INTERPRETING SHADOWS

Discussion about how to interpret shadows in satellite images. Includes earth images, 3D computer models, and images of shadows on Mars. [Long page with many images.]

RINGS

Ring shadows on Mars are used to determine the overall shape of the trees. Includes comparisons to ring nebulae and trees on Earth that cast ring shadows. [Long page with many charts and analysis.]

DIRECT IMAGE

This NASA MOC image, M20-01664, recorded at the maximum camera resolution, offers 5X greater resolution. The sun inclination angle is also higher than normal, so the dune casts no shadow. [Short page with several images.]

SIX MONTHS

Images of northern polar dunes taken over a span of six months. The spots on these dunes are all similar in size and line up with the sun. [A dozen images with short descriptions.]

MONITORING

Do the spots grow as the season warms? One dune was imaged four times over a six week period by NASA, and this page looks at those images in detail. [Short page with several images.]

3D MODEL AND VIDEO

A model of dunes and the calculated tree shape are rendered for an entire Martian day. The shadows cast by the model are compared to actual satellite images. [YouTube video uploaded in 2006. It is 9:52 long (too long) and needs to be improved]

SPOTS ON MARS

Analysis of the spots at the northern polar dunes. Investigates five aspects of shadows.  [Long page with many charts and technical details.]

SPACING

Often the spots appear to be spaced at regular intervals with the spacing interval dependent on spot size. A reason for this regularity is proposed. [Short page with several images and one chart.]