The Moon is likely to become the industrial hub of the Solar System, supplying the rocket fuels for its ships,
easily obtainable from the lunar rocks in the form of liquid oxygen. The reason lies in its gravity. Because the
Moon has only an eightieth of the Earth’s mass, it requires 97 percent less energy to travel the quarter of a
million miles from the Moon to Earth-orbit than the 200 mile-journey from Earth’s surface into orbit!
This may sound fantastic, but it is easily calculated. To escape from the Earth in a rocket, one must travel
at seven miles per second. The comparable speed from the Moon is only 1.5 miles per second. Because the
gravity on the Moon’s surface is only a sixth of Earth’s (remember how easily the Apollo astronauts bounded
along), it takes much less energy to accelerate to that 1.5 miles per second than it does on Earth.
Moon-dwellers will be able to fly in space at only three percent of the cost of similar journeys by their
terrestrial cousins.
Arthur C.Clark once suggested a revolutionary idea passes through three phases:
1. ‘It’s impossible – don’t waste my time.’
2. ‘It’s possible, but not worth doing.’
3. ‘I said it was a god idea all along.’
The idea of colonizing Mars – a world 160 times more distant than the Moon – will move decisively from
the second phase to the third, when a significant number of people are living permanently in space. Mars
has an extraordinary fascination for would –by voyagers. America, Russia and Europe are filled with
enthusiasts – many of them serious and senior scientists – who dream of sending people to it. Their aim is
understandable. It is the one world in the Solar System that is most like the Earth. It is a world of red
sandy deserts( hence its name – the Red Planet), cloudless skies, savage sandstorms, chasms wider than
the Grand Canyon and at least one mountain more than twice as tall as Everest. It seems ideal for settlement.