‘Science fiction is now science fact.’ So said Doug McCuisition, director of the Mars Exploration Program at NASA Headquarters, on the day that the latest Mars rover, Curiosity, set off on its journey to the red planet. "We're flying to Mars. We'll get it on the ground... and see what we find."
Both Viking 1 and Viking 2, which landed on the surface of Mars in August and September 1976, carried life detection instrument packages. The Pyrotic Release Experiment incubated fragments of Martian soil in a simulated atmosphere with simulated before testing to see if organic material had become active. The Gas Exchange Experiment similarly tested for organics. The Labelled Release Experiment was a repeat of something like the Miller-Urey experiment in that it added the key ingredients for life to a soil sample and then monitored for any gases emitted. Additionally, the Gas Chromatograph Mass Spectrometer tested for organic residues in the soil.
What did they show? The results for the Pyrotic Release and Gas Exchange Experiments suggested that non-biological processes only were operating. Meanwhile the Labelled Release Experiment produced ambiguous results. The most significant result arguably came from the GCMS – it found chloromethane and dichloromethane, compounds interpreted at the time as contaminants from Earth, but otherwise fewer organic compounds than Apollo identified in the lunar regolith. Overall, there seemed no real evidence for carbon-based life on Mars.
In 2008, these results began to look less damning. NASA’s Phoenix lander discovered perchlorate in the Martian arctic, and an re-run of the Viking experiments with soil form the Chilean desert found that when perchlorate was added to the mix, chloromethane and dichloromethane appeared again. ‘Our results suggest that not only organics, but also perchlorate, may have been present in the soil at both Viking landing sites,’ according to Rafael Navarro-González, who led the re-analysis of the Viking processes.
In other words, we might have been looking for the wrong thing and in the wrong way. The Viking landers, incredible instruments in their time, were just not able to undertake the analyses that were necessary.
Curiosity is a mobile laboratory. Its ten scientific instruments will explore the Gale Crater (shown here) to establish whether there was microbial life in early Martian history. Specifically, it will examine those layers of the crater that belong to epochs when there was surface water on the planet. We know from orbital missions and from the evidence of the Opportunity and Spirit rovers that there was water on the planet once. There may even be now, in small seasonal flows.
What Curiosity will not be able to do is detect present-day life. This may seem odd, but the consensus of all the data at the moment is that there is none. In fact, there are a few reasons for thinking that life could not have developed far on Mars. The planet has a thin atmosphere, low temperatures, violent dust storms and no stabilising satellite like our Moon, Phobos and Deimos being too small to do the job. If there is life on Mars, it is likely to be deep underground where there is still liquid water. Curiosity is carrying a small drill.
So, to refine a little what I said before, Curiosity is an eye looking at Martian history. The evidence it is likely to find will take the form of signatures, if you like, the markers that life was once there.
This will hardly prove right the wilder fancies of science fiction. But we should be wary before dismissing all that has been dreamt onto the surface of the red planet.
Let’s take as an example Mars’ pair of moons. Phobos and Deimos were discovered by the American astronomer Asaph Hall in 1877, but they had been well known in fiction for centuries before that. Jonathan Swift speaks of a pair of Martian moons in Gulliver's Travels (1727) and Voltaire's Micromégas (1750) also refers in passing to the same two moons. The logic might have been that, since the Earth had one moon and Jupiter was known at the time to have four, Mars must have had an intermediate number, i.e. two. Alternatively, they might have drawn their inspiration from Johannes Kepler, who speculated that there were two Martian satellites in 1610.
Whatever its origin, Phobos and Deimos are a strange example of fiction preceding fact. Now all three – Kepler, Swift and Voltaire – are remembered for their prophecies upon the surfaces of the planets. The Kepler Dorsum on Phobos is a long ridge. The only named features on Deimos are the Craters Swift and Voltaire.
Mars has long been the resting place of human hopes and, in greater number, fears. It has acted as a screen onto which we have shone images of what we might be. Utopias jostle with dystopic glimpses of devastation. This is Philip K Dick in Survey Team:
Beyond the ruined city stretched out... fields of twisted installations, towers and pipes and machinery. ...A whole race had burrowed in and dug in trying to stay alive. The Martians had sucked Mars dry and then fled.
For good or ill, we have always wanted Martians. To tell our future. To meet unmediated, pure nature. To find out where we came from. To be assured that we are not alone. So the bravest, probably, of all the visions for the red planet is that there is nothing. This is what Kim Stanley Robinson writes of in his empty Mars:
There were not, and never had been, any canal builders, no lamppost creatures with heat-beam eyes, no angels and no devils, ...not a funhouse mirror image of any kind.
Which fiction will prove to be right? Curiosity will answer the questions of today. It will also pose the next set, because Mars will not go away. It is lodged inside us, hopes and fears both.