New answers tagged mars
2
Regarding the question that is in the title ("Why are the hemispheres so different?"), this sharp contrast between the Northern and Southern hemispheres is known as the Martian dichotomy.
The elevation on Mars follows a bimodal distribution. That is most of the land is either 4 km under the mean altitude or 1.5 km above the mean altitude.
But not ...
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Go outside.
Pick a star, any star and watch it for a while. It moves. As the Earth spins all the stars move across the sky, taking 23hr 56 min to move all around the sky to the same place. This is due to the rotation of the Earth (less than 24 hours due to the orbit of the Earth). We sometimes say the "celestial sphere" appears to rotate around ...
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You are right. If Mars orbited in exactly the same plane as the Earth, instead of an S or a loop, we would see Mars moving prograde relative for the stars along the ecliptic, then slowing and stopping, moving retrograde for a few months, as Earth overtakes it, still on the ecliptic, then moving prograde again.
But Mars doesn't orbit in the same plane, so it ...
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