HOME PAGE Web Site Contents Mars Report Contents Mars Report Abstract CV for Dr. David Roffman Diplomas PhD Thesis PhD Thesis Powerpoint Mars PowerPoint MSL Weather Reports Base on Mars? Seasonal Pressure Altitude Calculations Seismic Activity on Mars? Perserverance Weather Data MSL Years 5-6 Winter MSL Year 5 FALL MSL Year 5 Summer MSL Year 5 Spring MSL Years 4-5 Winter MSL Year 4 FALL MSL Year 4 Summer Weather MSL Year 4 Spring Weather MSL Yr 3-4 Winter Weather MSL Fall Yr 3 Weather MSL Yr. 3 Summer Weather MSL Yr. 3 Spring Weather Martian plume March 25 2017 MSL Ultraviolet 3 YEARS OF MSL UV Desai, EDL, Parachutes & ExoMars Mars winter vs. summer temps Helo to Mars Sea at Utopia Planitia, Mars Tree Stump at MSL? Spherical life on Mars? Mars Report Abstract, 1-1.2 Mars Report Sec.2-2.1 Report 2.2-2.4 Report 2.5-2.5.2 Report 2.5.3-2.7 Report 3-4 Report 4.1-4.1.2 Report 5 to 6 Report  7-7.2.1 Report 8 Report 9 Report 10 Report 11 Global Dust Storm Report 12 Report  13-13.2 Report 13.3-13.5 Report 13.6 Report 14-15 Report 15.1 Report 15.2-15.3 Report 15.4-15.6.2 Report - Report Report 16-16.1 Report 17-20 Report References Rebuttal of REMS Report Running water on Mars MSL Year 0 Weather MSL Yr 2 Winter-Spring Weather MSL Yr 2 Summer Weather MSL Yr 2 Fall Weather MSL Yr 2-3 Winter Weather Adiabatics MSL Hi Temps MSL Low Temps Organic Chem found by MSL Oxygen in Mars Air MSL Day length & Temp Warm winter ground temps 155-Mile High Mars Plume Radiation Diurnal Air Temp Variation Mars Temps Fahrenheit Beagle found JPL/NASA Pressure Mistakes Enter MarsCorrect Sol 370, 1160 & 1161 Histories Mars-Radio-Show JPL Fudges Pressure Curves MSL Temp. ∆ Mast to Ground High & Low Pressures Normalized Mars soil 2% water Moving rock Mars MAVEN MSL Relative Humidity Claim Ashima Concedes Original MSL Weather Record Old MSL Weather Record MSL Summer Weather Pressure Estimate REMS Wind MSL Pressures REMS Reports Curiosity Geology CERN-2013-pics Daylight Math MSL Errors P1 MSL Errors P2 MSL-Chute-Flap MSL daylight Ashima Sols 15 to 111 Ashima Sol 112 to 226 Ashima Sol 227 on New Ashima Sols 270+ MSL Summer to Sol 316 Updated Secrets of Mars Weather Forecast Wind Booms MSL Credibility MSL Temp. Swings MSL Temperatures Sample Analysis at Mars (SAM) VL2 - MSL Ls Comparson Ashima MIT Mars GCM Dust Storm Nonsense Mars Slideshow Moving Sand & Martian Wind 3 DEC12 Press Conf. MSL Press Conf. 15NOV2012 Sol Numbering MSL Pressure Graph to Ls 218.8 MSL Sky Color Mars Sky Color DATA DEBATE! Zubrin's Letter Phoenix Vaisala Vaisala Pressure Sensors Phoenix &MSL Flawed MSL REMS Viking pressure sensors failed MSL landing site Mars Landings Phobos Grunt Martian Air Supersaturation Mars & CH4 Mars and MSL Time Viking Pressure Audit Links Mars Society 2008 Quant Finance Frontiers Home Front. Preface Frontiers Ch. 1 Frontiers Ch. 2 Antimatter Lightning Frontiers Ch. 3 Frontiers Ch. 4 Frontiers Ch. 5 Frontiers Ch. 6 Frontiers Ch. 7 Frontiers Ch. 8 Frontiers Ch. 9 Frontiers Ch 10 Frontiers Ch 11 Frontiers Ch 12 Frontiers Ch 13 Frontiers Ch 14 Frontiers Ch 15 Frontiers Ch 16 Frontiers Ch 17 Frontiers Ch 18 Frontiers Ch 19 Frontiers Ch 20 Frontiers Ch 21 Frontiers Ch 22 World Tour Spring-Break -13 Other Travels Asteroid Impact? ExoMars data Unit Issues Viking Pressures Tavis CADs Landing Long Scale Heights LS of Max/Min Pressures Tavis Report Tavis Failures Lander Altitude Martian Trees? Code Experiment Gedanken Report Mars Nuke? Martian Flares Mach Numbers MOLA (altitude) Original Mars Report Mariner 9 & Pressure Mars  Temps MSL Time MPF Pressure Blog Debates Spring Pendulum Plasma Model Reporting Errors Orbital Parameters Anderson Localization P. 1 Anderson Localization P. 2 Moving rock old Navigating Mars Mars Report Section Links Mars Report Figure Link Gillespie Lake rock outcrop MSL Sol 200 Anomaly Sol 1300&1301 Anomalies Gilbert Levin & Labeled Release Brine on Mars Ceres Lights Yr 1 Table 1 Missing data Mitchell Report Old Mars Report All MPF Temps ExoMars fails Did Spirit find past life? MSL ground temps go haywire OPACITY AT MSL Luminescence on Mars Dust Storms & Microorganisms 2018 Global Dust Storm Links to Sections of the Basic Report

