A Falcon 9 launches the Dragon spacecraft - which orbited and then reentered the atmosphere to splashdown in the Pacific in December 2010 (SpaceX/Chris Thompson)

We live in interesting times. Just as NASA's most recent budgetary rearrangements seemingly threaten the very core of solar system exploration, with cuts that might pull the agency out of its participation in exciting efforts with Europe on the ExoMars project, the private space industry appears to be on an accelerating course to more real flights, real missions, and real exploration.

Elon Musk, the driving force behind SpaceX, has expressed his clear intentions to not only get humans to Mars in the next 10-20 years, but to get lots of humans to Mars, perhaps 10,000, perhaps many more. Such hubris could seem a little silly coming from almost anybody else, but Musk is poised to turn the spaceflight business topsy-turvy, making the missteps of others appear positively comical. If SpaceX says it's going to Mars, it means it. Musk's stated long-term motivation is nothing less than to ensure the survival of the species, by making us a multi-planet race. Funnily enough I find myself agreeing with him on this point, but (as I'll describe below) also very nervous about what happens during the process.

The objection that people typically make to his kind of announcement is pretty hackneyed, and it goes along the lines of "we have enough problems here on Earth without spending money and resources to go to other planets, think of all the things we could solve here first." Well, yes, and no. This is part of a much bigger debate, but I think a couple of points are worth mentioning. First, it seems pretty clear at this stage in human history that no successful large society really solves its problems by forgoing activities that push technology, science, exploration and inquiry forward. There is simply far too much momentum and dynamic change in a large human collective to keep it in safe stasis. Like it or not, the problems of our overwhelming presence on this world (in numbers, thirst, and hunger) are very, very unlikely to be solved if we just divert all our resources to medicine, green energy, and good deeds. This is not to say that we shouldn't be chasing those things, but rather than senselessly trashing exploration and basic science to shore up resources we should try to stop waging wars and try to halt truly dysfunctional economic practices when we spot them (phew, there, I said it).

In the grand experiment of evolution we have a remarkable opportunity to put members of our kind on other worlds. Even if, like Mars, these places are far from comfortable, they are really only another extreme environment, and we've become very, very good at coping with those. It may be that going interplanetary is ultimately too challenging, but we won't really know until we try, and I think there is greater risk for the distant future of our species if we don't make the attempt.

Cute, but do we want these on Mars? (National Park Service)

But there is a catch with a gung-ho approach, and it's a basic one, with many precedents here on Earth. Take for example the case of the genus Rattus, the not-so-humble rat. Over the past few centuries the flourishing of European and Asian ocean travel and exploration has allowed stowaway rats (particularly the Black, Brown, and Norwegian varieties) to jump ashore on over 90% of the world's islands and island chains. The consequences have been devastating for seabird populations, rats are hungry little buggers, and eggs and chicks are a veritable a la carte menu for rodents. Other native species also suffer as rats gobble up fruits and seeds, disrupting the entire food chain. Some thirty percent (about 100 species) of seabirds are now considered to be at risk of global extinction, and the prime culprit is accidental rat contamination on previously isolated land masses. Exactly what this is going to do to the global environment over the long term is unknown, the physical isolation of these places is still a buffer, but for people living in some of these places it profoundly alters their otherwise sustainable economies and livelihoods.

Earth's recent history is littered with stories like this, and its deep past is undoubtedly also replete with 'contamination events' caused by either instinctively driven migration and exploration of species, or sheer random chance. There is however one critical difference when it comes to human-driven events, we may have selfish and intellectual reasons to want to intervene and prevent such things. A defining characteristic of our species is the ability to observe and learn. It has served us incredibly well in the ferocious and unforgiving torrent that is biological evolution, and we'll need it if we want to carry on across the solar system.

From a planetary contamination point of view one of the dirtiest things you can place in a pristine environment is an organism like a human, replete with our 100 trillion cells of microbiome each of us is a walking bio-hazard. We breathe out, we excrete chemicals and waste, our skin is constantly shedding. It would be next to impossible to keep ourselves isolated from the martian environment - especially if there were 10,000 of us there. Obviously we don't know how bad a thing this might actually be, Mars could be (and have forever been) utterly sterile, in which case we'd not precipitate normal ecological disaster. But we might still want to be very careful about what microbial populations we first unleash; although bacteria are smaller than rats, they're many times more potent.

Perhaps a more likely scenario is that Mars is no stranger to contaminants (an argument I made in an earlier post), nonetheless it will never have seen the kind of complex filth we would bring with us. Purely selfishly we would want to be extremely cautious about what we set in motion on a new world, and scientifically we would be foolish to be anything but careful, since Mars could hold keys to understanding our origins.

It has often been said that one of the motivations for finding life elsewhere in the universe is to increase our sample size - which is currently one. Extinct or extant organisms on Mars, whether related to us already or not, would offer a vital clue to the origins of life in this little corner of the cosmos. It would be truly awful irony if the first thing we did in transcending our planet-bound evolutionary path was to destroy the very evidence that would tell us where were came from in the first place.

So, SpaceX, what you're doing is wonderful and exciting, and potentially critical for our species, just please, please tread softly.

The future on Mars? (SpaceX)