Mars orbits close (enough) to the Sun
•Habitable Zone: Just outside Venus’s orbit to Mars
•Habitable Zone will expand as the Sun gets older and hotter
•Mars Orbital distance: 205 – 246 million km
–Closest to Earth: 53 million kilometers
–Farthest from Earth: ~400 million kilometers
•Inverse square law of gravitation: surprisingly, energy needed to get to Mars is almost the same as that to get to Moon
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Why Mars colonization first ?