MarsDial

[1] The MarsDial can function as a gnomon, the stick or other vertical part of a sundial.

[2][3] The length and direction of the shadow cast by the stick allows observers to calculate the time of day.

[2] The sundial design team[4] included Bill Nye "The Science Guy," space artist Jon Lomberg, and astronomers Woodruff Sullivan, Steve Squyres, James Bell and Tyler Nordgren.

[3] There is a mirrored section on the middle circle to reflect the sky.

[3] The sundials are also "message artifacts"—something for future human explorers to find.

An image of MarsDial
MarsDial on Spirit rover on Mars
Time-lapse video of an analemma from Mars, plotting the course of the Sun over a Martian year (about two Earth years)