Have all the planets in our solar system had an atmosphere at some point?
Question:
Answer:
Yes. The first atmospheres were composed of hydrogen and helium.
When the protosun began nuclear fusion in its core it soon started blasting the planets with radiation. The atmospheres heated up and since heat is kinetic energy in between atoms and molecules it now became possible for atmospheric elements to reach escape velocity and leave their respective planet.
Mercurys atmosphere was doomed from the beginning being so close to the sun and having so little mass. Although there are some gasses left, like sodium, those gasses are also being blasted off into space. Mercurys atmosphere is so thin it is a more perfect vacuum than we can reproduce here on earth.
Venus lost most of its hydrogen and helium. The water vapour was split into hydrogen and oxygen by ultraviolet radiation with the hydrogen quickly escaping. Heavier gasses like CO2 and nitrogen remains. Venus has about as much nitrogen, per mass, in its atmosphere as earth does and about as much CO2 that earth had in the beginning.
For earth every atom lighter than 3 U can reach escape velocity. That is why there is no He3 left while there is still some He4. Earths atmosphere was alot denser in the beginning. After the lighter elements had been blasted off there was enormous amounts of CO2 in the atmosphere. Unlike Venus earth became cold enough to condensate the water vapour. The CO2 began dissolving into the primordial oceans where chemical reactions began turning the H2CO3 into solid carbonates that settled on the bottom. This thinning was later accelerated by life. Finally life began producing oxygen that also got trapped by biochemical reactions as ironoxides that settled onto the bottom of the oceans. It took billions of years for the oceans to run out of iron until eventually oxygen began building up in the atmosphere. The atmopshere earth has now is earths third.
Mars was also too small to keep a significant atmosphere but it was able to survive for much longer than on Mercury because it is farther from the sun. Still only a little CO2 remains while even the nitrogen, which had to have been there, has escaped. Most of the water has suffered the same fate as the water on Venus. Interesting that mars has about the same amount of CO2, by mass, in its atmosphere while Venus has about the same amount of nitrogen. Percentage wise Venus atmosphere is almost identical to Mars only about 10000 times as dense.
Further out the gas giants have been able to hold on to their primordial atmospheres despite relentless solar radiation.
they do have different types of atmosheres...methane ect.
I think so. But, some planets like Pluto had really thin ones.
yeah all planets still have them but in little quantity, depends a lot on the mass of the planet, cooling down of planet, and of course distance from the sun
I think all of them were made of gas while forming, so the answer would have to be yes. Mercury still has a tiny one thanks to solar wind. Pluto also has a tiny bit. The others have enough still that the atmospheres are visible.
After the planets formed they all had transient atmospheres of hydrogen and helium. These light gasses escaped from all but the most massive planets (Jupiter, Saturn, Uranus, Neptune). The atmospheres that we see on the smaller planets today are a result of geological activity releasing gas into the atmosphere (venus, earth, mars). Mercury traps solar wind particles, and thus sort of has an atmosphere, and Pluto's surface gets warm enough to produce gas when it is on the near side of it's orbit. The atmosphere on Pluto is thought to only be temporary, when it reaches the far part of it's orbit the atmosphere may well disapear.
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