The Red Planet
Named after the Roman God of war, Mars has sparked and sustained curiosity than any other planet in our solar system. Astronomers and Geologist have studied the surface of Mars dating back to 1965 when Mariner 4 swept by the planet. Photographs of the planet showed a barren surface scarred by numerous craters. It wasn?t until 1976 that scientist got their first glimpse of the Martian Landscape from its surface. As we take a closer look at Mars we may find many similarities as well as differences compared to our planet earth.
Mars may be considered one of the smallest terrestrial planets, but it has some of the largest volcanic and tectonic features in the solar system. The largest volcano on Mars and largest recorded in our solar system is Olympus Mons. Know to Geologist as a shield volcano, Olympus Mons is 15 miles above the surrounding planes and 16 miles above Martian topographic datum. The central caldera is roughly 55 miles across and the steep cliffs at the base of the volcano are 3.5 miles high. On a geological scale Olympus Mons bears the scars of very few meteorite impacts indicating that it is a young volcano. Geologists estimate the last eruption may have been as recent as 100 million years ago. Olympus Mons is almost wide enough to cover Spain and has enough congealed lava to make the island of Hawaii a hundred times over. The amount of lava and its rate of flow to create Olympus Mons may have been 10 to 100 times greater than any volcano on earth. Olympus Mons is located in the Tharsis Rise. The Tharsis Rise is the division between the highland and lowland, and has the greatest concentration of volcanoes on Mars. Although Olympus Mons is the showpiece of Mars?s volcanoes it is far from unique. The widest volcano on Mars is Alba Patera. The Alba Patera is roughly 1600 kilometers across and is the source of lava flows extending up to 1,000 miles from its center. Although it shows up on the photographs from Mars orbit, you would probably not notice Alba Patera at all if you were traveling over the surface of Mars: after walking for a quarter of an hour towards its summit you would be only 10 meters higher than when you started (Henbest 88). Three other large shield cones (Arsia Mons, Pavonis Mons, and Ascraeus Mons are all over 12 miles high and form part of the
volcanic chain near the center of the Tharsis Rise (Waters 117). The reason why the volcanoes on Mars are so large is because, Mars is a one-plate planet. The magma supplied by the hot spots allows the volcanoes to grow until the hot spot themselves disappears.
The Polar caps on Mars are covered with layered deposits of water ice, carbon dioxide frost, and dust. Carbon dioxide freezes to form a large white polar cap of dry ice. The dry ice evaporates as the temperature rises returning carbon dioxide to the atmosphere leaving a cap of water ice during the spring and summer. Deep valleys that spiral outward from the poles are formed when the layered deposits have eroded. As the ice caps grow and recede, the seasonal winds blow dust back and forth, layer upon layer of slightly different soils have piled up in the polar regions (Henbest 90). During the winter months the temperature on Mars can be so cold that the air freezes and during the summer months especially in the mid-latitudes, noontime temperatures reach 72 degrees Fahrenheit. As much as a third of the atmosphere may be frozen at the poles at times. Evaporation, condensation, and freezing of carbon dioxide and water vapor create changes in the sizes of the polar caps.
The surface of Mars can be compared to that of Earth. Fine grain soil has been blown by the wind into dunes, creating a landscape not very different from places in the Western Desert of Egypt. The rocks at two sites on Mars may be volcanic in origin and basalt-like in composition, and they may have been excavated by impacts (Watters 113). The primary component of the soil contains an iron-rich clay, similar to the clay produced by the weathering of basalt. This gives the soil its orange-red color. The surface of the planet can be divided into two main components: an ancient cratered highlands, covering most of the Southern Hemisphere, and low-lying plains that are mostly at high northern latitudes. The cratered highlands cover almost two thirds of the planet. They are mostly at elevations of 1-4 km above the datum, in contrast to the northern plains, which are mostly 1-2 km below the datum. The cause of the division between the highlands and plains is unclear but it may be the result of a very large impact at the end of accretion. The density of impact craters in the Martian highlands is comparable to the lunar highlands. The surface clearly dates back to the very earliest history of the planet when impact rates were high. The Martian highlands differ from the lunar highlands in three main ways: most of the Martian craters are highly degraded, the ejecta around craters 5-100 km in diameter is commonly arrayed in discrete lobes, each lobe being outlined by a low ridge, and in the Martian highlands are numerous branching valley networks that superficially resemble terrestrial river valleys. The highly degraded nature of many of the craters has been attributed to high erosion rates on early
Mars, possibly a result of warmer climatic conditions. The plains are located mostly in the Northern Hemisphere. The number of superimposed craters on them varies substantially, indicating that they continued to form throughout the history of the planet. The plains are diverse in origin. The most unambiguous in origin are those on which numerous flow fronts are visible. They are clearly formed from lava flows superimposed one on another, and are most common around the volcanic centers of Tharsis and Elysium. On other plains, such as Lunae Planum, flows are rare but wrinkle ridges like those on the Moon are common. These are also assumed to be volcanic. But the vast majority of the low-lying northern plains lack obvious volcanic features. Instead they are curiously textured and fractured. Many of their characteristics have been attributed to the action of ground ice, or to their location at the ends of large flood features, where lakes must have formed and sediments been deposited. In some areas, particularly around the North Pole, dune fields are visible. In yet other areas are features that have been attributed to the interaction of volcanism and ground-ice. Thus, the plains appear to be complex in origin, having variously formed by volcanism and different forms of sedimentation, and then subsequently been modified by tectonism and by wind, water and ice. One of the most puzzling aspects of Martian geology is the role that water has played in the evolution of the planet. Although liquid water is unstable at the surface under present conditions, we see abundant evidence of water erosion. Landforms on Mars seem to be created by flowing water. Geologists believe that some features such as the valley networks in the highlands may have been formed by rain when the atmosphere was denser and the climate was warmer. Massive flooding occurred, some having discharges one hundred times the annual outflow of the Mississippi river. The cause of the large floods is unclear, and they may not all be of the same origin. One possibility is that Mars has an extensive groundwater system and that in low areas the large floods are the result of extreme artesian pressures. Another possibility is catastrophic release of water dammed in lakes. Sediments within the large equatorial canyons suggest that the canyons at one time contained lakes, probably as a result of groundwater flow out from under the surrounding plateau. Catastrophic release of water from these lakes may have caused some of the large channels that connect with the canyons to the east. After the floods were over, large lakes must have been left at the ends of the channels, and several linear features at the ends of the channels have been interpreted as shorelines of former lakes. Water that once existed in liquid form now is believed to exist as permafrost in the northern lowlands, either permafrost or possibly groundwater in the heavily fractured and cratered highlands, and as ice at the poles.
Mars, like the planet Earth, has had a diverse geologic history. An ancient heavily cratered surface preserves evidence of events of the planet’s earliest history. Volcanic activity continued throughout the planet’s history, and resulted in the formation of extensive lava plains and large shield volcanoes. The evidence of the existence of water is evident throughout the formations of the great and powerful canyons and valleys. Despite its thin atmosphere and chill temperatures, Mars is the only planet in our solar system where people could live permanently. Hopefully during my lifetime independent Martian colonies will become viable, and ?intelligent Martians? will cease to be a myth and become a reality.