Doin' reasonably well, Dan... how about yerself? Got a little bit worried there for a while...

As for the "snow line"...

The region is Terra Cimmeria -- where there are all kinds of interesting things going on, and apparently they have been going on for a very long time.

The rubbly areas at the top of the frame are duplicated throughout much of this region. So is the more or less smooth stuff like we see toward the bottom of the frame. The rubble is a clue to me that the area may once have been mantled by ice (cf: Argyre, etc.)

There are some areas throughout Cimmeria that look like they are snow-mantled or heavily icy, resembling high latitude northern plains. They have a sort of closely spaced rolling hummocky appearance that is associated with icy areas in the north.

One thing about this region is that its elevations is relatively low compared to much of the Southern Highlands (~ <1000 meters - ~ <3000 meters).

There are lots of runoff channels, too, some of them very large. To the east is Ma'adim Vallis, one of the main runoff channels of the Southern Highlands. There has been some speculation that the Terra Cimmeria depression once was a lake that was drained into the Northern Lowlands by Ma'adim.

It seems that most workers have interpreted the region as a more or less typical flood lava ridged plain, similar to those found nearby, say in Hesperia and Tyrrhena.

But there is a whole raft of distinctive features here, including a tremendous magnetic anomaly, which has been interpreted to mean that subsurface melting occurred repeatedly, and a striped strong magnetic signature was induced in the bedrock. This magnetic striping, BTW, is at a 90° angle to the planet's current axis. And of course there is no perceptible magnetic field on Mars today.

Another anomalous condition in this area is the "wrinkle ridges" -- the "snow line" appears to be found on one. These are not quite like other wrinkle ridges found on Mars and other planetary bodies. Instead, these are mostly relatively smooth-looking scarps, seemingly associated with Apollinaris Patera many kilometers to the north.

Small, apparently extinct, volcanic cones are found in various places in Terra Cimmeria, indicating a once active surface.

Conventional crater counting seems to indicate that much of the surface is around 3.7 billion years old, but many here are aware of my reservations about accepting age-dating by crater counting on Mars without some skepticism.

I asked about this particular formation because it does show a distinct edge, and it shows the lighter, smoother material draping over the crater rim. A lava flow might do this, but more likely would flow around the crater -- unless it were very thick. Given the apparent age of the surface, I would expect more erosion than we see if it were a lava formation.

Snowfall might mantle the whole surface. Relatively nearby formations that appear somewhat similar to this one also seem to have surfaces sculpted into wave-like shapes. This yells out "ice!" to me. But this area is between 35° S and 50° S latitude, definitely "mid-latitudes." How can ice persist here?

Some links:

http://www.lpi.usra.edu/meetings/lpsc2003/pdf/1298.pdf

http://web99.arc.nasa.gov/~vgulick/MSLS99_Wkshp/Nelson_Elysium-Cimmeria_abs.pdf

MOLA Map
http://planetarynames.wr.usgs.gov/images/mc23_mola.pdf

http://www.planetary.brown.edu/planetary/documents/2756.pdf

There's lots more, but that's plenty much for now.

Cheers, BRFelix