This article is copied from our Basic Report. (Updated 9/15/2017 after a visit from the FMI - IP Address AS1741 Tieteen Tietototekniikan Keskus Oy)

Segments from Section 2.2 and 2.4 on Mars Pathfinder (MPF) and Phoenix Pressure Issues.

The range of sensitivity and accuracy of the Vaisala Barocap® and Tavis sensors are crucial. With Mars Phoenix, three Barocap sensors [LL(B1), and RSP1 (B2, B3)] were used.  They had problems associated with a nearby heat source.  Problems were particularly noted when temperatures rose above 0ºC.  According to Taylor et al. (2009) calibration coefficients were also withheld from the Finnish Meteorological Institute (FMI) due to International Traffic in Arms Regulations (ITAR). The 5-12 mbar range of Barocaps was probably due to the data from the Tavis sensors before, but Tavis sensors were limited due to radio occultation pressure experiments (not as accurate as in situ measurements) by the Mariners. Radio occultation results are discussed further in Section 5.

An issue with respect to how fast the dust filters for transducers on landers could have clogged relates to when the air tube was initially exposed to ambient conditions. If open to space all the way down, then air might not rush in so fast; while if the tube were suddenly opened on the surface, more dust might be expected to rush in, even at supersonic speeds. Alvin Seiff, et al. (1997) indicates that for Pathfinder the plan was for atmospheric pressure (and temperature) to be measured during parachute descent from ~8 km to the surface. The air inlet was connected to the flared tube fitting shown in Figure 10B by one meter of 2 mm inside diameter tubing. Dr. Robert Sulliavan (Cornell University) told us (on July 27, 2011) that while 1µ particles on the surface of Mars clump together quickly, larger particles that were easier to move would be lifted on landing. He was not sure about whether they would clog a dust filter as fast. But if MPF suddenly ingested 1µ particles suspended in the air below 8 km right after parachute deployment, the hot air associated with the entry-related heat might cause a problem for the tiny filter.

