Desperately Seeking Eden: The True Mission of the Starship Enterprise
by Athena Andreadis
Hooked on sure-fire recipes, Hollywood has always borrowed heavily from two sources -- the Bible, and Greek myths and plays. The latest Star Trek film outing, Star Trek IX: Insurrection, scheduled to be released on December 11, follows this hallowed tradition by essentially retelling the expulsion from Eden and the Abel/Cain rivalry. In futuristic terms, Insurrection braids together two themes: immortality and planetary colonization.
In Insurrection, two branches of the same sentient humanoid race have taken the high and low roads to both these endeavors. The Ba'ku, laid-back Southern California types who voluntarily renounced technology, live in an environment that is clearly meant to be Eden before the Fall (and which, as ever in Star Trek, looks like California). As a reward for not having bitten the Apple, the planet's rings conveniently emit "metaphasic radiation" that arrests aging and repairs any damage in the Ba'ku, forcing them into a static social configuration.
The Son'a have gone to the opposite extreme, resorting to regeneration and genetic engineering acrobatics that would turn plastic surgeons green with envy. Expelled from the Ba'ku planetary paradise because they were tempted by the serpent of technology, they have now returned to claim their share of the inheritance by extracting the life-giving radiation from the planet's rings -- making the planet uninhabitable in the process. Because the Ba'ku plan to resist passively (a notoriously ineffective ploy), Captain Picard and the crew of the Enterprise intervene to save the day. In doing so, they must rebel against Federation brass, who have allied themselves with the Son'a.
Star Trek often mangles its science (in one Star Trek: Voyager episode, for instance, a "crack" develops in a black hole's event horizon), but it does use science to pose some fundamental questions; in this case, the fragility and transience of life. Indeed, immortality and colonization of extraterrestrial planets are facets of the same problem: Can we humans flourish if we extend our life significantly, or if we live in a place that is not optimal for us?
Because of fundamental biological construction constraints, we probably cannot do much to lengthen our lifespan. But colonizing other planets is something we must eventually attempt to survive our sun's evolution, regardless of how well these New Worlds can accommodate us. I'll leave the means of bridging the enormous distances to extrasolar planets to physicists and engineers. What I will delve into is how likely we are to find surrogate Earths to harbor us, and how truly compatible such planets will prove to be.
Location, Location, Location!
Our Star Trek heroes live in a universe that is excessively endowed with Earth-like planets. Even when shuttles are forced to perform unscheduled emergency landings, they usually manage to crash on planets where neither breathing apparatuses nor protective clothing are necessary, and which often tempt the crew with hanging fruit. But how likely is the existence of the Ba'ku planetary paradise - or of all the other Xerox copies of Earth that have been paraded throughout the rest of Star Trek?
The nature of stars places restrictions on habitable planets. Stars that start their lives with less than half the mass of the sun may have a habitable zone so close to the star that the planet tidally locks, always presenting one face to its primary. The sun-facing hemisphere will be too hot, the other too cold. Stars more than twice the sun's mass probably exhaust their nuclear fuel too quickly to allow life to evolve on habitable planets. Planets in multiple star systems may end up with unstable orbits or orbits that result in extreme climate fluctuations, unless they circle one member of a widely separated double star.
Even with a decent primary star, the list of restrictions goes on and on. A planet at the inner edge of its star's habitable zone may end up with its water vaporized and a runaway greenhouse effect, like Venus. Conversely, a planet at the outer edge of the zone may end up in deep freeze with its water trapped in the crust, like Mars. Jupiter-sized outer planets are probably necessary to deflect comets, whose steady pummeling would prevent emerging life from taking hold. A large satellite may also be required to provide tidal zones, which act as midwives to evolving life. An atmosphere with the right pressure and composition is also a must.
So, contrary to Star Trek's explicit optimism, we're unlikely to ever find a twin Earth. If we find planets within another star's habitable zone, we will probably need to either terraform them extensively or genetically engineer the colonists so that they can survive without external aid -- for example, make them able to hibernate.
Either route is so expensive and ethically charged that artificial habitats might be better, though the sad tale of Biosphere 2 is cautionary: The first experiment to create a totally enclosed, self-sufficient environment ended up with oxygen leaks, ecological breakdown, and severe carbon dioxide poisoning -- plus virulent infighting among the participants. Fortunately, Biosphere 2 was set up on Earth, where the surroundings could easily come to the rescue.
The Devil's in the Details
But let's suppose that we do find an unspoiled second Earth. Even if it fulfills all the requirements of the long astrophysical/planetological list, details are also important.
For instance, one issue rarely discussed in science fiction is that all molecules involved in life display the property of chirality (Greek for "hand"). That is, they are fundamentally asymmetric. This happens because carbon, the basis for terrestrial life -- and the best candidate for life anywhere else -- can bond to four other atoms. If all four atoms are different, the resulting compound can adopt one of two mirror-image configurations. Life on Earth has exclusively chosen one of the two possible configurations -- the "left-handed" orientation -- and has stuck to it throughout its evolution.
If the biochemistry of New Earth is right-handed, we won't be able to digest any native foodstuffs, because our digestive apparatus will not be able to degrade them into useful units nor use them for energy. No matter how luscious the fruit appears, it will be strictly eye candy. The alternative will be to introduce terrestrial animals and plants, which may overwhelm indigenous life.
