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Solar System
The planetary system formed from a spinning disk of gas and dust, the solar nebula, surrounding the proto-Sun about 4.6 billon years ago. The solid materials, beyond Neptune, never accreted into major planets, but remained as a vast collection of objects known as the Kuiper Belt Objects (KBOs). These icy bodies hold clues to the origin of prebiological organic materials on Earth. These small KBOs are thought to be relatively unchanged since the inception of the Solar System because of the very cold temperatures at the trans-Neptunian distances. These smaller objects are less likely to undergo internal differentiation, leaving them virtually in their interstellar origins. By studying the chemical compositions of KBOs, scientists have learned much about the volatile and organic molecular materials that are found on Earth. The Kuiper Belt is the birth place of short-period comets. Examining samples from them is like examining materials from which planets were formed. Scientists think that the current Earth's atmosphere is not the original one. The change in atmospheres of planets was mostly caused by volcanism on them.
The Solar System is made up of the Sun, our star, the nine planets and all their moons, asteroids, comets, and planetary stuff. The terrestrial planets are Mercury, Venus, Earth, and Mars. The Jovian planets are larger than the Earth and are much farther from the Sun. They are Jupiter, Saturn, Uranus, and Neptune. The Jovian planets are very massive and their escape velocity is also large. They are able to retain much of their hydrogen. Their atmosphere is much like that of the Sun. These large planets' surfaces are not solid, and there are no volcanoes on them. Whereas the smaller inner planets escape velocity is low and the Hydrogen, being very light, gets ejected out of their atmospheres. They have solid surfaces and either active or dead volcanoes. Pluto is a very small planet located beyond the Neptunian distances. Since the age of the space exploration, unmanned satellites have visited every planet except Pluto. Images from these visits have documented Mercury's cratered surfaces, Venus's poisonous cloud cover, and Mar's enormous canyons and extinct volcanoes. Volcanic activities on Io, the rings of Jupiter and Saturn, and Neptune's active atmosphere have all been seen through the eyes of satellites.
Mercury is the nearest planet to the Sun and has a diameter of 4878 kilometers (3031 miles) and is 0.387 astronomical units from the Sun. Its surface is hard and rocky. It is freezing cold at night and burning hot during the day, denoted by its temperature range of 350º C to -170ºC. Mercury has no moons. It's atmosphere is essentially none. Mercury surface is covered with thousands of craters. There are no volcanoes on this planet, either dead or alive. Mercury is a small planet, less than half the size of the Earth and is slightly larger than the Moon. Alternately, it is baked on the side facing the Sun and frozen on the side away from it. Mercury conditions are inhospitable to life.
Venus is our nearest planetary neighbor and is called our sister because of its resemblance in size, and mass. It is near the size of the Earth with a diameter of approximately 12104 kilometers (7521 miles). Venus's surface is hard and rocky, and has many mountains. Venus is only 0.723 astronomical units from the Sun, making it the second nearest planet to the Sun. Venus is the hottest planet in the Solar System. Its temperature is in the range of 800 degrees Fahrenheit. The temperature is hot enough to melt lead. What makes Venus so hot, hotter than Mercury which is closer to the Sun? The thick atmosphere that surrounds Venus, accounts for the high temperatures. The clouds are formed mostly by carbon dioxide probably from volcanic activity. Carbon dioxide is 96.5% of Venus's atmosphere, which is about one million times more than is in the atmosphere of the Earth. The dense atmosphere produces a Greenhouse Effect sealing in the planet's heat, and preventing it from escaping into space (Jastrow,99). The trapped heat raises the temperature tremendously. The Earth's temperature would be hostile to terrestrial life if it was also covered with a thick blanket of carbon dioxide.
In 1969 the spacecrafts Venera 5 and 6 gathered information useful for answering the question, why did two planets formed at the same time out of similar materials and located at comfortable distances from the Sun evolved so differently? The Earth is hospitable to life, while Venus is hot and dry, and most of its water depleted. Venus 4 spacecraft instruments, used for detecting water, showed only small traces of water vapor in the atmosphere of Venus. If this water vapor were condensed to liquid water, it would cover a depth of 1 foot over the surface of Venus. If the ocean were spread out over the Earth, the Earth would be covered in depth of up to 8000 feet of water. (Jastron, 100).
