A growing bounty of images from NASA's Mars Reconnaissance Orbiter reveals that the timing of new activity in one type of the enigmatic gullies on Mars implicates carbon-dioxide frost, rather than water, as the agent causing fresh flows of sand.
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Gullies that look like this on Earth are caused by flowing water, but Mars is a different planet with its own mysteries," said Serina Diniega, lead author of a report on these findings in the November issue of the journal Geology.
Yippee !
There's part of me that has been eagerly awaiting a study like this one !
To date, just about all of the flow-related geological evidence observed on the surface, seems to have automatically led to the conclusion that volumes of liquid H2O have caused it. I've never seen any serious consideration given to the possibility of other mechanisms.
At last someone is starting to consider the possibility that large amounts of sublimating, (& other physical state), CO2 may be behind it.
This report has made my day. So far, discussing this possibility around here has been out of the question, but now that we have some scientific analysis on it … who knows what directions our conversations about life existing and human colonisation of Mars might take !!
Can't wait to read the report .. I just hope I can get hold of it !
Those images are impressive,being able to see some sort of movement on the surface.
Though i thought Sublimation is when carbon dioxide skips the liquid state and freezes to form what is commonly referred to as dry ice (no?).So when it melts it doesn't turn into liquid but turns straight into a gas(right?)
It would be awesome if it was H2O causing the erosion.
Other suggested mechanisms are that gas from sublimating frost could lubricate a flow of dry sand or erupt in puffs energetic enough to trigger slides.
There's a lot of ice also on the poles of Mars.
The exact mixture of carbon dioxide and water in that ice, is not yet precisely known.
Some of the probes have measured the composition of small samples and they have also taken photos of ice sublimating in the trenches of the 'scoops' they made. Because of the slow sublimation rate measured from the photos, they believe that ice is composed mainly of water (H2O).
So have they done any tests on the composition of the polar ice caps?
It Would be interesting to know how much water there really is on mars.
It would be very interesting to know what had really happened in Mars's past.It could of been very much like Earth,something must of went terribly wrong in its distant past.
I Wouldn't mind volunteering to go to mars to see it all for myself yet i think it is a little inhospitable right now .
So, you know that I mentioned that its Ok to believe something but its always good to keep the facts separated from your beliefs ?
Well, answering your question requires me to separate what I would like to believe, and the facts. So, I'm going to try and give you a balanced answer. Here goes ..
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Originally Posted by orestis
Thanks Craig for the explanation .
So have they done any tests on the composition of the polar ice caps?
Yes. As far as I'm aware, the most direct measurements taken from orbit of the southern polar region were taken by the Mars Express 'MARSIS' instrument which used primarily, ground penetrating radar as its detection mechanism. The radar could penetrate to considerable depths, but at the end of the day, the chemical composition of the material being penetrated is still 'inferred' (you may have to look this word up). Having said this, the lander samples are clearly not inferred. Carl and I had posts on this in the past.
The Mars Global Surveyor and Mars Odyssey also did high resolution and thermal imaging of the polar caps from orbit. From these (images only), it was concluded that the polar caps were made from mostly water ice with layers of about one metre to 8 metres of dry ice (CO2) over the top. Here's a page to read up on this.
The Phoenix lander also confirmed by direct measurements from the TEGA instrument, (Thermal and Evolved-Gas Analyzer), which is a very accurate mass spectrometer, the existence of water vapour from a scoop sample taken in 2008. I recall that they were unable to repeat this measurement/result again.
Clearly, there is H2O on Mars. The quantity of it is still approximated using models and inferred results, rather than by direct measurements. Large volumes of frozen CO2 have not been entirely discounted as a possibility as the origin of some of the geological formations on the surface. As they look more into this aspect, some of the geological evidence supporting the large volumes of liquid H2O theory may, (or may not), erode the supporting case.
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It Would be interesting to know how much water there really is on mars.
I agree. It seems that direct sampling using spectrometers and other chemical sampling methods, over a wide geographical polar area might be the best method to come up with an accurate answer to this question.
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It would be very interesting to know what had really happened in Mars's past. It could of been very much like Earth, something must of went terribly wrong in its distant past.
The so called Mars 'devastation' theory depends on the inferred results of the above mentioned data, which leads to the conclusion that there was a lot of liquid H2O on Mars in the past. The possibility that there wasn't a lot of H2O is not inconsiderable, which is why I still have doubts. I can keep my doubts separated from the facts, however. I continue to look for more data to satisfy my questions about it all. Let me know if you find any.
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I Wouldn't mind volunteering to go to mars to see it all for myself yet i think it is a little inhospitable right now .
I wouldn't be going there without a lot of water. Its pretty dry and humans need water to survive.
Your questions are right on the mark. Keep 'em coming.
Spectroscopy is used to find out the chemical composition of stars can't they use it to find out the ratio of dry ice to water ice.Or is this a very difficult process.
Lets use a little imagination here.Suggest there was a lot of water on mars creating the river valleys and other geological features,How could it all disappear,just like that.
Just wondering, Can you have life that can breathe co2 on earth?
I know trees can but they also need oxygen during the night but then again they make oxygen so maybe its just a big cycle.
Spectroscopy is used to find out the chemical composition of stars can't they use it to find out the ratio of dry ice to water ice.Or is this a very difficult process.
