TCS Daily

The Mars Bug

By Glenn Harlan Reynolds - May 15, 2002 12:00 AM

Imagine that you've got a lot of money. No, more than that. A lot of money. Now imagine that you want to go to Mars. Oh, you already do? Me too. Then imagine that with your money you've built a spaceship -- perhaps along the lines of Bob Zubrin's Mars Direct mission architecture, though for our purposes the details don't matter. If you prefer, you may substitute antigravity or the Mannschenn Drive as your mechanism of choice.

Regardless of technology, you've got a craft that will take you to Mars and back, in one piece, along with sufficient supplies on the outbound leg and some samples when you come back. You're going to find out firsthand what Viking couldn't settle: whether there's life on Mars. You'll also do some research aimed at laying the groundwork for Martian colonization. Are you ready to go?

Not quite. You see, there might be life on Mars.

Well, duh. That's what you're going to find out, isn't it?

Yes. But if you find it's there, then what? You see, the 1967 Outer Space Treaty requires its signatories to conduct explorations of celestial bodies "so as to avoid their harmful contamination and also adverse changes in the environment of the Earth resulting from the introduction of extraterrestrial matter." When you got to Mars you may create the first, and if there's life on Mars, you may create the second -- assuming that you plan to return to Earth.

That human explorers will "contaminate" Mars is inevitable -- humans contain oceans of bacteria, and a human presence on Mars is sure to leave some behind. Even if all wastes are bagged and returned to Earth (unlikely because of the expense involved), some germs are bound to escape via air leaks, transport on surfaces of Mars suits and other objects that exit the spacecraft, etc.

NASA now takes extensive steps to sterilize unmanned spacecraft so as to keep Earth germs from reaching other planets, something known in the trade as "forward contamination." Such precautions may be adequate for robotic missions, but it is simply impossible to ensure that missions involving people won't result in contamination. They will.

Of course, the Treaty doesn't forbid "contamination." It prohibits harmful contamination. What does that mean? Well, if Mars is lifeless, harmful contamination can only be contamination that interferes with human purposes. To scientists at the moment, any contamination seems harmful, since it may make it harder for them to determine if Mars has native life when it might have come from Earth ("Hey, look, Mars has E. Coli! Er, or some space-probe-manufacturing guy on Earth has poor personal hygiene.") But once humans go to Mars, the framework is likely to change.

If Mars has life of its own (unlikely, but not impossible, especially in light of some intriguing new evidence) the situation gets harder. First, we may have to consider whether Martian bacteria or lichens or whatever may be harmed by whatever organisms humans bring. Then we have to decide whether we care about that. Is harm to bacteria the sort of harm the Outer Space Treaty was meant to prevent? Almost certainly not, but no doubt bacteria-rights advocates will do their best to get a debate fermenting here on Earth.

Martian bacteria raise another question: the question of "back contamination," as it's called -- contamination of the Earth by Martian organisms. That, too, will be difficult to rule out in the event of a manned mission. Oh, it's unlikely that bacteria that can survive in the Martian environment will flourish on Earth, and even less likely that they would prove harmful to Earth life. But unlikely isn't the same as impossible, and people are likely to worry. In fact, they already have worried about it in the context of robotic sample-return missions.

Mars colonization fans -- of whom I am certainly one -- need to ensure that the same questions have been addressed long before any humans set out for Mars. As we've learned in many other contexts, sometimes the environmental impact statement takes longer than the underlying project.

Of course, this may all be much ado about nothing -- as the National Research Council has noted, nontrivial quantities of Martian material have been deposited on Earth as meteorites, blasted loose from Mars by asteroidal impacts, and it is entirely possible that bacteria could have survived the journey. Smaller quantities (because of Earth's greater gravity) of Earth material have presumably gone to Mars in the same fashion. And in the early days of the Solar System, when life was new, the greater degree of celestial bombardment on both planets would have made such exchanges far more frequent. Which means that if we find life on Mars it may turn out simply to be Earth life that has beaten us there. Or perhaps it will be our ancestral Mars life welcoming us home.

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