Space Colonization
Are We Alone ?
by Tania Rojas
Extraterrestrial life may not just be the stuff of science fiction. Based on scientific principles alone, the possibility of other worlds teeming with life is plausible.
The scientific search for extra-terrestrial life is known as astrobiology. It entails finding organisms and conditions similar to those that evolved on earth, and not little green men.
Scientists believe that life on earth began from primordial soup, a dense, chemically rich compound. The simple molecules in the primordial soup evolved into more complex structures such as amino acids and sugars. These combined to form structures that metabolize energy more efficiently, paving the way for cells, the fundamental units of life.
Cells were able to replicate with the advent of DNA the universal code of sugar bases that can direct the formation and regulation of organisms.
Between one billion and 600 million years ago, cells converged to form multi-cellular organisms, capable of higher functions. Beginning with the first ocean life forms, a variety of organisms with varying traits evolved in the earth's numerous environments. The remarkable result is that in all habitats, from scorching volcano vents to stark acidic pools, life has found a way to survive.
Planets throughout the universe are also host to seemingly inhospitable environments. Scientists have narrowed down the requirements for the possibility of life. In "Life in the Universe" authors Jeffrey Bennet, Seth Shostak, and Bruce Jakosky, illustrate the current consensus.
The most important factor is the presence of elements necessary to make cell components, This includes the elements oxygen, carbon, hydrogen, nitrogen, which makes up 96 percent of organic matter.
A second requirement is an energy source to fuel metabolism, such as chemical vents, internal heat, or, in our case, sunlight. The universe has a tendency to go toward disorder, known as the second law of thermodynamics. This measure is known as entropy and favors spontaneous processes. Cells need energy to fuel the non-spontaneous reactions that keep them alive, such as the bonding of molecules. Thus, in planets without an energy source, molecules will usually never bond, meaning that life cannot emerge.
Lastly, a third requirement for life to emerge is the presence of water. Liquid water plays an integral role in making molecules available for chemical reactions, transporting chemicals out of cells, and is a versatile medium for cell metabolism. Other liquid compounds could possibly fulfill this function too, but water is by far the most likely candidate.
Given these requirements, we can already find evidence of life-preceding conditions throughout our solar system. Currently, there are indications that water may lie beneath the surface of Mars, our moon, and Europa, one of Jupiter's moons.
Considering that there 2,500 stars within 50 light-years of earth, around 100 billion solar star systems in our galaxy, and about 100 billion galaxies in the universe, the possibility of life existing elsewhere is relatively substantial. We would have no way of knowing, however, what these organisms may look like, how they metabolize, and what level of intelligence they would exhibit.
Finding intelligent life seems impossible but, taking into account the mechanisms of evolution, their existence is also plausible. Organisms can evolve similar traits despite different genetic backgrounds by occupying similar habitats. In the animal kingdom at least eighty traits, from horned snouts to eyes, have evolved independently in different organisms. This suggests that there are prevalent adaptations favored by nature. If intelligence is such an example, the existence of other beings like us is possible.
In fact, the mathematician Sir Francis Drake postulated a formula to surmise the probability of contacting such extra-terrestrial life. This formula is known as the Drake Equation: Number of alien civilizations out there= Nhp x Flife x Fciv x Fnow.
Nhp is the number of hospitable planets. Flife is the fraction of hospitable planets that have life. Fciv is the fraction of these life forms that would be capable of communicating, implying the capacity for civilization. Fnow is the fraction these life-forms that would exist now.
If such intelligent life exists, perhaps thousands or even millions of years more advanced than humans, why is it that we have not yet heard from them? This is the gist of what is known as Fermi's paradox. Considering our exponential growth of technology, advanced extra-terrestrial civilizations should have developed interstellar transportation to travel throughout the universe and make their presence known. As of yet, however, we have found no evidence of extra-terrestrial life outside our solar system.
Fermi's paradox has three solutions: Either interstellar travel is too hard, or alien civilizations do not want to make themselves known, or we are really alone. Nevertheless, gazing at the night sky, it is hard to believe that life is rare.
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