Viking 1, Viking 2, and MSL High and Low Pressures Reported Normalized to Areoid

This article will look at highest and lowest Martian air pressures reported for Viking 1, Viking 2 and Mars Science Laboratory (MSL) landers and how they compare when normalized to Mars areoid (the equivalent of Martian sea level). All of these landers touched down well below areoid. For Viking 1 the landing altitude was 4,495 meters below areoid. Viking 2 was only 3,637 meters below areoid, while MSL was 4,400 meters below areoid. Vikings 1 and 2 were stationary, but MSL is a rover (Curiosity) which does change altitude, however such changes are not part of the calculation (yet, at least). Table 1 shows the average pressures anticipated at landing altitudes as well as the highest and lowest pressures reported from these sites. The Viking Computer Facility Viking 1 and Viking 2 data source offered something akin to hourly pressues rather than average daily pressures provided by the MSL Rover Environmental Monitoring Station, so average pressures for sols with Viking mission high or low pressures are calculated on Table 2 with results posted also posted in the J column for Table 1.

RESULTS OF THE NORMALIZATION STUDY.

       Average pressure at Mars areoid is generally given as 6.1 mbar, however Smith and Zuber (see http://authors.library.caltech.edu/27881/1/SMIjgre01.pdf) claim that “Seasonal variations in atmospheric pressure associated with the exchange of CO₂ between the atmosphere and polar caps are expected to produce vertical variations in the height of the 6.1 mbar surface of 1.5 to 2.5 km over the course of the Martian year.”

    Further complicating the situation is an article by Smith and Zuber in the Smithsonian/NASA Astrophysics Data System that states that, “The MOLA topography of Mars is based on a new mean radius of the planet and new equipotential surface for the areoid. The mean atmospheric pressure surface of 6.1 mbars that has been used in the past as a reference level for topography does not apply to the zero level of MOLA elevations. The MOLA mean radius of the planet is 3,389,508 meters and the mean equatorial radius is 3,396,000 meters (Zuber incorrectly gives it as 339,600 meters). The areoid of the zero level of the MOLA altimetry is defined to be the potential surface with the same potential as the mean equatorial radius. The MOLA topography differs from the USGS digital elevation data by approximately 1.6 km, with MOLA higher. The average pressure on the MOLA reference surface for Ls =0 is approximately 5.1 mbars and has been derived from occultation data obtained from the tracking of Viking, Mariner, and MGS spacecraft and interpolated with the aid of the Ames Mars GCM. The new topography and the new occultation data are providing a more reliable relationship between elevation and surface pressure.”

     Having stated the above caveats, we use the mean atmospheric pressure surface of 6.1 mbars as a starting point. Using s scale height of 10.8, we move up from the landing latitudes with the high and low pressures reported to areoid to see how the pressures projected there stack up, As is indicated on Table 2, with respect to high pressures reported (and in the case of MSL Sol 370, altered after we pointed out that an 11.49 mbar (1149 Pa – see Figure 1) first reported as an average daily pressure implies that the Vaisala pressure sensor on MSL must have pegged out at its maximum capacity. Their fudged new report is prima fascie evidence for why we think their published data is not trustworthy.

       So what were the high pressure normalization results? The VL-2 maximum pressure and official maximum pressure ever measured by a lander (10.72 mbar) was seen at Ls 270.930 (early winter at VL-2, but early summer at the Martian South Pole. The VL-1 maximum pressure was seen at Ls 277.724. The same seasons apply. For MSL, which sits slightly south of the Martian equator, there are now two Martian years of what looks to be maximum pressure at 9.25 mbar (925 Pa). These pressures were advertised for Ls 252 to 253 in MSL Year 1 and again at 9.25 mbar at Ls 257 in MSL Year 2. This is late fall in the northern hemisphere, but late spring in the southern hemisphere. The initial advertised maximum pressure for its sol 370 of 11.49 mbar was at Ls 9 = early spring in the northern hemisphere, but early fall in MSL’s southern hemisphere. This pressure was obviously enormously out of place in terms of seasons because “the party line” was that the CO₂ ice at the Martian South Pole had to return to a gaseous state to drive up pressures worldwide on Mars. Note how much variation was seen in the above figures, but also note that in the end JPL ensured (at least to this point) that the maximum pressure given, (likely allowed) was exactly the same on both Martian years, 925 Pa (9.25 mbar). It is this lack of variation that first attracted our attention (and suspicion) when examining pressures given for much of the Martian year for the Vikings (especially for Viking 1 - see Figure 2 below).

       Without considering the controversial Sol 370 pressure at areoid are calculated as:

      (1) 7.07 mbar for Viking 2 Year 2.

      (2) 6.83 mbar for Viking 1.

      (3) 6.15 for both MSL years. 

       With inclusion of the controversial Sol 370 pressure of 11.49 mbar, then at areoid pressures are calculated as:

     (1) 7.64 mbar for MSL Year 1 (but the pressure would have been higher because the 11.49 figure represents a maxed out pressure sensor that was only rated at 11.5 mbar (these ratings tend to be approximate).

