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#1
08-01-2021, 09:20 AM
 yusufcam (Colin) Registered User Join Date: Mar 2010 Location: Sydney Posts: 123
temp variations Mars vs Earth

the answer to this might be obvious, but I couldn't google it out...

if the the temperature difference between the earths equator and poles is explained as the difference in the axis of the earth (seasons) and its curvature creating varying distances to the sun. How would you end up with temperatures of up to 86 F recorded at Mars equator. Which has distances from the sun which dwarf the difference between Earths equator and its poles.

Additionally heat is related to the density of atmosphere (more molecules to excite, thus space is cold) and Mars having little of it. How would it be achieving those types of temperatures.

Aroused my curiosity.
#2
08-01-2021, 11:02 AM
 JA ..... Join Date: Oct 2016 Location: Melbourne, Australia Posts: 1,960
Quote:
 Originally Posted by yusufcam the answer to this might be obvious, but I couldn't google it out... if the the temperature difference between the earths equator and poles is explained as the difference in the axis of the earth (seasons) and its curvature creating varying distances to the sun. How would you end up with temperatures of up to 86 F recorded at Mars equator. Which has distances from the sun which dwarf the difference between Earths equator and its poles. Additionally heat is related to the density of atmosphere (more molecules to excite, thus space is cold) and Mars having little of it. How would it be achieving those types of temperatures. Aroused my curiosity.
Hi Colin,

I don't know that you'll find a direct answer on that specific a question on google, but you never know. Keep hunting perhaps. In the meantime there are quite a few pieces in the puzzle to an answer to consider:

1. The Orbital Variables such as Orbit eccentricity, Obliquity (tilt), precession, orbit radius, etc... differences between Earth and Mars. Mars, for instance has a high eccentric (elliptical) orbit compared with the almost circular orbit of the Earth. Mars also has a slightly higher angle of tilt than the Earth. Both of these and other variables would factor in to differences in radiative heat transfer between the two planets and affect temperature and/or rate of change of temperature

2. The Planetary Variables such as atmospheric density, atmospheric chemical composition, reflectivity to Solar radiation (albedo), etc... differences between Earth and Mars. There is, for instance, a significant difference in the chemical composition of the Martian atmosphere (95% CO2, 3% N etc...) versus that of the Earth (78%N, 21%O2, 0.4% H2O as water vapour, 0.04%CO2, etc...). These differences effect radiative heat transfer to the planet and hence temperature. It is interesting to note that the Earth with an albedo of ~0.3 is almost twice as reflective to solar radiation as Mars which has an albedo around 0.16. That is a huge difference.

I'm sure there are other factors that would compound in to a fuller answer to allow you to compute the temperatures in a model, but at least you have some of the competing variables to consider.

Best
JA
#3
08-01-2021, 11:59 AM
 yusufcam (Colin) Registered User Join Date: Mar 2010 Location: Sydney Posts: 123
what you're saying makes sense but its hard to understand in light of the distances from the Sun (at least at this point for me).

could atmospheric composition outweigh density to that degree? They reckon that Mars atmospheres density is equivalent to being at a 35km height above ground level on earth, and the temperature at that height is about -54 C.

I wonder if the actual air temperature is affected by the radiant heat from the planet rather than atmosphere in some way that gives those livable temperatures they have been able to record.

Just curious how it would work
#4
08-01-2021, 12:13 PM
 JA ..... Join Date: Oct 2016 Location: Melbourne, Australia Posts: 1,960
Quote:
 Originally Posted by yusufcam what you're saying makes sense but its hard to understand in light of the distances from the Sun (at least at this point for me). could atmospheric composition outweigh density to that degree? They reckon that Mars atmospheres density is equivalent to being at a 35km height above ground level on earth, and the temperature at that height is about -54 C. I wonder if the actual air temperature is affected by the radiant heat from the planet rather than atmosphere in some way that gives those livable temperatures they have been able to record. Just curious how it would work
There is a huge difference in the atmospheric pressure at the surface of Mars (~0.6 kPa) compared to that of the Earth (~101.3kPa), i.e: ~170x greater atmsopheric pressure on Earth, which (under certain assumptions) relates also to differences in density factoring different temperatures in to the mix, via the Ideal Gas Law. As to the 35km question: If you travel high enough in our atmosphere you will reach a similar pressure.

Air temperature and surface temperatures are effected by radiant heat transfer. There is a good representation of this by a Scientist by the name of Trenberth (I think it was) who quantified the Earth's energy balance. I will see if I can find a link later.

EDIT added Trenberth et al 2009 - Earth Energy Balance....

Best
JA

Last edited by JA; 08-01-2021 at 12:25 PM. Reason: added image
#5
08-01-2021, 12:17 PM
 yusufcam (Colin) Registered User Join Date: Mar 2010 Location: Sydney Posts: 123
suspended dust is playing a big factor in Mars atmosphere apparently (and probably doesn't count as atmosphere). This is why it has a bright rather than translucent sky (can see out into space) even though its only 0.7% as dense as earths.

Maybe that's a variable as well.

https://www.forbes.com/sites/startsw...h=5ed8ae293453
#6
08-01-2021, 12:26 PM
 yusufcam (Colin) Registered User Join Date: Mar 2010 Location: Sydney Posts: 123
Quote:
 Originally Posted by JA There is a huge difference in the atmospheric pressure at the surface of Mars (~0.6 kPa) compared to that of the Earth (~101.3kPa), i.e: ~170x greater atmsopheric pressure on Earth, which (under certain assumptions) relates also to differences in density factoring different temperatures in to the mix, via the Ideal Gas Law. As to the 35km question: If you travel high enough in our atmosphere you will reach a similar pressure. Air temperature and surface temperatures are effected by radiant heat transfer. There is a good representation of this by a Scientist by the name of Trenberth (I think it was) who quantified the Earth's energy balance. I will see if I can find a link later. Best JA
Radiant heat is probably whats going on, I would guess, the equator being in direct sunlight rather than being tangentially exposed like the poles. Perhaps
#7
08-01-2021, 12:29 PM
 JA ..... Join Date: Oct 2016 Location: Melbourne, Australia Posts: 1,960
Quote:
 Originally Posted by yusufcam suspended dust is playing a big factor in Mars atmosphere apparently (and probably doesn't count as atmosphere). This is why it has a bright rather than translucent sky (can see out into space) even though its only 0.7% as dense as earths. Maybe that's a variable as well. https://www.forbes.com/sites/startsw...h=5ed8ae293453
Yes it would be. Dust is also a factor on the Earth's climate system and variations in surface temperatures can be seen during extended volcanic periods/fire seasons on Earth.

Best
JA

Last edited by JA; 08-01-2021 at 12:41 PM.

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