Is Extraterrestrial Life Possible in our Solar System?

Some have speculated it may have evolved on Io, Europa, Mars, etc. If these places can really support life, we should be looking for microbes and, perhaps, more complex life forms on earth that could be adapted and transplanted there. If there is anything like a “prime directive” for mankind, it is to insure that the life that has evolved on our planet survives. Transplanting it to other worlds, in whatever form they can support, is something we must do as soon as possible to insure that it does.

Solar Sails and Interstellar Colonization

The Japanese spacecraft Icarus has apparently spread its solar sail, and we will soon see whether the novel propulsion system, familiar in the realm of science fiction, will also work in practice. There’s no question about the fact that photons from the sun will exert pressure on the sail. The goal of the mission is to determine whether the resulting acceleration can be controlled for accurate navigation. The efficiency of thin film solar panels embedded in the sail will also be measured to determine their potential for powering an auxiliary ion engine that might be used on future flights for more precise navigational control. Such an engine powers the NASA Dawn asteroid exploration probe, which recently established a new speed change record of 9600 miles per hour and counting, using only 363 pounds of xenon propellant in the process.

Sail technology is not necessarily limited to the vicinity of the sun. The photons required for propulsion might also be supplied by ground based lasers or masers to enable sail-based interstellar travel. (Related links are here, here and here.)  Unfortunately, human travel using such systems is out of the question for the time being because of the inordinate amount of energy that would be needed to drive a manned spacecraft to the speeds required to cross interstellar distances within a human lifetime. However, it may be feasible to accelerate very small payloads of a few tens of grams to the speeds necessary to cross interstellar distances in times on the order of decades and decelerate them at their targets. Given continued advances in nanotechnology, useful scientific instruments of sufficiently small size might be developed to fit in such tiny craft.   More importantly, life in the form of spores or bacteria might be sent to seed promising planets. Given the very real possiblity that we will exterminate ourselves here on earth, and that survival trumps any other purpose or goal that we might reasonably set for ourselves, it seems to me that this should be one of our highest priorities.  We are related to every other life form on the planet, but are the only species capable of preserving that life indefinitely.  We should do so. 

Given the energy limitations noted above, it will probably be impractical to send spacecraft large enough to support a human crew over interstellar distances any time in the foreseeable future, barring some unforeseen advance in an enabling technology.  However, All the information necessary to assemble a human being is contained in the nucleus of every cell in our bodies.  It may prove more practical to send self-replicating nano-robots, programmed to eventually build the larger machines necessary to create dwellings, begin agriculture, etc., and finally build artificial wombs and “nannies” of human size.  At that point, eggs and sperm, which it would be much more practical to send over interstellar distances in a reasonable time, could be combined to form a human population.  Fanciful?  Certainly, but it sounds better, to me at least, than waiting around for our extinction, which is inveitable and will probably occur sooner rather than later if we are foolhardy enough to remain on one planet.

Stephen Hawking, Genetic Engineering, and the Future of Mankind

The Daily Galaxy has chosen Stephen Hawking’s contention that the human species has entered a new stage of evolution as the top story of 2009.  It was included in his Life in the Universe lecture, along with many other thought provoking observations about the human condition.  I don’t agree with his suggestion that we need to redefine the word “evolution” to include the collective knowledge we’ve accumulated since the invention of written language.  The old definition will do just fine, and conflating it with something different can only lead to confusion.  Still, if “top story” billing will get more people to read the lecture, I’m all in favor of it, because it’s well worth the effort.  Agree with him or not, Hawking has a keen eye for picking topics of cosmic importance.  By “cosmic importance,” I mean more likely to retain their relevance 100 years from now than, say, the latest wrinkles in the health care debate or the minutiae of Tiger Woods’ sex life.

Hawking begins with a salutary demolition of the Creationist argument that life could not have evolved because of the Second Law of Thermodynamics.  The fact that the use of this argument implies ignorance of the relevant theory has done little to deter religious obscurantists from using it, so the more scientists of Hawking’s stature point out its absurdity, the better. 

