MSL PRESSURES - INITIAL ANALYSIS INDICATES ANOTHER CLOGGED DUST FILTER AND INCORRECT PRESSURES.
Caresless mistakes about pressure units & the correct month on Mars mar confidence in the Remote Environment Monitoring Station team credibility. Initial analysis just focusing on Sol 10 shows a correlation between temperature and the inverse of pressure data. Figure 1D suggests that (as with Vikings) pressure increases were due to heat from RTGs being applied to an area with trapped air behind a clogged dust filter. (Updated 10/2/2012)
FIGURE 1 above - Daily pressure and temperature fluxuations are shown with pressures in Pascals and temperature in Pascals. The hypothesis with the Vikings was that when it got colder outside, the RTG heaters pumped more heat into the area around the pressure transducers. Air trapped behind a clogged dust filter then saw its pressure rise as the heat was applied. When the RTG heat was no longer shipped there, the pressure fell. A first look at sol 10 suggests something like this might hav happened again. This will need to be related to initial confusion about methane detected by the SAM. It turned out that it was not Martian air, but rather it was trapped terrestrial air.
FIGURE 2A and 2B below. Figure 2A shows gtound and air temperatures for MSL Sols 10 through 11.6. Figure 2B shows MSL pressures for Sols 9.5 to 13.
Initial REMS data was not what teams expected which was the first sign of a larger problem associated with the REMS Instrument. During REMS checkouts, it was found that the boom looking to the side was sending saturated wind data at either high or low levels which was not valid. The issue was traced back to the exposed circuit boards of the REMS Wind Sensor and it was determined that two of three boards on the boom in question had damaged wiring. Teams assessed the situation and came to the conclusion that this type of damage was permanent without a chance of recovery. The REMS instrument and its wind sensors were successfully checked during cruise so that instrument health following launch and ascent aboard the Atlas V rocket back in November 2011 was confirmed.
With the instruments starting to send bad data after landing while functioning during cruise has led to teams assuming that the instrument's circuit boards were damaged during Entry, Descent and Landing.
Ashwin Vasavada, Curiosity deputy project scientist, has stressed that there is
now way (typo -correction - no way) of finding out what exactly happened to the hardware, but that teams have developed the hypothesis of small rocks damaging the tiny wires of the circuit boards during the propulsive landing. Following landing, images have shown small pebbles on the Rover Deck that were picked up by the Mars Landing Engines while the Descent Stage was hovering above Curiosity during landing.
Possibly, these pebbles could have hit the fragile hardware on the mast which was in its stowed position with the REMS booms facing outward, leading to the damage teams are seeing. With this permanent damage on their sensors, the REMS team had to start the process of learning how to take satisfactory wind data with one degraded sensor. Luckily, REMS has wind sensors on both of its booms so that there was still the option of returning sufficient wind data to meet the science objectives of the instrument. Comment – all REMS daily weather reports published up until September 8, 2012 show wind from the east at 2 m/s. This wind is not anywhere near the velocity required to move sand dunes or to fill in rover tracks as is discussed elsewhere on this web site at MOVING SAND AND MARTIAN WIND. Further, the data will be suspect until there is some variation in direction or wind strength seen.
After instrument commissioning was complete, REMS began nominal operations, performing 5 minutes of data acquisition during each hour on Mars with 60 additional minutes of each Sol for scheduled observations and event-triggered instrument operation. Suggestion: For ease of comparison, adopt the system used for Viking 1 and 2. There each was sol was divided into 25 time bins, each a little over 59 minutes long. See the presentation method at http://www-k12.atmos.washington.edu/k12/mars/data/vl1/segment1.html, but be sure that data published is easy to transfer to spreadsheets for further analysis.
Landing on Mars in early August placed MSL in the late northern-Summer Season on the planet. True, but because MSL was south of the equator, it was late winter there.
The average pressure detected during the first 19 Sols on Mars was 730Pa which was as expected. The pressure on Mars shows a daily variation and a seasonal variation. The seasonal change is caused by Carbon Dioxide being converted into its solid phase at the Poles according to a seasonal cycle – meaning that gaseous CO2 is removed from the atmosphere resulting in a loss of total atmospheric mass and pressure. Comment – This is as has been widely accepted since the Viking missions. However, it supposes that the Viking pressure curves are correct and that they reflect ambient atmospheric conditions. We challenge that assumption, believing that just as landing conditions knocked out at least one wind boom on MSL, the dust clogged all dust filters and left transducers to measure pressure changes all due to RTGs on the Vikings and Pathfinder, or the steady drop in pressure as the temperature fell on Phoenix where there was no RTG. As Figure 1D shows above, there is an extremely suspect link seen again on MSL between falling temperatures and rising pressures. This is properly seen on Figure 1B, but shown with an inverted pressure curve on Figure 1D to emphasize how very similar the relationship appears to be. We are therefore confident that the pressures being transmitted from Mars do not correspond to actual ambient pressure.
