Distance, Mars to Sun (max.) 249.22X 106 kilometers 154.86X 106 miles
Distance, Mars to Sun (min.) 206.66X 106 kilometers 128.41 X 106 miles
Distance, Mars to Sun (average) 228X 106 kilometers 142X 106 miles
Martian orbit, major axis 455.88X 106 kilometers 283.27X 10® miles
Martian orbit, eccentricity 0.0933
Orbital speed (max.) 26.4 kilometers (16.4 miles) per second
Orbital speed (min.) 22.0 kilometers (13.6 miles) per second
Orbital speed (average) 24.1 kilometers (15.0 miles) per second
Orbital period (sidereal) 686.980 (Earth) days
Orbital period (synodic from Earth) 779.935 (Earth) days
Inclination of orbit to ecliptic 1.85 degrees
Inclination of equator to orbital plane 25 degrees
Earth-Mars opposition distance (max.) 101 X 106 kilometers 63 X 106 miles
Earth-Mars opposition distance (min.) 56X 106 kilometers 35X 106 miles
During the local spring and summer in the southern hemisphere, when Mars is near perihelion, this hemisphere receives much more heat than does the northern hemisphere during the same local seasons. In spite of its shorter duration, the summer is hotter than in the northern hemisphere. As a result the south polar cap of Mars frequently disappears during the local summer, but the north polar cap has never been known to do so. Because Mars is in the vicinty of aphelion during the southern autumn and winter, the winter is colder, as well as longer, than in the northern hemisphere. The foregoing conclusions concerning the Martian seasons can thus be summarized in the following manner.
Northern Hemisphere Winter shorter and warmer Summer longer and cooler
Southern Hemisphere Winter longer and colder Summer shorter and hotter
The lengths of the periods of daylight and darkness of Mars during the various seasons vary in much the same way as they do on Earth. This is the case because the angle of inclination of the Martian axis is not very different from that of Earth's axis. The temperatures on Mars, however, may be expected to respond more closely to the hours of sunshine because there are no bodies of water and the atmosphere is very tenuous. Consequently, maximum and minimum temperatures should be attained soon after the local summer and winter solstices, respectively.
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