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Table of Contents
Venus: The Facts
Venus is the second of the four terrestrial planets with regard to distance from the sun. This distance is about 67 million miles, so about 70 percent of Earth’s(which is 93 million miles). The mass of Venus is 4.9*10^24 kilograms. An interesting thing about Venus’s orbit is that it is retrograde in comparison to Earth’s. This simply means that Venus rotates in the opposite direction that Earth does(rotation is the spin of the planet, revolution is the orbit around the Sun). Somethings can appear to move in retrograde across the sky, such as other planets like Jupiter, because of the way our orbits work. When the Earth starts passing Jupiter, for example, it looks like the planet is going backwards in the sky(West to East), even though both Earth and Jupiter orbit the Sun in the same direction. This is called apparent retrograde motion and is caused simply by Earth passing Jupiter, and once it passes, Jupiter appears to move forward again. Anyhow, Venus is believed to have a molten core, not solid, because of the small mass of the planet. It likely does not exert enough pressure to be totally solid, just like Mercury. What makes Venus special is just how hot it gets. Venus has the thickest atmosphere out of all the planets, and it is mostly carbon dioxide. You likely already know that carbon dioxide traps heat; it is a greenhouse gas. In small quantities on Earth, we see temperatures rise. However it makes up less than one percent of the atmosphere. In Venus, 97 percent of the atmosphere is nothing but this gas! Thus, even though Mercury is closer to the Sun, Venus is the hottest planet, and it has a relatively stable temperature. This can go up to 880 degrees Fahrenheit!
Surface of Venus
Venus has a rocky surface like Earth, and also has mountains, craters, and volcanoes. It also has very long lava channels, the longest is called Baltis Vallis and is 6800 kilometers long. Volcanoes on Venus are generally shield volcanoes, which are very wide volcanoes but are short. The largest volcano is Maat Mons. The most notable fact about Venus’s Surface is that although it has craters, these are sparse and overall the surface is very smooth. These large, and smooth, regions are called basaltic plains, because the smooth rock is basalt. This type of rock is formed by the slow cooling of lava. Remember how volcanoes are very abundant, so every time a volcano erupts massive amounts of lava flows out of these shield volcanoes. This lava spreads over the surface of the planet and very slowly cools(the surface can reach 880 Fahreinheit so this “cooling”, which is solidification of the lava. takes an extremely long time). Since it cools so slowly, it becomes very smooth and thus forms these smooth plains, rather than being rugged and bumpy. Over time, you may expect this surface to get rugged with craters from asteroids, but it is not so. This is best explained by the lava cooling being very recent(past couple million years), so not much has been able to impact it, along with this new surface covering up all the old craters.
The Very Thick Atmosphere Of Venus
Venus has a very thick atmosphere, with the pressure from the atmosphere being 90 times that of Earth’s! That would be the pressure 900 meters deep underwater(this could crush many things). The atmosphere is mainly(96%) carbon dioxide, or CO₂, gas, which allows for it to trap heat in very well. This massive amount of this gas accounts for why Venus is so hot. The rest of the atmosphere is mainly nitrogen gas(3%). In the remaining 1%, a unique occurrence of sulfuric acid occurs. Since Venus is so hot, the sulfuric acid is evaporated and forms clouds. Specifically, this happens because of the interaction of SO₂ and H₂O(sulfur dioxide and water), which forms this acid. Acid rain on Earth happens the same way, but since this acid is not common at all(the acid rain on Earth is because of pollutants), we do not see clouds of it happen. On Venus, the sulfuric acid is more common so it is able to vaporize and form clouds.
Every post I do was intended to have a for educators section, but when it comes to an individual planet, I do not think it is necessary. Each planet should only be discussed briefly, when teaching astronomy, its more important to give the big picture and get people attracted to astronomy. As such, I am going to skip this section for most of the planets. I think a short talk about each planet is sufficient. If you have anything you’d like in this section, please let me know.
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