Mars: Location and Orbit

Facts in Brief

Aphelion	2.49 x 10⁸ km
Perihelion	2.07 x 10⁸ km
Minimum Distance from Earth	5.57 x 10⁷ km
Rotational Period	24.6 Hours (1.03 Days)
Orbital Period	1.88 Years* (687 Days) * The approximation of 365.256 days per year is used.
Orbital Inclination	1.85^o
Eccentricity	0.0934
Axial Tilt	25^o 12"

Relative Location

Mars is the first superior planet, one whose orbit encompasses Earth's. The difference between its aphelion (when it is farthest from the Sun) and perihelion (when it is closest to the Sun) is 4.20 x 10⁷ km, an eccentricity of nearly one percent. The planet averages an orbital radius of 2.28 x 10⁸ km and takes 1.88 years, or 687 days, to make one complete revolution. A Martian day is about 24.6 hours.
Mars's two moons, Deimos and Phobos, were named after the god's fierce dogs.

Seeing Mars from Earth

Mars is between 5.57 x 10^7 km and 3.99 x 10^8 km from the Earth at any given time. This proximity allows an amateur astronomer to spot the planet without the aid of binoculars or telescope. The planet appears a fiery red star making an annual trek acoss Earth's sky. Also known as the Red Planet, Mars will appear to move backwards for the short period when it nears Earth. This back-tracking was always a spoke in the wheel of the geocentric solar system--never effectively accounted for, it was often ignored. A telescope will aid the observer in witnessing the seasonal color changes on Mars. Percival Lowell suggested that the greenish colors during the warmer months were actually Martian crops planted by the planet's inhabitants. His theory of a Martian civilization, however, has been shattered by more recent interplanetary missions and more sophisticated telescopes. Now scientists attribute the colors to an optical illusion.

Copyright © 2000 by Gary Chan and Matthew McDermott. All rights reserved.