Mars doesn't really have an atmosphere...Atmospheric pressure measurements are unique among the meteorological variables that can be measured at a single site on the surface of MARS, providing the widest ranging study of phenomena and of space and time scales. Atmospheric pressure on MARS is approximately 1% of that on Earth and varies about plus/minus 15% during the year due to condensation and sublimation of its primarily CO2 atmosphere on to and from its polar caps. Spatial processes from "dust devil" size structures, to "fronts" to regional and global dust storms, have been investigated from orbit, while temporal variations from the transient dust devils, to fronts, to seasonal and the dramatic year to year presence or absence of the global storms, have been studied by these single point, long term, Viking observations. The Viking Lander observations provided the first and most complete description of the weather at the surface of MARS, and the only Martian meteorology station Climate Record; this is described in the MARS component of Live from Earth and MARS .
www-k12.atmos.washington.edu
Ozone blocks UV light from reaching the surface. Has nothing to do with keeping CO2 in, although it is a greenhouse gas. Gravity keeps O3, CO2, O2, H20, N2 from flying out into space.
Boltzman Black Body calculations for Earth...
Temperature of the Earth
Similarly we can calculate the temperature of the Earth TE by equating the energy received from the Sun and the energy transmitted by the Earth:
where TS is the temperature of the Sun, rS the radius of the Sun and a0 astronomical unit, giving 6°C.
Summarizing: the surface of the Sun is 21 times as hot as that of the Earth, therefore it emits 190,000 times as much energy per square meter. The distance from the Sun to the Earth is 215 times the radius of the Sun, reducing the energy per square metre by a factor 46,000. Taking into account that the cross-section of a sphere is 1/4 of its surface area, we see that there is equilibrium (342 W per m2 surface area, 1,370 W per m2 cross-sectional area). This shows roughly why T ~ 300 K is the temperature of our world. The slightest change of the distance from the Sun might change the average Earth's temperature.
The above derivation is a rough approximation only as it assumes a black Earth. If one includes the effect of Terrestrial albedo which is about 30% (meaning the actual amount of solar energy absorbed by our planet is 70% of top of atmosphere irradiation), the above equation gives an average Earth surface temperature of 255 K only. The "missing" 33 K between such calculated value and the actual measured one (288 K) is deemed to be the result of greenhouse gases, namely water vapor, carbon dioxide and methane [3].
en.wikipedia.org |
