Mars from NASA’s Hubble Space Telescope
The hunt is now on for the offending ‘missing ingredient’: “Carbon dioxide is a strong greenhouse gas, so it really was the leading candidate to explain the drying out of Mars,” said Kite, an expert on the climates of other worlds. “But these results suggest it’s not so simple.” The article calls this ‘unusual’, but is what it considers usual really so?
– – –
Mars once ran red with rivers, says Phys.org.
The telltale tracks of past rivers, streams and lakes are visible today all over the planet.
But about three billion years ago, they all dried up—and no one knows why.
“People have put forward different ideas, but we’re not sure what caused the climate to change so dramatically,” said University of Chicago geophysical scientist Edwin Kite. “We’d really like to understand, especially because it’s the only planet we definitely know changed from habitable to uninhabitable.”
Kite is the first author of a new study that examines the tracks of Martian rivers to see what they can reveal about the history of the planet’s water and atmosphere.
Previously, many scientists had assumed that losing carbon dioxide from the atmosphere, which helped to keep Mars warm, caused the trouble.
But the new findings, published May 25 in Science Advances, suggest that the change was caused by the loss of some other important ingredient that maintained the planet warm enough for running water.
But we still don’t know what it is.
Water, water everywhere, and not a drop to drink
In 1972, scientists were astonished to see pictures from NASA’s Mariner 9 mission as it circled Mars from orbit. The photos revealed a landscape full of riverbeds—evidence that the planet once had plenty of liquid water, even though it’s dry as a bone today.
Since Mars doesn’t have tectonic plates to shift and bury the rock over time, ancient river tracks still lie on the surface like evidence abandoned in a hurry.
This allowed Kite and his collaborators, including University of Chicago graduate student Bowen Fan as well as scientists from the Smithsonian Institution, Planetary Science Institute, California Institute of Technology Jet Propulsion Laboratory, and Aeolis Research, to analyze maps based on thousands of pictures taken from orbit by satellites.
Based on which tracks overlap which, and how weathered they are, the team pieced together a timeline of how river activity changed in elevation and latitude over billions of years.
Then they could combine that with simulations of different climate conditions, and see which matched best.
Planetary climates are enormously complex, with many, many variables to account for—especially if you want to keep your planet in the “Goldilocks” zone where it’s exactly warm enough for water to be liquid but not so hot that it boils.
Heat can come from a planet’s sun, but it has to be near enough to receive radiation but not so near that the radiation strips away the atmosphere. Greenhouse gases, such as carbon dioxide and methane, can trap heat near a planet’s surface.
Water itself plays a role, too; it can exist as clouds in the atmosphere or as snow and ice on the surface. Snowcaps tend to act as a mirror to reflect away sunlight back into space, but clouds can either trap or reflect away light, depending on their height and composition.
Kite and his collaborators ran many different combinations of these factors in their simulations, looking for conditions that could cause the planet to be warm enough for at least some liquid water to exist in rivers for more than billion years—but then abruptly lose it.
But as they compared different simulations, they saw something surprising. Changing the amount of carbon dioxide in the atmosphere didn’t change the outcome. That is, the driving force of the change didn’t seem to be carbon dioxide.
“Carbon dioxide is a strong greenhouse gas, so it really was the leading candidate to explain the drying out of Mars,” said Kite, an expert on the climates of other worlds. “But these results suggest it’s not so simple.”
Full article here.
Tallbloke's Talkshop 
But as they compared different simulations, they saw something surprising. Changing the amount of carbon dioxide in the atmosphere didn’t change the outcome. That is, the driving force of the change didn’t seem to be carbon dioxide.
Maybe they should try those simulations on Earth 😎
[…] Why did Mars dry out? Carbon dioxide loss not a factor, say scientists […]
“Carbon dioxide is a strong greenhouse gas, so it really was the leading candidate to explain the drying out of Mars”
Curious, I’d have thought that if there were sufficient quantities of liquid water on the Martian surface to permit rivers water vapour would have been the dominant GHG.
