AS16-1412

This image was scanned from a photograph taken by the Apollo 16 mapping camera. It shows the same region of the moon as AS16-0849, but at a much higher sun angle. The discussion here is primarily a comparison of the views of features that can be seen in both images. The pixel coordinates refer to the positions in Frame AS16-1412 here.

In this image, with a sun angle of 11 degrees, the shadows of objects projected onto horizontal surfaces are 5 times longer than the height of the objects. In AS16-0849, the sun angle was only 2 degrees, and the lengths of shadows are 29 times longer than the objects casting them. This is the primary reason for the noticeable differences in appearance of features in the two photographs.

Information On Downloadable JPEG Image:

The full JPEG, llnd1412.jpg,  from which the inserts below were taken can be downloaded here.

The Big Z

(825,485) The "Z" shaped regions of Frame 849 are much less-pronounced here, but the largest of them can be seen clearly. The views of this object from both photographs are shown below:

Angular ridge, Frame 1412  Same ridges, Frame 0849

The "Bridges" (again)

(424,385) and (460,366) In the insert below, the "bridges" from Frame 849 can still be seen extending over the scarp and ending at points on either side of a crater on the upper left. Due to the higher sun angle and some foreshortening caused by a slightly different viewing angle, the scarp does not appear as wide as it does in Frame 849 and the bridges, especially the one on the upper-right, are not as easily visible.While the higher sun angle in Frame 1412 exposes  part of the floor of the scarp, it can bee seen that the sections of the scarp floor at which the two ridges cross are still in shadow.

"Bridges," Frame 1412 Frame 849

The "Star"

(550,555) The "star". This feature appears much more symmetrical than it actually is due to foreshortening caused by the viewing angle. However, it is still rather interesting. It apparently consists of two roughly-parallel ridges separated by a very black depression that is obviously not a crater. The oddest thing about it is that one of the "Z" shaped ridges on the surrounding plain crosses right over the black opening from the right,makes a slight jog at a node near the center of the black area, and then exits over the ridge on the left. The inserts below show how it looks in both Frames 1412 and 849.

"Star," Frame 1412  Same feature, Frame 849

AS16-1412 Photograph Support Data

Spacecraft Altitude = 115km

Principal Point in Photograph = 6.0 degrees South, 7.2 degrees West.

Sun Elevation at Principal Point = 13 degrees

Angle between the camera's line of sight and the local surface normal at Lalande = 60 degrees (estimated from the elliptical appearance of the craters, which would be circular when viewed looking straight down.)