[X] My Assistant

[Tesheiner]

Yesterday the download of that 12x3 pancam mosaic (180 x 45 degrees) was finished, at least on the L7 filter.

Here is the result with autostitch (compressed and reduced to half size).

PS: This was the first of two panos taken to obtain a good stereo map of the inner basin. It was taken on L7R1, so no true colorization should be expected for this one. The second one (same 12x3) was taken on sols 594, 595, and 597 using L257R127 filters.

[dvandorn]

In this perspective, the "dark mound" behind Home Plate looks more and more like an erosion-resistant tongue of the rock beds uplifted when the Columbia Hills were formed. It has a strike very similar to the hills themselves, and its strike is also very similar to those of the other outcrops we can see in this view that poke up, here and there, in the inter-hill valley of the Inner Basin and up the sides of Ramon Hill.

Home Plate itself -- it looks very much, in this view, like the remnant of an old impact crater. The way it sits on a little pedestal in the middle of the basin, and the way the edges of the pedestal sort of peel down, just remind me strongly of a rockbed that's been deformed and brecciated by an impact.

Now, that fascinating non-circular ring that makes up Home Plate's perimeter -- well, if Home Plate was a crater that's mostly been eroded away, then that feature represents some kind of cross-section of the crater floor. Or possibly of a portion of the brecciated, shocked and impact-melted rock directly below the floor of the crater.

It seems to me that if the Columbia Hills were uplifted *before* Gusev became a lake, it's possible that craters within the uplifted hills (especially in valleys between the hills, like the Inner Basin) may also have filled with water. Home Plate may have been a pond within the otherwise high-and-dry Columbia Hills, fed by either rainfall or artesian water pressure through fractures leading up into its brecciated floor unit.

If so, Home Plate may be the most exposed version of evaporite outcrop available for examination within Gusev Crater. Especially, within reach within Gusev Crater.

Of course, it might not be evaporite. But it might be the cross-section of lacustrine materials, or even a layer of highly altered rock that used to lie within the Columbia Hill's aquifer. In any event, a close look at Home Plate might be the biggest scientific payoff of the entire MER mission.

-the other Doug