Seasons on Earth are caused not by the change in distance from the sun
(the orbit is very close to cirular) but by the tilt of the Earth's
axis. Remember that when it's winter here in the northern hemisphere,
it's summer in the southern hemisphere. So it's a question of which
parts of the Earth are more directly facing the Sun at which parts of
the year.
The Earth's axis is tilted 23.45 degrees from vertical. Mars is
very similar to earth in that it is tilted by 25.19 degrees. So the
seasons on Mars will be very similar to those on Earth. The difference
is that they are going to be about twice as long since Mars take about
2 years (687 days) to make one trip around the sun. So (just like on
Earth) the part of Mars experiencing winter gets less sunlight per area
than the part experiencing summer.
This is a good website that helps explain the seasons:
http://astrosun.tn.cornell.edu/courses/astro201/seasons.htm
-James (and mike)
(published on 10/22/2007)
