Astronomy Exploration of Planets and Satellites in Comparison With the Earth Essay

The evidence related to the internal structure of the earth comes from two approaches, direct and indirect. The indirect method requires the measurement of seismic waves. These seismic waves are shocks and vibrations which pass through the earth due to various reasons such as earthquakes and artificial explosions. The difference in the composition and density of the earth’s structure provides an idea of the mineral and chemical composition. There are two types of waves which measure these waves. P- Waves are pressure waves which pass through solid and liquid while S-Waves are shearing waves which pass only through solids. Seismic waves can provide information on the internal composition of Mars and Jupiter. However, due to limited information on the seismic activity on those two planets, efforts have not been successful (McBride and Gilmour).

Impact cratering, volcanism, tectonics, and erosion are the four major processes that affect planetary surfaces. Briefly explain any two and give examples on the Earth and as observed on other planets/moons. Impact Cratering is a process by which large meteors, asteroids or comets collide with planets or satellites and create geological landmarks known as craters. These impact craters are essential in learning the geological history of our planet. An example of a crater on earth would be the Barringer Meteor Crater in Arizona, while the moon has several hundred craters which have been named (Hamilton). Volcanism is a process by which geological landmarks known as volcanoes bring up materials from the internal structure of the planet to the surface. This is a process which is used by the planet to vent heat. Geysers and hot springs are also a part of this activity. Two examples of active volcanoes on earth include Mount Fuji and Krakatoa. Jupiter’s moon also shows a form of volcanism involving water known as icy volcanism (Windows Team).

Though the age of the Earth and the Moon are nearly the same, the surface of the moon does not have any more volcanic activity. The Earth however having a young surface still has much evidence of volcanism. There are many active volcanoes which still exist on the Earth’s surface today. On the moon however the existence of volcanoes though having been proven, has shown they are all inactive. The cooling off of the magma on the moon’s surface along with its crystallization provides scientists with rocks which are millions of years older than those on Earth (Reich). The method used to provide the dates for these rocks is called radiometric dating. Radiometric dating analysis the composition of lead 206 and 207 due to the decay of radioactive uranium 235 and 238 to provide an accurate date for the rocks collected (United States Geological Survey).

The popular theory now regarding the formation of the moon is known as the Giant Impact theory. In this theory scientists believe that a planet approximately the size of Mars was formed 4.6 billion years ago. This planetary body was called Theia. It was formed near enough to the earth that when it lost its orbit to its gravitational interactions or mass it crashed into the earth 4.53 billion years ago. They believe that Theia had an iron core which when collided with the earth combined with its core. Some of this iron and the Earth’s crust were ejected into space and came together to become the moon. The evidence for this was found from the Apollo moon landings which brought back a sample to Earth. This sample showed the same oxygen isotope compositions as those on Earth (Tyson).

Mercury has an average temperature of 167 Celsius or 440 Kelvin (National Space Science Data Center), while Venus has an average temperature of 464 Celsius and 737 Kelvin (National Space Science Data Center). Thus, it can clearly be seen the Mercury despite being closer to the sun has lower temperature than Venus. If asked which planet or planetary body in the solar system is similar to mercury. The answer would have to be Earth’s moon. The moon which orbits the earth is similar to mercury in terms of its surface character. Mercury like the moon has several impact craters. Both space bodies also lack a heavy atmosphere which causes their heavy cratering as well as removing any signs of prehistoric impact (Schombert).

In many ways Venus is called Earth’s sister planet since they share so many similarities in terms of size, gravity and mass. However, Venus’s atmosphere contains more carbon dioxide than earth’s since it has no organic life or surface features which can allow it to conduct the carbon cycle. The carbon cycle is a process by which organic materials such as plants take in carbon dioxide and release oxygen. This process is essential to the survival of all organic life on Earth including plants, animals and humans. The abundance of oceans and organic material on Earth allows this process to be possible while the absence of such on Venus does not (The Internet Encyclopedia of Science).

The Planet Neptune was discovered more than a hundred a fifty years before Uranus by Galileo. On Jan 28, 1613 Galileo was observing the four large moons of Jupiter when he noticed the presence of a nearby star which had not been recorded yet. On careful observation however, he found that his star moved relative to others indicating that it was a planet not a star. Previously it was thought that Johann Gottfried Galle and German astronomer used French mathematician Urbain Le Verrier’s chart to find and observe the planet on Sept 23, 1846. Previously, it was known to exist but no astronomer could be persuaded to look for it (Britt). Uranus however, was found by William Herschel when he was searching the skies methodically through his telescope on March 13, 1781. It had been seen many times before but had always been mistaken for a star (Arnet).

There are several asteroid bodies which enter into Earth’s orbit. However, they are small enough that they usually disintegrate on entering the atmosphere. Scientists believe that only an asteroid with a size of 100 to 500m landing on an Earth mass or in the ocean may cause major damage which could be considered a huge threat to humanity. Bodies which are larger than 500m however, could cause damage on a global scale and effectively cause a nuclear winter. The chances of such a comet or asteroid hitting earth in the next 100 years are remote at best. The probability of such an occurrence however, rises every 1,000 to 10,000 years. Thus, the chance of such an event occurring in 10,000 years is very much possible (Rabinowitz).

Works Cited

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2. Britt, Robert Roy. Galileo discovered Neptune, new theory claims. 2009.
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17. Windows Team. Volcanism. 1997.