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Charles Black, Founder and CEO of Sen
Mar 31, 2011, 7:00 UTC

Sen—Earth's other neighbour is Mars. Today Mars is a cold dead planet, the heat from the planet's core having radiated into space a long time ago.

Our exploration through the robotic rovers that have landed on the Martian surface shows giant canyons carved into the surface and deposits of gypsum (calcium sulphate dihydrate i.e. 2 molecules of water) which suggest that in the past Mars was covered with flowing water and oceans. Today the water is gone, Mars is a dry dusty and frozen planet. Although Mars has ice at its poles the planet appears red and rocky. As humans we associate freezing cold with snow, so looking at the pictures of Mars's surface its interesting that it looks like a red hot desert whilst in fact its surface temperature is colder than Earth's south pole! The red colour of the surface is because of iron particles.

Mars is home to the biggest mountain discovered in the solar system, Olympus Mons. Reaching a height of 25 kilometres it is nearly 3 times taller than Mount Everest on Earth.

Mars is about half the diameter of Earth. Its surface area is therefore one quarter of that of Earth (surface area being diameter squared) and its volume being one eighth of Earth (volume being diameter cubed). These physical facts are relevant in understanding why Earth is full of life whilst Mars is now a frozen dead planet.

The Martian atmosphere
Mars has a very thin atmosphere today, but this is almost certainly a very different planet today than when it was formed. The pressure on the Martian surface is less than one per cent that of Earth. Initially Mars, like Earth, would have had a hot molten core. Heat from all celestial bodies has to escape and makes its way to the surface where it radiates as infared light into cold space. Earth kept its heat, Mars lost it. Given the universal application of physics, what was the difference? The answer is that the surface area of Mars is proportionately larger than its volume when compared to Earth. The result was that Mars (which, being smaller than Earth had less heat to start with) radiated its heat much faster than Earth. The loss of heat had a significant knock-on effect - as a consequence of losing its hot core electric currents could not flow and Mars lost its magnetic shield. Without its magnetic shield against the solar winds the Martian atmosphere was stripped away into space, the gravity of Mars not being strong enough to hold on to it against the on-coming solar hurricane.

In summary: Mars is smaller than Earth, lost its heat to space, lost its shield against the solar winds and the atmosphere was blown away.

Mars' moons
Mars' moons were discovered in 1877 by Asaph Hall. Hall named Mars' moons after the mythological sons of Ares, the Greek counterpart of the Roman god, Mars. Deimos is the brother of Phobos.

They are very small moons and not round in their shape: Phobos measures 27 by 22 by 18 kilometres, whilst Deimos measures 15 by 12 by 11 kilometers.

Phobos and Deimos are both heavily cratered rocks and may have been asteroids captured by Mars' gravitational pull.

Phobos orbits very close to Mars at a distance of only a few thousand kilometres. No known moon orbits closer to its planet. Phobos orbits Mars 3 times a day.

Phobos is gradually spiraling inward and is predicted to crash into Mars in 50 million years.

Deimos orbits slightly further out and takes 30 hours for each orbit.
Phobos is gradually spiraling inward and is predicted to crash into Mars in 50 million years.