Lifetime of CO2 in Mars atmosphere

[frozenguy]

Homework Statement

Estimate the lifetime of CO₂ in the atmosphere of Mars.

Homework Equations

The Attempt at a Solution

What is he asking? How long has the CO2 been in the atmosphere? It just seems rather vague.

 

[gneill]

Mars is losing its atmosphere. Heavier molecules last longer than lighter ones. Think about temperatures, kinetic energy distributions, escape speeds,...

 

[frozenguy]

So is he asking to estimate how long until there is about 0% CO2 in the atmosphere? Or an average time before a molecule escapes?

 

[gneill]

So is he asking to estimate how long until there is about 0% CO2 in the atmosphere? Or an average time before a molecule escapes?

At a guess I'd say estimate a time constant for the decay ($~e^{-t/\tau}~$) and call $\approx 5\tau$ the lifetime.