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Abstract, Introduction, and Martian Dust Devils. Updated 5/22/2017.


ABSTRACT: We present evidence that NASA is seriously understating Martian air pressure. Our 8-year study critiques 1,699 Sols (well over two full Martian years) of highly problematic MSL Rover Environmental Monitoring Station (REM) weather data, and offers an in depth audit of over 8,311 hourly Viking 1 and 2 weather reports. We discuss analysis of technical papers, NASA documents, and personal interviews of transducer designers. We troubleshoot pressures based on radio occultation/spectroscopy, and the small pressure ranges that could be measured by Viking (18 mbar), Pathfinder and Phoenix (12 mbar), and MSL (11.5 mbar). For MSL there was a mean pressure of 11.49 mbar measured on its Sol 370. When we made an issue of it with JPL, it was revised to 8.65 mbar. The REMS Team then published pressures of 11.77 mbar (for Sol 1,160) and 12 mbar (for Sol 1,161). Again we made an issue of it, and they revised the figures to 8.98 and 8.97 mbar respectively. When they asserted a pressure 1154Pa for Sol 1301, we challenged it and they revised it to 752 Pa. In fact we demonstrate that JPL/REMS weather data was frequently revised after they studied critiques in working versions of this report and on our websites at and

Vikings and MSL showed consistent timing of daily pressure spikes. We link this to how gas pressure in a sealed container would vary with Absolute temperature, to heating by radioisotope thermoelectric generators (RTGs), and to dust clots at air access tubes and dust filters. Pathfinder, Phoenix and MSL wind measurement failures are disclosed. Phoenix and MSL pressure transducer design problems are highlighted with respect to confusion about dust filter location, and lack of information about nearby heat sources due to International Traffic and Arms Regulations (ITAR). NASA could not replicate dust devils at 10 mbar. Rapidly filled MER Spirit tracks required wind speeds of 80 mph at the assumed low pressures. These winds were never recorded on Mars. Nor could NASA explain drifting Barchan sand dunes. Based on the above and dust devils on Arsia Mons to altitudes of 17 km above areoid (Martian equivalent of sea level), spiral storms with 10 km eye-walls above Arsia Mons, dust storm opacity, snow at Phoenix, excessive aero braking, liquid water running on the surface in numerous locations at Recurring Slope Lineae (RSL) and stratus clouds 13 km above areoid, we argue for an average pressure at areoid of ~511 mbar rather than the accepted 6.1 mbar. This pressure grows to 1,050 mbar in the Hellas Basin.


Mars has long fascinated humanity and often been seen as a possible safe harbor for life. In July, 1964 that hope was dealt a crushing blow by Mariner 4. Images and data obtained from no closer than 9,846 km showed a heavily cratered, cold, and dead world. Air pressures posted on a NASA site were estimated at 4.1 to 7 mbar, ( although A. J. Kliore (1974) of JPL listed the Mariner 4-derived pressure range as 4.5 to 9 mbar2. Mariner 4 saw daytime temperatures of -100o C (not seen on landers), with no magnetic field. Mariners 6, 7 and 9 got closer but still did not give us a picture that was much friendlier. Mariner estimates for pressure, based on radio occultation, spanned a range of 1 or 2.8 to 10.3 mbar.3 All pressure estimates were close to a vacuum when compared to average pressure on Earth (1,013.25 mbar). However from a distance of 1,650 km, after a dust storm that obscured everything upon its arrival in orbit, Mariner 9 could see evidence of wind and water erosion, fog, and weather fronts.4 When Vikings 1 and 2 landed, we learned of a high frequency of dust devils on Mars too. Phoenix witnessed snow falling.5 The HIRISE and MER Spirit showed unexpected bedform (sand dune and ripple) movement.6

       All landers agreed that pressure at their respective locations was somewhere between 6.5 and 11.49 mbar (MSL Sol 370 at solar longitude [Ls] 9) or even 12 mbar (Sol 1,161), but these low pressures make it very hard to explain the weather plainly seen. This is particularly true of dust devils and blowing sand. NASA/JPL credibility suffered a major blow when, after 9 months of publishing constant winds of 2 m/s from the east, one of their partners, Ashima research, met our demands to change all wind reports to Not Available (N/A) and to alter all daily published sunrise/sunset times from 6 am and 5 pm between August 2012 and May 2013 (except for October 2, 2012) to match our calculated times at (within one minute)7 that reflected seasonal variations to be expected at 4.59° South on a planet with a 25.19° axial tilt. These alterations were two minor battles won in our dispute with NASA/JPL. They were accompanied by an e-mailed thank you from JPL’s public relations director, Guy Webster, but they do not constitute victory for our side. That comes only when NASA also reverses course on ridiculously low pressure claims that we believe our report can demolish.