Yes, the driving force behind Mars getting cold and drying out is definitely not CO2! It’s difficult for young scientists such as the lead author Dr. Edwin Kite (see his webpage: https://geosci.uchicago.edu/people/edwin-kite/) to figure out what really caused this dramatic change in Mars’ climate. That’s because these young colleagues operate within a wrong theoretical paradigm about the nature of the so-called “greenhouse effect”, which has been instilled in their minds by the existing system of higher education.
If these scientists understood that the Atmospheric Thermal Effect is not a radiative phenomenon but a pressure-induced adiabatic phenomenon, they would figure out that current climate models based on the radiative “greenhouse” theory would never give them the right answer.
The simple truth is that Mars got colder and dried out, because it lost most of its atmospheric mass and surface air pressure some 3 By ago. The NZ model allows for exact calculation of Mars’ surface atmospheric pressure, when rivers flowed on the Red Planet more than 3 By ago.
The current global average surface temperature of Mars is 190.6 K (-82.6 C). Assuming that, some 3.1 By ago, the Sun’s luminosity was 21.4% lower than today (based on the accepted model of Sun’s evolution) and Mars was at its present orbit (distance from the Sun), the surface atmospheric pressure should have been greater than 20.3 bar in order for the global surface temperature on the Red Planet to be above freezing (>0.1 C). If 3.1 By ago, the Sun’s luminosity was the same as it is now, then the minimum air pressure required for Mars’ global surface temperature to be above 0.1 C is 10.8 bar. For comparison, the current surface atmospheric pressure on Mars is only about 0.007 bar. Having a surface air pressure in excess of 20.3 bar on early Mars would not be unusual considering that the atmospheric pressure at the surface of Venus now is 93 bar!
I will send an email to the authors of this new paper to check, if they would be receptive to a new physical explanation for the cooling of Mars and the freezing of surface waters…
Thanks Ned, we await any response from the authors. At least they started a discussion.
– – –
catweazle – bearing in mind that a mere 0.04% CO2 in the atmosphere of Earth is supposed to be a fearsome amount requiring the world to be ‘saved’…
Kite apparently has never paid attention to the effect of soda pop or “sparkling” water on his tongue or gullet.
Why would CO2 change in Mars’ atmosphere anyway?
Phoenix – the study is here: https://www.science.org/doi/10.1126/sciadv.abo5894
Re your comment:
‘Candidate carbon sinks include escape to space, carbonate formation, and basal melting of CO2 ice. Alternatively, CO2 could have been reversibly sequestered as CO2 ice.’
Here is an example of how the current climate education exclusively focused on the false “greenhouse” theory makes young scientists come up with physically radicicolous scenarios to explain Mars’ past warm climate.
The Phys.org article quotes the lead author Edwin Kite (who got his PhD degree in 2017) proposing an alternative (non-CO2) scenario for how Mars got to be habitable with liquid water flowing on the surface some 3.6 By ago:
“The new evidence fits nicely with a scenario, suggested in a 2021 study from Kite, where a layer of thin, icy clouds high in Mars’ atmosphere acts like translucent greenhouse glass, trapping heat.”
One has to be pretty confused about atmospheric thermodynamics and physics in general to believe that an open, convective atmosphere can have clouds that “trap heat” by reflecting IR radiation like a mirror back to the surface! Not to mention that even in a real greenhouse, the glass does not act to trap radiant heat inside. A real greenhouse maintains a warm interior by impeding the convective heat exchange with the outside environment, which has nothing to do with IR trapping… Trapping of heat by free gases is perhaps the most unphysical and idiotic premise of the “Greenhouse” theory!
It’s sad to see these young scientists being so poorly educated about basic physical principles.
Reblogged this on Climate Collections.
I just sent this email to the lead author Dr. Edwin Kite and several co-authors:
========================================
Dear Dr. Kite,
I recently came across your paper “Changing spatial distribution of water flow charts major change in Mars’s greenhouse effect“. I think you and co-authors have done a fabulous job to document via geological evidence that Mars’ climate underwent a dramatic shift some 3.6 – 3.0 By ago from a habitable planet with flowing waters on the surface to a frozen, dry and inhospitable place we know it today. I appreciate your finding that the huge waning of the planet’s atmospheric greenhouse effect cannot be explained by changes in CO2, and that the driver of the cooling/drying of Mars’ climate remains a mystery at the moment.
