Ancient Lake on Mars

[yevaud]

University of Colorado team finds definitive evidence for ancient lake on Mars

First unambiguous evidence for shorelines on the surface of Mars, say researchers

A University of Colorado at Boulder research team has discovered the first definitive evidence of shorelines on Mars, an indication of a deep, ancient lake there and a finding with implications for the discovery of past life on the Red Planet.

Estimated to be more than 3 billion years old, the lake appears to have covered as much as 80 square miles and was up to 1,500 feet deep -- roughly the equivalent of Lake Champlain bordering the United States and Canada, said CU-Boulder Research Associate Gaetano Di Achille, who led the study. The shoreline evidence, found along a broad delta, included a series of alternating ridges and troughs thought to be surviving remnants of beach deposits.

"This is the first unambiguous evidence of shorelines on the surface of Mars," said Di Achille. "The identification of the shorelines and accompanying geological evidence allows us to calculate the size and volume of the lake, which appears to have formed about 3.4 billion years ago."

A paper on the subject by Di Achille, CU-Boulder Assistant Professor Brian Hynek and CU-Boulder Research Associate Mindi Searls, all of the Laboratory for Atmospheric and Space Physics, has been published online in Geophysical Research Letters, a publication of the American Geophysical Union.

Images used for the study were taken by a high-powered camera known as the High Resolution Imaging Science Experiment, or HiRISE. Riding on NASA's Mars Reconnaissance Orbiter, HiRISE can resolve features on the surface down to one meter in size from its orbit 200 miles above Mars.

An analysis of the HiRISE images indicate that water carved a 30-mile-long canyon that opened up into a valley, depositing sediment that formed a large delta. This delta and others surrounding the basin imply the existence of a large, long-lived lake, said Hynek, also an assistant professor in CU-Boulder's geological sciences department. The lake bed is located within a much larger valley known as the Shalbatana Vallis.

"Finding shorelines is a Holy Grail of sorts to us," said Hynek.

Full Article

 

[nimbus]

I can't find that paper.. It says it was just published (in that article dated mid june) online in Geophysical Research Letters.

 

[centsworth_II]

I can't find that paper..

I found this in the"Papers in Press" section:

"Papers in Press is a service for subscribers that allows immediate citation and access to accepted manuscripts prior to copyediting and formatting according to AGU style. Manuscripts are listed below in the correct citation format. They are removed upon publication."

Di Achille, G., B. M. Hynek, and M. L. Searls (2009), Positive identification of lake strandlines in Shalbatana Vallis, Mars,
Geophys. Res. Lett., doi:10.1029/2009GL038854, in press. [PDF] (accepted 4 June 2009)


It looks like you need to pay 9 dollars for an article once it's published and can't get it at all until then. Being in the "Papers in Press" section, it is still unavailable.

 

[nimbus]

Thank you Centsworth.

 

[aphh]

It might be worthvile to point Mars Express' MARSIS radar to that region to see whether some of the water is still there deposited below the surface.

If there's 3 billion year old water somewhere in that region, there could be traces of microbes or fossils aswell.

 

[dingo1]

As this lake is during the Hesperian period of the planet, it is likely that this is only the beginning of finding definitive proof of ancient lakes and other bodies of water. There is lots of evidence of ancient water all over the planet. Most scientists do agree on this. What the conditions were like however, is a matter of debate. As during this period, the magnetic field that helps protect the atmosphere was weakening as the planet core cooled down by approx 3700MY ago. Evidence of water declined over time, that by the start of the Amazonian period, surface water was history, though there is evidence of periodic episodes of water upswelling, which boils off almost immediately, happening within the last few MY

 

[aphh]

though there is evidence of periodic episodes of water upswelling, which boils off almost immediately, happening within the last few MY

Water evaporates, but where does it go then? Is ultraviolet radiation or solar wind strong enough on Mars to break the covalent bonds in water molecule?

This is a key question, because if radiation in Mars could not break water molecule into hydrogen and oxygen, that means that most of the water is still somewhere in Mars, in hidden or partially hidden glaciers or perhaps even in liquid form under the surface. Perhaps there was not that much water to begin with, but enough to have large lakes and reservoirs for a long time, even if they were not very deep reservoirs.

 

[michaelmozina]

though there is evidence of periodic episodes of water upswelling, which boils off almost immediately, happening within the last few MY

Water evaporates, but where does it go then? Is ultraviolet radiation or solar wind strong enough on Mars to break the covalent bonds in water molecule?

