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View Full Version : Why are Temperatures not lower on Mountain-Tops (Olympus) ?



Nirgal
2004-Apr-05, 11:55 AM
Interestingly, according to this chart:

http://emma.la.asu.edu/tdaydaily.gif

the surface temperature does not seem to be lower at all on the
large Mountains (Tharsis Vulcanos).
On Earth, one would expect the highlands (for the tharsis region
we talk abaout elevations of tens of kilometers !)
to be considerably cooler than the plains at "sea level"

Any explanation, anyone ?

John Kierein
2004-Apr-05, 12:18 PM
It's closer to the sun and near the equator. This is the same reason that the snow on Kilimanjaro is hotter than the snow at the south pole.

aurora
2004-Apr-05, 09:06 PM
Do we know if the temperatures were actually measured at the surface?

Since mars has such a thin atmosphere, there is a big difference between the temperature of the exposed rock versus even a few inches above it.

§rv
2004-Apr-05, 09:20 PM
One thing I have never understood is why the mountaintops are cooler than at sea level. Rays from the sun enter our atmosphere as insolation rays right...... and from what I have learnt, its temperature & intensity decreases as it nears the earth's surface. Therefore it would seem logical to think that the higher you go, the hotter it would become as you are nearing the sun. Yet in reality it is the opposite.

I suppose radiation from the earth has a big role to play in maintaining the temperature therefore the higher up you go the less warm it would
be.
#-o

Brady Yoon
2004-Apr-06, 12:45 AM
I suppose radiation from the earth has a big role to play in maintaining the temperature therefore the higher up you go the less warm it would
be.

Yep, that's right. :D The atmosphere is largely transparent to solar radiation. It is the infrared radiation that the Earth emits that heats the atmosphere. And if you climb a mountain, it will be more cold because there are less molecules. Less air molecules=less heat.


It's closer to the sun and near the equator. This is the same reason that the snow on Kilimanjaro is hotter than the snow at the south pole.

It's not the distance to the sun that matters, it's the solar angle and the length of day. If you want to be really nitpicky, yes, Olympus Mons is 15 km closer to the sun that the rest of Mars. :P


Interestingly, according to this chart:

http://emma.la.asu.edu/tdaydaily.gif

the surface temperature does not seem to be lower at all on the
large Mountains (Tharsis Vulcanos).
On Earth, one would expect the highlands (for the tharsis region
we talk abaout elevations of tens of kilometers !)
to be considerably cooler than the plains at "sea level"

Any explanation, anyone ?

I think it's because the atmosphere of Mars is so thin. Even at "sea level" of Mars (there is none), the air is 150 times thinner than our sea level pressure. That's essentialy the same as the interplanetary space vacuum. So the temperature would decrease [/i]somewhat [/i], but it's probably from around 250 K to 225 K or something like that.