Mars, a cosmic stepping stone

Reviewed by Tom Kennedy on 24 Feb 2009

Whoever steps out onto the surface of Mars is likely to be greeeted and shown around by Kevin Nolan. Kevin, lecturer in physics at Tallaght Institute of Technology probably knows more about Mars than most of know about Earth, and it is remarkable just how much we now know about the red planet.

For a number of years, Mars has been the target for mission after mission, all of which Kevin describes in some detail. Mars has been capturing the imagination since the "discovery" of what were thought to be canals, and in many ways that dream about life being out there persists. Mars has turned out to have a much harsher environment than the likes of H G Wells could have written into fiction, but even so, the odds are in favour of life being found there. In fact, given the conditions under which life first appeared on Earth, it would be downright peculiar not to find the same sort of pattern elsewhere.

The possibility of extra-terrestrial life is a strong motivator, but as Kevin explains, the main reason behind all these missions is that Mars is seen as our stepping stone into space. Once completely out of reach, we can now begin to seriously contemplate the idea of establishing some sort of base on Mars. It is a long way to go, and it could be a one-way journey, but as we know from our earlier exploration of the Earth, curiousity made us set sail for golden wonders beyond the edge of the world. Not many sailors returned from those trips.

We could continue to send robotic missions to Mars, and the data they have transmitted back is of amazingly high quality, but there comes a point when we would like to step into the picture. Apart from any other issues, could the cost of going there be too high? Humans, with their gravity bound, oxygen burning bodies, were never designed for space, so, unlike a set of sensors and micro-circuits, space travellers would need a lot of very expensive support. As Kevin points out, a fleet of robots could be sent for the cost of just one manned mission. "There is no right and wrong answer to this debate," he writes, but at the same time, he argues strongly, and convincingly, in favour of the hands-on approach. "We would not dream of sending robots to explore the remote Amazonian rainforests or the Antarctic."

The scenery, as we can see from the pictures, is spectacular, and in a way, what we see is a damaged world. Unlike Earth, which still has a hot core, Mars has no internal dynamo, and lacking a protective magnetic field, is open to intense bombardment of radiation from space. As a result, the atmosphere has been stripped down to a bare minimum, as rarified on the surface as Earth's is at 30km elevation.

The landscape gives us some idea of what Earth must have been like billions of years ago, and as such we can learn a lot about our own history. Features that would have been long since been obliterated on Earth have survived intact on Mars. One of the most prominent of these features is the giant Hellas crater, 2,000 km across and nine km deep. Such an impact, writes Kevin, would have "reset" the entire planetary surface. "Imagine, for example, a worldlet, several hundred km in diameter, colliding with the Earth at 30,000 km per hour." Everything on the surface would have been wiped out, the oceans would have vaporised. "Incredidibly, Earth suffered such a fate at least several times in its earliest history." Without Mars to look at, we might find it hard to imagine that Earth has such a violent past.