MadSci Network: Earth Science |
What would the Earth be like, physically and biologically, if it had one or two small moons instead of one large one? A very interesting question. Physically, the appearance of the Earth would probably not be much different. The greatest difference would be in the ocean tides. Since the moon or moons would have less mass than our actual Moon, there would be a smaller range between the elevations of high and low tides (assuming that the moon or moons are at a distance from the Earth similar to the real Moon). The orbital distance of the moons would also be a factor in the strength of their gravitational attraction, which causes tidal forces. The timing of the tides would also be different, and much more complex, if there were two moons. Tidal forces act in the Earth's crust as well as in the oceans. Some have suggested that these tidal forces may have a role in triggering earthquakes and other phenomena. The effects of Earth tides on geologic processes are not well understood, but their overall influence is probably minor in comparison to tectonic forces. The difference in tidal range would probably have an influence on the sedimentary rock record as well. Biologically, the effects would be much greater. Tidal ecosystems would be drastically affected. Any animals whose mating behavior is linked to the lunar cycle (such as the human menstrual cycle) would be affected. There would probably be some effect on the behavior of nocturnal creatures in general. Exactly what the differences would be is difficult to guess, but it would likely alter the course of evolution of many species. In addition, it is possible that the Moon may have intercepted or gravitationally deflected some small percentage of asteroids and comets that otherwise would have hit the Earth. Having a moon of lower mass might result in a slightly greater number of impacts on the Earth over the course of geologic time. Since these impacts are suspected as causes of mass extinctions, a change in their frequency and timing could have had a drastic influence on the evolution of all life on Earth. There really is no precise answer to your question, since the results of an alternative evolutionary path are impossible to predict. It might be fun to speculate, however. Good luck. ---- Sean Sherlock