Mars (2035 words) Essay Example For Students

Mars (2035 words) Essay MarsMars is the fourth planet from the sun and orbits the sun at a distance of about141 million mi. Mars is named for the Roman god of war because it appears fieryred in the earths night sky. Mars is a small planet that has about half thediameter of Earth and about one-tenth Earths mass. The force of gravity onthe surface of Mars is about one-third of that on Earth. Mars has twice thediameter and twice the surface gravity of Earths moon. The surface area ofMars 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 abouta half an hour longer than an Earth day. Its year, or the time it takes torevolve once around the sun, is about two Earth years long. Mars has two moons,Phobos and Deimos. THE INTERIOR OF MARS Scientists believe that Marssinterior consists of a crust, mantle, and core like Earths interior, but theydo not know the relative sizes of these components. Because no spacecraft hasever brought instruments that can study Marss interior to the planet, theonly real data that scientists have about the planets structure are its mass,size, and the structure of the gravity field. Compared to Earth, Mars probablyhas a relatively thick crust. Beneath the surface is an area of volcanicactivity in the northern hemisphere, it may be as thick as 80 mi. Beneath thelanding site of the United States spacecraft Viking 2, it may be as thin as 9mi. 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, thecore may be quite large. Mars does not have a significant magnetic field, soscientists believe that Marss core is probably solid. Mars does not, andprobably did not ever, have active plate tectonics. Because Mars is so muchsmaller than Earth, it must cooled quickly after formation and the crustthickened, forming one solid piece and eliminating any possibility of platetectonics as it was on and still is on Earth. Though the Martian crust is notbroken into separate plates, Marss liquid mantle has sculpted the planetssurface. The molten rock has broken through the crust to form volcanoes and itsmotion has cracked the crust to form large rifts. THE SURFACE OF MARS Thesurface of Mars would be a harsh place for humans, but it is more like thesurface of Earth than any other planet. The temperature on Mars does not getmuch cooler than the temperature at Antarctica. At the surface it ranges fromabout -140? C to 15? C (about -225? F to 60? F). During most of the yearwind speeds are normally low around 4.5 mph, but during dust storms they canapproach 40 to 50 mph. These winds often originate in large basins in thesouthern hemisphere and carry large volumes of dust from the basins to otherregions, sometimes covering the entire planet in the storm. The dust is notsandy, as in a sandstorm on the earth, but has the consistency of flour. Thenorthern and southern hemispheres of Mars have different characteristics. Thesouthern hemisphere has many impact craters and has a generally much higherelevation than the northern hemisphere. The southern highlands are probably theoldest ground on Mars. The northern hemisphere of Mars contains a much widervariety of geologic features, including large volcanoes, a great rift valley,and a variety of channels. The northern hemisphere also contains large expansesof relatively featureless plains. Mars has the largest volcano in the solarsystem, Olympus Mons. It is 16 mi high (almost twice as high as the earthsMount Everest) and covers an area comparable to the state of Arizona. Near it,three other volcanoes almost as large-Arsia Mons, Pavonis Mons, and AscraeusMons-form a line running from southwest to northeast. These four volcanoes arethe most noticeable features of a large bulge in the surface of Mars, calledTharsis. Another volcano, Alba Patera, is also part of the Tharsis bulge, but isquite different in appearance. It is probably less than 4 mi high, but has adiameter of 1000 mi. None of Marss volcanoes appear to be active. The Tharsisbulge has had a large effect on the appearance of the surface of Mars. TheTharsis bulge includes many smaller volcanoes and stress fractures, in additionto the large volcanoes. Its presence affects the weather on Mars and may havechanged the climate by changing the rotation of the planet. Valles Marineris(named for the U.S. Mariner spacecraft that discovered it) is the most notablestress feature associated with the Tharsis bulge. It is a great rift valleyextending from the Tharsis region away to the east-southeast. It is about thesame length as the distance from New York to California. This canyon systemreaches widths of 440 mi and depths of 4 mi. Three types of channels on Marswere probably formed by the action of water. These channels are unrelated to thecanals thought to be seen in early telescopic views of Mars. Channelnetworks are similar in appearance to streambeds on the earth and occur in thesouthern highlands. These channels may date from a time early in Marsshistory when the atmosphere was thicker and liquid water could flow on thesurface. Outflow channels, which giant floods may have formed, occur on theboundary between the southern highlands and the northern plains regions. AresVallis, where the Mars Pathfinder spacecraft landed, is one of these outflowchannels. Landslides and other erosion probably formed fretted channels byenlarging preexisting channels. The Mars Pathfinder s pacecraft found minerals inAres Vallis that are similar to minerals that form near water on Earth,supporting the theory that Mars had liquid water at some point in its history. Nutrition for Lean Muscle EssayGerman astronaut Thomas Reiter arrived at Mir aboard Soyuz-TM 22 in September1995. He returned to earth in February 1996, after 179 days in space, havingcompleted two space walks to install European instruments outside of thestation. Mir was over a decade old when its career was nearing an end. In 1997the station experienced a small fire, failure of the oxygen generation system, atemperature-control failure that made the living quarters uncomfortably warm,failures of Mirs main computer and navigation system, and a collision with asupply ship. None of the onboard cosmonauts and astronauts were hurt, but theincidents caused crew members and engineers to monitor the stations conditionmore closely. Just as scientific equipment from Salyut 7 was transferred to Mir,equipment from Mir will be transferred to Mirs planned follower ship, theInternational Space Station (ISS), at the end of Mirs career. Space shuttlemissions to Mir ended in mid-1998 and the first component of ISS was scheduledfor launch in late 1998. ISS was assembled in orbit from U.S., Russian,European, Japanese, and Canadian parts.