Researchers calculate size of particles in Martian clouds of CO2 snow

Researchers have determined the size of CO2 snow particles on Mars, depicted in this artist’s rendering as a mist or fog that eventually settles to the surface as carbon dioxide snow. Photo – Image: NASA, Christine Daniloff/MIT News

Mars’ carbon dioxide ‘snowflakes’ are about the size of red blood cells.

In the dead of a Martian winter, clouds of snow blanket the Red Planet’s poles — but unlike our water-based snow, the particles on Mars are frozen crystals of carbon dioxide. Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.

Now researchers at MIT have calculated the size of snow particles in clouds at both Martian poles from data gathered by orbiting spacecraft. From their calculations, the group found snow particles in the south are slightly smaller than snow in the north — but particles at both poles are about the size of a red blood cell.

“These are very fine particles, not big flakes,” says Kerri Cahoy, the Boeing Career Development Assistant Professor of Aeronautics and Astronautics at MIT. If the carbon dioxide particles were eventually to fall and settle on the Martian surface, “you would probably see it as a fog, because they’re so small.”

Cahoy and graduate student Renyu Hu worked with Maria Zuber, the E.A. Griswold Professor of Geophysics at MIT, to analyze vast libraries of data gathered from instruments onboard the Mars Global Surveyor (MGS) and Mars Reconnaissance Orbiter (MRO). From the data, they determined the size of carbon dioxide snow particles in clouds, using measurements of the maximum buildup of surface snow at both poles. The buildup is about 50 percent larger at Mars’ south pole than its north pole.

Over the course of a Martian year (a protracted 687 days, versus Earth’s 365), the researchers observed that as it gets colder and darker from fall to winter, snow clouds expand from the planet’s poles toward its equator. The snow reaches halfway to the equator before shrinking back toward the poles as winter turns to spring, much like on Earth.

“For the first time, using only spacecraft data, we really revealed this phenomenon on Mars,” says Hu, lead author of a paper published in the Journal of Geophysical Research, which details the group’s results.

Diving through data

To get an accurate picture of carbon dioxide condensation on Mars, Hu analyzed an immense amount of data, including temperature and pressure profiles taken by the MRO every 30 seconds over the course of five Martian years (more than nine years on Earth). The researchers looked through the data to see where and when conditions would allow carbon dioxide cloud particles to form.

The team also sifted through measurements from the MGS’ laser altimeter, which measured the topography of the planet by sending laser pulses to the surface, then timing how long it took for the beams to bounce back. Every once in a while, the instrument picked up a strange signal when the beam bounced back faster than anticipated, reflecting off an anomalously high point above the planet’s surface. Scientists figured these laser beams had encountered clouds in the atmosphere.

Hu analyzed these cloud returns, looking for additional evidence to confirm carbon dioxide condensation. He looked at every case where a cloud was detected, then tried to match the laser altimeter data with concurrent data on local temperature and pressure. In 11 instances, the laser altimeter detected clouds when temperature and pressure conditions were ripe for carbon dioxide to condense. Hu then analyzed the opacity of each cloud — the amount of light reflected — and through calculations, determined the density of carbon dioxide in each cloud.

To estimate the total mass of carbon dioxide snow deposited at both poles, Hu used earlier measurements of seasonal variations in the Martian gravitational field done by Zuber’s group: As snow piles up at Mars’ poles each winter, the planet’s gravitational field changes by a tiny amount.  By analyzing the gravitational difference through the seasons, the researchers determined the total mass of snow at the north and south poles. Using the total mass, Hu figured out the number of snow particles in a given volume of snow cover, and from that, determined the size of the particles. In the north, molecules of condensed carbon dioxide ranged from 8 to 22 microns, while particles in the south were a smaller 4 to 13 microns.

“It’s neat to think that we’ve had spacecraft on or around Mars for over 10 years, and we have all these great datasets,” Cahoy says. “If you put different pieces of them together, you can learn something new just from the data.”

Since carbon dioxide makes up most of the Martian climate, understanding how it behaves on the planet will help scientists understand Mars’ overall climate, says Paul Hayne, a postdoc in planetary sciences at the California Institute of Technology.

“The big-picture question this addresses is how the seasonal ice caps on Mars form,” says Hayne, who was not involved in the research. “The ice could be freezing directly at the surface, or forming as snow particles in the atmosphere and snowing down on the surface … this work seems to show that at least in some cases it’s snowfall rather than direct ice deposition. That’s been suspected for a long time, but this may be the strongest evidence.”

What can the size of snow tell us?

