From Concepción to the "Twin Craters", and beyond... Options

[SFJCody]

"Twin Craters" = San Antonio. There are images of San Antonio West scheduled for 2196.

[kenny]

It's a while since I took O-level geography, but perhaps arête would be a more suitable term? A sharp topographic ridge left between two areas of erosion.

Well, arête is usually an erosional mountain feature, as you say, and what we're seeing is a deposition feature feature, so a different term is apporpriate. Isthmus is probably neutral in this regard.

I think the best term is septum, "a partition separating two cavities or spaces". This is the term used on the moon for a ridge between two adjacent craters.

[Tesheiner]

"Twin Craters" = San Antonio. There are images of San Antonio West scheduled for 2196.

I think we're talking about a ship from Magellan's expedition. Rui, you're the expert, what do you think?
http://en.wikipedia.org/wiki/Victoria_(ship)

Victoria (or Nao Victoria, as well as Vittoria) was a Spanish carrack and the first ship to successfully circumnavigate the world.
...
The four other ships were Trinidad (110 tons, crew 55), San Antonio (120 tons, crew 60), Concepcion (90 tons, crew 45), and Santiago (75 tons, crew 32).

[climber]

Arête, as you write it, is a french name which means "ridge" and is more likely to be applied in mountains, not in this case.
Now, if you use it in English (like it's written here), I cannot tell.

[ustrax]

I think we're talking about a ship from Magellan's expedition. Rui, you're the expert, what do you think?

Yes, looks like it, although I was expecting to see the rest of Magellan's fleet used to name more proeminent features...
Looking forward for Santiago!

[CryptoEngineer]

Arête, as you write it, is a french name which means "ridge" and is more likely to be applied in mountains, not in this case.
Now, if you use it in English (like it's written here), I cannot tell.

The rarity of twin craters on Earth means that the terminology for describing them is poorly developed. "Arête" is probably workable: English isn't shy about using words from other languages (ref James Nicoll). 'Septum' doesn't really work for me, I tend to associate it with anatomical structures. However, if its the accepted term of art, so be it. 'Divider', or 'dividing ridge' seem most descriptive, if unimaginative.

I wonder if its possible to look at the pair and figure out which hit first, or from which direction. Even a few milliseconds difference in arrival time would, I think, produce a difference in shape.

CE

[AndyG]

'Septum' doesn't really work for me, I tend to associate it with anatomical structures.

I agree (while rubbing my philtrum, under my septum, with my finger.)

I wonder if its possible to look at the pair and figure out which hit first, or from which direction. Even a few milliseconds difference in arrival time would, I think, produce a difference in shape.

I would have thought that things would still be "up in the air" at a few milliseconds after the first impact, during crater formation. But it will be interesting to see the details.

Andy

[ngunn]

still be "up in the air"

If I understand correctly Bill's post 143 about directed shockwaves in mine blasts, I think "already moving but not yet up in the air" might describe it better.

[Stu]

Hadrian's Wall looking good over there, Dan...



... but not much else to see... this might be a flying visit....

[fredk]

Unfortunately no new views of the Twins in the latest downlink. But we're seeing many versions of some images - I don't recall ever seeing the "product version number" become a letter, like the "A" at the end of the filename of this image:
http://qt.exploratorium.edu/mars/opportuni...VRP2597R1MA.JPG
(Very cool image, I think, with the tracks veering to the left in the choppy see of dunes...)

[NickF]

One would assume that the Twins are older and that the ejecta rubble has simply weathered and eroded.

If Concepcion was in the order of 10^4 years old, do we have an estimate for the age of the Twins? An order of magnitude older? Two? Older still? (presumably impact features like this fill up with dust eventually)

[Bill Harris]

Right, fredk, Oppy's been having some trouble with the uplink to the relay satellite and I guess that the "product version numbers" have gotten around to exceeding "9", so they've gone alpha. Anyone "with connectionc" care to venture a guess why?

The ripples have gotten to look like choppy seas, I don't thik this is a effect of the cratering at San Antionio since we've been seeing this since we arrived at Concepcion. We "crested the hilltop" there and are headed downhill-ish so I think that this is an orographic effect.

--Bill

[ngunn]

Why has all the dust from inside San Antonio West (and East?) been blown out in one particular direction to form a single big dune? Other craters on the same HiRise image don't look like this has happened to them. It doesn't seem to me like the result of a gradual process but rather the effect of a strong wind that blew for a short time, temporarily revealing Hadrian's Wall. Then there's all those choppy dunes - another localised phenomenon. The relief around here is really slight so I can hardly believe that orographic effects alone would produce such striking changes. I have no explanation to offer but I think it's at least worth considering whether something unusual could have happened here fairly recently in Martian terms (post San Antonio but pre Concepcion).

EDIT: Think Tunguska - flattened trees but no crater. A big tornado might also do the trick; we don't really know what happens on smaller scales inside Martian dust storms.

[BrianL]

... but not much else to see... this might be a flying visit....

All aboard the Opportunity Express. Next stop... Santa Maria. Woo-woo!
Well, I can hope...

Brian

[Guest_Bobby_*]

How safe does it look like for the Rover to go inside this crater to investigate any exposed bedrock???