2.4 Issues Raised by the FMI. The FMI report by Kahanpää and Polkko (2009) discusses the Vaisala pressure sensor that it designed for use on Phoenix.  It states,"We should find out how the pressure tube is mounted in the spacecraft and if there are additional filters etc."  The one and only filter for the Vaisala transducer is shown on the top of Figure 11A (with its near twin for MSL shown on the bottom of Figure 11A). I challenged the above statement on November 14, 2009, and published a criticism of it on my web site on November 17, 2009.  Kahanpää’s partial response from the FMI to my assertion that, "something stinks" about his request for information on additional filters was a follows:

“Your nose smelled also a real issue. The fact that we at FMI did not know how our sensor was mounted in the spacecraft and how many filters there were shows that the exchange of information between NASA and the foreign subcontractors did not work optimally in this mission!” (Kahanpää, personal communication, December 15, 2009).

 In his e-mail of December 15, 2009, Kahanpää made clear that there was no extra filter. However, the confusion in his report highlights another possibility.  As is shown in Figure 11B, the filter is very small (~10 mm2).

Figure 11A above The top transducer is for Phoenix. Note the tiny dust filter shown under Praw (adapted from Doc. No: FMI_S-PHX-BAR-TN-00 FM-00 Revision 1.0 dated 2009-02-26). The report is entitled The Time Response of the PHOENIX Pressure Sensor). An area of concern for clogging by dust is highlighted. The photo on the right is adapted from The bottom pictures (Figure 11B) are for MSL

       Like the Tavis transducers that were used for Vikings and Pathfinder, the Vaisala transducer was exposed to a vacuum on the way from Earth to Mars.  Again, when Phoenix landed, a lot of dust was raised by the retrorocket.  The air pressure outside was supposed to be low, almost as low as outer space.  The flow of air into the transducer therefore should not have been too fast.  However, if the pressure outside was higher than expected, the rate of flow of air and dust into the Phoenix would be faster than planned for, with the result that dust would be rapidly sucked in just like a vacuum cleaner would inhale it.  A tiny filter might well quickly clog with dust so fast (at supersonic speeds) that it would prevent more air from reaching the pressure transducer.

With a clogged filter, pressure at the Barocap pressure sensor head would stay pegged at a low pressure reading. If there was a higher pressure on the outer side of the dust clog, it could not be felt on the inner side where the Barocap resided. This could explain the confusion by Kahanpää & Polkko and why they asked in their report about more filters being present. Even if the FMI team eventually received the needed information about relocation of heat sources, corrections to the pressure indicated at the Barocap pressure sensor head would not reflect what the true pressure was on the other side of the dust clog. 

One difference between the Vikings and both Pathfinder and Phoenix is that the latter two landers did not include Radioisotope Thermoelectric Generator (RTG) heaters. Therefore, it would be expected that as the sun grew lower on the horizon and temperatures dropped, pressure would go down steadily. In looking at data for Phoenix derived from Nelli et al., 2009, this is exactly what happened (see Figure 12A).  The pressure fell in a nearly linear fashion.  

Figure 12A is extracted from graphs produced by Nelli et al. (2009).3 Their graphs included projections made from a General Circulation Model (GCM) with values hypothesized for 3 am, 9 am, 3 pm and 9 pm local time at Phoenix. We added Ls and data about day length for clarity. Phoenix landed in the Martian arctic in late spring. There was no sunset until Ls 121.1 on its 96th sol on September 1, 2008. By the time the mission ended there were about 16.7 hours of sun light each day.


Figure 12A - Pressure and Temperatures Recorded by Phoenix (adapted from Nelli et al, 2009). Ls and day length data has been added to the top graph.

       The pressure data appears to be sol averaged, while the temperatures are not. But what kind of pressure drop would be expected if the average temperature dropped from 195K to 180 K, with a starting pressure of 8.5 mbar? The answer is about 7.85 mbar. The actual pressure at the end of the series shown on the graph is about 7.4 mbar, which is better than a 94% match with the prediction based on Gay-Lussac’s Law and a clogged pressure tube. However, when Phoenix landed on Mars on May 25, 2008, it was not yet summer.  The summer solstice occurred on June 24, 2008. By that time there was no change in the temperatures evident on Figure 12A, but pressure was running about 8.2 mbar. Using the same temperatures as above with an entering argument of 8.2 mbar the projected pressure would be 7.57 mbar. That is an agreement of 97.78%.

