Mars Essays (2035 words) - Shield Volcanoes, Mars, Pavonis Mons

Mars Mars is the fourth planet from the sun and orbits the sun at a distance of about 141 million mi. Mars is named for the Roman god of war because it appears fiery red in the earth's night sky. Mars is a small planet that has about half the diameter of Earth and about one-tenth Earth's mass. The force of gravity on the surface of Mars is about one-third of that on Earth. Mars has twice the diameter and twice the surface gravity of Earth's moon. The surface area of Mars is almost exactly the same as the surface area of the dry land on Earth. The Martian day, or the time it takes Mars to rotate once on its axis, is about a half an hour longer than an Earth day. Its year, or the time it takes to revolve once around the sun, is about two Earth years long. Mars has two moons, Phobos and Deimos. THE INTERIOR OF MARS Scientists believe that Mars's interior consists of a crust, mantle, and core like Earth's interior, but they do not know the relative sizes of these components. Because no spacecraft has ever brought instruments that can study Mars's interior to the planet, the only real data that scientists have about the planet's structure are its mass, size, and the structure of the gravity field. Compared to Earth, Mars probably has a relatively thick crust. Beneath the surface is an area of volcanic activity in the northern hemisphere, it may be as thick as 80 mi. Beneath the landing site of the United States spacecraft Viking 2, it may be as thin as 9 mi. The core is probably consists of mostly iron, with a small amount of nickel. Other light elements, mainly sulfur, could exist in the core also. If so, the core may be quite large. Mars does not have a significant magnetic field, so scientists believe that Mars's core is probably solid. Mars does not, and probably did not ever, have active plate tectonics. Because Mars is so much smaller than Earth, it must cooled quickly after formation and the crust thickened, forming one solid piece and eliminating any possibility of plate tectonics as it was on and still is on Earth. Though the Martian crust is not broken into separate plates, Mars's liquid mantle has sculpted the planet's surface. The molten rock has broken through the crust to form volcanoes and its motion has cracked the crust to form large rifts. THE SURFACE OF MARS The surface of Mars would be a harsh place for humans, but it is more like the surface of Earth than any other planet. The temperature on Mars does not get much cooler than the temperature at Antarctica. At the surface it ranges from about -140? C to 15? C (about -225? F to 60? F). During most of the year wind speeds are normally low around 4.5 mph, but during dust storms they can approach 40 to 50 mph. These winds often originate in large basins in the southern hemisphere and carry large volumes of dust from the basins to other regions, sometimes covering the entire planet in the storm. The dust is not sandy, as in a sandstorm on the earth, but has the consistency of flour. The northern and southern hemispheres of Mars have different characteristics. The southern hemisphere has many impact craters and has a generally much higher elevation than the northern hemisphere. The southern highlands are probably the oldest ground on Mars. The northern hemisphere of Mars contains a much wider variety of geologic features, including large volcanoes, a great rift valley, and a variety of channels. The northern hemisphere also contains large expanses of relatively featureless plains. Mars has the largest volcano in the solar system, Olympus Mons. It is 16 mi high (almost twice as high as the earth's Mount Everest) and covers an area comparable to the state of Arizona. Near it, three other volcanoes almost as large-Arsia Mons, Pavonis Mons, and Ascraeus Mons-form a line running from southwest to northeast. These four volcanoes are the most noticeable features of a large bulge in the surface of Mars, called Tharsis. Another volcano, Alba Patera, is also part of the Tharsis bulge, but is quite different in appearance. It is probably less than 4 mi high, but has a diameter of 1000 mi. None of Mars's volcanoes appear to be active. The Tharsis bulge has had a large effect on the appearance of the surface of Mars. The Tharsis bulge