Hu says knowing the size of carbon dioxide snow cloud particles on Mars may help researchers understand the properties and behavior of dust in the planet’s atmosphere. For snow to form, carbon dioxide requires something around which to condense — for instance, a small silicate or dust particle. “What kinds of dust do you need to have this kind of condensation?” Hu asks. “Do you need tiny dust particles? Do you need a water coating around that dust to facilitate cloud formation?”

Just as snow on Earth affects the way heat is distributed around the planet, Hu says snow particles on Mars may have a similar effect, reflecting sunlight in various ways, depending on the size of each particle. “They could be completely different in their contribution to the energy budget of the planet,” Hu says. “These datasets could be used to study many problems.”

This research was funded by the Radio Science Gravity investigation of the NASA Mars Reconnaissance Orbiter mission.

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Jennifer Chu, MIT News Office

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39 Responses to Researchers calculate size of particles in Martian clouds of CO2 snow

  1. emediacoder says:

    As A result of globalization we see and learn more about what is happening around the globe. Social media programs show us targets and ways of living that we have never seen before and due to on how to be social, not on how to do social. For some people this has created the need to keep in touch with people all over the world we encounter in our travels. As I’m writing this article, I am a Dutch woman, lives in Switzerland, working on an international project. The technique is only satisfy the need to stay in touch with people, cultures and societies around the world.

  2. Andy Smith says:

    Ok, so we know how big it is. It would also be nice to know if they had figured out how much of the stuff there is and how deep it gets.

  3. mfo says:

    Mars Rover, Curiosity, lands on August 6 2012, with the following unstruments:

    – Mast Camera (Mastcam)
    – Chemistry & Camera (ChemCam)
    – Alpha Particle X-ray Spectrometer (APXS)
    – Mars Hand Lens Imager (MAHLI)
    – Chemistry & Mineralogy (CheMin)
    – Sample Analysis at Mars (SAM)
    – Radiation Assessment Detector (RAD)
    – Rover Environmental Monitoring Station (REMS)
    – Dynamic Albedo of Neutrons (DAN)
    – Mars Descent Imager (MARDI)
    – MSL EDL Instrument (MEDLI) Suite

    http://msl-scicorner.jpl.nasa.gov/Instruments/

    The MSL mission has four primary science objectives to meet the overall habitability assessment goal:

    The first is to assess the biological potential of at least one target environment by determining the nature and inventory of organic carbon compounds, searching for the chemical building blocks of life, and identifying features that may record the actions of biologically relevant processes.

    The second objective is to characterize the geology of the landing region at all appropriate spatial scales by investigating the chemical, isotopic, and mineralogical composition of surface and near-surface materials, and interpreting the processes that have formed rocks and soils.

    The third objective is to investigate planetary processes of relevance to past habitability (including the role of water) by assessing the long timescale atmospheric evolution and determining the present state, distribution, and cycling of water and carbon dioxide.

    The fourth objective is to characterize the broad spectrum of surface radiation, including galactic cosmic radiation, solar proton events, and secondary neutrons.

    A fascinating visual representation, NASA’s Eyes on the Solar System:

    http://solarsystem.nasa.gov/eyes/player/?document=http://solarsystem.nasa.gov/eyes/content/documents/msl/msl.xml

  4. En Passant says:

    Nice try with your little joke, but I know you are having us on. The giveaway is the line:
    ” the particles on Mars are frozen crystals of carbon dioxide. Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.”

    As James Hansen conclusively proved (by being arrested so many times) the Martian climate is a runaway hothouse. You probably fooled some people but not us catastrophists and propheteers

  5. George E. Smith; says:

    CO2 “Snow” is prohibited at WUWT; and I ain’t too keen about having it on Mars either; so there !!

  6. indrdev200 says:

    temperatures in centigrade will be helpful.

  7. richard verney says:

    Anthony

    Good to see posts dealing with other scientific issues.

    Mars is a potential laboratory where we can measure conditions and effects un poluted by human activity. We really should send some equipment ti various locations to measure the effect of any chnages caused by changes in solar activity and brought about by changes in levels of CO2.

    Of course, the Martian atmosphere is not as complex nor as dense as that of Earth’s and cosmic ray seeding theory may not operate with thye same effect in those conditions, but nontheless it could provide useful input into the radiative theory behind climate science, and whether the sun is an important driver or not

  8. Steve R says:

    “Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.”

    This statement needs much more explanation. Are they trying to say frozen alcohol has something to do with CO2 deposition? The idea that alcohol exists in the Martian atmosphere at all is news to me. The rest of the article only discusses dust as a possible nuclei.

