Geophysics of Saturn's Moon Titan - Coursework Example

Saturns Moon Titan Titan, one of the largest moons in the solar system, has intrigued mankind as it was often thought to mirror earths composition and possibly have the ingredients necessary to support life. Shrouded in a dark and heavy atmosphere, the moon defied mans ability to survey the surface, which led to speculation of liquid methane oceans and frozen water ice. The knowledge we have of Titan has been an evolution of learning that began with earth based observations and theoretical explanations. However, all that would change with the launching of the Cassini spacecraft and the Huygens space probe. The Huygens probe has been able to penetrate the atmosphere of Titan, land, and survey the surface of Saturns most important moon. The highly successful Cassini/Huygens mission began sending data back to earth in the spring of 2005, and since that date man has documented volumes of data concerning this moon once a mystery to mankind. While Titan is uninhabitable by man, "Scientists believe that Titans environment may be similar to that of the Earths before life began putting oxygen into the atmosphere" (Hamilton). The image of a primordial earth has added to Titans mystique as the Cassini orbiter continues to map and reveal the surface and composition of Saturns moon, Titan. Understanding the geophysical characteristics of Titan begins with a picture of its chemical composition and the temperature range that it exists in. The atmosphere of Titan, the only moon in the solar system to have a dense atmosphere, is composed primarily of nitrogen and methane (Ocean May Exist). There are also trace amounts of organic chemicals in the atmosphere, though the conditions are far from ideal for the creation of life. The moon has a gravitational force of about 15 percent of earths and the temperature hovers around a cold minus 289 degrees Fahrenheit (Britt, "Smog on Saturns Moon"). In 2002, scientists studying Titan believed that, "High in the Titan sky, solar radiation helps fuel chemical reactions that break the nitrogen and methane down into other substances. Eventually, lower down, some of these molecules serve as seeds for clouds. Methane condenses on the seeds to form rain or hailstones that fall to the surface" (Britt, "Smog on Saturns Moon"). Indeed, three years later the Huygens probe would land during a methane rain as it broke through the atmosphere on Titan. These early and initial observations of Titan created more questions than they answered. What was the source of all the methane on the planet? In a solar system that is routinely impacted by objects from space, why was Titan surface relatively smooth, as if it had escaped the force of impacts? The Cassini mission and the Huygens probe would provide the data necessary to begin to answer these questions. Much of what we know about Titan came from a descent and landing on Titans surface of the Huygens probe, a part of the European Space Agencys Cassini program. There has been a keen interest in Titan since the early days of astronomy as scientists speculated on a world that "is extraordinarily like Earth, with rivers, rain, islands, seas and mountains, but is otherwise a totally alien world where geology and chemistry are turned on their heads" (Walker). Launched in 1997, the Huygens probe separated from the Cassini orbiter and entered Titans thick atmosphere in late 2004. Though it was not designed to be a lander, Huygens survived the descent and continued to relay data back to Earth for approximately 90 minutes. The first images sent back from Huygens were remarkable. According to Eddy, "Huygens landed at the shoreline of what appears to be large body of liquid when it ended a seven-year journey". Landing in a rain of methane, the Huygens probe landed in an area that was typical of Titans surface. "European Space Agency scientists said at a press conference in Paris that the consistency of the surface was like icy wet mud" (Walker). The Cassini orbiter is still active and continues to survey the moon as it makes passes near Titan on a regular basis. Photographs, and imaging data, taken by Cassini have revealed large flat and dark areas, which scientists believed to be methane oceans with shorelines. The initial images sent back from the Huygens probe revealed long channels and straight lines that appeared to be cut by flowing liquid, possibly liquid methane. "Some of them may have been produced by precipitation run-off, producing a dense network of narrow channels and features with sharp branching angles" (First Full Mosaics). However, these early photographs were being pieced together and suffered from an early lack of perspective information. Further analysis led to speculation that there were rivers of methane, complete with shorelines and deltas. According to Hamilton, "Like the mysterious dark markings on Mars that once haunted astronomer Percival Lowell, shadowy features and mysterious markings appear to stain the surface of puzzling Titan". These early renderings of the surface features of Titan would heighten the interest in its surface features, and the Huygens space probe would continue to feed mans curiosity. The Huygens probe, part of the European Space Agencys Cassini mission, would settle on the surface and begin close-up exploration that provided data that is still being analyzed today. An early photograph from 2005 reveals a surface not unlike a barren desert (See Figure 1). "Bathed in an eerie orange light at ground level, rocks strewn about the scene could well be composed of water and hydrocarbons frozen solid at an inhospitable temperature of - 179 degrees C" (Astronomy Picture of the Day). The surface was covered with rocks that Figure 1 (Astronomy Picture of the Day) approximated the size of a softball, about 15 cm across. It was speculated at the time that Titans surface looked a lot like earth, but had a different composition. Earth had liquid water, while Titans rivers were methane. According to Walker, "Instead of silicate rocks, Titan has water ice. Instead of dirt, Titan has hydrocarbon particles settling from the orange atmosphere. Instead of lava, Titans volcanos spew very cold ice". These images and their interpretations would fuel further debate and raise the international interest in Titan. Recent data sent back from Cassini has not only confirmed the existence of liquid methane, but the vast quantities of organic hydrocarbons has come as a surprise to the scientific community. On earth, methane is a flammable gas that can become explosive when it accumulates in a confined