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Range and sensitivity of pressure sensors sent to Mars. This section updated on 8/16/2017.

14.6.3 Mixed messages about the range and sensitivity of pressure sensors sent to Mars.

       It has on been our position that NASA has understated Martian pressure by two orders of magnitude. On Figure 44 we made a case for a pressure at areoid of about 511 mbar (vs. the accepted pressure of 6.1mbar),  at Mars Pathfinder of ~719 mbar, at MSL ~768 mbar, at the Valles Marineris 835 mbar and in the Hellas Basis about 1,054 mbar (more than average pressure of 1,013.25 mbar at sea level on Earth). While mbar are the pressure units that we most prefer, others in the scientific community use pascals (Pa) or hectopascals (hPa). We have often noted mistakes in publication where hPa are confused with Pa and vice versa. The difference between these units is two orders of magnitude (i.e., two decimal places).

       The problem first came to our attention when we found that the REMS Team originally published pressures ranging from 737 to 747 hPa between August 30, 2012 and September 5, 2017. On September 2, 2012 we called Guy Webster, the PR man at JPL, and told him that if these pressures were correct, he needed to parade out the President of the United States to announce the greatest discovery in astronomy – that Mars has air pressure like than on Earth. On September 5, 2012 REMS said the pressure was 747 hPa (i.e., 747 mbar). The next day they published a pressure of 747 Pa (i.e. 7.47 mbar). This was captured by print-screen on Figure 17A. Soon after that they changed all the high pressures, rolling them back from hPa to Pa. Was this a simple accident?

       We have worked for eight years with Viking 1 and 2 data taken from "Mars Meteorology Data; Viking Lander." Mars Meteorology Data; Viking Lander. N.p., n.d. Web. 10 Feb. 2015. This is found at On July 12, 2017 we received an e-mail from an engineer by the name of Nathan Mariels, CEO at Global Electric Technology. In it he wrote:

Pa is not equal to hPa. From Viking logs: "Pressure mb = millibars, 1 mb = 100 hPa, where hPa = hecta Pascals" This is incorrect.    1 mb = 1 hPa = 100 Pa.

       The above error was repeated on every data set for Viking 1 and 2. A sample is captured by print-screen on Figure 66.

       Nathan found similar errors on MSL data that he examined. He also found different pressure ranges for landers than what we found, although we noted on Figures 10A and 10B that three of four sensor ordered by NASA from Tavis were rated for maximum pressures under 25 mbar, one of them – Tavis Dash Number 1 was rated at 15 PSIA which converts to 1,034 mbar. Pathfinder pressure problems were discussed earlier in Section 11 of this report. The Vikings and Pathfinder all used Tavis pressure transducers which are discussed in great detail in Annex G of this report ( While it seems hard to believe that a mere copying over of wrong units from one page to another caused serious problems, that’s what might have happened with all of the Viking 1 and 2 data at

       The problem with accepting the accident explanation for the Vikings is that it still leaves us with an order in 1976 by Dr. James Fletcher to manually alter the color of the Martian sky on all JPL monitors, and it leaves us with 36 years of altered sky color until we were finally permitted to see blue sky at Gale Crater, Mars in 2012.

Figure 66 – Viking 1 and Viking 2 error in unit conversion.

       Now, let’s look at another problem brought to my attention by Nathan – an inconsistency with respect to the pressure range and sensitivity on MSL. In particular, let’s look at the Abstract put out by the Finnish Meteorological Institute, which created the pressure sensors on Phoenix and MSL. 

        First let's look at a statement that backs the 1150 Pa figure: In Section 11 of the REMS Calibration Plan (Document No, CAB-REMS-PLN-002, Issue 002, it states: 

REMS shall measure the Ambient Pressure in the range of 1 to 1150 Pa with a resolution of 0.5 Pa and accuracy of 10 Pa BOL and 20 Pa EOL. Requirement 012 (PLD-20), REMS shall measure the Ambient Pressure at a minimum sampling rate of 1 Hz for at least 5 minutes each hour continuously over the mission.

But, in their Abstract to the American Geophysical Union for the Fall 2012 meeting the FMI states:

The pressure device measurement range is 0 - 1025 hPa in temperature range of -45°C - 55°C, but its calibration is optimized for the Martian pressure range of 4 - 12 hPa.

Note: 1025 hPa = 1,025 mbar. So, while it was supposedly optimized for 4 to 12 (not 11.5 mbar – meaning that the problem is not one of a sliding decimal place), it was still capable of measuring up to 1,025 mbar. Again, average pressure on Earth at sea level is 1,013.25 mbar. This is, to borrow a phrase from the Wizard of Oz, a horse of a different color. As for the temperature range, at MSL there were no reports of low temperatures as warm as -45°C that were not changed to much colder temperatures. For example, there was an air temperature low of -46°C reported by the REMS Team for Sol 880 on January 27, 2014, but they altered it after we highlighted it on our REMS data spreadsheets at and in particular the print-screen record seen below as Figure 67.

For the record, we have preserved the FMI abstract showing the 1,025 mbar capacity with the print-screen on Figure 68.

Figure 67 – The REMS Team would not permit low temperatures warmer than -50°C.


Figure 68 – Print-screen (recorded on July 23, 2017) of the FMI Abstract entitled Pressure and Humidity Measurements at the MSL Landing Site Supported by Modeling of the Atmospheric Conditions.

In contrast to what they submitted to the American Geophysical Union in 2012, the standard REMS position on the range of their MSL pressure sensor is shown on Figure 69.

Figure 69 - The Vaisala Pressure sensor and its range as depicted by

        On July 24, 2017 we found that the REMS Team again altered the maximum pressure to 1400 Pa (14 mbar). See Figure 70. After they raised the maximum pressure from 1150 to 1400 Pa, they published a maximum pressure of 1,294 Pa for Sol 1784 on August 13, 2017. On the previous sol (1783) the presure published was only 879 Pa. Yet even with the newer (likely false) upper pressure range of 1,400 Pa, when we challenged it with our colored spreadsheet and print-screen (, the REMS Team dropped the 1,294 Pa for that sol to 883 Pa. 


Figure 70 – REMS puts out a new maximum pressure for MSL. This time it’s 1400 Pa (14 mbar). Here they also claim a relative accuracy (repeatability in the time scale of hours) of less than 2 PA and a resolution of 0.2 Pa. On Figure 69 the resolution was 0.5 Pa.

14.6.4. A Possible Excuse for REMS Errors.

       Nathan Mariels examined the Planetary Data System (PDS) for MSL data. On July 18, 2017 at 8:07 PM, he wrote:

“There are a lot of data points. Every 5 minutes, unless an event occurs, which causes it to sample 512 points at short intervals. The triggers and timing change depending on the code version.  REMS is on version 7.  I think that's why you see the pressure from past dates sometimes change.  The format of the data changes, so the weather software gets changed, but some older data is then getting converted wrong if the software thinks it's all in the new format.”