The first man (or woman) to land on Mars has probably been born already. It is the planet most suitable for humans to try to live on, but despite this is quite inhospitable and hard to reach. At its closest, it comes to within 36 million 3 hundred thousand miles from the Earth during its orbit of the Sun, and at that range it is reachable.
A visitor to Mars would find a small planet, 4,217 miles in diameter, with a pink sky. Two tiny moons, Phobos and Deimos (probably captured asteroids) orbit the planet. The surface temperature varies, but is cold. Like Earth, Mars has a seasonal tilt on its axis from vertical, 24 degrees in fact, so it has ‘seasons’ of a sort, but a warm summer’s day might be no warmer than freezing point. Minimum temperatures plummet to minus 80 Celsius or below. Massive dust storms rage across the Martian landscape from time to time and tornadoes 5 miles high have been detected.
The Martian atmosphere is very thin indeed, but contains mainly carbon dioxide (over 95%), with a little nitrogen and argon. Gravity is only 38% of Earth’s. There are signs that the planet has had an active past, with weathering of the landscape by liquid water. Frozen water and carbon dioxide seem now to form the polar ice caps which have been detected and traces of frozen water may lie beneath the surface of the red, dusty, surface. It seems that in the past Mars had a thicker atmosphere and was a warmer planet. With liquid water, some form of life might have begun.
There are also giant volcanoes. The biggest is Olympus Mons, 17 miles high and with a base 435 miles across. Its crater is 53 miles across! This volcano seems to be extinct, but there are smaller ones which are thought to be active still. Mars also has massive canyons. Valles Marineres can be traced for 3100 miles and is up to 370 miles wide in places. It is up to 4 1/2 miles deep.
Mars is the fourth planet from the Sun. Its mean distance from the Sun is 141,500,000 miles and it takes 687 days (1.88 years) to complete its orbit. Its distance from Earth varies, as both planets follow orbits which are elliptical not circular. When at its closest to Earth, Mars is the brightest object in the night sky after the Moon and Venus. Its redness, caused by iron oxide dust on the surface, is then very evident. It takes Mars 24 hours, 37 minutes and 22.6 seconds to rotate on its axis, so a Martian day is very close in length to an Earth day; handy for any visiting astronauts or future settlers!