area. However, the temperatures on Titan keep the methane in a liquid state, which has facilitated the formation of large methane oceans on Titans surface. "Several hundred lakes and seas have been observed, with each of several dozen estimated to contain more hydrocarbon liquid than Earths oil and gas reserves. The dark dunes that run along the equator contain a volume of organics several hundred times larger than Earths coal reserves" (Titan’s Surface Organics). The appearance of these methane lakes and seas would give Titan an almost earth like appearance. Lakes of liquid would give way to mountainous regions that rise up on the shores of the bodies of methane. Titans earth like surface is devoid of any life as we know it and there are no plants that could survive the harsh conditions, but it is a very geologically active surface. According to Ralph Lorenz, Cassini radar scientist at the Johns Hopkins Applied Physics Laboratory in Maryland, USA, "With its organic dunes, lakes, channels and mountains, Titan has one of the most varied, active and Earth-like surfaces in the solar system" (qtd. in Ocean May Exist). By surveying the surface of Titan, scientists were able to discern a landscape where landmarks had shifted by as much as 30 km from their expected positions. This activity is similar to the effect of plate tectonics on Earth. "A systematic displacement of surface features would be difficult to explain unless the moons icy crust was decoupled from its core by an internal ocean, making it easier for the crust to move" (Ocean May Exist). It is now believed that the surface is floating on a core that consists of an internal sea of liquid. Bryan Stiles of NASAs Jet Propulsion Laboratory speculates that, "We believe that about 100 km beneath the ice and organic-rich surface is an internal ocean of liquid water mixed with ammonia" (qtd. in Ocean May Exist). This adds to the mystique of Titan as a place where the necessary organic components of life exist just below the surface. One of the mysteries that has been presented by the enormous amount of data gathered on Titan is the relatively smooth surface of the moon. The other moons and planets in our solar system are bombarded regularly by meteors, asteroids, and other space debris. Yet, Titan shows little evidence of any impacts throughout its history. In 2005, scientists spotted a large volcano that may help explain the absence of impact craters. According to Britt, "the baby-faced appearance suggests Titans surface is constantly remade, possibly by eruptions of volcanoes" ("Unmasking Titan"). In addition, a volcanic system could help explain the prevalence of the methane that decays over time and yet is always abundant. Titans close proximity to Saturn creates a large gravitational pull on the moon and creates tidal forces similar to the ones felt on earth from the pull of the moon. As the gravitational force pulls on Titan, the moon stretches and compacts in its elliptical orbit around Saturn. These forces pressurize the liquid methane and heat it. According to Britt, "Because Titans orbit is elliptical, and because Saturn is so massive, tidal motion would be strong enough to generate heat within the moon. That heat could drive eruptions" ("Unmasking Titan"). The heated methane expands and makes its way to the surface in the form of a methane volcano. These constant volcano eruptions release methane into the atmosphere and continually reshape the surface to remove any trace of previous impact craters. This volcanic action also replenishes the methane that breaks down and escapes into the Titan atmosphere. The abundance of organic chemicals on Titan and the expanses of water and ammonia ice just beneath the surface have fuelled the debate over the possibility of life on Titan. Presently, the frigid temperature on the moons surface keep the methane in a liquid state and presents a hostile environment for life that needs oxygen. Walker states, "Titan should explode into flames with its huge quantity of methane, but the extreme cold of minus 180 degrees keeps the methane liquid". However, all this could change at some time in the future. As the solar system ages and the sun begins to expend its energy, the sun will expand and turn into a red giant. This will make life on Earth impossibly hot, but may warm Titans surface enough to evaporate the methane and melt the water-based ice. According to Walker, "The water ice will melt, oxygen will be released and because we have the basic building blocks of life in the form of organic molecules, then for a brief time Titan might be a rather good place for life". However, this will not occur for another 4 billion years. In conclusion, Titan is a world that shares many of the geological features of earth as well as many of the components that make up life on earth. Yet, it is a foreign and hostile environment that prohibits life as we know it from being established. Temperatures of minus 179 degrees Celsius keep the methane liquid and the water frozen. The supply of methane on the surface of Titan is continually replenished by volcanic action similar to the volcanos found on earth that erases any record of cosmic impacts with the surface. The methane settles on the surface in lakes and oceans of liquid methane. The landscape has rivers and mountains, deserts and shorelines. The world on Titan is eerily similar to the planet earth. Similar in geology and composition, but its difference lies in the freezing temperatures that may one day be eliminated as the solar system evolves and heats the moon Titan into a range that is more friendly to life as we know it. Works Cited Astronomy Picture of the Day. 17 Jan. 2005. NASA. 13 Nov. 2008 . Britt, Robert R. "Smog on Saturns Moon Titan Reveals Weather Patterns." SpaceCom. 21 Aug. 2002. Imaginova. 13 Nov. 2008 . Britt, Robert R. "Unmasking Titan: Volcano Spotted on Saturns Smoggy Moon." SpaceCom. 8 June 2005. Imaginova. 13 Nov. 2008 . Eddy, Melissa. "Europes Huygens Probe Landed in Titan Mud." SpaceCom. 18 Jan. 2005. Imaginova. 13 Nov. 2008 . "First Full Mosaics of Titan’s Surface." ESA- Cassini Huygens. 13 May 2005. European Space Agency. 13 Nov. 2008 . Hamilton, Calvin J. "Titan." Solar Views. 2007. 13 Nov. 2008 . "Ocean May Exist Beneath Titans Crust." ESA- Cassini Huygens. 25 March 2008. European Space Agency. 13 Nov. 2008 . "Titan’s Surface Organics Surpass Oil Reserves on Earth." ESA- Cassini Huygens. 13 February 2008. European Space Agency. 13 Nov. 2008 . Walker, Frank. "Titan an Alien World - That Looks Remarkably like Earth." Sydney Morning Herald 23 Jan. 2005. 13 Nov. 2008 . Read More