The Case for Mars (23 page)

The point I’m making is simply this: If you abstract yourself from America’s contemporary comforts and look at human history, everywhere you will see people chosen essentially at random—whether as front line soldiers, refugees in hiding, prisoners, submariners, explorers, trappers, or pre-tntieth-century merchant seamen—all of whom had to, and by and large did, competently endure long-term conditions of isolation, privation, and psychological stress greatly exceeding what the select crew of a piloted Mars mission will face. Humans are tough. We have to be. We’re the survivors of the saber-tooth tigers and the glaciers, of
tyrannical empires and barbarian invasions, of horrible famines and devastating plagues. You name it, you’ve got ancestors that have faced it, and overcome it. The same can certainly be said of the hand-picked and highly trained crews of the first human missions to Mars.

The human psyche will not be the weak link in the chain on a piloted mission to Mars. On the contrary, it is likely to be the strongest.

DUST STORMS

The fourth dragon, the Martian Dust Storm, is actually the oldest, and so has lost a few of its teeth, especially since its primary potential beneficiaries, the Mars atmospheric scientists, lack the keen commercial instincts of other critics. However, it still scares some. Moreover, since this particular dragon is more of an exaggeration than an illusion, it’s worth our while to address it here.

The existence of powerful dust storms on Mars was suspected by telescopic observers from the nineteenth century on, and the robotic spacecraft exploration programs conducted by the United States and Soviet Union since the 1960s have provided ample data to confirm the hypothesis. Mars’ orbit is eccentric. During its southern hemisphere’s summer, it comes about 9 percent closer to the Sun than the year-round average, while during the southern winter, it is 9 percent farther from the Sun than average. This combination of expected summer season heating with the extra warmth generated by being closer to the Sun than usual causes the planet’s southern hemisphere to have extreme seasonal temperature variations (and the out-of-phase northern hemisphere to have very mild seasons). During the extra-cold southern winter, large amounts of carbon dioxide precipitate out of the atmosphere on the southern polar cap (which is made of dry ice) and adsorb into the Antarctic regolith. This extra layer of frozen and adsorbed carbon dioxide is then blasted back into the atmosphere when the strong heating of the early southern summer hits the south polar regions. This sudden addition of gas to the planet’s atmosphere is so large that it actually raises the planet’s atmospheric pressure by about 12 percent in the course of a few months (the full-year winter-summer pressure swing be
ing nearly twice that), in the process causing huge winds that pick up and transport a considerable amount of dust. These dust storms, therefore, originate in the early southern summer near the south pole, and then spread north, occasionally going so far as to engulf the entire planet. Wind speeds in these storms have been clocked between 50 and 100 km/hour. The storms, which recur occasionally throughout the southern summer, gradually die out with the approach of the southern autumn. As in the case of weather on Earth, there is some randomness in all this—in some years dust storm activity is almost nonexistent, while in others it dominates the entire planet for virtually the whole southern summer. However, in general, clear weather can be expected in the north during that hemisphere’s spring, summer, and fall.

That’s the story, and it sounds pretty formidable. Indeed, in November 1971 when the U.S.
Mariner 9
orbiter and the Soviet
Mars 2
and 3 lander probes reached Mars, a global dust storm was in progress. For four months the surface of the planet was entirely blocked out by dust and
Mariner 9
couldn’t see a thing. This didn’t hurt iner 9’s mission very much—it just waited in Mars orbit until things cleared up and then proceeded to image the entire planet without difficulty. However, in the case of the Soviet landers, the story was very different. They had been preprogrammed to target for landing sites near 45° south latitude, and that’s where they went—parachuting right into the heart of the maelstrom. Both were destroyed.

