There must be some factor other than gravity that contributes to an atmosphere’s pressure level because Earth and Venus have almost the same mass.
In: 3
[removed]
Imagine Venus as a planet with a very thick blanket of air around it. This blanket is called the atmosphere. The atmosphere on Venus is much thicker and heavier than the atmosphere on Earth, which means there is a lot more pressure.
There are a few reasons why Venus has so much more atmospheric pressure than Earth. One reason is that Venus is closer to the Sun than Earth, so it receives more heat and energy from the Sun. This extra heat causes the gases in Venus’ atmosphere to move faster and collide with each other more frequently, creating higher pressure.
Another reason is that Venus has a lot of greenhouse gases in its atmosphere. Greenhouse gases, like carbon dioxide, trap heat from the Sun and keep it near the planet’s surface. This makes Venus very hot, much hotter than Earth. The high temperature causes the air molecules to move faster and increases the pressure.
Also, Venus does not have oceans like Earth does. On Earth, water in the oceans helps regulate the temperature and absorb some of the Sun’s energy. Without oceans, Venus doesn’t have this balancing effect, and the atmosphere is free to absorb and trap more heat, resulting in higher pressure.
There’s simply more mass in Venus’ atmosphere, which doesn’t affect the mass comparison between the two planets because the mass of the atmospheres are insignificant in comparison to the mass of the planets involved. Venus’ atmosphere is also composed of almost entirely Carbon Dioxide, which (as a triatomic molecule) is going to hold a lot more heat than what you’d see in the mostly diatomic nitrogen and oxygen molecules that compose Earth’s atmosphere.
The other big contributor is Venus’ proximity to the Sun, meaning they get more heat, and thus will have a higher temperature.
more of venus’ mass is its atmosphere.
it might be more helpful to think of it less as atmosphere and more as an ocean. the pressure on venus is so incredibly high that the carbon dioxide is a supercritical fluid. think something trying to be liquid and gas at the same time. the atmosphere only behaves like a gaseous atmosphere well above the rocky surface.
Venus’s atmosphere has more pressure because there is more of it: the mass of Venus’s atmosphere is about a hundred times the mass of Earth’s.
Largely this is just a fluke of how we define “atmosphere”, distinguishing between liquids and gasses. If we considered liquids to be part of a planet’s atmosphere, we’d describe the two planets as having similar atmospheric mass. And if we considered Earth’s surface to be the floor of the ocean rather than the top of the ocean, we’d describe the two planets as having similar surface pressure.
First off, to correct *many* wrong claims in answers here. Temperature of an atmosphere *does not* affect pressure directly. If you have a sealed box of gas and raise its temperature, yes, the pressure will go up. However, an atmosphere is free to expand outwards – that’s exactly what happens if you heat it up. Instead, the pressure is just the weight of everything above you – if you heat an atmosphere it will readjust its density to make this true (see: equation of hydrostatic equilibrium).
As to why Venus’s pressure is higher, in one sense the answer is simple. Because there is more stuff in the atmosphere. Why that is, though, is more interesting. The main answer seems to be runaway greenhouse effect evaporated the oceans, which in turn [turned off plate tectonics](https://www.space.com/venus-runaway-greenhouse-effect-earth-next.html). Once that happens, carbon that would have gotten sequestered from plate tectonics stuck around and got released into the atmosphere. Way, way more CO2 in atmosphere means higher pressure.
Latest Answers