Thread: atmosphere density

I read that venus's atmosphere is 81 times as dense as earth's, even though earth's gravity is a bit higher, and venus is a bit closer to the sun, causing the escape velocity of venus to be higher.
The only reason i can come up with, is that carbon dioxide's relative weight is significantly higher than that of nitrogen.
What is the reason that venus' atmosphere is so much denser?

And this also gives me thee question: why is mars' atmosphere so much less dense than earth's? Is it just because of lower gravity? or are there more variables?

There are more variables, although I think gravity is the most important. Also, you're right that heavier molecules will hang around more readily than lighter ones. (I can't find any good references right now, so someone correct me if I'm wrong.)

There is also simply the amount of gases in the atmosphere. If there is more of the gases, than the atmosphere will be denser. Simple as that.

Originally Posted by Sindrato

There is also simply the amount of gases in the atmosphere. If there is more of the gases, than the atmosphere will be denser. Simple as that.

Ok, but this doesn't completely anser my question, and I also don't know if u got that from a credible source.

I doubt that it has been measured. I can't think of a way to measure that. It's just my guess.

Originally Posted by questioner1

I read that venus's atmosphere is 81 times as dense as earth's, even though earth's gravity is a bit higher, and venus is a bit closer to the sun, causing the escape velocity of venus to be higher.

The escape velocity of Venus is lower than that of the Earth because the earth's gravity is a bit higher.

Escape Velocity Earth 11.2 km/sec
Escape Velocity Venus 10.3 km/sec

Moreover, escape velocity generally refers to the velocity that must be attained by an object departing from the surface. At higher levels it becomes progressively lower. Since Venus's atmosphere is not only dense, but thick, the escape velocity at the nominal top of Venus's atmosphere will be even less, proportionally, than at the top of Earth's atmosphere.

The atmosphere is denser primarily because it is more massive. The mass of the Venusian atmosphere is approximately ninety times as great as that of the terrestrial atmosphere. This is mainly bacause on the Earth the bulk of the carbon dioxide has been removed by biological, physical and chemical activity. Thus carbon is trapped in biomass, dissolved in water, and - the most relevant - trapped within carbonates by either biological action or chemical precipitation.

And this also gives me thee question: why is mars' atmosphere so much less dense than earth's? Is it just because of lower gravity? or are there more variables?

This is one of the important reasons. Other issues relate to the absence of any significant magnetic field. Without the field the impact of the solar wind on the upper layers of the Martian atmosphere erodes it over time. At present the temperature of the planets surface is important, since much of the atmopshere is tied up in polar ice fields of carbon dioxide, which undergo seasonal and longer term changes.

Originally Posted by Ophiolite

Originally Posted by questioner1

I read that venus's atmosphere is 81 times as dense as earth's, even though earth's gravity is a bit higher, and venus is a bit closer to the sun, causing the escape velocity of venus to be higher.

The escape velocity of Venus is lower than that of the Earth because the earth's gravity is a bit higher.

Escape Velocity Earth 11.2 km/sec
Escape Velocity Venus 10.3 km/sec

Moreover, escape velocity generally refers to the velocity that must be attained by an object departing from the surface. At higher levels it becomes progressively lower. Since Venus's atmosphere is not only dense, but thick, the escape velocity at the nominal top of Venus's atmosphere will be even less, proportionally, than at the top of Earth's atmosphere.

The atmosphere is denser primarily because it is more massive. The mass of the Venusian atmosphere is approximately ninety times as great as that of the terrestrial atmosphere. This is mainly bacause on the Earth the bulk of the carbon dioxide has been removed by biological, physical and chemical activity. Thus carbon is trapped in biomass, dissolved in water, and - the most relevant - trapped within carbonates by either biological action or chemical precipitation.

And this also gives me thee question: why is mars' atmosphere so much less dense than earth's? Is it just because of lower gravity? or are there more variables?

This is one of the important reasons. Other issues relate to the absence of any significant magnetic field. Without the field the impact of the solar wind on the upper layers of the Martian atmosphere erodes it over time. At present the temperature of the planets surface is important, since much of the atmopshere is tied up in polar ice fields of carbon dioxide, which undergo seasonal and longer term changes.

Interesting.
It seems to me that the amount of atmosphere has a maximum, depending on the mass of the terrestial planet, and the surface temperature.
Is this so?

And is it also true, that would all the carbon dioxide on earth be dispenced in the atmosphere, we would get a venus-like atmosphere?
My guess is that venus' surface area is ALOT higher than it would be with earth's atmosphere on the venusian distance from the sun, due to the greenhouse effect?

Originally Posted by questioner1

My guess is that venus' surface area is ALOT higher than it would be with earth's atmosphere on the venusian distance from the sun, due to the greenhouse effect?

Your guess would be wrong. Consider the gas giants, like Jupiter.

sorry, i made a typing error.
I meant: venus's surface temperature

Originally Posted by questioner1

It seems to me that the amount of atmosphere has a maximum, depending on the mass of the terrestial planet, and the surface temperature.
Is this so?

No. These two factors will influence the maximum, but so too will the original composition, the impact history, the strength and consistency of the magnetic field, the intensity and character of tectonic activity, the intensity and character of volcanic activity, the character and quantity of life, etc, etc.

Originally Posted by questioner1

And is it also true, that would all the carbon dioxide on earth be dispenced in the atmosphere, we would get a venus-like atmosphere?

Broadly speaking, yes, but the water content would be higher because hydrogen loss woul be reduced through the presence of the magentic field. There would be a score of other minor, but significant differences also -I base this statement on logic, not knowledge.

Originally Posted by Ophiolite

Originally Posted by questioner1

It seems to me that the amount of atmosphere has a maximum, depending on the mass of the terrestial planet, and the surface temperature.
Is this so?

No. These two factors will influence the maximum, but so too will the original composition, the impact history, the strength and consistency of the magnetic field, the intensity and character of tectonic activity, the intensity and character of volcanic activity, the character and quantity of life, etc, etc.

Originally Posted by questioner1

And is it also true, that would all the carbon dioxide on earth be dispenced in the atmosphere, we would get a venus-like atmosphere?

Broadly speaking, yes, but the water content would be higher because hydrogen loss woul be reduced through the presence of the magentic field. There would be a score of other minor, but significant differences also -I base this statement on logic, not knowledge.

very interesting.
I guess you know sometihing about this, so do you have anything I can read on the internet about atmospheres? i've looked but not found anything. (I admit, i'm not very good with google)

Wikipedia is often a good place to start.
The Atmosphere of Venus
The Atmosphere of Mars
The Atmosphere of the Earth