Venus and Earth should have an equal abundance of carbon dioxide, but they do not. The difference in carbon dioxide on these two planets is due to the slightly higher temperature on Venus during the formation of the Solar System. When the Earth was formed, carbon dioxide was absorbed from the atmosphere by rocks. Atmospheric carbon dioxide reacted with rocks to form carbonates, somewhat like oxygen combines with iron in the air to form rust (iron oxide). These reactions do not take place at an accomplished rate if the rocks on the surface are very hot or dry. Since Venus was closer to Sun and hotter, its rocks could not absorb the carbon dioxide. It piled in layers, forming the thick atmosphere. Venus's atmosphere is very dense, some 200 times heavier than that of the Earth. There is strong indirect evidence for recent volcanic activity on this planet, but to date we have not been able to directly detect an active volcano.
Earth is 12756 kilometers (7926 miles) across in diameter and is one astronomical unit from the Sun. Earth's surface is rocky and its atmosphere is approximately 78% Nitrogen, 21% Oxygen, 0.4% carbon dioxide, and 0.6% of other rare gases and water vapor. The Earth's atmosphere has no Hydrogen because the light Hydrogen atoms escaped the atmosphere during the time the Earth was formed. In fact, there is evidence that the young Earth was so hot that all of its original atmosphere was lost, and that the present atmosphere is principally due to volcanic out gassing. Volcanoes eject primarily carbon dioxide, nitrogen, and water vapor. Most of the carbon Dioxide on Earth was absorbed by rocks, and diluted in the oceans.
Earth is the only planet with a differentiated atmosphere suitable for life as we know it. It has one moon that revolves around it once every 28 days. The Earth is very volcanically active. The Earth's face also chronicles many inactive or dead volcanoes, such as, Sacred Mountain Crater at the summit of Mount Fuji, Japan's tallest mountain located on the Island of Honshu, West of Japan. Earth is the only planet that has active confirmed volcanoes. Most of the Earth's volcanoes are dormant, which means they are currently inactive, but more than 600 are active. The active volcanoes sometimes spew smoke, steam, ash, cinders and flows of lava (Synder, Feather, Hesser, 388).
Mars is believed to be composed of rocky materials similar to that of the Earth. Its density is about the same as that of Venus and Earth. Mars' diameter is about 6796 km (4223 miles). Mars is about 1.524 astronomical units from the Sun. The Mars temperature ranges from about 20ºC to -120ºC. Mars is small and its radius is a little over half than that of the Earth. Mars has two moons. Its surface is rocky and covered with craters and old volcanoes. Mars is volcanic inactive.
Jupiter is enormous in size. Its diameter is 142,984 km (88,846 miles) and is located 5.203 astronomical units from the Sun. Its surface is covered with red and yellow clouds. Jupiter's atmosphere is composed of mostly, Hydrogen, and Helium, with significant amounts of Methane and Ammonia. Jupiter's temperature is extremely cold and it has 63 known satellites. Jupiter is not volcanically active, but Io, one of its four Galilean moons, is the most volcanically active object in the Solar System.
Saturn is 9.5 astronomical units from the Sun. In July 2005, The New York Times reported discoveries made by the Cassini-Huygens spacecraft as they entered Saturn's orbit. The Huygens probe transmitted 350 images which revealed that Titan's (Saturn's largest moon) surface is much like that of the Earth, "complete with evidence for methane rain, erosion, stream like drainage channels, and dry lake beds." Titan's temperature is minus 290 degrees Fahrenheit and has a global ocean of liquid methane. Titan is the only satellite in the Solar System with a substantial amount of Nitrogen and methane (about 3 percent). Images from the Cassini-Huygens also showed swirling storms, lighting, and auroras at both poles. Further the Cassini orbiter provided the first view of possible volcanoes, a lake, craters, diverse terrain, and a complex hydrocarbon atmosphere. The strongest evidence for volcanoes on Titan is inferred from an image of a 20 mile icy circular feature interpreted as an icy volcano or cryovolcano. The image has the shape of an Earth volcano known as a caldera, and its surface appears to have "two flow" patterns similar to Earth and Venus, that may have been caused by an erupting volcano. The ejecta consisted mainly of water, ice, and methane. The eruptions of Titan may be caused by tidal heating; a flexing of the Moon's interior as it moves in an elliptical orbit.
Neptune's largest moon, Triton, has shown evidence of volcanism. Voyager II photographed ice geysers spewing from a volcano on Triton's surface. From future space fly bys and exploration, volcanoes on this satellite will become more fully known. Heat for volcanism on Triton is due to tidal heating produced by the changing gravitational forces between Neptune and Triton.
Pluto is a tiny planet located 39.537 astronomical units from the Sun. It is very cold, around -233 degrees Celsius. It is only 2300 kilometers (1430 miles) across. It has one moon and no volcanoes.
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