Is the orbit around the sun so elliptical that the entire planet experiences winter at the same time?
Spirit, with an odometer reading of over 3.5 kilometers (2.2 miles), has already traveled six times its designed capacity.
Well, I guess that answers the question about following summer to the other side of the equator! ;O)
Money well spent!
Of the nine planets, the orbit of Mars has the third highest eccentricity (0.093) after Mercury (0.250) and Pluto (0.206) so it probably does play a part in temperature variations at the planet's surface; however, the equator of Mars is inclined 24.0 degrees to the plane of its orbit: I'm guessing that causes greater temperature variations, particularly at higher Martian latitudes.