Mars looks quite hospitable in the photos, but all is not quite as it seems. Our Earth based intuitions lead us astray, and the planet is full of surprises. Though great to explore, it might not be so ideal as a second home.

Mars looks Earth like

You might think from the photos, that Mars looks like a reasonable enough place to live in. It looks pretty much like a desert landscape here on Earth, and you can imagine that if you set up lots of greenhouses, and use the resources of the desert itself to make new greenhouses, you could hope eventually to colonize the entire desert. 

Robert Zubrin says that there are no contamination issues involved in colonizing Mars, because microbes get transferred between the planets all the time on meteorites. His ideas get a lot of publicity, and so did a paper earlier this year "The overprotection of Mars". However there is another possibility, that life on Mars might be interestingly different from Earth life.

Mars is a fascinating planet, the most like Earth of all the planets in the solar system, and may help us to understand much about the origins of life on Earth. Undoubtedly, it's a wonderful place to explore, especially with augmented reality vision. But though it was quite Earth-like in its first few hundred million years, it is not at all Earth like now. Earth remains by far the most habitable place in our solar system. The most inhospitable places on Earth, such as Antarctica, even in the depths of winter, and at the centre of the continent, are far more habitable than anywhere else in our solar system. Space colonies and the poles of the Moon, are both more easily habitable than Mars, and more easy to make self sufficient. Why is that? Read on to find out more.

It would be great to study Mars "on location". You could do as much in a day or two, as our rovers could do in years. But there's a conundrum to face. Humans are host to hundreds of trillions of micro-organisms, and we can't be sterilized like a rover; we would die. Can humans explore Mars without introducing Earth life?

What makes Mars so special?

Mars is the planet in our solar system most similar to Earth. It probably had oceans early on, like Earth. Sadly we know almost nothing about the very beginnings of life on Earth.

For the first time, astronomers have measured the true colour of a planet in orbit around another star, and it is cobalt blue. This blue however, is probably the colour of a continuous rain of liquid glass, on a hot and windy planet. If you could make continuous observations of the overall colour of an exoplanet for half of its year, you could build up images of its surface. In the case of an Earth like exoplanet, you could map its continents, ice caps, cloud cover and any vegetation by the remarkable technique of Spin Orbit Tomography.

This new planet is HD 189733b. At 63 light years away, it's one of the closest planets discovered by the transit method. It's orbit is almost edge on, so that regularly it passes directly between its parent star and ourselves.