In this regard, I’d like bring your attention to a new concept developed over the past 5 years that can explain the climatic shift on Mars 3.5 By ago in a whole different way. This concept rests on a new understanding of the Atmospheric Thermal Effect (ATE), a.k.a. “greenhouse effect” that emerged from a novel analysis of NASA planetary data across the Solar System. We found that ATE is not a radiative phenomenon as previously thought, but a form of adiabatic compression heating caused by total atmospheric pressure that is independent of atmospheric composition (for details, see Nikolov & Zeller 2017). We also found that the atmospheric infrared LW radiation is just a consequence (or byproduct) of ATE, and as such, it has no effect on the global surface temperature of a planet. Our discovery has significant implications for the current climate theory and our understanding of climate drivers on various time scales. For example, these 2 videos presented at the 101st AMS Annual Meeting in Jan of 2021 discuss drivers of Earth’s paleoclimate and modern climate change from the perspective of the new pressure-based ATE concept:
“Implications of a Semi-empirical Planetary Temperature Model for a New Understanding of Earth’s Paleoclimate History and Polar Amplification”
“Role of Albedo in Planetary Climates: New Insights from a Semi-empirical Global Surface Temperature Model”
With respect to early Mars, our ATE concept suggests that the Red Planet became cold and dry as a result of a major loss of atmospheric mass and surface air pressure between 3.6 and 3.0 By ago. It was the depressurization of the surface that caused the ambient temperature to drop some 89 K locking up all water at the surface into ice, which was later covered by dust. Our semi-empirical global planetary temperature model, which is valid for any rocky body in the Solar System, allows an accurate estimation of the surface atmospheric pressure required to produce a surface temperature above freezing on Mars 3.6 By ago. Assuming that the Sun’s luminosity was 24% lower 3.6 By ago than at present, and Mars was at the same distance from the Sun, the minimum air pressure required for the presence of liquid water at the surface of the Red Planet is 21.9 bar. Mars’ current surface atmospheric pressure is about 0.007 bar. Considering that Venus has now a surface atmospheric pressure of 93 bar, it is conceivable that early Mars could have had a surface air pressure in excess of 22 bar. An important consequence of such a high pressure predicted by our model is that it would have made the surface of Mars virtually isothermal, i.e. the the equator-to-pole annual temperature gradient would have been essentially zero. In other words, if our hypothesis is correct, there should be geological evidence that early Mars was latitudinally isothermal.
If you’d like to try out our planetary temperature model, see Equation 20 in this recent blog article:
“Exact Formulas for Estimating the Equilibrium Climate Sensitivity of Rocky Planets & Moons to Total Solar Irradiance, Absorbed Shortwave Radiation, Planetary Albedo and Surface Atmospheric Pressure”
I’d be happy to answer your questions… I’m looking forward to your comments.
Regards,
Ned
———————————————-
Ned Nikolov, Ph.D.
Physical Scientist
US Forest Service
Caring for the land and serving people
——————————————————–
Oldbrew, thanks for the link. I’m not sure how you get formation of dry ice without a pretty dramatic drop in temperature before that! And vice-versa. I’ve long understood that the problem is Mars lost much of its atmosphere for some reason, not changes in composition before that happened. It’s a bit sad that these guys do a fair bit of sensible work then blame an unknown GHG. Not sure what gas that could be, where it might have come from or why it went away! But temperatures are completely controlled by GHGs…
Phoenix – an ‘unknown’ GHG (so-called) that vanished without trace only seems to have one realistic candidate: water vapour.
@Phoenix44
We should stop referring to CO2, water vapor and other gases with higher IR absorptivity as “greenhouse gases”, because none of these gases can increase the global surface temperature of a planet by the virtue of its IR radiative properties! Substances of high IR emissivity/absorptivity (including gases) only promote cooling, because they do not reflect IR radiation.