       Unlike pressure calculations based on an inverse of normal temperature and pressure relationships that factor in RTG heat becoming available to Viking transducers, on Phoenix there was no RTG. If there was no heater, pressures would be expected to fall directly with the fall in ambient pressures. This happened, but there were indeed four heaters that were turned off just before the lander died ( The third one operated the Surface Stereo Imager –and the meteorological suite of instruments. It was thought that electronics that operate the meteorological instruments should generate enough heat on their own to keep most of those instruments and the camera functioning. This sounds like there was no need to pump heat into the pressure transducer. If so, there may indeed have been slow cooling of the air trapped behind   the clogged dust filter, with no timed heat pumps to cause pressure spikes seen with the Vikings and MSL.  

    There was nothing to keep Phoenix alive once it got too cold. Its death supposedly came when ice built up on and broke the solar arrays (

With respect to Phoenix design, Kahanpää & Polkko repeatedly mentioned funding problems, although the meteorology package for Phoenix cost $37,000,000.  Not only was an anemometer unfunded, but a way to change the dust filter was also left off the shopping list. Indeed it is unclear if anyone conducted tests to see to how much dust was required to clog the filters, or if such tests were conducted, what size dust particles, and what density of dust particles were involved.  

Kahanpää & Polkko (2009) stated that the Mars Science Laboratory (MSL), launched in 2011, is a $2 billion cornerstone mission and is therefore handled in a different way than the $454 million dollar scout mission Phoenix. The actual cost of MSL was $2.5 billion. However, MSL’s FMI-built sensors (delivered in 2008, see are in the 0.01 to 11.5 mbar range (see, still too low(the REMS Team reported a mean pressure of 11.49 mbar for Sol 370). I discussed this problem with Dr. Ashwin Vasavada, JPL’s Deputy Director of the MSL, but the inadequate transducer was apparently sent anyway.

On December 9, 2012 at we published a prediction that maximum pressure published for MSL would occur around January 31, 2013. Initially our estimate of the date was only off by 2 days, but our 9.45 to 9.5 mbar estimate was higher than the 9.25 mbar published by the REMS Team. But on July 3, 2013 REMS changed all its data. Our estimate was then listed as off by 19 days, but the new pressure was 9.4 mbar, quite close to our 9.45 to 9.5 figure. Our slightly off eye-balled prediction was only  based on our beliefs that the REMS Team would extrapolate (politically expedient) results from pressure curves seen by Viking I and 2 (see Figure 12B), making sure to keep all their invented data points between those of Viking 1 and Viking 2 because MSL’s altitude was between those two probes.  Sure enough when we called attention to four MSL pressures that were above the curve in August and September 2012 (see the red hexagon on Figure 12B and Table 3); JPL dropped them back to match the curve when they revised their data on July 3. Likewise, after a pressure of 11.49 mbar was reported for MSL sol 370 and we called JPL about it, the next sol (371) pressure was back down to 8.65 mbar. By March, 2014 JPL/the REMS Team altered the pressure for Sol 370 too and rolled it back to only 8.65 mbar (865 Pa).

Figure 12B: Except for Sol 370 the black MSL pressure curve is suspiciously too close to the Viking 2 curve (usually) above it and the Viking 1 curve always below it.

TABLE 3 – 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




Initial Pressure Reported

Pressure for the previous sol

Final Pressure Reported after JPL Revisions

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


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


Table 3 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 13, 2017 after we either brought the deviations up to JPL Public Relations Director Guy Webster, or published them on our and website

Figure 12C: Pressures originally published by the REMS Team and JPL that were more than 7 Pa off the expected curves were altered to fit the curve.