The lecture continues with some observations on the possible reasons we have not yet detected intelligent life outside our own planet.  These reasons are summarized as follows:

1. The probability of life appearing is very low
2. The probability of life is reasonable, but the probability of intelligence is low
3. The probability of evolving to our present state is reasonable, but then civilization destroys itself
4. There is other intelligent life in the galaxy, but it has not bothered to come here

My two cents worth:  I think the probability of life appearing is low, but the probability that it is limited to earth is also low.  It would be surprising if life only evolved on one planet, but managed to survive long enough on that one planet for intelligent beings like ourselves to evolve.  On the other hand, we may be the only intelligent life form in the universe.  If not, why haven’t we heard from or detected the others?  Let us hope that the proponents of the third possibility are overly pessimistic.

Later in the lecture, after noting the explosion of human knowledge over the last 300 years, Hawking observes:

This has meant that no one person can be the master of more than a small corner of human knowledge. People have to specialise, in narrower and narrower fields. This is likely to be a major limitation in the future. We certainly cannot continue, for long, with the exponential rate of growth of knowledge that we have had in the last three hundred years. An even greater limitation and danger for future generations, is that we still have the instincts, and in particular, the aggressive impulses, that we had in cave man days. Aggression, in the form of subjugating or killing other men, and taking their women and food, has had definite survival advantage, up to the present time. But now it could destroy the entire human race, and much of the rest of life on Earth. A nuclear war is still the most immediate danger, but there are others, such as the release of a genetically engineered virus. Or the green house effect becoming unstable.

I would differ with him on some of the details here.  For example, the bit about aggression oversimplifies the evolution of innate predispositions.  Back in the day when Konrad Lorenz published “On Aggression,” the behaviorists would have dismissed even a gentle soul like Hawking as a “fascist” for speaking of an “instinct” of aggression in such indelicate terms.  Nevertheless, when it comes to the basic premise of the sentence, Hawking gets it right.  We are not purely rational beings, nor is our behavior determined solely by culture and environment.  Rather, we act in response to predispositions that were hard-wired in our brains at a time when our manner of existence was vastly different than it is today.  They had survival value then.  They may doom us in the world of today unless we learn to understand and control them.

Hawking continues:

There is no time, to wait for Darwinian evolution, to make us more intelligent, and better natured. But we are now entering a new phase, of what might be called, self designed evolution, in which we will be able to change and improve our DNA. There is a project now on, to map the entire sequence of human DNA. It will cost a few billion dollars, but that is chicken feed, for a project of this importance. Once we have read the book of life, we will start writing in corrections. At first, these changes will be confined to the repair of genetic defects, like cystic fibrosis, and muscular dystrophy. These are controlled by single genes, and so are fairly easy to identify, and correct. Other qualities, such as intelligence, are probably controlled by a large number of genes. It will be much more difficult to find them, and work out the relations between them. Nevertheless, I am sure that during the next century, people will discover how to modify both intelligence, and instincts like aggression.

Laws will be passed against genetic engineering with humans. But some people won’t be able to resist the temptation, to improve human characteristics, such as size of memory, resistance to disease, and length of life. Once such super humans appear, there are going to be major political problems, with the unimproved humans, who won’t be able to compete. Presumably, they will die out, or become unimportant. Instead, there will be a race of self-designing beings, who are improving themselves at an ever-increasing rate.

Here, he is right on.  Unless we manage to destroy ourselves in the near future, or at least our highly developed technological societies, individuals will inevitably begin to take advantage of the potential of genetic engineering.  That is a good thing, to the extent that our survival is a good thing, because we are unlikely to survive unless we do develop into what Hawking calls “self-designing beings.”  We have certainly made a hash of things at our present level of development in a very short time.  We can’t go on long the way we are now. 