Trapping of IR radiation within a system is only possible through the use of materials of very low IR absorptivity and correspondingly high IR reflectivity such as aluminum foil, silver and gold. These materials are called “radiant barriers” in thermal engineering. No gas can act as a radiant barrier!
The claim made by the “Greenhouse” theory over 120 years ago that the absorption of long-wave radiation by water vapor and CO2 in a free, convective atmosphere “traps” heat in the climate system is physically completely preposterous. Scientists of the 19th-Century such as Tyndall, Arrhenius and Ekholm had very little understanding of atmospheric thermodynamics; hence, they had an excuse. The problem is that the ridiculous concept of “heat trapping” in an open atmosphere continues to be promulgated as “established physics” by climate scientists of the 21st Century as well!
Atmospheric gases create a surface thermal effect only adiabatically through their combined pressure regardless of their IR radiative properties. This makes the Atmospheric Thermal Effect (ATE) a thermodynamic phenomenon, not a radiative one! Thus, the atmospheric IR radiation is simply a byproduct (effect) of ATE.
Ned,
I have to disagree with you here. The planet Mars, like our Earth, is a rapid daily rotator, Venus by contrast is not. The latitudinal reach of a planet’s Hadley cell is determined by the Coriolis effect. On Earth there are three basic cells, Hadley, Ferrel and Polar, similarly on Mars there are also the same three basic cells of Hadley, Ferrel and Polar.
See Figure 2: Schematic illustration of the general circulation on Mars. In Haberle, R.M., 2003. Planetary atmospheres| Mars. Elsevier NASA/Ames Research Center, Moffett Field, CA, USA. where the Martian Ferrel cell zone of Baroclinic waves, storm systems and fronts is clearly represented.
Even with a high surface pressure the meteorology of the early Martian atmosphere would still respond to the rapid planetary rotation inducing forced descent in the mid-latitudes and thereby increasing surface radiant loss of thermal energy to space. Rapidly rotating Mars, unlike slowly rotating Venus, would not achieve an isothermal state.
Phillip,
Your argument is based on “theoretical”, non-quantitative considerations. My statement is based on actual quantitative relationships derived from NASA planetary data. So, what I said is not a matter of opinion, but a numerical fact. These relationships also accurately predict the observed polar amplifications in Earth’s paleoclimatic record. Watch this video for details:
No Ned, my argument is based on data.
Please, show me the actual relationships, Phillip, that support your argument about rotation speed affecting meridional temperature gradient… Our data analysis showed no effect of spin rate!
Ned,
The latitudinal reach of the Earth’s Hadley cell is an observed property of Meteorology. In his fundamental description of Earth’s climate Aristotle described the existence of 3 climatic zones. In our paper’s abstract Return to Earth: A New Mathematical Model of the Earth’s Climate we noted the direct relationship of these three climate zones of Aristotle to the presence of the three atmospheric circulation cells of the Earth:
The role of the Coriolis Effect is a well-studied part of the Science of Meteorology. I refer you to:
Persson, A. O., 2005. The Coriolis Effect: Four centuries of conflict between common sense and mathematics, Part I: A history to 1885. International Commission on the History of Meteorology 2, 24pp.
Phillip,
The sizes (width) of the Hadley Cell, Ferrel Cells, and Polar Cells are functions of total pressure, not rotation speed. As the atmospheric mass and pressure increase, so does the molar density of air and the ability of the atmosphere to efficiently transport heat meridionally (i.e. across latitudes). This is why a higher mean surface pressure reduces the equator-to-pole temperature gradient, while a lower pressure increases that gradient. If the pressure is high enough, the planet surface becomes isothermal. The simultaneous response of the equator-to-pole temperature gradient to pressure and solar irradiance is shown in our video (we call it Meridional Temperature Gradient or MTG). Start watching here:
Ned,
If that is true then how do you explain that on low pressure Mars it has a triple cell structure with similar extents to that of the Earth?
Isn’t Venus a one cell atmospheric system?
Yes.
The Venusian Insolation Atmospheric Topside Thermal Heating Pool
Personal lifetime observations.
Please feel free to edit, expand, fill in the blanks.
Follows NZ.
