Archive for July, 2014
A few weeks ago I finished reading David Waltham’s book, Lucky Planet, and I’d like to comment on it in this blog post. This is not in the nature of a book review, although I do recommend the book if you’re into the question of life on other worlds. (It was published by Basic Books in 2014). Dr. Waltham’s main point is that our Earth has had a phenomenal run of luck during its 4-billion-plus lifespan, and that has allowed life not only to arise about two billion years ago, but to flourish and result in the development of us humans. He notes that the conditions on Earth have been remarkably constant for the past two billion years in spite of asteroid impacts and mass extinctions, constant enough that although many life forms have gone extinct, at no time has life ever been totally extinguished, and other forms have been able to take the place of the extinct species. Temperatures have certainly fluctuated on Earth, but never has the temperature gone so high or so low that life was ever wiped out once it got started. It is an amazing set of circumstances. I never thought of it that way until I read his book. It is this stable climate that is at the heart of Dr. Waltham’s book.
Dr. Waltham goes into some detail about his theory that Earth has been extremely lucky over the past several billion years, and I won’t try to summarize the arguments. I’m not sure I followed all of them, anyway. He does state near the beginning of the book that if we take all the different facets of evolution that have led to the development and maintenance of life on this planet, such as being in the habitable zone, having a magnetic field that protects us from radiation, having an atmosphere, having a moon that stabilized Earth’s orbit, having large outer planets in our solar system that gobbled up stray asteroids to prevent them from bombarding us too often (but not so often that life wasn’t shaken up now and then), and so forth, and if we add all those up, the number of conditions would be so large that the presence of life on Earth would not only be unique in our galaxy, but perhaps in all galaxies. With the number of planets in our galaxy alone (in the range of hundreds of billions) that probably isn’t very likely. But it is possible that our planet has been just lucky enough to allow life to develop and thrive, perhaps lucky enough that there aren’t any other planets that have achieved the same result.
More recently, in the past few weeks, astronomers have begun to say that they are confident they will find life on another world within twenty years or so. Seems a little like braggadocio to me, considering how long we’ve been looking for life on other worlds and not found squat. I have no doubt that life will be found on another planet or moon sooner or later. But I’m only saying “life of any sort.” A few bacteria-like organisms would fulfill that prediction. I’m not talking about intelligent life capable of traveling the galaxy. Life is fabulously complex, and the emergence of intelligent species will take time. Lots of time, and that requires conditions on the birthing planet to be constant and mild for a very long time. How many other planets out there will fulfill those requirements?
One topic that comes up frequently in discussions of life on other planets is the question of how life got started on Earth in the first place. Did it develop here all by itself under the pressure of the energy present in sunlight, or was it dropped here by an asteroid or comet or passing piece of space rock that landed and seeded the infant Earth? No one has the answer to that question right now, and many years may pass before anyone can give a definitive answer. But simply raising that question puts us here on this little blue planet in a rather awkward position.
We Earthlings will eventually journey to other worlds. We’ve already been to the moon and no doubt left some of our germs there. That probably isn’t a terrible situation since none of our germs (bacteria, viruses, fungi and fungal spores, etc.) are likely to survive there for more than a short time. The moon is so inimical to life that a problem probably doesn’t exist. True, some bacterial and fungal spores may last for a long time, but unless they were seriously protected, the radiation from the sun likely killed everything soon after the Apollo astronauts left.
But eventually Earthlings will travel to other planets and moons, and the sterility problem may not be so straightforward. Some moons of the outer planets in our solar system are thought to possess large amounts of water, in some cases in the liquid form, which could potentially be the breeding grounds for microorganisms. In that case, an Earthling spacecraft landing there could potentially introduce Earth organisms. The spacecraft would have to be decontaminated, but I’m not so sure that total decontamination of a spacecraft, even unmanned and remotely operated spacecraft, could ever be achieved. How can you guarantee such a decontamination? How do you take a “decontaminated” spacecraft on a trip from Earth that far out into the solar system and guide it down to the surface without getting it contaminated? Decontamination would have to result not only in the killing of microorganisms, but in their total removal as well. The process of decontamination usually only kills microbial life, it doesn’t necessarily remove it. Foreign, if denatured, DNA and RNA could still be present on a spacecraft even if all the tests we usually do to check for it (viability, microscopic, PCR, etc.) come up negative. And seeding DNA in any form on a pristine planet is the most egregious form of Earthling arrogance I can think of.
Therefore, I propose that Earth-based spacecraft stay away from any moon or planet which could have water, such as Europa. Don’t seed the planet with a “decontaminated” spacecraft, however well-intentioned. One tiny microbe may be all it takes to “seed” a planet or moon. Let’s maintain the sterility of the system. Flyby missions which only take pictures and make scans are okay. The Moon and Mars are already contaminated, much to our chagrin, and should be allowed to remain the only two. We have walked on the moon, and we will walk on Mars, and may even walk on asteroids and other waterless, atmosphere-minus planets. Let’s leave it at that. I would hate to see Europa or Callisto or Titan or others pockmarked with Earth probes.