  9. coldlynx says:

    Temperature where CO2 form snow on Mars are similar to the coldest part of the troposphere on earth. Then must we also have CO2 snow on earth but in our atmosphere.
    Could a stationary polar CO2 snow cloud be responsible for abrupt global cooling and the dissolving of the same cloud be responsible for abrubt global warming?

  10. Ibbo says:

    Sorry, Mars is freezing cold, yet has an atmosphere composed of quantities of C02 far in excess of ours ? How does that work then ?

  11. On one side of us, a planet with so much CO2 it’s becme a hothouse.

    On the other side, a planet that can get so cold, that it’s CO2 falls as snow.

    It’s great to be living on a planet that’s just right…

  12. En Passant says:
    June 20, 2012 at 2:04 am
    Nice try with your little joke, but I know you are having us on. The giveaway is the line:
    ” the particles on Mars are frozen crystals of carbon dioxide. Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.”

    As James Hansen conclusively proved (by being arrested so many times) the Martian climate is a runaway hothouse. You probably fooled some people but not us catastrophists and propheteers

    The Martian atmosphere is 1% of the density of ours and has 95% CO2. Since CO2 makes up about 0.039% of our atmosphere, approximately 1/30th, of the Martian value, then the greenhouse effect should be more noticeable on Mars than it is here.

  13. SPreserv says:

    Ibbo says:
    June 20, 2012 at 3:34 am

    Sorry, Mars is freezing cold, yet has an atmosphere composed of quantities of C02 far in excess of ours ? How does that work then ?

    atmospheric pressure ?

  14. Babsy says:

    andrewmharding says:
    June 20, 2012 at 5:27 am

    Where are the abandoned well sites and SUVs that produced all that CO2?

  15. Kevin Schurig says:

    How much does the temperature of a planet’s core play into all of this as well? It is said that Mars’ core is cold. or cooling, so where does Venus’ core rank in all this? And how much does that play into a planet’s overall temperature? Now the big question, how much can we model what is happening on Earth by using other planets that really are not the same as Earth? And the reverse, how can we use what happens on Earth and extrapolate that on other planets? As someone above stated, nice to be on the planet that is just right.

  16. Bill Tuttle says:

    coldlynx says:
    June 20, 2012 at 3:01 am
    Temperature where CO2 form snow on Mars are similar to the coldest part of the troposphere on earth. Then must we also have CO2 snow on earth but in our atmosphere.
    Could a stationary polar CO2 snow cloud be responsible for abrupt global cooling and the dissolving of the same cloud be responsible for abrubt global warming?

    Change “responsible for” to “result from” and you’ll have the question right…

  17. H.R. says:

    I’d be more interested in the convection process that gets enough CO2 high enough to form clouds that condense out as CO2 ‘snow.’ Without the ocean and land that Earth has, I would think Mars’ thermostat would be confined to a less variable band.

    BTW, I didn’t catch a mention of the altitude of the clouds. Did I miss it?

  18. John Campbell says:

    “Most of the Martian atmosphere is composed of carbon dioxide…”
    Wow, it must be really hot-hot-hot there!

  19. Werner Brozek says:

    Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.

    This is a rather convoluted way of saying that it gets to -117 C, (the freezing temperature of ethyl alcohol), and since the freezing temperature of CO2 is -78.5 C, CO2 freezes.

  20. johnmcguire says:

    These scientists can’t even figure out the earth’s atmosphere and now they are going to tell us what is happening on Mars? Spend that time and money on figuring out the earth’s problems, for instance how about cancer research. Yeah man is so smart and people on earth are still dieing untimely deaths due to a number of reasons that could be solved with the application of all this money that is being thrown away on wild ventures. Yeah , I already hear the sanctimoious screams about the importamce of all this knowledge they will accumulate up there. No , I’m not a luddite. I think technolodgical advancement is good and important , but I see projects such as this as waste.

  21. End-The-Fed says:

    Reblogged this on Nuclear Dawn Help and commented:
    We can measure CO2 on other planets, yet we can’t on our own….HMMMMMM.

  22. kramer says:

    Speaking of Mars, anybody know if the ice caps on it are still shrinking or not?

  23. Chris Colose says:

    The reason CO2 can’t generate a strong greenhouse effect on Mars is because of the atmospheric pressure…but not in a Steve Goddard way. The opacity is directly related to the atmospheric pressure, since collisions between molecules “spread out” the absorption features of a greenhouse gas. The greenhouse effect on Earth would be much weaker if you could strip the air of N2 and O2 for example, even though they don’t directly contribute the greenhouse effect very much.

