I listened to a series of Naked Scientists podcasts recently, on the various competing plans to launch a human mission to Mars. One episode stood out in particular, asking whether this was something that we need to spend money actually doing. They assembled a panel of various experts and authorities to debate the issue, and while they all raised interesting points, they also all seemed to miss the bigger implications. The two main reasons brought up in the debate were scientific research and the “lifeboat” principle.
The science argument in favour of sending humans on the next mission to Mars states that while rovers, orbiters and other robotic laboratories do incredible work, they have their limits. Apart from being built to meet specific mission objectives, and designed to fit within a budget, they also travel so far that real-time control by humans back on Earth is impossible. Radio waves travel at the speed of light, but space is so vast that the signals that would only take a few seconds to arrive on the Moon can take minutes or even hours for a one-way trip to planets like Mars or Saturn. The movements and activities of a robotic explorer must be planned in advance and compiled into a list of instructions which get sent out. The mission crew then wait for their signal to reach its destination, for the instructions to be carried out, and for confirmation and results to make the same trip back. It’s slow and frustrating, and if something unexpected happens (Perhaps they see an interesting rock formation in the corner of a camera’s view), they cannot simply turn the camera for a better look. They have to rework all the plans, create a new mission profile, and start the process over.
A human explorer, by contrast, would simply turn his or her head, decide whether there was actually anything worth investigating, then walk over and take a quick look before getting back to work.
The counter argument was that it is hugely, vastly more difficult and expensive to send a human to other worlds. Robots are made from metal and plastic and can be powered down for the bulk of their journey. Humans are soft and vulnerable and need feeding, heating, thick radiation shields and enough space to wander around and stay sane for the year-long journey. And of course, they need enough extra fuel and supplies to make a return trip because, unlike robots, we have to bring them home after they complete their mission.
However, the science arguments are too narrowly focused. They assume that science is the only reason for sending explorers on a mission to Mars. So the other main topic in the debate was the Lifeboat justification. The idea is that we need to build colonies on other planets as a matter of preserving our own species. Life is too precious to keep on only one planet. It is dangerous to keep all our eggs in one basket.
And the counter-argument? We should NOT have a lifeboat because then we will stop looking after this world, knowing that we can always just move on when things get bad. Which is the most small-minded crap I’ve ever heard. Presumably the person making this argument feels that the Titanic could have been saved, if only the builders had chosen to not install any lifeboats so that the crew would keep their minds on preserving the one ship that they had! They seemed to think that continuing degradation of the Earth environment, through pollution, human encroachment into animal habitats, overfishing of the seas, and climate change, represents the worst threat to humanity.
Why we need that mission to Mars
First up, conservation issues ARE important. Climate change is already having marked negative impacts, and those who will suffer the most are the poor, living in un-industrialised countries – the very people who likely would not have access to the Martian lifeboat. Aside from any emotional need we have to protect the heritage of our planet, there are strong pragmatic reasons for keeping our air breathable, our night skies dark, our water clean and our ecosystems diverse. But even if it all goes wrong, many humans will survive. So no, our impact on the environment is not why we need a lifeboat.
We need to spread to other worlds because Nature has some very nasty tricks up her sleeves. Every few hundred million years, a big asteroid hits the Earth. The heat dumped into our climate, the global fires started from rains of molten rock, the nuclear winter from dust and ash thrown high into the atmosphere; all are devastating. We call these “Extinction Events” because so many living things die, that entire species simply vanish from the face of the Earth (One such event wiped out 70% of all species on land and 95% of all species in the ocean). And it’s not just asteroids; supervolcanic eruptions, radiation from exploding supernovae in our stellar neighbourhood, and even significant climate changes can wipe us out quite thoroughly. If humanity is to survive, and if you think it is a good thing that our children and grandchildren will survive to have kids of their own, then you have to agree that we need to diversify our living arrangements!
So why Mars? Simply because it’s the least inhospitable place in the Solar System, after Earth. Make no mistake, it is no picnic. You can’t go outside without a pressure suit, and you can’t fill your pressurised home with the local air because it has no oxygen. Although we’ve found water, you can’t drink it because it’s spectacularly salty and poisonous. You can’t grow food because there is no soil – only sterile regolith. You can’t live off the land because there are no living things to eat, or turn into shelter or tools. But it’s still the best choice – Mercury has no atmosphere at all and is thoroughly baked and irradiated by the Sun. Venus has a surface atmospheric pressure as high as in our deepest oceans, weather hot enough to melt lead and sulphuric acid for rain. Jupiter, Saturn, Uranus and Neptune don’t even have surfaces – they’re just tens of thousands of kilometers of increasingly dense gas. And Pluto is so far and distant, there is no practical way to get there. So if the worst happens to Earth, we will need to have already girded our loins and built homes on Mars.
Because if we don’t, there’s no question that we will die out. It’s only a matter of When.