Other problems could doom would-be colonizers. Excessive storms, floods, quakes, or volcanic eruptions may disqualify an otherwise lovely planet. Gravity significantly lower than terrestrial will make our muscles atrophy and turn our hip and leg bones brittle. A day of different length will confound our biological rhythms. A primary star of a different color will do the same to our vision. Such dislocations would drastically decrease our ability to survive, because the compatibility of inner and outer cues intimately affects competence and health. And this is only a very partial list.
Contemporary Westerners tend to forget that even Earth presented humans with major survival challenges before the advent of antibiotics, sterile medical procedures, and clean water. Isolated pockets of humanity were lethal to one another before the development of vaccines -- witness the effect of European diseases on native Americans and Australians.
Moreover, the more Earth-like a planet is, the more likely it is to hold bacteria and viruses that will decimate us, because we'll act as novel hosts. Consider viruses for example. These parasites weaken their hosts, yet can't afford to kill them altogether. Most viruses initially lethal to humans are actually benign to their true hosts (for example, influenza to pigs and ducks). Though viruses are wizards at rapid change, they will be much harder on new hosts to which they haven't adapted -- as is evident from the recent emergence of the Ebola virus, whose symptoms are similar to those caused by radioactive fallout from a nuclear explosion.
Should We Bring Beads and Whiskey?
Even if we find an ideal planet, should we even try to colonize it, given the dismal record of human colonization on Earth? An Earth-like planet such as the Ba'ku adopted home world could evolve intelligent indigenous life. This is a controversial issue. Some prominent scientists believe that self-aware intelligence might be a "fluke" and hence very rare in the universe. They point out that humanity is the only species that became sentient on Earth, even though billions of other species have existed during the planet's 4.6 billion year history.
I think that is too pessimistic an assessment. The fact that humans stand alone does not preclude non-human sentience, on Earth or elsewhere. Once humans developed intelligence they cut off the possible evolution to sentience of any other terrestrial species, even of close humanoid cousins who were already making the transition to high intelligence. The dice of evolution never fall the same way twice -- fortune might have smiled on another branch of the tree of life, given enough time and a different path. If events had occurred just slightly differently on Earth, humans wouldn't have appeared. For example, the impact of the large meteor on the Yucatán Peninsula 65 million years ago, which wiped out the dinosaurs, gave mammals their big chance.
Though humans are unique in the cosmos, intelligence most likely is not. If a planet is Earth-like enough to tempt us to settle on it, I think it will be favorable enough to eventually grow its own version of intelligence. This raises a seroius ethical dilemma, although this issue has never stopped humans from devastating the homes of other humans.
Homesteading with Cellular Phones
Despite all the obstacles to planetary colonization, let's give Insurrection a very long rope, and assume that the deus ex machina of metaphasic radiation has repaired any ravages caused by incompatibilities between the Ba'ku and their planet. What would happen to a humanoid colony such as the Ba'ku left on an extrasolar planet without technology? Well, they would not be contemplating the metaphysics inherent in a hummingbird's flight. Even immortals need food and shelter. Living with primitive technology is obviously tenable if difficult, but only if the population is kept low to conserve resources. This requires either borderline starvation to render the women infertile or some form of infanticide, both practiced by low-tech terrestrial cultures. However, low population leads to inbreeding and lethal recessive traits surface.
Terrestrial examples of isolated settlements illustrate the dangers of inappropriate technology and population growth. The medieval Norse settlements on Greenland perished despite their advanced iron technology, and their exhumed skeletons were stunted because the people from malnutrition. The Polynesians of Pitcairn and Easter Islands stripped their lush islands of vegetation (including the trees needed to make canoes and catamarans), resorted to cannibalism, and became extinct within a few hundred years of their arrival.
The flip side of this coin is that isolated human colonies may be the springboard for continued speciation of our species, which our increased homogenization has negated. The differentiation of humans into truly separate branches will force us to face our hard-wired fear of anyone who is almost like us, but not quite. The last true such encounter was roughly 40,000 years ago, between the Neanderthals and the Cro-Magnon, though it has been replayed in countless first contact situations between cultures ever since (not to mention the exchanges between the sexes). This xenophobia served us well when we emerged from the African savanna, but now it has become counterproductive. It will be interesting to find out if our brains have expanded on that subject -- for true contact with extraterrestrials would require much greater flexibility.
At some point, humans will have no choice but to expand beyond Earth. Even if we take infinite care of our finite resources, the sun will eventually enter the red giant phase - and it will have vaporized our oceans long before then. It is easy to say that we should colonize reverently like the Ba'ku, not be pillagers like the Son'a. However, ethics fade when survival is at stake and past human behavior is not reassuring on this point. We, unlike the Enterprise crew, will be faced with hard problems and probably even harder solutions.
If we have to alter extrasolar Earth-like planets but have some leeway as to when and how, perhaps our best and most adventurous gambit is to send not humans, but other terrestrial flora and fauna. It is possible that these will generate their own intelligent offshoots and, since their original life code is identical to ours, they may give us true companions in the billions of years left to the universe -- and, with luck and care, to us.
This article first appeared in Astronomy in January 1999, with the title "Good Planets are Hard to Find." It may be not be used for profit, must be reproduced with no changes, editing, or additions whatsoever, and must be accompanied by the following copyright notice: Copyright © 1999 by Athena Andreadis. All rights reserved
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