Mars: A Century of Exploration

Mars: The Specs

When comparing Mars with Earth, we first notice that it is about half the diameter of our home planet. Here are several of the physical parameters for Mars and Earth.
If we are interested in visiting Mars and returning, then the numbers presented here that are of primary concern are surface gravity, orbital period and rotational period. The force of gravity at the surface of Mars is about 40% of that at the surface of the Earth. This means that it will take much less energy to launch astronauts from the surface of Mars than from the surface of Earth. We have already mentioned that the orbital periods of Earth and Mars imply that the two planets are "close together" only every two years. Finally, an interesting coincidence is that the rotational periods of Earth and Mars differ by only about 3%, meaning that a Martian day is about 42 minutes longer than an Earth day.
The average surface air pressure on Mars is only about 0.6% of the average surface pressure on Earth. The average surface temperature on Mars is about equal to the coldest temperatures ever recorded on the surface of the Erath. Also, the molecular composition of the Martian atmosphere is quite different from that on Earth. These three properties imply that astronauts on mars will need heated, pressurized suits with onboard oxygen supplies.


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