  24. Gary Pearse says:

    ““It’s neat to think that we’ve had spacecraft on or around Mars for over 10 years, and we have all these great datasets,” Cahoy says. “If you put different pieces of them together, you can learn something new just from the data.”

    Hey there’s an idea for climate scientists. These researchers didn’t have to homogenize data, change the size of the snowflakes, or construct fanciful models instead of learning from the data.

  25. Phil. says:

    Werner Brozek says:
    June 20, 2012 at 8:12 am
    Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.

    This is a rather convoluted way of saying that it gets to -117 C, (the freezing temperature of ethyl alcohol), and since the freezing temperature of CO2 is -78.5 C, CO2 freezes.

    Strictly the sublimation point of CO2 at 1atm partial pressure is -78.5ºC, at about 0.006atm (the Martian surface pressure the sublimation point is about -125ºC. Freezing of CO2 only happens at partial pressures above the Triple point (-56.6ºC, 5.11atm).

    http://tinyurl.com/d7mwm77

  26. Larry Butler says:

    Isn’t it amazing how there is not a single human, or his SUV, or his oil company, to blame for the huge concentration of CO2 in the Martian atmosphere. It’s, almost, (gasp) as if, (gasp) CO2 is NATURAL!

    How can that be?

  27. offshore bank account says:

    To estimate the total mass of carbon dioxide snow deposited at both poles, Hu used earlier measurements of seasonal variations in the Martian gravitational field done by Zuber’s group: As snow piles up at Mars’ poles each winter, the planet’s gravitational field changes by a tiny amount. By analyzing the gravitational difference through the seasons, the researchers determined the total mass of snow at the north and south poles. Using the total mass, Hu figured out the number of snow particles in a given volume of snow cover, and from that, determined the size of the particles. In the north, molecules of condensed carbon dioxide ranged from 8 to 22 microns, while particles in the south were a smaller 4 to 13 microns.

  28. AGWDenier says:

    “Most of the Martian atmosphere is composed of carbon dioxide”

    In which case, why isn’t Mars just burning up? The AGW alarmists of course will simply argue, ‘Because there’s no water vapor in the Martian atmosphere to amplify the warming effect of its high carbon dioxide content’. Fair enough. Except that the alarmists routinely use this very argument to explain why Venus is so hot! There’s no water vapor there either! They can’t have it both ways.

  29. George E. Smith; says:

    “””””…..June 20, 2012 at 4:11 pm

    Werner Brozek says:
    June 20, 2012 at 8:12 am
    Most of the Martian atmosphere is composed of carbon dioxide, and in the winter, the poles get so cold — cold enough to freeze alcohol — that the gas condenses, forming tiny particles of snow.

    This is a rather convoluted way of saying that it gets to -117 C, (the freezing temperature of ethyl alcohol), and since the freezing temperature of CO2 is -78.5 C, CO2 freezes.

    Strictly the sublimation point of CO2 at 1atm partial pressure is -78.5ºC, at about 0.006atm (the Martian surface pressure the sublimation point is about -125ºC. Freezing of CO2 only happens at partial pressures above the Triple point (-56.6ºC, 5.11atm). …..”””””

    Phil to our rescue again. As I said earlier, we don’t allow CO2 snow here; brings back awful nighmares.

    George

  30. Chuck Bradley says:

    At 8:01 pm offshore bank account quoted the method of the study. I can see how the changed gravity field, could be used to calculate the mass of the snow, but I suspect the result would not be very accurate. I don’t see how to convert mass to number of particles. The particles are not molecules. A further mystery is how to determine the distribution of particle sizes. More details appreciated. Thanks.

  31. david brown says:

    Larry Butler. Mars has a different atmosphere to Earth. Little thermal inertia. The albedo effect controls climate. On Earth it is the greenhouse gases, especially C02 that stops us freezing

  32. david brown says:

    AGW denier. I suggest you reread what the scientists say. They do not want it both ways. It has to do with the different atmospheres of each planet. Though Venus shows that the runaway greenhouse effect is not a fantasy. And Venus is our ”sister ” planet. We are more like Venus than Mars. Not a very nice thought

  33. david brown says:

    AGW denier. There is water vapour on Venus. There could have even been oceans at one point .Logic should say that it is far easier to study conditions on Earth than any other planet. I would rely more on research involving the planet we live on

  34. david brown says:

    Larry Butler . Whoever said naturally occurring C02 did not exist? but naturally occurring C02 is absorbed by the carbon sinks. It is called the carbon cycle. What man puts into the atmosphere is not part of the natural carbon cycle. and thus, what we put into the atmosphere does not get absorbed by the sinks and accumulates in the atmosphere raising C02 levels . natural versus manmade is in relation to the carbon cycle, not C02 itself. naturally occurring C02 levels rise very slowly. a rise of a 100 ppm can take 5000- 20,000 years. A rise of 100 ppm now, has taken just over a 150 years. And that is not natural.

