Curiosity find Mars’ icecaps suck up its atmosphere

Written by Simon Sharwood

NASA boffins have crunched 34 million weather observations collected by the Curiosity rover its two full Martian years trundling about the red planet.

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The basics are pretty simple: Mars is reliably cold, dry and windy, while the thin atmosphere means not much heat is retained so air temperature “usually plummets by more than 100 Fahrenheit degrees (55 Celsius degrees) between the afternoon high and the overnight low.”

NASA’s analysis also shows that the atmosphere is so thin that air pressure fluctuates seasonally as atmospheric carbon dioxide freezes into Mars’ ice caps.

Curiosity is in the Gale Crater at 5° South, but its measurements aren’t particularly biased by that location because Mars’ northern ice cap is smaller than its Southern cousin. That state of affairs came about because Mars’ orbit is elliptical, so the South receives less solar energy than the North.

The southern winter therefore sees more atmospheric CO2 captured and produces lower air pressure, which in turn means the southern winter produces air less conducive to heat capture.

Hence Mars’ reliably unpleasant weather.

NASA’s cooked up charts to explain this all, embedded below or available here if your browser is hostile to iFrames.


Comments (4)

  • Avatar

    Peter Champness


    Thanks Simon,

    I was looking for information on the Martian atmosphere with the idea of finding a test for the Greenhouse Gas Effect Theory. Your article has given me several leads.

    A lot of information already on the web see,s to be erroneous or out of date

    • Avatar



      I would like to find more information about planetary lapse rates but there really isn’t much available except Earth and one Venusian probe.

      But Joe Postma’s oft repeated analogy of how the principal “greenhouse gas” – water vapour – lowers the hypothetical lapse rate from a theoretical value of almost 10 to the observed value of ~6.5 K/1000m appears at odds with the main claim that “greenhouse gases” “trap” radiation leading to a warmer surface and a cooler upper atmospheric radiating level.

      Such a claimed effect – warmer surface and cooler TOA radiating level – MUST raise the theoretical lapse rate but it simply is not true – surely a significant failing in the “greenhouse effect” hypothesis.

      There is an observed lapse rate on planets with an atmosphere and “greenhouse gases” appear to have little, if anything, to do with it.

      • Avatar

        Peter Champness


        Thanks Rosco,

        You are correct. I have not found a temperature profile of the Martian atmosphere which is what I was looking for. I do not think that NASA planetary science has got there yet.

        With respect to the lapse rate;
        Doug Cotton says that increased CO2 reduces the lapse rate but the TOA stays at the same level, hence increased CO2 causes cooling at the surface,
        Warmists say that the lapse rate stays the same but increased CO2 causes the TOA to rise causing surface warming.
        David Evans says that radiation absorbed by CO2 gets transferred to other molecules and escapes by other pathways.
        A n atmospheric temperature profile of Mars would be helpful evidence to resolve the issue. Also a satellite observation of the OLR of Mars. I don’t know if that has been done yet either.

        • Avatar



          What evidence there is indicates that observed lapse rates are lower than theoretical.

          Water vapour certainly seems to be primarily responsible for this on Earth.

          On Venus with its high CO2 levels there is also an observed lowering of the hypothetical lapse rate.

 shows a table of theoretical lapse rates for Venus, Earth and Mars. It is interesting that the author of the site calls the difference between “blackbody” temperature and surface temperature the greenhouse effect whilst simply ignoring the problem that the lapse rate is lowered which is at odds with the central tenet of the hypothesis.

          Of course the Venus calculation is problematic because we really have very sketchy knowledge about Venus atmosphere.

          What data there is indicates that the observed lapse rate for Venus is about 8 versus a hypothetical rate of 10.4. This site produced a “profile” graph – – from which you can estimate the 8 value from the Magellan orbit data in 1991.

          Warmists have absolutely NO evidence that the radiating level of the atmosphere has risen due to increased CO2 !

          Satellites unequivocally indicate Earth IS radiating MORE to space NOT less.

          There is ample evidence that the observed lapse rate for Earth and Venus is lower not higher and up to 3.3 K/1000m is not an insignificant difference – 9.8 versus 6.5 on Earth and ~10.4 versus ~ 8 for Venus – ~2.4 K/1000m.

          But then Warmists say a transparent non radiating atmosphere would induce snowball Earth.

          I never get an answer from them as to how they think such an atmosphere could ever shed “heat”.

          Apparently they think it could not absorb any “heat” because it is transparent so shedding “heat” isn’t an issue.

          They simply ignore the fact that 99.9% of the atmosphere which isn’t a “greenhouse gas” still manages to somehow increase in temperature from 6 C to 25 C as recorded at Alice Springs the other day.

          If they believe this phenomenon is predominately due to transfer from trace amounts of the atmosphere – desert locations have low humidity – heated by radiative absorption they are deluded.

          And yet the nearest thing we have to such an atmosphere exists in desert locations where the highest temperatures are recorded at surface levels – if you believe O2 and N2 don’t radiate.

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