This Viking 1 image is one of first images of a sunset as seen from the surface of Mars.
The image shows the Chryse Planitia region of Mars about 15 minutes before sunset on Aug. 21, 1976. The camera is pointed southwest and the Sun is at an elevation angle of 3 or 4 degrees above the horizon and about 50 degrees clockwise from the right edge of the frame.
The low Sun angle highlights topographic features.
- A depression is visible near the center of the picture, just above the lander's leg support structure, which was not evident in previous pictures taken at higher Sun angles.
- Just beyond the depression are large rocks about 1 foot (30 centimeters) across.
- The diffuse shadows are due to the sunlight that has been scattered by the dusty Martian atmosphere as a result of the long path length from the setting Sun.
- Toward the horizon, several bright patches of bare bedrock are revealed.