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JPL, the REMS Team, and Ashima Research Were Out of Line in Their Dust Storm Conclusions. (Updated 8/12/2018)

Figure 1 above: Regional dust storm on Mars that never reached MSL or Opportunity.

Figure 2A- JPL, the REMS Team and Ashima Research have published only a single chart for hourly pressures for MSL Sols 9.5 to 13. They have NOT published any such data for the period of time covering the dust storm shown on Figure 1. Figure 2B shows the pressure variation for Sol 11. We have only seen questionable sol-averaged pressures, with a huge number of ridiculous mistakes. As such, the assertions made on Figure 2A seem to be not credible.


       Figure 2A purports to show how pressure varied from the norm during a dust storm on Mars that reached neither Opportunity (it missed it by 840 miles), which had no pressures instruments, nor MSL Curiosity on the opposite side of the planet. Curiosity had the questionable Vaisala pressure transducer on board. The main problem here is the timing of the dust storm, and the paucity of data put out by JPL, the REMS Team and Ashima Research leading up to this graph. Before August 23, 2012 those responsible for weather reports from MSL issued a single report that graphed pressures for MSL Sols 9.5 to 13 only. The same report only graphed temperatures for MSL Sol 10 to 11.5. There were promises that more data like this would be published at the PDS site, but 4.5 months later these promises are unfilled, hinting at what looks very much like a cover-up. When Figure 2A is inserted onto Figure 3 in the area of the chart where the dust storm discussed in this page is located, we found that between the first report of the storm at Sol 102 on November 18 at Ls 208.8 and the last report at Sol 108 (Ls 213.1 on November 25), the REMS and Ashima daily weather reports had no data for Sol 103 (Ls 209.4 on November 19), Sol 104 (Ls 210 on November 20), and Sol 105 (Ls 210.6 on November 21).

       REMS revised its weather reports in the summer of 2013. As of April 30, 2014 REMS and Ashima differ on the critical period here as follows:




                              ON 30 APRIL 2014

























          NOTE: We are not sure if we played a role in driving Ashima Research out of the business of reporting on MSL weather, but after numerous critiques of their work that we published they pulled down their web site by early 2016.

       The data after then suggests a slow, steady increase pressure that would be indicated by Viking 2 results; but the key point here is that red curve on Figure 2A is based on what appears to be missing (and therefore imagined?) data. Note that Figure 2A does not actually name either the Sol of the blue or red curves. If the REMS Team has more data than it publishes, why is it hiding it? We can only conclude from what we see here for Figure 2A is not supported by data required.    

       Figure 2A has other major problems too. As is shown, Figure 2B is a near clone of the data presented for Sol 11, the only day that the REMS Team ever published a pressure graph and temperature graph for in the first 4.5 months of operation. The blue curve on Figure 2A appears to be taken from Figure 2B, but for that early period of MSL pressure reporting operations data was anything but fully stable. While the chart presented for sols 9.5 to 13 was consistent with respect to day to day operations; that ended very quickly. Sol 13 was on August 20, 2012. No pressure was originally published for Sol 14 (but a year later it was assigned a pressure of 7.4 hPa (740 Pa). On Sol 15 there was an original average pressure of 7.3 hPa (7.3 mbar) published, but it was changed almost a year later to 7.4 hPa. The only relative humidity ever published for MSL (7%) on Sol 15 was eliminated in revised reports next year. Sol 16 pressure was reported as 7.4 hPa. For the next two days (sols 17 and 18) no pressure was originally published, but a year later REMS claimed 7.42 hPA for sol 17. Sol 19 was interesting. Average pressure climbed to 7.85 hPa originally, but after we questioned it REMS changed it to N/A. Nothing was reported on August 26, but on August 27 (sol 21) it had originally risen to 7.9 hPa. Again, when we questioned this pressure because it was above the expected curve, the REMS Team dropped it back to 7.41 hPa.  With two original exceptions that vanished later, a  pressure of 7.9 hPa was not seen again on the typical pressure curve until Sol 74 on October 20, 2012. The two exceptions were also fairly early in MSL weather reports - 7.99 hPa (later dropped to 7.49 hPa) on Sol 35 (September 11) and 8.04 hPa (later dropped to 7.53 hPa) on Sol 40 (September 16). Clearly the REMS Team has been acting like slaves to the Viking pressure curves. They have consistently altered data to stick to those curves.  The data published by JPL is absolutely untrustworthy (with the possible exception of their original reports between September 1 and 5, 2012 that showed pressures between 742 hPa and 747 hPa (mbar) before they reduced it by changing hPa unist to Pa units. Thus 747 hPa became 7.47 hPa - which is like exchanging dollars for the same number of cents. The higher pressures match the weather plainly seen on Mars. While they might represent a rebellion in the REMS team where somebody wanted us to know the truth, it seems more likely that they were working with the same faulty transducer with a jammed dust filter, and that they merely used hPa units when they meant to use Pa which they did in fact use after this period of confusion.

