The solar nebula is a massive form of clouds and gases that is said to have formed our entire solar system. The solar nebula is the beginning of the theory we have on how our solar system was formed called the nebular theory. When the solar nebula first began it is said to have been a large and spherical cloud of very cold, low-density gas. This cloud of gas would have been spread out beyond our belief, covering light-years of space and gravity alone may not have been able to make this whole cloud of cold gases start spinning. An explosion of a dying star could have started the spinning process along with the gravitational pull. Once this explosion happened the gravity would ensure that it would continue to spin. Over a long period of time the solar nebula shrinks in size looking much smaller like a spinning disk. Through this process of heating, spinning, and flattening we have the beginning of a solar system (Bennett, Donahue, Schneider & Voit, 2012, p.160-161).
A protostar is a group of gases that will eventually become a star. Protostars are not true stars at this point of formation because their cores are not hot enough for nuclear fusion. The Sun is a high-mass star and it will have the nuclear fusion life span of about 10 billion years. The Suns core is at the point of processes nuclear fusion but over the next 5 billion years the nuclear fusion is the Sun will cease and will enter a new phase in it's life span (Bennett, Donahue, Schneider & Voit, 2012, p.336-341). Both terrestrial and jovian planets are born from metal and rock; they both also are made up of mostly hydrogen and helium gases. The terrestrial planets are only made up of metals and rock, the reason they may be smaller from the jovian planets is because metal and rock made up 2 such a small amount in the solar nebula. Through the process of collecting solid bits of metal and rock they basically slammed into each other eventually making them large enough to call them planetesimals. Only the largest planetesimals survived all the collisions they encountered eventually making the inner four terrestrial planets.
The process of accretion, which is the process of making a planet, should have worked the same way on the jovian planets beyond the frost line in our solar system but it did not due to the seeds of ice. During formation of the Jovian planets they were surrounded by disks of gas making them large icy planetesimals. The jovian planets built up so much gas that they became one big icy seed in the end just as the started with icy seeds and also small amounts of metal and rock, but much less metal and rock than the terrestrial planets. As we know the main properties of the solar nebula are hydrogen and helium compounds. The frost line in our solar system is the point at which it is far enough from the sun to allow hydrogen compounds to turn into ices. The frost line lies between the present day of the obits of mars and Jupiter. Hence explaining the four inner planets known as terrestrial planets and the four once five outer planets known as the jovian planets. During the Earth's formation as planetesimals, water and gases became trapped under the Earth's surface. Through the process of volcanism be releasing gases that are mainly made up of water vapor, carbon dioxide, and nitrogen; this is what has made the Earth's atmosphere. Much of the nitrogen still remains in the Earth's atmosphere. This is also what made the Earth's oceans thanks to our greenhouse effect. Oxygen is mainly a mystery but we do know that is was created originally on Earth by photosynthetic life. When our planet was made the inner core was the hottest when it was young. Over the years by letting of gases through volcanism created an atmosphere which also allowed water to be created on Earth. The process continues today as the 3 gases come out of erupting volcanoes, the gases go up into our atmosphere to be made into rainwater which then returns to the Earth breaking down the minerals from rock back into the sea to repeat the whole process over again. Through this process of giving us an atmosphere and liquid water on Earth provided a home for plants and microorganisms which intake CO2 and release oxygen allowing human life to then be created (Bennett, Donahue, Schneider & Voit, 2012, p.218-220).
Scientist believe our moon was created by a giant impact between the Earth and another large planetesimals, which then blasted the outer layers of the moon into space forming what we know call the Moon. The Moon contains very little metal and also has a smaller proportion of easily evaporated ingredients, this would also support the theory that our Moon was created by a giant impact because the force of the impact would have evaporated those things off the layers of Earth that were blasted off during the impact. In the end it is believed that our Moon is made from a part of the Earth. The moons of Mars are more likely just captured asteroids that have been captured by Mars' atmosphere when it was extended a long time ago. These asteroids may have once orbited the sun but then became caught up in Mars own orbit a long time ago. Mars moons are call captured moons because they once orbited the sun. Our own moon is way to big to be captured which has brought about the theory of the giant impact (Bennett, Donahue, Schneider & Voit, 2012, p.168-169).