     (2) 7.07 mbar for Viking 2 Year 2.

     (3) 6.83 mbar for Viking 1.

     (4) 6.15 for both MSL Year 2

       The above figures overlook the issue of single daily average pressures given for MSL vs. maximum pressures given for the Vikings. If we use the averages generated on Table 2, then the ranks would be:

(1) 7.64 mbar for MSL Year (same caveat as above)

(2) 6.709 mbar for Viking 2 Year 2.

(3) 6.376 mbar for Viking 1.

(4) 6.15 for MSL Year 2. 

           A caveat for understanding the differences in high pressure seen as that Vikings 1 and 2 were experiencing global dust storms when they measured maximum pressures. However, based on how pressure increased at Luke Air Force Base by 6.6 mbar (see Sections 8 and 9 of our Basic Report and in particular Figure 35), we think that even with gravity that is only 38% of Earth's, a similar storm on Mars should drive up pressures by at least 2.5 mbar, and that big an increase is not shown on Figure 2. Frankly, having seen how many times JPL's REMS Team revised its data, especially after we challenged it, we would recommend placing no confidence in REMS generated pressures.

       We believe that JPL/REMS Team figures are generated based on political considerations. As an example, from the August, 2012 landing of the Mars Science Laboratory until May, 2013, JPL via the REMS Team and Ashima Research published false information showing an absolutely constant wind of 2 m/s (7.2 km/hr) from the East. They knew they had a problem early on. In fact, Curiosity Deputy Project Scientist Ashwin Vasavada of NASA's Jet Propulsion Laboratory, Pasadena, California stated early on that "One possibility is that pebbles lofted during the landing hit the delicate circuit boards on one of the two REMS booms." He also said," We will have to be more clever about using the remaining wind sensor to get wind speed and direction." But they were neither clever enough to get the winds right at Gale Crater, nor honest enough to pull the erroneous daily reports until after we gave Guy Webster, their P.R. man, holy hell about it. During an argumentative phone call with Webster we reminded him that he was responsible because he was the man in charge of what got released to the public, and because he knew that what he was publishing under his name was wrong. He couldn't defend his position, and so, shortly after, as we demanded, he ensured that all wind reports for MSL were changed to Not Available. Ashima Research then did the same. See Figure 44 in our Basic Report.

Ls of Minimum Pressure.

In conducting the research for this report, and most especially in seeing how our questioning of pressures reported by JPL seemed to cause JPL to alter those pressures (see Table 5 below) to match the Viking pressure curves shown on Figure 21, it became apparent that to question the Viking pressure curves was tantamount to heresy in JPL eyes and other eyes. These curves were primarily due to the efforts of Professor James Tillman at the University of Washington’s Viking Computer Facility. In explaining the pressure curves Tillman wrote: 

 "The first minimum of pressure, about sol 100 (aerocentric longitude (Ls) 145) corresponds to the maximum amount of carbon dioxide sublimation in the south polar region, while the second, about sol 434 (Ls 346), corresponds to northern winter. Because of the elipticity of the Martian orbit, the difference in the semiannual heating and cooling produces this semiannual difference in the amount of carbon dioxide in the polar regions.”⁴¹

 With regard to the absolute minimum pressure seen by landers on Mars, we now have 4 Martian years of data for the time around Ls 145 – one for Viking 1, two for Viking 2, and one for MSL. The data is summed up on Table 4. If we assume that the data was accurate, the average Ls was actually 149.8.

When low pressures seen by VL-1, VL-2 and MSL are normalized to areoid, they rank as follows (from lowest to highest pressure): 

      (1) 4.6487 mbar for Viking 1 that indicated 6.51 mbar

      (2) 4.777 mbar for MSL original pressure of 7.18 mbar.

      (3) 4.8572 mbar for MSL revised to 7.3 mbar (this seems to have changed again to 7.32 mbar).     

      (4) 4.8080 mbar for Viking 2 Year 2 that indicated 7.29 mbar.

       The above figures overlook the issue of single daily average pressures given for MSL vs. maximum pressures given for the Vikings. If we use the averages generated on Table 2, then the ranks would be:

      (1) 4.777 mbar for MSL original pressure of 7.18 mbar.

      (2) 4.8572 mbar for MSL revised to 7.3 mbar (this seems to have changed again to 7.32 mbar).     

           (3) 4.8626 mbar for Viking 1 that indicated 6.51 mbar.

           (4) 4.8735 mbar for Viking 2 Year 2 that indicated 7.29 mbar.

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Table 5 shows some (not all) of how JPL/REMS altered off the curve data for August and September 2012 and August 2013 and on through at least November 8, 2016 after we either brought the deviations up to JPL Public Relations Director Guy Webster, or published on our davidaroffman.com and marscorrect.com websites.