       The bottom line on Figure 2A is that by no means was the pressure situation stabilized by this point in MSL operations to compare normal pressure cycles with dust pressure cycles; and even if it were the dust storm never reached MSL. Therefore Figure 2A is utter nonsense.

Figure 3 - Pressure data at MSL up until Ls 218.6 on December 4, 2012.


Dust storms can radically alter the density equations in short order. A dust storm at Luke Air Force Base on July 5, 2011 turned day to night in surrounding areas (see Figure 4). While the measured pressure increased by at least 6.6 mbar (more than average pressure at Mars areoid), pressure was only taken once per hour; all the increase was due to dust in a cloud that only rose to somewhere between 5,000 and 8,000 feet. Dust storms also turn day to night on Mars (see Figure 5). The essential question is, “What ambient Martian air density is required to support such a mass of dust?” 

       The Vaisala pressure transducer used for MSL was rated for a maximum pressure of 11.5 mbar. The initial pressures reported showed average daily pressures of 7.3 to 8.04 mbar at a time that Mars was supposed to be experiencing pressures near its minimal values when it was late winter in the southern hemisphere where MSL landed. If the pressure, which seemed to be following the values seen by Viking 2, continued to increase as was seen in Viking 2, the maximum average daily pressure should gave increased to something around the 9.45 to 9.5 mbar around January 31, 2013 unless there is is a dust storm that reached the MSL. That's if the pressures seen at Viking 2 were correct (which I doubt). Based on Viking 2, if there was a global dust storm, then pressure at MSL should have grown to 9.9 or 10 mbar. Keep in mind that the Vaisala pressure transducer maxes out at 11.5 mbar (which essentially happened on Sol 370 until the pressure was politically reduced from 11.49 mbar to 8.65 mbar), not very much more than what Viking 2's data would allow us to predict. HOWEVER, if the added  adensity due to a dust storm on Mars is similar to what was seen in the Phoenix, Arizona storm, and if we add the 6.6 mbar increase in pressure to the maximum pressure expected without a dust storm, 9.45 mbar + 6.6 mbar = 16.05 mbar.  It can quickly be seen that the 11.5 mbar cap was not prudent. 

       Sol 370 was not the only Martian day where JPL/REMS revised pressure data after I called JPL Public Relations man Guy Webster. This Table sums up other specific days where such changes occurred. There were also huge revisions of temperature data. Figure 6 documents the changes made for sols 1260 and 1261 where pressures initially published were 11.77 and 12 mbar. More print-screens for similar changes are found at MSL SOL 370, 1160 and 1161, and 1330 to 1331 Pressure Changes by JPL and Ashima.

TABLE 1 – Pressures revised by JPL/REMS after we highlighted them or published them in earlier versions of our Report




Initial Pressure Reported

Pressure for the previous sol

Final Pressure Reported after JPL Revisions

Aug 25, 2012



785 Pa


719 Pa– then changed to N/A

Aug 27, 2012



790 Pa


741 Pa

Sept 1 to Sept 5, 2012



 742 to 747 hPa       74200 to 74700 (Pa)

743 Pa

745, 743, 745, 747 and 747 Pa 

Sep 12, 2012 (This date later changed to 9/11/2012)



799 Pa

749 Pa

750 Pa

Sep 16, 2012 (date later altered)



804 Pa

750 Pa

753 Pa – then changed to 751 Pa  

Sep 16, 2012 (date later altered)



804 Pa

750 Pa

753 Pa – then changed to 751 Pa 


Oct 3, 2012

Series alteration starts here and goes to 10/12/2012



779 Pa

770 Pa

769 – Pa. Note the steady progression without reversals that were seen between 10/3/2012 and 10/12/2012 in initial results. This series looks very fudged.