Continuing with Hawking:

If this race manages to redesign itself, to reduce or eliminate the risk of self-destruction, it will probably spread out, and colonise other planets and stars. However, long distance space travel, will be difficult for chemically based life forms, like DNA. The natural lifetime for such beings is short, compared to the travel time. According to the theory of relativity, nothing can travel faster than light. So the round trip to the nearest star would take at least 8 years, and to the centre of the galaxy, about a hundred thousand years. In science fiction, they overcome this difficulty, by space warps, or travel through extra dimensions. But I don’t think these will ever be possible, no matter how intelligent life becomes. In the theory of relativity, if one can travel faster than light, one can also travel back in time. This would lead to problems with people going back, and changing the past. One would also expect to have seen large numbers of tourists from the future, curious to look at our quaint, old-fashioned ways.

In fact, covering galactic and inter-galactic distances is not theoretically out of the question.  One may not be able to exceed the speed of light, but one can reduce the distances one has to travel via the Lorenz contraction.  Thus, if I could find some means to accelerate myself to nearly the speed of light, the apparent distance to, for example, the Andromeda galaxy would shrink until, finally, I could reach it in a time short compared to a human lifetime.  The only problem is, if I were able to turn around and come back the same way, the Milky Way would be about 3 million years older than when I left.  Accelerating objects the size of a human being to nearly the speed of light and ensuring their survival over large distances would not be easy.  However, accelerating the DNA required to create a human being, along with, say, self-replicating nano-machinery that could create an environment for and then use the DNA to bring a human being to life would be much easier, and, I think plausible.  It may be the way we eventually colonize distant star systems with suitable earth-like planets.  I am not on board with the alternative suggested by Hawking:

It might be possible to use genetic engineering, to make DNA based life survive indefinitely, or at least for a hundred thousand years. But an easier way, which is almost within our capabilities already, would be to send machines. These could be designed to last long enough for interstellar travel. When they arrived at a new star, they could land on a suitable planet, and mine material to produce more machines, which could be sent on to yet more stars. These machines would be a new form of life, based on mechanical and electronic components, rather than macromolecules. They could eventually replace DNA based life, just as DNA may have replaced an earlier form of life.

It puzzles me that someone as brilliant as Hawking could find such a vision of the future attractive.  Perhaps he has made the mistake of conflating our consciousness with ourselves, and thinks that “eternal life” is merely a matter of perpetuating consciousness in machines.  In fact, consciousness is just an evolved trait.  Like all our other evolved traits, it exists because it helped to promote our survival.  “We” are not our consciousness.  “We” are our genetic material.  That “we” has lived for many hundreds of millions of years, and is potentially immortal.  Consciousness is just a trait that comes and goes with each reproductive cycle.  If our consciousness fools us into believing that it is really the substantial and important thing about us, and its perpetuation is a good in itself, it may mean the emergence of a new race of machines.  Regardless of their consciousness, however, they won’t be “us.”  Rather, “we” will have finally succeeded in annihilating ourselves, and the future evolution of the universe will have become as pointless as far as we are concerned as if life had never evolved at all.


Extraterrestrial Life and Random Numbers

According to a paper cited here (found via Instapundit), extraterrestrial life must be rare in our galaxy. As far as the numbers the two Spanish authors came up with are concerned, I think this comment left by “dnivie” about nails it:

This seems like an excellent example of “If I’m allowed to pick any numbers I like, and multiply them with eachothers, I can arrive at any answer I want”

Be that as it may, life should exist elsewhere. After all, it seems unlikely that all life would eventually evolve into intelligent life. It took about 3.5 billion years of relatively benign conditions, or at least benign enough not to wipe out all life, for us to evolve. That’s more likely to be the exception than the rule. On the other hand, intelligent life must be extremely rare, if not unique. I’m not so sure about the probes mentioned in the paper, but it seems if it were otherwise we should have detected some electromagnetic signal in all the years we’ve been listening. Then again, maybe Carl Sagan’s conjecture was right. Maybe intelligent life forms do tend to self-destruct shortly after they evolve intelligence.