       To borrow from some military terms, there is an issue of how to best conduct this “war,” and it is important that we establish our “rules of engagement” up front. Before Guy Webster, Ashima Research, and the MSL REMS Team also began to change their reports to match the corrections that we detailed on our web site and in this report, Webster insisted that I submit this full report (which is in fact updated approximately every month now for six years), to Icarus.

       The full report is about 960 pages in length. As alluded to above, it is a living document that is constantly updated and expanded. However this is not the problem with formal publication at the venue he suggests. The problem is that our report goes beyond mere data analysis to delve into the nature of the specific people who have published what we feel is clearly erroneous data. We have gotten to know many of them quite well. The staff of Icarus is, in large part, composed of JPL personnel, with agendas and personal reputations at stake. To submit this report to them alone is to fight our war on their turf. We prefer to fight the war on our turf, and this means through the media (television, radio 8 and Internet and/or public debate. Having set the stage for the “war,” we fire the opening shots with an in depth look at the issue of Martian dust devils.

1.1. Comparison of Martian and Terrestrial Dust Devils 

Dust devils on Earth and Mars are similar with respect to geographic formation regions, seasonal occurrences, electrical properties, size, shape, diurnal formation rate, lifetime and frequency of occurrence, wind speed, core temperature excursions, and dust particle size.9  The only significant differences lie in measured absolute and   relative pressure excursions in the cores of Martian and terrestrial dust devils. Clogged dust filters and pressure equalization ports on landers may have diminished accuracy of dust devil pressure change measurements (see sections 2.1 through 2.6 below).

1.1.1 Geographic occurrences and the Greenhouse and Thermophoresis Effect

Thousands of dust devils per week occur in the Peruvian Andes near the Subancaya volcano (Metzger, 2001) which is 5,900 meters high.10 Dust devils are also seen in abundance on a Martian volcano, Arsia Mons.  But the base altitude of some dust devils there has been about 17,000 meters.11 Such an altitude on Mars supposedly would have about 1.2 mbar pressure, compared to about 478 mbar at Subancaya on Earth.  Reis et al. state that 28 active dust devils were reported in their study region for Arsia Mons, with 11 of them at altitudes greater than 16 km, and most inside the caldera (see Figure 1).  They don't fully understand how particles that are a few microns in size can be lifted there, and state that 1 mbar “requires wind speeds 2-3 times higher than at the Mars mean elevation for particle entanglement.”

Figure 1 Arsia Mons Dust Devils (reproduced from Reis et al., 2009)

       Reis et al. (2009) suggest a greenhouse-thermophoretic (GT) effect that they believe explains ~1 mbar dust lifting at Arsia Mons.11 Their article states that “Laboratory and microgravity experiments show that the light flux needed for lift to occur is in the same range as that of solar insolation available on Mars.” They concede that high altitude dust devils do not follow the season of maximum insolation, but indicate that the GT-effect would be strongest around pressures of 1 mbar. However, if anything we would expect such dust lifted at high altitude to just drift away.  The GT effect does not explain the structure of these events at high altitude, or why the dust rotates in columns that match dust devils produced at lower altitudes.  Further, Figure 1 shows that dust devils form at successively lower levels (i.e., higher pressures) as altitudes decline from 17 km to about 7 km, so there is nothing unique about reaching the theorized ~1 mbar-level at the top of Arsia Mons. 

1.1.2 Seasonal Occurrences and Electrical Properties.  

       Dust devils usually occur in the regional summer on Earth. On Mars their tracks are most often seen during regional spring and summer. 12 There are indications that there may be high voltage electric fields associated with Martian dust devils. Such fields would mirror terrestrial dust devils, where estimates are as large as 0.8 MV for one such event.13

1.1.3. Size and Shape

       About 8% of terrestrial dust devils exceed 300 m in height.  Bell (1967) reports some seen from the air that are 2,500 m high.14 Mars orbiters have shown dust devils there often are a few kilometers high and hundreds of meters in diameter, outdoing the larger terrestrial events. Martian dust devils can be 50 times as wide and 10 times as high as terrestrial ones.15 Still, a NASA Spirit press release (8/19/2005) stated, “Martian and terrestrial dust devils are similar in morphology and can be extremely common.”