Carbon Dioxide is a major component of the Martian Atmosphere (95%). The daily variation of pressure with a minimum of 685 and a maximum of nearly 785Pa during the first Sols is caused by tides. Martian tides cannot be compared to tides on Earth which are caused by the gravitational force of the Moon. On Mars, tides are large atmospheric scale waves that are caused by heating due to the sun. These tides are sensitive to the distribution of clouds and atmospheric dust as well as a large-scale pattern of jet-stream like winds.
During the first Sols, REMS also detected smaller pressure variations which could have been caused by minor atmospheric flows within the Gale Crater System, but more data is required to analyze these small localized phenomena.
FIGURE 3 below - To understand Martian weather you need to know both the pressure and the month. Both have been listed incorrectly by the REMS team. Now that the mistakes have been corrected we can start to analyze the data to see if it truly represents ambient conditions on Mars.
FIGURE 4 - The REMS Team, after our repeated nagging of JPL's Guy Webster on his issue, finally changed the units it was using from hPA back to Pa. This makes to harder to prove higher than advertised Martian air pressure than advertised, but given the errors that we caught above, it does not end our investigation, as Figure 1D indicates.
WEB SITES REPORTING WEATHER AT MSL AS OF OCTOBER 4, 2012. There are two web sites linked to the REMS team that offer weather reports for the MSL. The first is the one referred to above at http://cab.inta-csic.es/rems/marsweather.html. In addition to its confusion for five days in September about units (hPa vs. Pa), it also offered confusion about the month on Mars. It started with month 3 (incorrect), changed that to month 6 (correct) and then slipped back on September 13, 2012 to month 3 again. After I published the previous sentence, they fixed it once more the following day. The current month is 7.
A second web site with a weather report is at http://marsweather.com/first-rems-weather-report/comment-page-1#comment-254. But it too has problems. Until October 4, 2012 it always listed the length of daylight on Mars as 11 hours and night time as 13 hours, with sunrise at 6 AM and sunset at 5 PM. Obviously this was an original approximation, but it should show the daylight time as longer than the night time, especially now that the equinox has passed and the MSL site moved from late winter into early spring by September 30 when Ls 180 was reached. The MSL touched down at latitude -4.59 (that is, 4.59 degrees south). At a similar latitude on Earth is Mombasa, Kenya. The tilt of the Martian axis is similar to that of Earth, 25.19 degrees (compared to 23.4 degrees on Earth). If we look at the sunrise and sunset times in Mombasa for August 22, 2012, a month before our equinox, the sunrise is at 6:24 AM and the sunset is exactly 12 hour later at 6:24 PM. This close to the equator, as should be true on Mars, sunrise and sunset times don't vary widely during the year. At the equinox on September 22, 2012, sunrise on Mombasa is at 6:11 AM and sunset is at 6:17 PM. The amount of daylight in Mombasa on the solstices only varies between 11 hours 53 minutes on June 21 and 12 hours 21 minutes on December 21. Given the extra 1.8 degrees of axial tilt on Mars, there should be a little bit more variation in daylight at MSL than on Earth over the year there, but not a lot. On October 4, 2012 Ashima finally posted a change in sunrise and sunset times, with sunrise listed for October 2 (Sol 56) at 5:31 AM and sunset at 5:09 PM. That still amounts to a longer night than day by 22 minutes.
The other question that remains about the second website is who controls it. The site states that “MarsWeather and MeteoMarte are provided as a service by Ashima Research. These websites are / were not funded by NASA, by any agency of the US government, nor by any agency of the governments of Spain or Finland.” But elsewhere it states, “Ashima Research is a part of the science team for the Rover Environmental Monitoring Station (REMS) – the rover’s weather station.” So they first allow for no Government responsibility, and then they reveal that they are a paid part of the NASA assigned REMS team. Despite the odd disclaimer, the Ashima folks seem to be a serious group.
Of immediate interest is that the Ashima people have developed a new General Circulation Model which I have only skimmed through. They state that, "The good news is that the new model does much better than all prior Mars GCMs. The bad news is that the model still under-predicts argon in the southern polar winter." One might think that more argon than they predicted would imply more air pressure than they planned for, but that is not (yet, at least) their conclusion, which asserts, "We are also able to reproduce a seasonal CO2 cycle that closely matches the surface pressure measurements at Viking Lander 1 and 2."
While Ashima began a blog on August 31, 2012, they have not responded to or printed comments by anyone after September 2, 2012, when the last amusing entry was entered by someone named Philco wrote, "CAB (Centro de Astrobiologia), lost in comma... REMS data from CAB has an average daily ground pressure of 742 hPA? Good, but then where was I when Man terraformed Mars?" Ashima has deleted all our questions and comments from their blog. For now I'll give them the benefit of the doubt and say that this is probably because they have been too busy preparing for a convention in Copehagen on September 14, 2012. Meanwhile, we may well have to wait until the full data set is published at the PDS website before we can see what the Government contends is really going on weatherwise at MSL.
Some of the weather reports that I missed at the above two weather sites were available at https://twitter.com/MarsWxReport. It did report the extremely high pressures above 740 hPa for Sols 26 to 29 (September 2 to 5), but for Sol 25 (September 1) it reported 7.42 hPa rather than the 742 hPa reported at http://cab.inta-csic.es/rems/marsweather.html.