Which of the planets have an atmosphere? All of the planets in our solar system except for Merucry actually have an atmosphere, but they vary in thickness.
We all obviously know that our planet has an atmosphere and what it is made of. It is 78% nitrogen, 21% oxygen, 0.9% argon, and the rest is trace gases. All of the carbon dioxide that is causing so much trouble on our planet is in that 0.1% of the atmosphere. That is why such a small increase in it can have such a big impact. We also know that our atmosphere weighs … well, one atmosphere. One atmosphere is the weight of all the gas that is in a column on top of you when you walk on the planet. The atmosphere goes up 10,000 km. although there is not much in it from about 700 km and on. So, whenever you are outside, there is the weight of a column of gas 700 km high on your head, and that is one atmosphere. The gases in our atmosphere are constantly trying to escape into space, but our gravity holds them in and our magnetic field protects them from being blown away by the solar winds. So, what about on other planets? Let’s start from the closest to the sun.
Mercury is the closest planet to the sun at only 58 million kilometers away. It is so close to the sun that the temperature gets up to 430℃ on the daylight side of the planet. Mercury has a very thin atmosphere that is called an exosphere. Our exosphere is that part of the atmosphere with almost no gas that is above 700 km. Mercury’s is right on the surface. It contains a few gases and atoms that have come from the surface of the planet, but they are very quickly blown out into space. Mercury doesn’t have an atmosphere for the same reasons that Earth does have one. It doesn’t have enough gravity to hold the atmosphere in and it doesn’t have a magnetic field to shield it from the sun’s winds.
Venus has a much thicker and heavier atmosphere than Mercury. The atmosphere of Venus is made up of 96% carbon dioxide, and the rest is nitrogen and other gases. Venus doesn’t have a bigger atmosphere than Earth, it just has a much denser atmosphere. Carbon dioxide is far denser than nitrogen and oxygen, so the atmosphere of Venus is 93 times denser that ours. If you were standing on the surface of Venus, you would be crushed in milliseconds. Because of the carbon dioxide, Venus also has a runaway greenhouse effect, which makes the planet incredibly hot. It’s not as close to the sun as Mercury, but Venus is hotter, with surface temperatures of 460℃. Venus does lose some of its atmosphere, but it has a huge amount of volcanic activity that replenishes it.
The atmosphere of Mars is closer to that of Mercury than of Earth. It is made of mostly carbon dioxide, 95%, but it is much thinner than Venus’s atmosphere. The atmosphere of Mars is so thin because it doesn’t have much gravity, being only half the size of Earth. That means most of its atmosphere has escaped into space. It also doesn’t have a magnetic field to deflect the solar winds. A lot of Mars’ atmosphere is made up of dust that blows off the planets surface and hangs in the air. The atmospheric pressure is only about 1% that of Earth.
The last four planets, Jupiter, Saturn, Uranus, and Neptune, are all gas giants so they have to have an atmosphere. However, with the gas giants, it can be difficult to know where the atmosphere ends because there is no rocky planet surface. The atmosphere of Jupiter is made up of mostly hydrogen (89%) and helium (10%). There are other gases as well. In fact, if Jupiter was 80 times bigger, it would have enough gravity for the pressure to ignite the hydrogen and for nuclear fission to start. Then we would have had two suns. There is no way of knowing where Jupiter’s atmosphere ends, but at a certain point the pressure is too great and the gases turn into liquid and possibly even a solid core.
Saturn, Uranus, and Neptune are also made of mostly hydrogen and some helium. They could also have become stars if they had more gravity. Our solar system doesn’t have enough matter for two suns though. All of the planets combined wouldn’t create enough gravity for a star to be born. All three of these planets have the same situation as Jupiter. The atmosphere goes down until the pressure is so great that the gases compress into liquids and then solids. And this is what I learned today.
Sources
https://education.nationalgeographic.org/resource/atmosphere
https://science.nasa.gov/mercury/facts
https://www.britannica.com/science/atmosphere/The-atmospheres-of-other-planets
https://www.space.com/18527-venus-atmosphere.html
https://marsed.asu.edu/mep/atmosphere
https://www.nasa.gov/wp-content/uploads/2015/01/YOSS_Act_4.pdf
https://science.nasa.gov/jupiter/jupiter-facts
By NASA/JPL – http://photojournal.jpl.nasa.gov/catalog/PIA00104, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11826