1.1.4. Diurnal Formation Times

       About 80 convective vortices were recorded by Pathfinder.  Most occurred between 1200 and 1300 Local True Solar Time.16 On Earth noon is about the peak time.

1.1.5 Wind Speeds

        Stanzel et al. assert that dust devil velocities were directly measured by Mars Express Orbiter between January 2004 and July 2006.17 They had a range of speeds from 1 m/s (2.2 mph) to 59 m/s (132 mph).  Even on the high end, we do not see the 70 m/s required to lift dust by a NASA Ames apparatus discussed below in section 1.2.

1.1.6 Core Temperature Excursions

        Balme and Greeley18 state, “Positive temperature excursions in vortices measured by Viking and MPF landers had maximum values of 5-6 K. These values are similar to terrestrial measurements.”  However they note low sampling rates on Mars, “measurements with an order of magnitude higher sampling rate show temperature excursions as great as 20ºC.”  Ellehoj et al.19 indicate that core excursions for Martian dust devils can be up to 10 K (ºC).

1.1.7 Dust Particle Size - The Problem of Martian Dust <2 Microns and Wind Speeds

       Balme and Greeley18 also state, “The Martian atmosphere is thinner than Earth’s… so much higher wind speeds are required to pick up sand or dust on Mars.  Wind tunnel studies have shown that, like Earth, particles with diameter 80-100 μm (fine sand) are the easiest to move, having the lowest static threshold friction velocity, and that larger and smaller particles require stronger winds to entrain them into the flow.  However, much of Mars’ atmospheric dust load is very small, and the boundary layer wind speeds required to entrain such fine material are in excess of those measured at the surface (Magalhaes et al., 1999).20 Nevertheless, fine dust is somehow being injected into the atmosphere to support… haze and … local… and global… dust storms.”

       The problem of dust particle size is more serious than indicated above.  Optimum particle size for direct lifting by the wind (with the lowest threshold velocity) is around 90 μm. This requires a wind at 5 meters altitude to be around 30-40 m/s. For smaller particles like the 1 μm size dust typically suspended in the air over Mars, the threshold velocity is extremely high, requiring enormous wind speeds (>500 m/s) at 5 m altitude which would never occur.  It is thus argued that saltation must be crucial to the lifting of very small particles into the air (Read and Lewis, 2004, 190).9

       Saltation occurs when large particles are briefly lifted into air by surface winds, and then soon fall out by sedimentation.21 On impact with the surface, they may dislodge smaller particles and lift them into the air.  Read and Lewis indicate that the velocity that fine sand (~ 100 μm) would have on impact is only about 50 to 80 cm per second (1.8 to 2.88 kph).9

1.1.8. Core Pressure Excursions 

       Roy E. Wyatt (1954) of the Weather Bureau Regional Office in Salt Lake City, Utah reported that a small, approximately ~15 m high, 15 to 18 m wide dust devil had its center pass within 2.4 to 3 m of a microbarograph on August 12, 1953 in St. George, Utah (Figure 2) at an altitude of ~899 m above sea level.22 A drop from 913.644 to 912.289 mbar was recorded.  This 1.355 mbar drop in pressure equals 0.148%.

Figure 2 Dust devil pressure drop in Salt Lake City, Utah where a small, ~50-foot high, ~60 foot wide dust devil had its center pass 8-10 feet from a microbarograph on August 12, 1953 in St. George, Utah.

Balme and Greeley (2006) report that Pathfinder “identified 79 possible convective vortices from pressure data.”12 Recorded pressure drops were from ~0.075% to ~0.75%.   Figure 3 shows dust devil events for Pathfinder and Phoenix. If we examine the pressure drop seen by Phoenix from 8.425 to 8.422 mbar, that 0.003 mbar pressure drop is only about 0.036%. The Pathfinder event shows a drop in pressure from about 6.735 to 6.705 mbar (0.03 mbar). That is about a 0.445% drop. While the percent pressure drop is larger on the Pathfinder event than the Utah event, it was smaller for the Phoenix event. So absolute and percent pressure drops on Mars are producing almost the exact same storms, indeed often bigger storms, than we see on Earth. It might be argued that pressure is smaller on Mars; but so too is kinetic energy. Clearly, as we approach a vacuum, if we are going to see weather events based on pressure differences, there should be at least the same size percent pressure drops to drive them, not smaller ones.  However, most telling is that while the percent drops on Martian dust devils appear to overlap their terrestrial cousins; for hundreds of days Viking 1 and 2 almost always saw much larger pressure increases each sol about 7:30 AM local time with increases up to 0.62 mbar from the previous hour at that time.

