I'm not sure anyone fully understands these formations. We may be looking at an impact crater or at something else again...

A while back, Malin and Edgett proposedto explain all the layered deposits of white stuff as sedimentation in crater lakes, craters that were subsequently buried, sometimes under many kilometers of dust and debris, only to be exposed by later faulting and erosion to our prying eyes.

Well...

We need to understand what we are seeing here, and the caption is particularly uninformative.

This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows layered sedimentary rock outcrops in Becquerel Crater of western Arabia Terra. These materials were deposited in the crater some time in the distant past, and later eroded to their present form. They probably consist of fine-grained sediments; they could have been deposited directly from dust and/or volcanic ash settling out of the martian atmosphere, or silt and sand settling to the floor of an ancient lake. The image does not provide enough information to distinguish between the two possibilities. The picture is located near 21.5°N, 8.1°W. Sunlight illuminates the scene from the lower left.

Since there is no context with the image, the caption makes little sense unless you're familiar with the Becquerel deposit. In fact, the image is a tiny part of a full traverse of the Becquerel deposit. The selected section is near the summit.

In Viking images, and in more recent THEMIS images, a small conical hill is visible at what apears to be the actual summit of the formation.

This hill appears to be visualizedin the full traverse, and it appears to be an arrowhead shaped layered mesa, not exactly "conical" at all.

However, the layered material at the base of this mesa turns out to be very interesting. Though it may be hard to make out clearly, there is a depression at the base of the mesa. At least eleven layers step down into this depression. There is a low, narrow ridge cutting diagonally across the surface, starting at the mesa. This ridge appears to have served as a barricade of sorts. There is a discontinuity in the layering between one side of the ridge and the other.

Below the data loss area of the image, we see an extremely sinuous margin to the layers. These layers step down from a flat surface just at the point of data loss.

The hole or crater is in these sinuous stairsteps.

There appears to be something of a discontinuity in the area of the hole/crater as well. It could be a small impact crater that formed in one specific layer, but as these layers are very thin, it no doubt broke through to layers below if it is an impact formation. On the other hand, it may be something like a sinkhole, forming through the dissolution of the layered material. There may be a way to tell remotely, but I don't know what it is.

Note that at the bottom of these very thin, sinuous stairsteps, the layers once again climb upwards toward the bottom left of the image. There's a disconinuity here as well. It is almost as if the material that formed the thin, sinuous layers was deposited as a kind of slurry in a hollow or depression, perhaps in a kind of eruption from below.

The way it has eroded makes it look wet even now.

And note, too, that each thin white layer is interbedded with an even thinner layer of dark material. This dark material seems grainy compared to the hard, smooth white material associated with it. But note some of the erosion of the white material, especially at and near the summit, seems to scallop and etch the edges of the white material. This form of erosion may be a clue to its composition.

Given the appearance of the summit of the Becquerel formation, I wonder whether this formation and possibly others like it is the result of a kind of slow, gentle eruption from below.

Cheers, BRFelix