FIRST ESTIMATES OF PRESSURE ON MARS
Martian Pressure in the Hellas Basin May Exceed Earth Pressure at Sea Level (4/29/2013)
The High End of Pressure Estimates for Mars.
While the 51 mbar estimate based on the MSL SAM is almost an order of magnitude greater than accepted pressures, it equates to an altitude of 63,057 feet (19,220 meters) above Earth. Walking around at such a low pressure would still require a pressure suit. But there is evidence that suggests pressure far higher than this. The evidence begins with photos and wording found on a JPL web site. The page is at http://mars.jpl.nasa.gov/MPF/ops/clouds_sunset.html. The photo can be found at http://mars.jpl.nasa.gov/MPF/ops/82453_full.jpg. The quote of interest for the photo is as follows:
“This is the first color image ever taken from the surface of Mars of an overcast sky. Featured are pink stratus clouds coming from the northeast at about 15 miles per hour (6.7 meters/second) at an approximate height of ten miles (16 kilometers) above the surface… The clouds consist of water ice condensed on reddish dust particles suspended in the atmosphere. Clouds on Mars are sometimes localized and can sometimes cover entire regions, but have not yet been observed to cover the entire planet. The image was taken about an hour and forty minutes before sunrise by the Imager for Mars Pathfinder (IMP) on Sol 16 at about ten degrees up from the eastern Martian horizon.”
Pathfinder landed at 3.682 km below areoid, so 16 km above that would be an altitude of 12.318 km above areoid. Pathfinder is unlikely to have its own changed altitude significantly over 16 sols.
We first focus on what minimum pressure is required for stratus clouds to form in Earth’s atmosphere. The highest stratus clouds are cirrostratus. They occur at altitudes up to 13,000 meters (http://voices.yahoo.com/how-clouds-predict-weather-2147190.html). As is shown on Figure 38, at 13,000 meters the expected pressure on Earth is 163.33 mbar. With this pressure in mind we can make an estimate of pressure on Mars, but first we state the caveats. The pressures calculated do not factor in higher than terrestrial dust loads in the Martian atmosphere. Nor do they consider the gas composition of the Martian atmosphere (95% CO2 vs. about 0.04% on Earth). So at best we are shooting here for a ball park estimate. As is shown on Figure 38, if we assume that (cirro) stratus clouds on Mars cannot form at a lower pressure than similar clouds on Earth, then using a scale height of 10.8 our spreadsheet indicates pressures of around 511 mbar at areoid, and pressures as high as 1,054 mbar at the bottom of the Hellas Basin. Using this same logic the indicated pressure for the MSL, 4.4 km below areoid, is about 767 mbar (767 hPa). While most of the pressures put out by the MSL Remote Environmental Monitoring Station (REMS) Team are only about 1% of this, for five days - September 1 to September 5, 2012, the REMS Team published figures that were 97% in agreement with this calculation. The essential issue thus comes down to whether REMS published results that confused 747 hecto Pascals with 747 Pascals (7.47 hPa or 7.47 mbar). Or, did someone in the REMS Team rebel against expected results and in fact give us the truth until silenced? One REMS Team member was Henrik Kahanpää, the designer of the Vaisala pressure sensors used for both Phoenix and MSL. He was discussed earlier in Section 2.4. Again, he wrote, "We should find out how the pressure tube is mounted in the spacecraft and if there are additional filters etc." We challenged the above statement on November 14, 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).
And so when this particular man allows reports to be issued for five days that back our projected pressures, issues of personnel, agendas, and possible disinformation should not be overlooked. The REMS reports in question were shown below on Figure 2.