Critique of All NASA Mars Weather Data - Part 11
By David A. Roffman and Barry S. Roffman (updated 9/11/2013).
13. RELATIVE HUMIDITY. On 4/9/2013 a statement appeared on FoxNews.Com about relative humidity at MSL. It went as follows:
The Curiosity rover team reported the new results today (April 8) at the 2013 European Geosciences Union General Assembly in Vienna, where scientists also provided other updates about the rover's recent discoveries.
For example, Curiosity's onboard weather station, known as REMS (for Rover Environmental Monitoring Station) has shown that humidity varies from place to place along the robot's route inside Mars' huge Gale Crater. REMS' observations are the first systematic measurements of humidity on the Martian surface, researchers said.
Figure 42 below: Adapted from the REMS Team: On June 27, 2013 REMS published this chart, but it continues to leave relative humidity reported only as --% on all its daily MSL weather reports.
On June 27, 2013 the information below appeared on the REMS Team website. Figure 42 was also on their site, although we cleaned up the fonts/text for clarification purposes. The relative humidity figures offered do not match any of the daily weather reports by the REMS Team, which continues to list all RH data as --%.
4.08.2013 Humidity in Gale Crater: Scant and Variable. This graphic tracks the maximum relative humidity and the temperature at which that maximum occurred each Martian day, or sol, for about one-fourth of a Martian year, as measured by the Remote Environmental Monitoring Station (REMS) on NASA's Curiosity Mars rover. These are the first systematic measurements of humidity on Mars. The data are graphed by sol number (starting with Curiosity's landing day as Sol 0), for a period from mid-August 2012 to mid-February 2013, corresponding to late winter through late spring in Mars' southern hemisphere. Four vertical lines on the graph mark progress points of the rover's traverse. While air temperature is not strongly tied to the rover's location, REMS has measured significantly different relative humidity in the different terrain units where the rover has been. All of the sites along the rover's traverse are extremely dry compared with Earth. Image Credit: NASA/JPL-Caltech/CAB(CSIC INTA)/FMI/Ashima Research.
OUR COMMENT: As we illustrate on Figure 43, when the relative humidities and sol numbers on Figure 42 are matched with actual position, as published by the JPL, it can be seen that all variation in relative humidity, from about 60% down to less than 10% actually only occurs over a distance of about 400 meters. The description above was given by NASA/JPL-Caltech/CAB(CSIC-INTA on April 8, 2013. It must be noted again that as of September 1, 2013, no relative humidity figure has been incorporated into a REMS weather report. Relative humidity is the ratio of the partial pressure of water vapor in an air-water mixture to the saturated vapor pressure of water at a prescribed temperature. As such, the relative humidity of air depends on temperature and the pressure of the system of interest. If the assumptions about air pressure are wrong, as we believe is the case on Mars, then attempts to measure relative humidity will be worthless. This might be why these figures are left off of REMS weather reports.