[X] My Assistant

[Juramike]

I put together a sequence of craters of similar erosion state (Recent or Fresh)starting from the Equatorial Zones up to the higher latitudes. Presumed average wind direction based on presumed drifts is indicated.



The Equatorial zone craters in the Sand Sea basins, like Ksa and Sinlap, have clear rims, interiors and debris aprons. Dunes are at the margins.



Further north, the T23 Crater which sits in Fensal basin, has a clear rim and debris apron, although the surrounding terrain has slightly RADAR-brighter wispiness (drifts?) as downwind streaks.
The recently released image of the Dilmun Crater at the same latitude, but on a bright area, has the same RADAR-brighter wispiness as downwind streaks and symmetrically placed at the edges of the windshadow of the crater.

The Dilmun Crater also looks very similar to the circular feature seen in the T16 Swath. I'd be pretty confident calling the T16 circular feature an impact crater based on it's similarity to the Dilmun Crater. [The streak to the left of the T16 crater is the RADAR SAR seam, other RADAR-bright streaks are in the immediate area and are downwind. Wind coming from the upper left in the image] The interior rim is also similarly crenellated. The T16 Crater is very similar to the Dilmun crater, but slightly buried so that the margin of the debris apron is less distinct.

The T23, Dilmun, and T16 craters are all at about 30N. Above this latitude there are very few identified craters.



The next graphic shows a circular feature at 58N latitude. Extrapolating the trend from Equatorial regions to the higher latitudes, we would expect it to be buried - which it appears. Only the rim is clearly visible. Topograpy seems to show that the center has been almost completely infilled.

At least with this limited sample, the trend is for craters to have subtle RADAR bright windstreaks and to become progressively buried as one goes from the Equatorial zones to the higher latitudes.

-Mike

[Juramike]

Further away from the Equatorial Sand Sea margin, the dune sands disappear and are replaced by gentle RADAR-bright wind drifts that continue to indicate the averaged wind vector around bright uplands. This is seen in the T28 and T21 swaths, although at different latitudes. A detail of the section indicated in green is shown in the next graphic.



In this zoomed area, the RADAR units are indicated by a color overlay. The brightest RADAR reflection comes from the bright upland terrain, these are probably sections of tectonic ridge poking up above the drifts. Downwind of this is an area of RADAR dark smooth terrain. At the margins of the dark smooth upland terrain, is a RADAR brighter terrain (although still grey). RADAR-bright drifts are seen in some sections of this terrain. These drifts also go around the RADAR-darker terrain, further evidence that the RADAR dark terrain is upland terrain. Below the bright margin wind-drift terrain, there is a slightly RADAR darker terrain, this seems to be valley fill. In areas close to the Sand Sea margins, dark channels can be seen to come from the valley mouths. This is evident , but hard to see in T21, but it is very evident in the lower section of the T28 tectonic ridges that are closer to Fensal.

Here is the sequence from highest altitude to lowest in the Basin margin Mid-latitudes.

• RADAR-Bright tectonic ridges
• Dark grey upland/windshadow terrain
• Bright grey wind drift margin terrain
• Slightly dark grey valley fill terrain
• (Darker channel-like features)

In some areas the RADAR bright tectonic ridges are not seen (burial?) and the dark channel features may not be seen either. In this case the bright grey wind drift margin terrain is the most obvious, and it will be necessary to look at the pattern of the darker material to see if it corresponds to windshadow/upland or to valley fill.

In general, upland will lie downwind of the concave face of the bright wind drift margin, while valley fill will lie upwind of the concave face of the bright wind-drift margin.



In the graphic above for the T21 Swath and the recently released T43 Dilmun crater image, the upper ridges are indicated by red arrows, while the valley floors are indicated by blue arrows.

By analogy with Tseghi, I’ll speculate that the Dancing Monkey feature is a series of intersecting graben that just happen to lie at the level and close enough to the Sand Sea margin to be infilled with Deep Black unit material (with very little dune sands). Like Shiwanna Virgae, I’ll further predict that this feature will be very evident by VIMS (2.7/2.8 um ratio’d image). I’ll predict that this graben structure extends well beyond the SW and NE ISS-visible borders of the feature, but that the lack of deep infill decreases contrast. I’ll also predict that more features like the Dancing Monkey will be observed in areas marginal to the Sand Sea basins. A great place to look for these would be in NE Shangri-La, as well as in N Belet, north of the Cyclops dude feature. [SE Adiri, Ching-Tu, S Senkyo are also likely targets for this type of feature].

-Mike