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In his work, The Republic (X.616E–617B), the Greek philosopher Plato provided the oldest known statement defining the order of the planets in Greek astronomical tradition. His list, in order of the nearest to the most distant from the Earth, was as follows: the Moon, Sun, Venus, Mercury, Mars, Jupiter, Saturn, and the fixed stars
Unfortunately, practical difficulties in crater counting [7] and uncertainties in estimating the flux still create huge uncertainties in the ages derived from these methods. Martian meteorites have provided datable samples that are consistent with ages calculated thus far, [ 8 ] but the locations on Mars from where the meteorites came ...
The maximum angular separation of the Earth and Moon varies considerably according to the relative distance between the Earth and Mars: it is about 25′ when Earth is closest to Mars (near inferior conjunction) but only about 3.5′ when the Earth is farthest from Mars (near superior conjunction). For comparison, the apparent diameter of the ...
Mars is a rocky planet, like Earth, that formed around the same time, yet with only half the diameter of Earth, and a thin atmosphere; it has a cold and desert-like surface. [ 10 ] One way the surface of Mars has been categorized, is by thirty " quadrangles ", with each quadrangle named for a prominent physiographic feature within that quadrangle.
This was a radical discovery because, according to Aristotelian cosmology, all heavenly bodies revolve around the Earth and a planet with moons obviously contradicted that popular belief. [20] While contradicting Aristotelian belief, it supported Copernican cosmology which stated that Earth is a planet like all others.
The magnetic field of Mars is the magnetic field generated from Mars's interior. Today, Mars does not have a global magnetic field. However, Mars did power an early dynamo that produced a strong magnetic field 4 billion years ago, comparable to Earth's present surface field. After the early dynamo ceased, a weak late dynamo was reactivated (or ...
The northern part is an enormous topographic depression. About one-third of the surface (mostly in the northern hemisphere) lies 3–6 km lower in elevation than the southern two-thirds. This is a first-order relief feature on par with the elevation difference between Earth's continents and ocean basins. [12]
A large ocean in the northern hemisphere would explain why there is a southern limit to valley networks; the southernmost regions of Mars, farthest from the water reservoir, would get little rainfall and would develop no valleys. In a similar fashion the lack of rainfall would explain why Martian valleys become shallower from north to south. [22]