mars                 earth




The purpose of this website is to offer a simple explanation to some of the unknowns about the planet Mars, specifically how a units error in regards to the atmospheric pressure of Mars is a source of inconsistencies in observed data compared to expected observations.

A simple explanation is that the atmospheric pressure of Mars is 9 PSI, not the 0.09 PSI currently assumed. The source of this error is from the pressure units of Pa and hPa being used interchangeably.

The sky is not black when viewed from Mars rovers, and you can see details in the soft shadows.

At an altitude of 113,000 feet on Earth, the pressure is similar to the currently accepted pressure on Mars, the sky is black, and the shadows are harsh.

If the diffuse light on Mars is from the dust, what is holding up the dust?   (Most likely not turtles. *)

Recent Mars Weather:

minor details

1 Pa = 1 Pascal, a unit of pressure
1 hPa = 100 Pa
1 kPa = 1,000 Pa
1 MPa = 1,000,000 Pa
1 GPa = 1,000,000,000 Pa

From Viking logs (First successful US lander on Mars, July 20, 1976 - Units error in conversion of pressure data - off by a factor of 100)

"C Pressure         mb = millibars, 1 mb = 100 hPa, where

 C                        hPa = hecta Pascals"

-Viking Lander 1 Binned and Splined data Rev 2.2 97/6/19, JET, lines 50-51

The conversion factor above is incorrect.

The correct conversion factor is: 1 mb = 100 Pa or 1 mb = 1 hPa

Mars Science Laboratory (Currently operational US rover on Mars - Discrepancies in pressure units - Pa vs. hPa - off by a factor of 100) 

REMS Instrument Pressure Sensor (Vaisala Barocap):

"Pressure in the range of 1 to 1150 Pa with a resolution of 0.5 Pa"

- NASA website

"Pressure range       50 ... 1100 hPa"

"Resolution                           0.5 hPa"

- Vaisala Datasheet for PTB200 Barocap

REMS testing of Barocap: Capacitance varies from 14 to 12 pF over the range of 0-1000 Pa

- REMS Space Science Reviews 2012 DOI 10.1007/s11214-012-9921-1, figure 12

My testing of Barocap:      Capacitance varies from 14 to 12 pF over the range of 0-1000 hPa

- Nathan Mariels

Sample REMS pressure data close in time to SAM data below:

Log file: RME_399133183ESE00190000000ACQ____M1.TAB

REMS Barocap :       399177611.0 SECONDS, 721.15 Pa

SAM Instrument:

CDH:PRES_4_MN6: 399118971.8 SECONDS, 711.5 MILLIBARS

Unit #4, A-DIR, Direct atmospheric measurement, ADIR

Log file: sm25008f0018rdr1a_adir_hk__cdhlspd_2.csv

From the geographic features, we know Mars had an atmosphere similar

to Earth in the past. We assume it somehow (mostly) disappeared.

What is the simplest answer to what happened to it's atmosphere?

Nothing happened to the atmosphere of Mars.

Our assumption that it doesn't have (much of) one is wrong.

Without the NASA Mars rovers, I would have never known enough about Mars to be able to question any of the Mars data.

NASA has done a wonderful job in these rovers, and I am proposing that one of the many types of sensors these rovers

carry is being decoded wrong with the hopes of making what we know about Mars fit together is a simpler way.

How could we possibly land on Mars if the atmospheric pressure is 9 PSI and the current spacecraft are designed for 0.09 PSI? The spacecraft are designed with good engineering, and designed to handle unexpected situations.

In 1976, the US successfully landed two landers (Viking I and Viking 2) on Mars. Both landers landed and worked. They made almost no assumptions on what the atmospheric pressure was, relying on the parachute only to slow down, and then using rockets and radar altimeter to land.

The current rovers used dimensionally identical parachutes, and similar rocket landings systems as the Viking missions did.

Mars Atmospheric Pressure

Agrees with


620 hPa

60% of Earth's pressure

0.09 PSI

620 Pa

0.6% of Earth's pressure

Textbooks and currently accepted value



Rover images of geographic and atmospheric features



Parachute decent rates



Diffuse light in atmosphere



Images of dust devil movements



Schiaparelli lander root cause of failure



Simple atmospheric model for solar system



Range MSL pressure sensor can actually detect



Viking (1976) mission raw sensor data



CO2 ice seasonal variation at poles



Telemetry data from MSL



Failure of WRP pumps



Math/Software errors I found



Rover Image / Not Rover Image

rover image

rover image it is not

Liquid water on surface below 0C/32F



Mars Helicopter



Mars helicopter rotor speed for lowest hover power


~2500 RPM

Mars helicopter motor power at hover



Earth Calibrated Barometric Altimeter

~12,000 ft

~113,000 ft

Smoke from Skycrane crash rising up in column



Mars Helicopter: Nice job. Drones are fun.