Oct 4, 2012



779 Pa


769 Pa

Oct 5, 2012



781 Pa


771 Pa

Oct 6, 2012



785 Pa


772 Pa

Oct 7, 2012



779 Pa


772 Pa

Oct 8, 2012



782 Pa


774 Pa

Oct 9, 2012



786 Pa


775 Pa

Oct 10, 2012



785 Pa


776 Pa







Oct 11, 2012



785 Pa


777 Pa

Oct 12, 2012



781 Pa


778 Pa

Nov 11, 2012



815.53 Pa

822.43 Pa

822 Pa

Dec 8, 2012



865.4 Pa

867.5 Pa





Initial Pressure Reported

Pressure for the previous sol

Final Pressure Reported after JPL Revisions

Feb 19, 2013



940 Pa – a high until now. Pressures had been declining since a high of 925 Pa in late January 2013.



Feb 22, 2013



886 Pa – quite a large drop

Last 2 reports were 940 Pa on Feb 19 and 921 Pa on Feb 18, 2012


Feb 27, 2013



937 Pa

917 Pa


May 2, 2013



900 Pa

868.05 Pa


Aug 21, 2013



1,149 Pa

865 Pa

865 Pa

Aug 27, 2014



754 Pa

771 Pa

771 Pa

Oct 11, 2014



823 Pa

838 Pa

838 Pa

April 16, 2015



823 Pa

N/A – next sol 848 Pa


Nov 10, 2015



1177 Pa

898 Pa

899 Pa

Nov 12, 2015



1200 Pa

899 Pa (revised)

898 Pa

April 2, 2016



945 Pa

753 Pa

752 Pa

April 3, 2016



1154 Pa

753 Pa (2 sols earlier, 751 Pa on Sol 1302

752 Pa

Oct 17, 2016



921 Pa

906 Pa

910 Pa

Oct 23, 2016



897 Pa

909 Pa

907 Pa

Oct 27, 2016



928 Pa

903 Pa

907 Pa

Jan 10, 2017



860 Pa

868 Pa

871 Pa

Feb 10, 2017



815 Pa

850 Pa

846 Pa

Feb 15, 2017



864 Pa

847 Pa


Aug 13, 2017



1294 Pa

879 Pa

883 Pa

Mar 24, 2018



913 Pa

717 Pa

716 Pa

Mar 25, 2018



1167 Pa

913 revised to 716

715 Pa

Table 1 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 August 12, 2018 after we either brought the deviations up to JPL Public Relations Director Guy Webster, or published them on our davidaroffman.com and marscorrect.com websites.


Dust storms can greatly alter the opacity (τ) on Mars.  Figure 5 shows visibility for different values of opacity on Mars due to a dust storm at Opportunity between sols 1205 and 1235. All photos were taken between 10:53 and 11:30 local time. The dust in the Martian air over Opportunity blocked 99 percent of direct sunlight.  This fact alone makes it very hard to accept that pressures would be unaffected. Note: The dust storm shown on Figure 1 did not reach Opportunity. As is noted on Figure 1, Opportunity carried no pressure sensor. Thus any guess about how much pressure increases with a storm like that shown can only be based on what we see on Earth with similar storms.

Figure 4 Arizona Dust Storm of July 5, 2011. Pressure at Luke Air Force Base increased during the dust storm by 6.6 mbar more than average pressure (6.1 mbar) at areoid on Mars.

Figure 5 - Opacity changes at Opportunity from sols 1205 to 1235. Redrawn from http://www.jpl.nasa.gov/news/news.cfm?release=2007-080.

J. D. Parsons (2000) addresses the compressibility of dust storms and positive feedback for their formation.  Pre-dust storm density values are around 9.4 g/m3.  A sample dust storm given in Parsons paper would have additional densities of 17g/m3 in order to even be created.  This is an order of magnitude greater than terrestrial storms.  It also constitutes an increase of at least several hundred percent over previously accepted values.  In the Sahara, pressures have been observed to increase during dust storms.  Likewise when the huge dust storm hit Luke Air Force on July 5, 2011,  pressure rose by 6.6 mbar (more than accepted average pressure at Mars areoid) between the storm’s arrival at 0255Z 6 July 2011 (pressure 1004.7 mbar) and 0555Z when the pressure was up to 1011.3 mbar. Pressure dropped as visibility cleared at 0655Z (personal call to Luke AFB meteorology, July 6, 2011).

The Parsons (2000) paper proposes a gravity current analog for dust storms and mentions that such currents should be constrained to the height of the inversion layer (but dust storms on Mars can still have effects at 160 km). Perhaps most important, increased pressure makes it easier to entrain particles (hence higher pressure may explain dust storms and dust devils). During the Martian year opacity varies greatly.  The clear season is in the northern summer with optical depth τ values of ~0.3 to 0.5. During northern winter τ values of ~2 to 5 or higher were seen during dust storms (see Figure 7).  Black dots are the Year One data, black pluses are the Year Two data, and the red X’s are extrapolations from the pressure data. This is for Viking 1. There is a relation between pressure and opacity, however the figure adapted from page 181 in The Martian Climate Revisited by Read and Lewis, states that τ is derived from pressure data. This is the same pressure data that might be distorted by clogged pressure filters. There is a need to quantify how increased density and opacity due to dust storms affect pressure on Mars.

Figure 6: Changes made for sols 1260 and 1261 where pressures initially published were 11.77 and 12 mbar.

Figure 7: VL1 Pressure and Opacity, redrawn from Figure 7.2 in The Martian Climate Revisited, Read and Lewis (2004), adapted from Martin and Zurek (1993).