  35. Myrrh says:

    david brown says:
    June 21, 2012 at 10:24 am
    Larry Butler . Whoever said naturally occurring C02 did not exist? but naturally occurring C02 is absorbed by the carbon sinks. It is called the carbon cycle. What man puts into the atmosphere is not part of the natural carbon cycle. and thus, what we put into the atmosphere does not get absorbed by the sinks and accumulates in the atmosphere raising C02 levels .

    How can it accumulate? Wherever carbon dioxide comes from it becomes part of the natural cycle, and, it is also fully part of the Water Cycle which cools, the Earth – all pure clean rain is carbonic acid – it all comes back down to Earth in the natural Wash Cycle which cleans the air and brings carbon dioxide back to where the plants are waiting for it.

    natural versus manmade is in relation to the carbon cycle, not C02 itself. naturally occurring C02 levels rise very slowly. a rise of a 100 ppm can take 5000- 20,000 years. A rise of 100 ppm now, has taken just over a 150 years. And that is not natural.

    If I were you I’d check out just how that initial low figure was arrived at by Keeling and Co, it was cherry picked low to give an apparent rise so it could be blamed on coal. At the time the standard science average for CO2 was 400 ppm.

  36. AGWDenier says:

    david brown, There is so little water vapor on Venus it is not worth mentioning, and certainly insufficient to be cited as a suitable positive feedback for the very high levels of CO2 as the warmists would require in order to have their greenhouse model based on it. But water vapour in the Venusian atmosphere in quantity is indeed vital for any such CO2-based greenhouse to work. However, astronomer James Pollack pointed out that (Carl Sagan’s) “enhanced greenhouse effect” on Venus requires at least 0.1 per cent water vapour, in addition to the 96 per cent carbon dioxide, in the atmosphere. According Charles Ginenthal, “There is practically no water on Venus… This is based on careful spectroscopic analysis of the clouds”. So immediately we have a problem.

    Nothing has changed in this regard for forty years since this idea was debated with Sagan when he fostered his enhanced greenhouse model. According to a statement issued by the European Space Agency in 2010, “Venus has very little water. Were the contents of Earth’s oceans to be spread evenly across the world, they would create a layer 3 km deep. If you were to condense the amount of water vapour in Venus’ atmosphere onto its surface, it would create a global puddle just 3 cm deep”

    So if, according the AGW alarmists, Venus is the victim of an enhanced greenhouse effect that they base on water vapour as a positive feedback, how is it occurring on Venus when there isn’t any to be found? Furthermore, if Venus’ atmosphere is capable of sustaining thermal runaway without water vapour present, why doesn’t it also occur on Mars? All it requires, apparently, is sufficient CO2 in the atmosphere with or without water vapour.

    The solution to the conundrum is that Venus’ heat is NOT the consequence of thermal runaway due to its high atmospheric CO2 content.

  37. Sugel says:

    Most of Mars’ atmosphere is made up of carbon dioxide (CO2), so during the winter months the poles get so cold that gas condenses and forms tiny particles of snow.

  38. George E. Smith; says:

    “””””…..david brown says:

    June 21, 2012 at 7:59 am

    Larry Butler. Mars has a different atmosphere to Earth. Little thermal inertia. The albedo effect controls climate. On Earth it is the greenhouse gases, especially C02 that stops us freezing…..”””””

    And if we were freezing due to an absence or shortage of CO2, then more precipitation of rain, sleet, hail, snow, frogs, whatever, would leave us with a lot less cloud; which is made up of rain, sleet, hail, snow, frogs, whatever, in solid, liquid, vapor form, and a lot less cloud, would leave us wth a lot more solar radiation energy reaching the earth surface, to get stored in the deep oceans, which would warm up the earth so would not all be freezing.

    Ergo, CO2 is not stopping us all from freezing, because if it was, then we would not all be freezing due to extra sunshine.

  39. Brian H says:

    In the dead of a Martian winter, clouds of snow blanket the Red Planet’s poles — but unlike our water-based snow, the particles on Mars are frozen crystals of carbon dioxide.

    Not strictly true, IMO. Water ice/snow freezes out sooner, so much of the CO2 snow/frost overlays H2O ice.

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