As will be discussed later in this report, after Mars Science Laboratory data was scrubbed by JPL, there was not during one full Martian year of weather data (669 Martian sols) even one day where the average pressure from one day’s average pressure differed from the next by more than 0.09 mbar (MSL Sol 543 saw this drop from MSL Sol 542), although before they scrubbed the data there was an increase of pressure from MSL Sol 369 to MSL Sol 370 of 2.84 mbar (from 8.65 mbar to 11.49 mbar), and a drop on MSL 371 of the same 2.84 mbar back to 8.65 mbar. This report discusses MSL 370 in more detail later, but note that after we raised the issue of this pressure to Guy Webster at JPL, JPL altered the pressure reported for Sol 370 to 8.65 mbar, thus indicating no pressure change at all from MSL Sol 369 through Sol 371.

Figure 3 Pressure drops at Phoenix and Pathfinder during dust devils (adapted from Elohoj et al. 2009 and

       Figure 4 offers evidence that internal events on the Vikings were having a much greater impact on pressure readings than dramatic events like dust devils. Pressure increases at the 0.26 to 0.3 time-bins were comparable to pressure drops associated with global dust storms. An increase of 0.62 mbar in about 59 minutes that makes up one time-bin equates to a pressure rise 13 times greater than the largest (0.477 mbar) pressure fall shown for all 79 Pathfinder dust devil events, and about 21 times greater than the largest (.0289 mbar) pressure drop seen for a Phoenix dust devil.

Figure 4 above  Relative magnitude of 0.62 mbar increase in pressure for Viking 1 at its sol 332.3 and pressure drops for 79 convective vortices/dust devils at Mars pathfinder over its 83 sols. Source: Murphy, J. and Nelli, S., Mars Pathfinder Convective Vortices: Frequency of Occurrence (2002)

1.2. NASA Ames Test of Martian Pressures and Dust Devils 

An effort was made at the Ames facility to simulate Martian dust devils at a pressure of 10 mbar.  NASA (2005 article)23states that, “The high-pressure air draws thin air through the tunnel like a vacuum cleaner sucks air. Scientists also compare this process to a person sucking water through a straw. The resulting simulated Mars wind moves at about 230 feet per second (70 m/s).”  Actual recorded dust devil wind speeds seen on Mars by Pathfinder and Phoenix were about 6 m/s.24 Seventy m/s is 252 kilometers per hour, nearly the strength of a category 5 hurricane.  NASA Ames was unable to replicate a dust devil with a fan spinning at the 10 mbar pressure level. They state that “the simulated (10 mbar) Martian atmosphere in the wind tunnel is so tenuous that a fan would have to spin at too high a speed to blow thin wind through the test section.” As such, it becomes harder to accept that dust devils can occur in such low pressures. The problem becomes more severe when we see Martian dust devils operating at even lower speeds, or on Arsia Mons where pressure is ~1 mbar (see Table 1).

       Recent findings (Bridges, et al., 2012)25 based on HiRISE and MER Spirit photos of Martian bedforms (moving dunes and sand ripples) are also at odds with surface meteorological measurements and climate models which indicate that 129 kph winds (termed threshold winds) capable of moving sand are infrequent in the ~6 mbar atmosphere (Arvidson et al., 198326; Almeida et al., 200827). In fact, the required winds were never seen in 8,311 hourly pressures checked for Vikings 1 and 2. This will be discussed in greater detail later in Section 7.2.

TABLE 1 Pressure at various elevations on Mars based on a scale height of 10.8 and a pressure at Mars Areoid of 6.1 mbar. Atmospheric pressure decreases exponentially with altitude. In determining pressure for Earth, the formula for scale height is p = p0e-(h/h0) where p = atmospheric pressure (measured in bars on Earth), h = height (altitude), P0 = pressure at height h = 0 (surface pressure), and H0 = scale height.

This report is continued with Section 2 HERE.