What is an analemma, and what do the analemmas of Earth and Mars look like?
Essentially, an analemma is the pattern the sun makes in the sky if you plot its position at noon every day in the course of a year. If one had a sextant, a chronometer set to the time and date on the prime meridian, and an analemma chart, one could determine one’s position with fairly good accuracy. The shape of the analemma is influenced by the magnitude and phasing of two factors: axial inclination and orbital eccentricity. Earth’s analemma is a figure-eight, often shown on globes off the coast of South America. Mars’ analemma is shaped somewhat like an avocado (see figure). Would an Earth calendar work on Mars? What would be the problems of working with an Earth calendar? For two reasons, an Earth calendar will not work on Mars. First of all, a Martian sol is nearly forty minutes longer than an Earth day. This may not seem like much, but over the course of a month this difference accumulates to nearly an entire day. So if one tried to use an Earth calendar on Mars, the months that