However, while parachuting into a Martian dust storm is a bad idea, the story is very different if you are already on the ground when the dust storm hits. The Martian atmosphere is only about 1 percent as thick as the Earth’s, and, therefore, the dynamic pressure created by a 100 km/hour Martian wind is only equal to that of a 10 km/hour (6 knot) breeze on Earth.
Viking
landers
1
and 2 operated six and four years respectively on the surface (their design life was 90 days), and both were subjected to many dust storms during their stay. Despite this, no damage to the
Vikings
or any of their instruments was detected. Furthermore, while the dust storm can block visibility of the surface from orbit, local visibility on the surface is not seriously impaired. The dust does reduce light levels, much as an overcast day does on Earth, but to an observer on the su
rface the surrounding area is not fogged out. If a surface installation were powered by solar panels, some problems could be expected from dust storms reducing light levels. However, since photovoltaic panels can convert light to electricity even after it has been scattered by dust (a clear optical view of the Sun is not necessary), power loss would not be total. Instead, during a typical bad dust storm, one might expect solar power electric output to fall by about 50 percent. Thus, provided that the power system is designed to insure sufficient power for minimal life-support functions for the duration of the dust storms, things should be okay. Of course, if either a nuclear reactor or a radioisotope generator provides base power supply, or if a large power reserve is available in the form of locally produced chemical propellants (which can be burned in a chemical combustion engine to turn a generator), this problem becomes moot.

Some people have voiced concern that dust deposited by storms could obscure solar panels or other optical surfaces, such as windows or instruments. This problem was not observed on
Viking.
Apparently, the total quantity of dust actually suspended by the storms is rather small. However, in the case of a human Mars mission, dust deposition certainly wouldn’t be much of a problem. If a solar panel becomes covered with dust the solution is simple; send someone outside with a broom!

So, to sum up, the only real hazard represented by dust storms is to objects that are dominated by aerodynamic forces (because they have a lot of “sail area” compared to their weight), such as balloons or parachute suspended landers. If a lander does not use a parachute for landing (high-altitude drogues are okay too), and the Mars Direct landers do not need to, it should be able to punch its way through a dust storm as easily as an airplane can fly through a cloud. Of course, most pilots would prefer to land under conditions of complete visibility, and this is why the Mars Direct plan has the spacecraft brake into orbit prior to landing. If the weather is bad at the landing site when the hab arrives, the crew can just wait on orbit like
Mariner
9
until the skies clear. Interestingly, however, for the decade 2001 to 2010, it is possible to choose Earth-to-Mars trajectories during every launch year that have the ships arrive at Mars during
the clear weather season.

Dust storms won’t keep us from Mars.

<3 height="1em">BACK CONTAMINATION

The last of the five dragons infesting the maps of would-be Mars explorers is not only illusory, but hallucinatory. This is the “Threat of Back Contamination.”

The story goes like this: No Earth organism has ever been exposed to Martian organisms, and therefore we would have no resistance to diseases caused by Martian pathogens. Until we can be assured that Mars is free of harmful diseases, we cannot risk infecting the crew with such a peril that could easily kill them, or if it didn’t, return to Earth with the crew to destroy not only the human race but the entire terrestrial biosphere.

The kindest thing that can be said about the above argument is that
it is just plain nuts.
In the first place, if there are or ever were organisms on or near the Martian surface, then the Earth has already been, and continues to be, exposed to them. The reason for this is that over the past billions of years, millions of tons of Martian surface material has been blasted off the surface of the Red Planet by meteor strikes, and a considerable amount of this material has traveled through space to land on Earth. We know this for a fact because scientists have collected nearly a hundred kilograms of a certain kind of meteorite called “SNC meteorites,”
¹⁶
and compared the isotopic ratios of
their e
lements to those measured on the Martian surface by the
Viking
landers. The combinations of these ratios (things like the ratio of nitrogen-15 to nitrogen-14), as well as the fact that the gas trapped in the rock matches the Martian atmosphere, represent an irrefutable fingerprint proving that these materials originated on Mars. Despite the fact that in general each SNC meteorite must wander through space for millions of years before arrival at Earth, it is the opinion of experts in the area that neither this extended period traveling through hard vacuum, nor the trauma associated with either the initial ejection from Mars or reentry at Earth would have been sufficient to sterilize these objects, if they had originally contained bacterial spores.
¹⁷
Furthermore, on the basis of the amount we have found, it has been estimated that
these Martian rocks continue to rain down upon the Earth at a rate of about 500 kilograms per year. So, if you’re scared of Martian germs, your best bet is to leave Earth fast, because when it comes to Martian biological warfare projectiles, this planet is smack in the middle of torpedo alley. But don’t panic—they’re not so dangerous. In fact to date the only known casualty of the Martian barrage is a dog who was killed by one of the falling rocks in Nakhla, Eygpt in 1911. Statistically the hazard presented to pedestrians by furniture being thrown out onto the street from upper story windows is a far greater threat.