A question: What is the actual rotor speed in flight?
(Guessing ~400 RPM if torque control is being used.)

The black and white images show the shadow of the rotors not blurry. If that camera has max 1/480 sec capture rate, I would think the shadow of the rotors would be blurry at 2500 RPM.

Is it possible to get the raw audio for the flight without the bandpass filter filtering out all the interesting sounds? You want there to be 84 Hz rotor sounds, but maybe they are closer to 20 Hz?

The flight control loop is doing a good job for such a drastically different environment than design specification, but the high frequency oscillation could be damped better if modeled for 9 PSI atmospheric pressure.

A slower ramp on rotor spin-up might solve the watchdog trip issue.

If the atmospheric pressure is 9 PSI, all wind measurements will be 100 times lower, as the wind sensor is assuming heat transfer though 0.09 PSI.

Before the Viking spacecraft landed on Mars in 1976, it was thought that the atmospheric pressure of Mars was somewhere between 0.4 PSI and 4.4 PSI. When the Viking spacecraft landed, the pressure sensor appeared to indicate that the atmospheric pressure on the surface of Mars was 0.09 PSI.

There was a software error in the conversion of pressure sensor data, where Pa and hPa were not considered as different units, although they differ by a factor of 100. This implies that Mars has an atmospheric pressure of 9 PSI. This has rather large implications for our understanding of physics, and may be an explanation why most spacecraft attempting to land on Mars fail, and the ones that do land are many miles from the intended landing location.

Units errors have caused the loss of several spacecraft, including one to Mars.

"root cause for the loss of the MCO spacecraft was the failure to use metric units in the coding of a ground software file"
- Mars Climate Orbiter Mishap Investigation Board Phase I Report November 10, 1999

Additional data that supports the idea that Mars has an atmospheric pressure of 9 PSI (60% of Earths):

ESA Lander Failure (Mars atmosphere not as expected)

Root Cause of failure: "Insufficient uncertainty and configuration management in the modeling of the parachute dynamics"

-EXOMARS 2016 - Schiaparelli Anomaly Inquiry

MSL Heat shield (Mars atmosphere not as expected):

"The peak temperature at MISP 7 is ~210 deg C greater than model predictions."

-MSL Entry, Descent and Landing Instrumentation (MEDLI): Hardware Performance and Data Reconstruction - AAS 13-078

Analysis of Strategic Knowledge Gaps Associated with Potential Human Missions to the Martian System

"FINDING #1. The high-priority gaps for a human mission to Mars orbit relate to

a) atmospheric data and models ..."

-NASA, P-SAG_final_report_06-30-12_main_v26.pdf

Before the landers (The 30 mbar vs. 300 mbar problem)

"The principal difficulty affecting all of the photometric and polarimetric investigations is that of distinguishing between the amount of light scattered by the Martian surface, by the solid particles in the atmosphere and the atmosphere itself. The surface pressure can be computed also from the pressure broadening of the lines in the Martian band spectrum of CO2. The first results of the spectroscopic method disagree by an order of magnitude from previously accepted values, which were based on photometry and polarimetry. Other spectroscopic measurements made by numerous investigators in 1964 and 1965 confirmed this disagreement mentioned above."

-Karl D Rakos, The Atmospheric Pressure at the Surface of Mars, Lowell Observatory Bulletin No. 131, 1965

How is it possible a mistake like this was missed?

It started with a math/software error more than four decades ago on the Viking mission. The data was close enough to estimates, and it was the only data point. The following mission, also having the same type of error, returned the same value, but with a different type of sensor, so now there were two, both incorrect, data points that agreed.

The pressure sensors are calibrated by the same type of pressure sensor. The sensors work great, but the same software error in decoding the data affects both the calibration and the flight sensor.

The pressure sensors are not considered flight critical. That is, the spacecraft will still land without them. The problem is that the atmospheric pressure value is flight critical data for the next spacecraft, but that flight critical data is from sensors that did not undergo the same type of testing as flight critical hardware normally does.

What are units?

Temperature can be expressed in several ways. For example, 68 degrees Fahrenheit is the same as 20 degrees Celsius, and is considered comfortable by most people. 68 degrees Celsius is 154.4 degrees Fahrenheit will kill most living things very quickly. "Celsius" and "Fahrenheit" are units of temperature. Units are what relate a number to what the number represents.

Pressure can also be stated in several different units. In the US, Pounds Per Square Inch (PSI) is common, while Pascals (Pa) are common elsewhere.