Spectroscopy can be (and has been used) to determine the composition of the atmospheric gases surrounding Mars. From these measurements, CO2 comprises about 95% of the atmospheric gas. Water vapour is only about 0.03 %. So there is almost no water vapour. This might be because any water on the Martian surface is frozen. If it is frozen, the bulk of it would probably be found on the poles. In a way, the atmosphere should be an indirect indicator of the proportions.
Spectroscopy works if the samples are vapourised to release the gases.
Spectroscopy was used by a recent lander in its little laboratory, to determine the amounts of chemicals in the scoops they took. They did this by heating the sample until the gases were released, and then measured the 'absorption' wavelengths corresponding to the chemical composition of samples. The proportions of the compounds and elements in the sample could then be determined. I think they only got one reading, unfortunately.
This is the same process used to measure the gases in the atmospheres of stars. We can do this remotely from Earth, because the star vapourises the gases and provides a background light source.
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Lets use a little imagination here.Suggest there was a lot of water on mars creating the river valleys and other geological features,How could it all disappear,just like that.
They have ideas and hypotheses. I think the leading hypothesis is that any liquid H2O may still exist underground. It may have burned off, if Mars' magnetic field, (if it ever had one like Earth's), diminished (for unknown reasons). Either way, we probably need to go there to find out the real answers ! There is undeniably, a lot of geological evidence. I can also 'imagine' that there may have never been any 'big water' there and other unknown processes may explain some of the geological features. The geological processes on Mars could easily be ones we don't understand because the physical conditions on Mars are completely, (& quite radically), different from those here on Earth. Using Earth as a model could conceivably, result in the 'mystery' you speak of. We don't know, what we don't know, yet.
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Just wondering, Can you have life that can breathe co2 on earth?
I know trees can but they also need oxygen during the night but then again they make oxygen so maybe its just a big cycle.
Life (as we know it) needs to be able to metabolise (eat to release energy to do its thing). The energy stored in the CO2 molecule could be released to provide the energy which could be used by extra-terrestrial life. The soil on Mars contains 'perchlorate'. This possibly, could perform the same job. Complex topic.
I'm no biologist, but clearly all plant life on earth undergoes a metabolic cycle called photo-synthesis which uses CO2 for them to 'do their thing'. I think there are bacteria here, which can do the same.
The new findings help scientists to better understand what features and landscapes on Mars can be explained by current processes and which require environmental conditions no longer present on the planet.
"Understanding how Mars is changing today is a key first step to understanding basic planetary processes and how Mars changes over time," said HiRISE Principal Investigator Alfred McEwen, a professor in the UA's department of planetary sciences and a co-author of both reports. "There's lots of current activity in areas covered by seasonal carbon-dioxide frost, a process we don't see on Earth. It's important to understand the current effects of this unfamiliar process so we don't falsely associate them with different conditions in the past."
… more evidence in support of my words:
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Originally Posted by CraigS
Clearly, there is H2O on Mars. The quantity of it is still approximated using models and inferred results, rather than by direct measurements. Large volumes of frozen CO2 have not been entirely discounted as a possibility as the origin of some of the geological formations on the surface. As they look more into this aspect, some of the geological evidence supporting the large volumes of liquid H2O theory may, (or may not), erode the supporting case.
The so called Mars 'devastation' theory depends on the inferred results of the above mentioned data, which leads to the conclusion that there was a lot of liquid H2O on Mars in the past. The possibility that there wasn't a lot of H2O is not inconsiderable, which is why I still have doubts.
Though i thought Sublimation is when carbon dioxide skips the liquid state and freezes to form what is commonly referred to as dry ice (no?).So when it melts it doesn't turn into liquid but turns straight into a gas(right?)
Sublimation is the process when a substance transitions directly from a solid state into a gaseous one.
Deposition (or Precipitation) is the reverse of that process.
As for the state of various compounds on Mars, at 6millibars, CO2 can not exist in a liquid form on the surface of Mars.
Water should be able to exist on the day lit side if the atmospheric pressure rises above 0.006atm, requiring only temperature of greater than 0C for liquid water to be stable.
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Originally Posted by CraigS
In a way, the atmosphere should be an indirect indicator of the proportions.
I'm not sure I agree with this statement, as the composition of the atmosphere is directly related to the partial pressures of each component at Mars' atmospheric conditions. Reviewing the enclosed phase diagrams should give insight as to why taking the proportion or ratios of gases in any atmosphere is not directly related to the ratio of the compounds in the overall system. However, knowing the phase behavior of each and the conditions, we can back calculate (or estimate) the proportion of each in a static (adiabatic) system (which I guess could be described as ''indirect'' ).
Water should be able to exist on the day lit side if the atmospheric pressure rises above 0.006atm, requiring only temperature of greater than 0C for liquid water to be stable.
Yep .. good point ..
I think Mars might get up to a max of about 8.5 mbars so yep, its possible.
Wouldn't want to be looking for it, to save myself from dehydration, though. It probably wouldn't be around the polar regions, either .. which is where they say the 'big' water is.
Happy to be corrected, though.
There could also be liquid water at depths .. as the pressure is greater (as may be the temperatures, too). This may work in the polar regions, also. Bringing it to the surface might be a problem though, as it would sublimate again (unless it was kept at pressure). Can't think of how this could happen without human intervention (??). If it came up, and it contained life (say bacterium), then the pressure drop would kill off any life when it reached the surface (??)
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