Attached please find a JPEG (372 Kb) showing the revised location for the Athabasca Vallis ellipse. After a number of iterations with Laszlo Keszthelyi and Alfred McEwen from the University of Arizona, we have settled on the enclosed location. There is little room to move the ellipse as it is presently centered on the channel as well as being south of a number of high relief streamlined islands and craters and north of streamlined islands and craters. Even at this location, the ellipse includes streamlined islands near the center of the ellipse, fresh lava surfaces at either end, and ejecta from the large crater at the eastern end.

The new Athabasca Ellipse, should be referred to as EP49B3 and is located at:
9.08N, 204.20W in the MDIM2 reference system
8.99N, 155.67E in the MOLA reference system

The dashed ellipse is for the opening of the launch window and is 152 km by 16 km oriented at 95 deg. The solid ellipse is for the close of the launch window. The base map is the MDIM2 with MOLA elevations colored and MOC images through E11. The center elevation of the ellipse is -2600 m relative to the MOLA geoid. Within the ellipse, the minimum elevation is -2640 m and the maximum elevation -2450 m.

MOC and THEMIS images have been requested.