The fact of the matter, however, is that life almost certainly does not exist on the Martian surface. There is no (and cannot be) liquid water there—the average surface temperature and atmospheric pressure will not allow it. Moreover, the planet is covered with oxidizing dust and bathed in ultraviolet radiation to boot. Both of these last two features—peroxides and ultraviolet light—are commonly used on Earth as methods of sterilization. No, if there is life on Mars now, it almost surely must be ensconced in exceptional environments, such as a heated hydrothermal reservoir underground.

But couldn’t such life, if somehow unearthed by astronauts, be harmful? Absolutely not. Why? Because disease organisms are specially keyed to their hosts. Like any other organism, they are specially adapted to life in a particul environment. In the case of human disease organisms, this environment is the interior of the human body or that of a closely related species, such as another mammal. For almost four billion years the pathogens that afflict humans today waged a continuous biological arms race with the defenses developed by our ancestors. An organism that has not evolved to breach our defenses and survive in the microcosmic free-fire zone that constitutes our interiors will have no chance of successfully attacking us. This is why humans do not catch Dutch elm disease, and trees do not catch colds. Now, any indigenous Martian host organism would be far more distantly related from humans than elm trees are. In fact, there is no evidence for the existence of, and every reason to believe the impossibility of, macroscopic Martian fauna and flora. In other words, without indigenous hosts, the existence of Martian pathogens is impossible, and if there were hosts, the huge differences between them and terrestrial species would make the idea of common diseases an absurdity. Equally absurd is the idea of independent Martian microbes coming to Earth and competing with terrestrial microorganisms in the open environment. Microorganisms are adapted to specific environments. The notion of Martian organisms outcompeting terrestrial species on their home ground (or terrestrial species overwhelming Martian microbes on Mars) is as silly as the idea that sharks transported to the plains of Africa would replace lions as the local ecosystem’s leading predator.

If I appear to be spending excessive time on beating this idea, it’s partly as a result of a recent NASA planning meeting for the upcoming (robotic) Mars sample return mission during which someone seriously proposed that, to allay alleged public concerns, any sample acquired on Mars be
sterilized
by intense heat before returning it to Earth. While an extremely unlikely find, the greatest possible treasure a Mars sample return mission could provide would be a sample of Martian life. Yet, certain of those attending the meeting would destroy it preemptively (and a great deal of valuable mineralogical information in the sample as well). The proposal was so grotesque that I countered by asking the assembled scientists,
“If you should find a viable dinosaur egg, would you cook it?”
The question is not entirely out of line; after all, dinosaurs are our comparatively close relatives and they did have diseases. In fact, every time you turn over a shovelful of dirt you are returning a sample of the Earth’s disease-infested past to menace the current biosphere. Nevertheless, paleontologists do not wear decontamination gear.

Just as the discovery of a viable dinosaur egg would represent a biological treasure trove but no menace, so a sample of live Martian organisms would be a find beyond price, but certainly constitute no threat. In fact, by examining Martian life, we would have a chance to differentiate between those features of life that are idiosyncratic to terrestrial life and those that are generic to life itself. We could thus learn something fundamental about the very nature of
life.
Such basic knowledge could provide the basis for astonishing advances in genetic engineering, agriculture, and medicine. No one will ever die of a Martian disease, but it might be that thousands o
f people are dying today of terrestrial ailments whose cure would be apparent if only we had a sample of Martian life in our hands.