CLOUD COVER (<4k' AGL)
NONE OVERCAST
ToD (LocaL) 1500 0400 1500 0400
DESERT 0k' VH C H VW
DESERT 5k' VH VC H C
ARBORAL 0k' VW-W C W C
ARBORAL 5k' W C-VC W-C C
JUNGLE 0k' H H-VW H H
JUNGLE 5k' H W-VW W W-VW
CLOUD COVER: obscures sun during day
ToD: Time of Day
0k’ – 0 feet MSL, 5k’ – 5,000 feet MSL (Arbitrary)
VH: Very Hot
H: Hot
VW: Very Warm
C: Cold
VC: Very Cold
DESERT eg.: Sahara; Adjacent to Great Salt Lake, UT
ARBORAL eg.: Forested, ground vegetation, lakes, rivers (West Coast North America)
JUNGLE eg: Mouth of Amazon River Basin; Central Highlands, Viet Nam
Arrggh!
Lost formatting. Tried to chart my experienced temperatures which were, and are, primarily altitude and cloud cover/humidity dependent.
CLOUD COVER (<4,000')
NONE OVER CAST
ToD (Local) 1500 0400 1500 0400
DESERT 0k' VH C H VW
DESERT 5k' VH VC H C
ARBORAL 0k' VW-W C W C
ARBORAL 5k' W C-VC W-C C
JUNGLE 0k' H H-VW H H
JUNGLE 5k' H W-VW W W-VW
ToD: Time of Day – mid-summer
H: Hot
W: Warm
C: Cool
V*: Very *
Geophysical Research Letters:
Was Venus the First Habitable World of our Solar System?
…we find that such a world could have had moderate temperatures if Venus had a rotation period slower than about 16 Earth days, despite an incident solar flux 46−70% higher than modern Earth receives.
. . .
In this paper we use a 3-dimensional General Circulation Model (GCM) to explore scenarios under which an ancient Venus with shallow oceans and an Earth-like atmosphere may have been habitable and to estimate the potential duration of such a habitable phase.
Click to access 1608.00706.pdf
Key Points:
• Venus may have had a climate with liquid water on its surface for approximately 2 billion
years.
• The rotation rate and topography of Venus play crucial roles in its atmospheric dynamics.
• Venus’s climatic history has important implications for exoplanetary studies of the
habitable zone.
– – –
‘if Venus had a rotation period slower than about 16 Earth days,’
A big if.
Aliens. Also the reason we have a 1 bar atmosphere and the dinosaurs had 5-10 bar. 😇
@oldbrew:
This paper about Venus having been the fist habitable planet in the Solar System is based on a faulty climate computer model. There is no empirical evidence that the spin rate and/or topography of a planet affects the global surface temperature or the meridional temperature gradients. This is the type of junk science results one gets, when blindly trusting theoretical models!
Here is what the empirical evidence suggests: If 3.6 By ago Venus had a similar surface air pressure as today’s Earth (1 bar) and Sun’s luminosity was 24% lower than it is today, while the Venus-Sun distance was the same, then the average annual latitudinal temperatures on Venus would be as follows according to the NZ model based on actual planetary data:
Equator: 328.6 K (55.4 C)
20 deg latitude: 325.9 K (52.8 C)
38.5 deg latitude (also mean global temp.): 314.5 K (41.3 C)
60 deg latitude: 298.6 K (25.5 C)
75 deg latitude: 285.2 K (12.1 C)
Poles: 275.8 K (2.6 C)
Meridional Temp. Gradient: 52.8 K (C)
Mean annual temperatures above 40 C are not really supportive of higher life forms. Hence, most of the Venusian surface would have been under hot and poorly habitable conditions.
Uhm, why not Occam’s Razor?
Mars lost its atmosphere due to asteroid strikes or grazes ripping off the atmosphere. Hellas Planitia is a huge dent in Mars’ surface possibly an asteroid impact area. Being right next to the asteroid belt this would be the most likely explanation.
One need not buy into exotic theories like CO2 or even solar wind depleting the atmosphere. E.g. Venus is subject to intense solar wind due to its orbital distance with an atmosphere comprised mostly of CO2, yet it has a surface pressure of 92 bar.