Why Mercury, Venus, and the Moon Do not Have Significant Erosion – Assignment Example
The paper "Why Mercury, Venus, and the Moon Do not Have Significant Erosion" is a wonderful example of an astronomy assignment. Erosion refers to the process of ”movement of soil and rock material by agents such as running water, wind, moving ice, and gravitational creep” (Allaby, 1991). Together with impact cratering and tectonic activity, erosion is one of the ways in which the surface of a planet is transformed. Erosional activity on planets is affected by weather-driven conditions such as wind, rain, ice, snow etc., geological activity such as movements of the crust, earthquakes, and volcanoes, flow of liquids such as rivers and glaciers, and the activities of living organisms that live on them. Significant erosion, therefore, occurs if there is an atmosphere, geological or tectonic activity, the presence of liquids on the surface and if life forms are present on the planet. In addition to atmospheric erosion, tectonic and human activity, the solar wind and gravity slumping also cause erosion. Atmospheric erosion occurs over a shorter timescale than tectonic activity but usually has a stronger effect. The phenomenon of gravity slumping occurs over a much larger timescale on airless worlds. The Moon does not have significant erosion because it does not have an atmosphere. It is simply too small to hold onto one. Mercury has only “a thin exosphere… blasted off its surface by the solar wind” (NASA) and consequently “no wind erosion of the surface” (ibid) and little geological activity. So, Mercury being too close to the Sun has too high a surface temperature to sustain much of an atmosphere. Venus, on the other hand, does have some erosion due to its “extremely thick atmosphere” (New World Encyclopedia). But it is little and slower in comparison to the Earth or even Mars. Also, due to this thick atmosphere, incoming objects “are slowed down so much by the atmosphere that they do not create an impact crater” (ibid) so craters that do exist are small to cause any major surface transformation. Planets that are closer to the Sun have a higher temperature, so a lower chance of maintaining an atmosphere and therefore less likelihood of conditions that can cause erosion. They are just “too hot for rain, snow, ice and so have less erosion” (Regina1, 2008). It is the same for planets that are too far from the Sun to experience weather conditions. Erosion, however, is more directly related to the size or rather the mass of the planet. This is because the greater the mass, the easier it is able to retain an atmosphere due to the greater force of gravity. This is why larger planets such as Jupiter and Saturn experience great atmospheric erosion. And, atmospheric erosion as mentioned above has a shorter timescale so it is easily observable. Larger planets also “remain warm inside, promoting volcanism and tectonics” (ibid). Most erosion though occurs on planets with liquid water. For comparison, the Earth has significant erosion because it has all the factors that cause it mentioned above including an atmosphere, and the presence of abundant liquid and life forms. It is precisely the absence or limited quantity of these things on Mercury, Venus and the Moon, therefore, that means they do not experience significant erosion like the Earth. Mars for example also has erosion due to the wind and dust storms that take place on its surface. But interestingly, the converse has been used as evidence to claim that liquid water once existed on Mars i.e. from observing “the numerous surface features on the planet that resemble water erosion found on Earth” (msn Encarta).