sols, looking very carefully at the tracks and waiting for the MER Team to figure out how to proceed from here?

-the other Doug

[Trader]

I'm no geologist but as I look at this shot of Erebus:

http://www.marsgeo.com/Photos/Opportunity/Etched.jpg

It looks like there is a circumferential ring around the obvious center of the crater and that this ring crosses Opie's course right about where she got stuck! Could this be the origional outer edge of the crater which is much larger than supposed and has now been filled with dust? If one uses a lot of imagination one can see parts of a corresponding arc continuing around the southern side of the center. Could it be that Opie started to approach the original rim of the Erebus crater? I have a real bad feeling about going any closer to Erebus center from the north. Better to go around it and approach from the south if it looks more solid in the etched area?

[dilo]

I'm no geologist but as I look at this shot of Erebus:

http://www.marsgeo.com/Photos/Opportunity/Etched.jpg

It looks like there is a circumferential ring around the obvious center of the crater and that this ring crosses Opie's course right about where she got stuck!  Could this be the origional outer edge of the crater which is much larger than supposed and has now been filled with dust?  If one uses a lot of imagination one can see parts of a corresponding arc continuing around the southern side of the center.  Could it be that Opie started to approach the original rim of the Erebus crater?  I have a real bad feeling about going any closer to Erebus center from the north.  Better to go around it and approach from the south if it looks more solid in the etched area?

This "bad feeling" hit me too, when answering to and interesting question from Vladimorka in the other active thread (http://www.unmannedspaceflight.com/index.php?showtopic=947&view=findpost&p=11968)...
My fear is that, based on bottom of rover tracks profile, Opportunity is entering in a completely new terrain, were hard soil became deeper and is covered by thicker sand layer... extention of this new terrain is clearly visible in this elaborated version of your image (I highlighted upper border):

In the "route map" thread, someone theorized that this terrain (called "Terra Nova") could be an ancient, buried crater, eventually overlapping Erebus north Rim.
If this is true, they should avoid moving directly to South direction and try to circumnavigate the hidden crated going to east!

[Guest_Richard Trigaux_*]

Hi Trader and Dilo,

I am afraid you may be right. This suposed buried crater at north of Erebus is not obvious, but now that you showed it, it is visible.

Note that there is also one buried crater east of Erebus. Oppy should avoid both.

If so, you are right, Oppy should go east immediately and only after resume its road south to the etched terrain.

This etched terrain could be only the same layer of rock than in Endurance, just more exposed. But it could also be different, as the abundance of large craters indicates it is more ancient.

Anyway there seem to be, in etched terrain, larger dunes, rocks and pits, which make it very dangerous.

[dvandorn]

Hi Trader and Dilo,

I am afraid you may be right. This suposed buried crater at north of Erebus is not obvious, but now that you showed it, it is visible.

Note that there is also one buried crater east of Erebus. Oppy should avoid both.

If so, you are right, Oppy should go east immediately and only after resume its road south to the etched terrain.

This etched terrain could be only the same layer of rock than in Endurance, just more exposed. But it could also be different, as the abundance of large craters indicates it is more ancient.

Anyway there seem to be, in etched terrain, larger dunes, rocks and pits, which make it very dangerous.

I believe I disagree entirely. We have ground truth as to what the current terrain is like -- that scalloped, fish-scale pattern of light markings are high drifts of very soft material. The first time Oppy tried to drive through the center of the lightest portion of one of those scalloped features, it got stuck in very soft powder.

To the east (right), there is nothing but more of this fish-scale patterning. We know that this is going to be more of the rover-trap soft-powder dunes.

The darker area, on the other hand, looks like it's back to the blueberry pavement with low (10cm or less) drifts. It looks like far safer and faster driving than going to the east.

In fact, I'd head southwest to get to this darker unit as fast as possible, and then straighten out to the south and head for the rim of Erebus. Now, getting from Erebus to Victoria could be dicey, since there are a lot of obvious tall drifts and serious dunes crossing the rim and extending to the east -- just the direction you want to go to reach Victoria...

-the other Doug