The following are all equivalent ways of stating the pressure of the Earth's atmosphere at sea level: 14.7 PSI, 101325 Pa, 1013 hPa, 101.3 kPa, 760 mm hg, 760 mm, 1.013 bar, 1013 mbar, 1 ATM, 29.9" hg, 0 PSIG, 14.7 PSIA

Note 1: "Pa" and "hPa" are a factor of 100 different, while "mm hg" and "mm" are equivalent.

Note 2: Common pressure gages for tires and air compressors read the pressure relative to the atmospheric pressure (PSIG). When your car tire gauge reads 30 PSI, the tire has 44.7 PSI on the inside, 14.7 PSI on the outside, with a difference of 30 PSI between the inside and outside pressure. (At sea level)

Why does it matter if the pressure on the surface of Mars is 60% of the pressure on the surface of Earth?

We could use existing electric aircraft on Mars.

We could roam the planet of Mars without spacesuits using just warm clothing and rebreathers.

The mathematical equations of physics fit together in a nice way that currently can not be done.

The question above about where the diffuse light comes from has an answer: An atmospheric pressure of 9 PSI would cause diffuse light and could hold up the dust.

Arguments against the above:

1) The modifications to the Barocap for Mars may be different than what is documented. (Details are sparse.)

2) The WRP turbo pumps on MSL would not work if venting to 700 hPa. (Are they working? Is the Mass-Spec working without the pumps? Anyone have expected current draw and spin-up times? Are 77 seconds to 8K RPM, 14 more seconds to 40K RPM, and 43 more seconds to 100K RPM expected times? Could the second WRP be run backwards as a backing pump to get things working on MSL?)

mars wrp pump spinup times

3) Spacecraft would have burned up if the atmospheric pressure was 60% of Earth's. (Most of the landers/rovers that did successfully land used rockets and radar altimeters to do so, and were not dependent on the atmospheric pressure data. All of the landers/rovers landed downrange from where they expected, possibly from drifting in the atmosphere before the parachutes were cut free. See notes on MSL heat shield temps and ESA lander failure above.)

4) It goes against the standard scientific model of our solar system that so many people agree on. (For everything except the Martian atmospheric pressure, and what depends on it, I agree with the standard accepted view of the scientific community.)

This section is an idea that needs to be evaluated by others before being considered correct.

If we assume that the currently accepted values for atmospheric pressures of Mars and Venus are off by a factor of 100 and 0.01 respectively, the following equations work rather well:

Proposed Eq 1: maximum equilibrium surface pressure (Pa) = 32300 * square root of gravity (m/s^2)

Proposed Eq 2: maximum equilibrium surface pressure (PSI) = 4.69 * square root of gravity (m/s^2)

Proposed Eq 3: P1/P2 = sqrt (g1/g2), where P is the maximum equilibrium surface pressure a planet can support and g is the gravity of the planet in m/s^2

Three examples that show very good correlation for Proposed Eq 3:

Mars/Earth: 9.0/14.7 = 0.612, sqrt (3.7/9.8) = 0.614

Venus/Earth 14.0/14.7 = 0.952, sqrt (8.9/9.8) = 0.953

Mars/Venus 9.0/14.0 = 0.643, sqrt (3.7/8.9) = 0.645

Some estimated planetary surface pressures (in PSI): Mercury = 9.0,     Venus = 14.0 (not 1400),     Earth 14.7     Mars = 9.0 (not 0.09)     Uranus = 13.9     Neptune = 15.6

Some values of planetary gravity (in m/s^2):                Mercury = 3.7      Venus = 8.9                         Earth 9.8,      Mars = 3.7                     Uranus = 8.7,      Neptune = 11

Note: These equations imply that our Moon could support an atmospheric pressure of up to 5.9 PSI.

mars                 earth

Mars and Moon (Phobos) taken by Mars Orbiter Mission


Barocap Testing showing Pa vs. hPa discrepancy (factor of 100)


Earth's Moon, Apollo Mission
Low Atmospheric Pressure
Harsh Shadows


Earth's Moon, Chang'e-3 Lander
Low Atmospheric Pressure
Harsh Shadows


Mars, Insight Lander
??? Atmospheric Pressure
Soft Shadows


Mars, MSL Rover
??? Atmospheric Pressure
Soft Shadows


14.7 PSI Atmospheric Pressure
Soft Shadows


14.7 PSI Atmospheric Pressure
Soft Shadows

Mars Drilling

First two images: "Laboratory drilling under Martian conditions yields unexpected results",
JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 109, E07S10, doi:10.1029/2003JE002204, 2004
Third image: Mars Rover, MSL, CR0_580106913PRC_F0701752CCAM05056L1

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