The Greenhouse Effect
The atmospheres of Venus and Earth are very similar in the elements they once use to carry. Venus's atmosphere is made primarily of carbon dioxide. The Earth's atmosphere is made up of carbon dioxide also but also nitrogen and oxygen. The Earth has the same or even more 4 amount of carbon dioxide as Venus does, it is just found in different forms. Venus's atmosphere carries the carbon dioxide in gas form while so does the Earth but then it transforms into carbonated rocks through a process in which the carbon dioxide dissolves into water were it can start the chemical process of turning into rocks. The reason Venus keeps the carbon dioxide in the atmosphere is because it does not have the oceans to begin the process the Earth goes through in making carbon dioxide into rock form. One reason Venus does not have the oceans and liquid water as Earth does, is because it is closer to the Sun than the Earth is. The greater the intensity of the sunlight the faster liquid water such as oceans would dissolve. The evaporation of the liquid water would cause a water vapor to increase in the atmosphere which is still a considered a greenhouse gas. This would then drive the temperatures higher causing even more liquid water to evaporate. This whole process would cause a runaway greenhouse effect and continue until all oceans were evaporated and all carbon dioxide out of the rocks was evaporated back into the atmosphere. If this process would happen on the planet Earth over a period of time our planet would be made into another Venus. Though Venus and Earth are very similar, the placements of the planets from our Sun makes a big difference on how the chemicals react on our planet and what type of greenhouse effect the planet will have. The greenhouse effect on Earth is perfect; its cycle is repeatable and steady (Bennett, Donahue, Schneider & Voit, 2012, p.200-216).
In conclusion the place in which the Earth is placed from the Sun gives the Earth a good chance of a good greenhouse effect were the carbon dioxide that is in the atmosphere dissolves into rain water, which is carried through the oceans and mixes with eroded minerals in the oceans to make ricks such as limestone. Over millions of years the conveyor belt of the plate tectonics moves the rocks to zones in the ocean that are then carried downward. As they are then 5 pushed deeper into the mantle of the Earth some of the carbon dioxide is released so it is then outgassed back into the atmosphere through volcanoes. On Venus were there is a runaway greenhouse effect this whole process happens to quickly because of the heat from being closer to the sun and it making the planet warmer, higher temperatures holds more water vapor and additional water vapor increases the greenhouse effect (Bennett, Donahue, Schneider & Voit, 2012, p.216-217).
Over the years the CO2 levels in our atmosphere have raised a lot. Although it is being understood more today than ever, when the war on the change in climate and our atmosphere first had started was back in 1896, it has taken almost a century for scientist to come up with the right amount of evidence to prove human activity is the cause of the increased levels in CO2 in our atmosphere. In 1980 they drilled through into the Greenland and the Antarctic ice caps to measure the CO2 back to the last ice age, they had found that there was a very low levels of gases which correlated with the low level in temperatures (Weart, 2011). Because of the increased CO2 levels on Earth in our atmosphere, which is causing a global warming, which is causing a climate change; this is affecting many people that we do not realize. For example in the Philippines they are regularly battered by typhoons and many believe because of the climate change the typhoons are getting stronger and stronger. Before the industrial revolution the atmospheric carbon dioxide was 280 parts per million, now it is 391 parts per million. Just in that short amount of 109 years the global average temperature rose 1.3 degrees Fahrenheit (Groppe & Dileo, 2012). Although this does not seem to be much especially since it did not even happen in our own lifetime, it still does not say to much for the future of our humanity over billions of years. 6
References:
Bennett, J., Donahue, M., Schneider, N. & Voit, M. (2012) The essential cosmic perspective. (6th ed.) San Francisco, CA: Pearson
Addison-Wesley Weart, S. (2011). Global warming: How skepticism became denial. Bulletin Of The Atomic Scientists, 67(1), 41-50. doi:10.1177/0096340210392966
Groppe, E., & Dileo, D. R. (2012). Climate For Change. America, 206(10), 12-16.
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