Many people make a distinction between the origin of life and the evolution of life. In this view, biological evolution refers to the gradual development of the diversity of living things from a common ancestor, while the ultimate origin of life is a separate question.
This is a legitimate point, but evolution is about much more than just biology. The evolutionary worldview is that all of physical existence, both living and non-living, arose through purely natural processes. With this broad definition of evolution, abiogenesis--the spontaneous appearance of life from non-living matter--is a necessity. If life did arise on earth by itself, it would be inconceivable that this is the only planet upon which there is life. Otherwise, the earth would be a remarkably special place, and that could easily lead to theistic ideas. Consequently, most evolutionists believe that life must exist elsewhere in the universe.
A Powerful Test
The creation worldview is very different, because, as usual, we start with very different assumptions. We believe that life exists on earth because God created life here, but He first had to fashion the earth to be a suitable habitation for life. The evolutionist must believe that life is inevitable wherever conditions are suitable for life, but creationists understand that even if conditions on another planet could sustain life, life there is not possible--unless God created life there or permitted life somehow to travel to that planet from earth.
While we cannot prove biblically that God did not create life elsewhere, the strong implication of Scripture is that He did not. These very different predictions of the special creation and evolution models mean that the search for life elsewhere amounts to a powerful test between the two theories of origin.
Looking for Life on Mars
In recent years, there has been much discussion in astronomy circles over the search for extraterrestrial life, so much so that a new term has been coined for this study: astrobiology. Since there is yet no evidence that life exists elsewhere, astrobiology is a science for which there is no data, or at least no data in support of the science.
Since there is no support for the contention that life exists elsewhere, much attention has been diverted to searching for planetary conditions favorable for life. Mars has been the focus of this attention for a very long time. Mars is about half the size of the earth, and it has at least a thin atmosphere. Water exists on Mars, though likely not in abundance, and what water it does possess is in vapor or solid form. The temperature and atmospheric pressure on Mars are far too low to sustain liquid water.
The Viking craft that landed on the surface of Mars in 1976 contained three very robust experiments to detect signs of life. Two of the experiments showed no evidence of living organisms; the third experiment had weak but ambiguous data. Even the most optimistic searchers for extraterrestrial life agree that these slightly positive indications probably were the result of inorganic chemical reactions in the soil. Besides the bitter cold and sparseness of water, there are other impediments to life on Mars today. For instance, the thin Martian atmosphere provides no protection to solar ultraviolet radiation, which is lethal to living things. With these problems, interest in life on Mars has waned, though some hope is still held and many think that life may have existed on Mars in the past.
A Martian Flood
In recent years, the Mars Express Orbiter detected methane in the Martian atmosphere. Methane is a gas frequently produced by living things, though it can also form inorganically. The gamma ray spectrometer aboard the Mars Odyssey Orbiter detected a significant amount of hydrogen in the top few feet of the surface of Mars, a likely indication of abundant ice. The famous rovers Spirit and Opportunity produced conclusive evidence that liquid water once existed on the Martian surface. This latter point is confirmation of what we have known for decades--photographs from orbiting spacecraft had shown numerous features that are best interpreted as there having been much liquid water on Mars in the past. This would require Mars to have once had a much more substantial atmosphere than now, an atmosphere that provided enough pressure and warmth to sustain liquid water.
This has exciting possibilities for creationists. First, secular scientists have concluded that Mars, a planet with no liquid water, once experienced a near global flood, all the while denying that such a thing could happen on earth, a planet with abundant water. Second, many creationists think that the earth's atmosphere underwent tremendous change at the time of the Flood. Obviously, at least one other planet did experience a catastrophic change in its atmosphere as well.
Liquid Water, the Gold Standard
Notice that water figures prominently in the study of astrobiology. As the universal solvent, water is absolutely essential for life, making up the majority of the mass of many organisms. And water is one of the most abundant molecules in the universe. While water has been directly detected throughout the universe (even in the outer layers of cool stars!), we have never found liquid water anywhere in the universe. Liquid water is the gold standard for living things, for it appears that life is not possible without it. However, while water is a necessary condition for life, it is far from a sufficient condition for life--much more is required.
A few years ago, a stir was caused by the announcement of the possibility of a small ocean of liquid water beneath the surface of Europa, one of the larger satellites of Jupiter. Much of the case for this water relies upon surface features of Europa--there are large fractured segments that resemble features of polar ice pack on earth that result from upwelling water freezing between fractures. In addition, if the water were salty, it would help explain Europa's magnetic field. Since then, a similar argument has been put forth for Ganymede, another large satellite of Jupiter, though that case is not nearly as strong. Additionally, water vents on Enceladus, a medium-sized satellite of Saturn, have implied liquid water beneath its surface.
Many scientists now view Europa's possible subsurface ocean as the most likely place in the solar system to find life outside the earth. This ocean, if it exists, is very dark and likely is very cold. A few decades ago, living organisms in such a place would have been unthinkable. However, we have found organisms living in very hostile environments, such as hydrothermal vents deep in the earth's ocean. Furthermore, subsurface lakes exist far beneath the Antarctic ice sheet. The largest and most famous of these is Lake Vostok, 2.5 miles beneath the ice. While we don't know if life exists in these lakes, many scientists want to find out. They reason that if life could exist in the cold and dark of these terrestrial lakes, why could life not exist inside Europa?
Conclusion
For a long time, evolutionists thought that life on earth first evolved in warm, very hospitable pools and then colonized more difficult environments. Now many evolutionists think that life began at the margins, in very hostile locations, and then migrated the other direction to better locations.
Much of the motivation for this complete reversal in thinking stems from the need to find life elsewhere. As creationists, we ought to welcome the search for extraterrestrial life. We are confident that the experiments will continue to produce null results that verify our theory of origin while disproving the evolutionary theory of origin.
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