Mars Is Losing Its Atmosphere Fast
Measurements of Martian atmospheric loss rates imply incredible changes over the assumed billions of years of Mars’ history.
Either Mars is younger than thought, or its atmosphere was unbelievable billions of years ago. The MAVEN spacecraft (Mars Atmosphere and Volatile Evolution), launched in 2013, has taken atmospheric escape measurements for an entire Martian year. A Mars year is 687 Earth-days. How fast is gas being lost from the atmosphere? Quick answer is 1 to 2 kilograms per second. A report in Icarus does the math for moyboy assumptions that Mars formed 4.5 billion years ago.
The loss rate extrapolated back in time gives an estimate of the total loss of gas to space and its impact on Martian climate history; an estimated 0.8 bars or more of CO2 likely has been lost.
Mars is a dry, cold world today.
A bar is the pressure of one Earth atmosphere at sea level. For a planet as small as Mars, that’s a lot of gas to lose. The lost hydrogen and oxygen alone could have covered the planet 75 feet deep in water!
The H loss rate is not measured directly, but can be calculated from the H abundance assuming or deriving a coronal temperature. For the range in observed column abundance and temperature, the loss rate varies between ~ 1-11 x 1026 H atoms s-1. This is equivalent to a loss rate of ~ 160-1800 grams of H per second (g H s-1); assuming all of the H is coming from H2O, this is the equivalent of removal of about 1,400 – 16,000 g H2O s-1. At this rate, H from the entire column of atmospheric water at present (nominally, about 10 precipitable micrometers, or 10-3 g/cm2) would be removed in about 3,000 – 30,000 years. Over 4.2 b.y., loss at this rate would remove a global layer of water between ~ 3.6-25 m thick (see Table 2). Although we’ve expressed this as loss of water, these measurements refer to the loss of H only; we expect O from water to be lost as well, but the O loss is complicated by the fact that it also can come from CO2.
At minimum the global water layer would be 12 feet deep (3.6 m). At maximum, it would be 82 feet deep (25 m). The estimated carbon dioxide lost (0.8 bar) is also highly significant. CO2 is the remaining primary constituent of the Martian atmosphere, freezing out at the poles in seasonal cycles.
Lower Limits
One significant aspect of these measurements is that they are probably lower limits. Several times in the paper, the authors remark that the loss rates could have been higher in the past: e.g., “These loss rates could be a lower limit if there are mechanisms for loss that have not been identified or observed.”
The uncertainties in the extrapolation of today’s loss rates back in time get very large prior to 3.5 b.y.a., due both to uncertainties in the solar properties and to increasing uncertainties due to expected non-linearities in extrapolating atmospheric composition and properties back farther in time. We take the approach of using the extrapolated loss rates at 3.5 b.y.a. and assuming that they also apply as a constant loss rate at earlier times. This likely underestimates the loss rates at the earliest times (perhaps by as much as an order of magnitude) and the integrated loss (by a factor of several). This conservative approach therefore gives us a lower limit on the extrapolated loss.
If the conservative estimate is in fact off by several orders of magnitude, would that require a global ocean kilometers deep billions of years ago? A similar error exists for the carbon dioxide esimate: “the 0.8-bar loss described earlier again is likely to be a conservative lower limit on total loss, conceivably by orders of magnitude.” Nowhere do they say their figures might represent an upper limit.
Mars portrait (May 2002, NASA)
Dust Storms Aggravate Loss
On January 18, NASA’s Mars Exploration website headlined, “Dust Storms Linked to Gas Escape from Mars Atmosphere.” Measurements in that prior study indicated that gas loss is not in a steady state, as earlier believed, but becomes amplified during dust storms. The storms heave water vapor up high into the atmosphere, where it is more prone to escape:
The Mars Climate Sounder on MRO can scan the atmosphere to directly detect dust and ice particles and can indirectly sense water vapor concentrations from effects on temperature. [Nicholas] Heavens and co-authors of the new paper report the sounder’s data show slight increases in middle-atmosphere water vapor during regional dust storms and reveal a sharp jump in the altitude reached by water vapor during the 2007 global dust storm. Using recently refined analysis methods for the 2007 data, the researchers found an increase in water vapor by more than a hundred-fold in the middle atmosphere during that global storm.
The MAVEN measurements, taken over an entire Martian year, “smooth out” short-term fluctuations to give a more averaged escape rate that can be extrapolated. But there were no global dust storms during the measurement year. Since global dust storms occur regularly, and would have been frequent over billions of years, it seems safe to presume that the extrapolated values are, indeed, orders of magnitude too low.
Astrobiology Magazine admits that “The planet has lost the majority of its once much denser and wetter atmosphere, causing it to evolve into the dry, arid world we see today,” but does not mention the rapid rate of loss. It does, however, point out that the carbon dioxide that sublimates from the polar caps each season reaches much higher into the atmosphere than previously thought. “This sublimation process was thought to mostly only affect the lower atmosphere – we didn’t expect to see its effects clearly propagating upwards to higher levels,” said a scientist for ESA’s Mars Express mission. This fact could be in agreement with MAVEN’s conclusion that the atmosphere might have been lost more rapidly than the lower limit suggests. And how much “denser and wetter” would moyboys be willing to accept for a primordial Mars?
Implications
Art of dust devils on Mars
If these extrapolations billions of years into the past are reasonable, they imply a very, very different Mars than what we observe today. “Loss to space has been the major process driving climate change on Mars,” they note. The Mars we see today is dominated by sand dunes, a crackling-dry atmosphere charged with static electricty, a surface too cold for liquid water, dust devils, large shield volcanoes, a deep dry canyon thousands of miles long, and global dust storms like the one enveloping Mars right now (Phys.org). Are planetary scientists prepared to deal with a Mars possessing a thicker atmosphere than the Earth, covered possibly in a deep ocean of water? How did that form outside the habitable zone of a dimmer sun?
Watch the hydrobioscopy speculators jump on the possibility of life with all that water. They won’t, however, be able to point to the other geological features as underwater sand dunes and underwater volcanoes. They think those features formed eons ago. How much did Mars have to dry out before those volcanoes and dunes could even begin to form? The measured loss rate appears to put them in a hopeless bind: their view of Martian history contradicts the loss rate of the atmosphere. Creationists, get out your calculators; a clear alternative solution is that Mars is not billions of years old.