Sunday, October 02, 2016

Anuket Sobek Border Confusion

Some aspects of cometary science of 67P are more critical than others regarding accuracy. This is because measurements, maps, feature identification and so forth are shared among many scientists and used as inputs in many papers. Errors, mis-identification and inaccuracies in maps can trickle down and cause problems far into the future for seemingly unrelated papers.

The border of Anuket and Sobek is a case in point. There is a pre to post perihelion change near Anuket's southern border very closely associated with outbursts. There are three almost parallel ridges that look very similar in post perihelion images. These straddle the border, and are also close to the border with Neith. 

However, due to the different latitude of these ridges, most images do not show all three. The ones that do have all three, them in have different lighting angle which means they look different enough in the same image, but are easily confused when in separate images.

As can be seen below, the first map shown is overlaid onto a pre-perihelion image in which the northern most ridge has distinctive pointy overhangs. The border is (correctly, I believe) past the next Southerly ridge which is straighter.

The second map below is overlaid onto a *Post* perihelion image (because they show the southern areas better), but the ridges pointy overhangs have collapsed and the ridge looks like the next southern ridge because the overhang collapses have straightened the ridge. The map is therefore very misleading because it changes the region in which very important outburst have taken place. The highly publicised short outburst lands in Anuket in the top map, but Sobek in the bottom map.

This sort of error can be extremely embarrassing for science, and expensive to fix once papers have used both of the maps separately to come to different conclusions. I think an urgent audit of these maps is in order. It appears peer review has not picked up this and several other discrepancies.

Image Credits
Copyright ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0
To view a copy of this licence please visit:
All lines and dotted annotations by Marco Parigi

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