Mars: from God of War to habitable planet: Bob McDonald

That bright reddish dot in the sky to the south these nights is the planet Mars, as it nears its closest approach to Earth on May 30.

What you see is a planet we've studied, observed, fantasised andpuzzled over for centuries, with more myths and misunderstandings than any other world.

The last time Mars was this close(75,279,709 kilometres) and this bright in the sky was in 2005.

Mars is farther away from the sun thanEarth, so its year is roughly twice as long as ours, and even though our two planets do come close every time the Earth catches up to it, like a runner on an inside lane of a track.The orbits are elliptical, so some approaches are closer than others.

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This one is a particularly good chance for telescopes, such as the Hubble Space Telescope, to get better images of the Red Planet.

But before there were telescopes and robot cars driving around on the surface of Mars, that red dot generated fear and wonder, prompting the ancient Romans to name it the god of war for its blood-red colour.

Ancient astronomers noticed that during these times of extra brightness, the planet mysteriously "backs up" in a looping fashion as it wanders among the stars, a phenomenon now called retrograde motion, caused by the fact that the Earth is overtaking it in space.

After Galileo introduced the telescope to astronomy, skywatchers could see white areas at its north and south pole ice caps,just like Earth's. Dark markings on its surface moved and changed with the seasons, which some thought were signs of large seas or vegetation.

As telescopes improved, thin lines appeared to crisscross the planet, which at first were assumed to be channels, which are natural, butlater interpreted by American astronomer Percival Lowell as canals, which are artificial.

The idea of planet-wide canals on Mars suggests a civilization of remarkable Martian engineerscapable of building structures that make our Panama and Suez Canals look like mere cracks in a sidewalk. And if they can build enormous canals, could they also build spaceships?

Were Martians also looking through their telescopes at our beautiful blue planet, covered in so much water? Would they come here to try to take it?

Of course, this was great fodder for science fiction writers, who imagined marauding fleets of flying saucers wreaking havoc on Earth, culminating in H.G.Wells' famous tale,War of the Worlds, which was adapted into a radio drama and played on Halloween night in 1938. The play, directed by and starringOrson Welles, was so realistic thatmany people truly believed the Martians had landed.

No canals, unfortunately

By the 1960s, robot spacecraft began visiting Mars, which turned out to be a lot less exciting than its fictional image. No canals, no civilization, no Martians. Too bad, really.

Instead, Mars turned out to be a cold, dry, desert world. Even experiments aboard the Viking landers in 1976, whichwere designed to look for life, could not confirm the existence of even microscopic organisms in the soil. That doesn't necessarily mean Mars is a barren worldor never had life.We just haven't found it yet.

Today, a fleet of robots from many different countries orbits Mars, while two rovers drive around on the surface. These machines have revealed the history of the planet, showing that there was a time, about three billion years ago, when it was warm and wet,with rivers, lakes and possibly an ocean, whichwould have made it a second blue planet, instead of red.That was also a time when life was emerging on Earth. Did it appear there as well?

No fossils yet

So far, no fossils have been found on Mars, but we'll keep looking.

Our fascination with the Red Planet has seen it change from a god to the only other planet we can visit. It is the most Earthlike, with mountains, valleys, vast sand dunes and ice caps. All the other planets in our solar system are either too hot or too hostile for humans. Mars is the only one we have a chance to put bootprints on, which, if Elon Musk has his way, will happen soon.

So when you look up at that red dot in the night sky this week, think of it as a world that has grown in our imaginations from a terrifying placeto a planet that some future generations may one day call home.

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