This is a key question, because if radiation in Mars could not break water molecule into hydrogen and oxygen, that means that most of the water is still somewhere in Mars, in hidden or partially hidden glaciers or perhaps even in liquid form under the surface. Perhaps there was not that much water to begin with, but enough to have large lakes and reservoirs for a long time, even if they were not very deep reservoirs.

I've seen enough images of Venus losing atmosphere to the solar wind to know that it is likely that Mars can and does probably lose a portion of it's atmosphere to solar storms and such. It has a much weaker magnetic field as well. Your question about where the water goes is valid, but the answer (and options) may not be limited to Mars.

 

[aphh]

I've seen enough images of Venus losing atmosphere to the solar wind to know that it is likely that Mars can and does probably lose a portion of it's atmosphere to solar storms and such. It has a much weaker magnetic field as well. Your question about where the water goes is valid, but the answer (and options) may not be limited to Mars.

True, but Venus does not have water vapor in it's athmosphere. Water molecules are heavy and Mars has enough gravity to hold heavy molecules down. Mars gets much less solar wind than Venus also, because intensity drops in the square of distance.

So, if water vapor is blown away from Mars, what causes this? Could it be that there never was very much water in Mars?

I read that some glacier in the north made largely of H2O ice contains enough water to cover the whole planet with a few meters of water, if distributed evenly. Perhaps that's most of the surface water that ever was, which vaporized and concentrated at the poles, where the athmosphere freezes in the winter and rains down as CO2 and H2O ice.

 

[centsworth_II]

Someone over at unmannedspaceflight.com linked this paper:

NEW EVIDENCE FOR THE SHALBATANA VALLIS PALEOLAKE, MARS, FROM THE HIGH
RESOLUTION IMAGING SCIENCE EXPERIMENT (HiRISE)
http://www.lpi.usra.edu/meetings/lpsc2009/pdf/1939.pdf

 

[yevaud]

Water evaporates, but where does it go then? Is ultraviolet radiation or solar wind strong enough on Mars to break the covalent bonds in water molecule?

Yes, that is in fact correct.

Even though the surface and atmosphere temperatures of Mars are low, the combination of a almost non-existent geomagnetic field and low surface gravity means that the atmospheric escape velocity for H and O is fairly low, and there's nothing to assist in retaining it. And the solar wind is still fairly strong at the orbit of Mars, to sweep it away. UV Photodissociation is fairly extreme on Mars, amply sufficient to crack H2O.

Of course under the surface reservoirs of ice or water are a different matter; they're insulated from the UV flux at the surface.

 

[michaelmozina]

Water evaporates, but where does it go then? Is ultraviolet radiation or solar wind strong enough on Mars to break the covalent bonds in water molecule?

Yes, that is in fact correct.

Even though the surface and atmosphere temperatures of Mars are low, the combination of a almost non-existent geomagnetic field and low surface gravity means that the atmospheric escape velocity for H and O is fairly low, and there's nothing to assist in retaining it. And the solar wind is still fairly strong at the orbit of Mars, to sweep it away. UV Photodissociation is fairly extreme on Mars, amply sufficient to crack H2O.

Of course under the surface reservoirs of ice or water are a different matter; they're insulated from the UV flux at the surface.

It's probably also true that the lower gravity on Mars makes it easier for material to escape, and solar wind is less like to "stick" to the planet.

 

[yevaud]

Yes, G is one of the factors in Atmospheric Escape. Low G, even with low temperatures, means the atmospheric escape velocity, particularly for H, is low; it escape easily.

The velocity of a molecule of gas is determined by:

The rule of thumb is that a planet can retain a species for the age of the solar system, if the velocity of the gas is less than one-sixth the escape velocity:

 

[dingo1]

Yevaud,
This is correct. As for the amount of water that boiled off, some of it is blown away by solar wind and broke down by radiation. As Mars does not have a protective magnetic belt, nor an Ozone layer in it's atmosphere.

What little water remains refreezes at the poles, and is subject to breakdown by radiation as well

 

[yevaud]

Exactly so. Also, Mars experiences little or no outgassing, which replenishes lost species, so that in Mars' case, each successive step was a part of a positive feedback loop. Lose H and O; the atmosphere is less dense and not replaced; UV increases as a result; Photodissociation increases. More atmospheric species lost. Repeat.

(For the audience, this is a similar mechanism to how Venus became a living hell via the greenhouse effect, except that the conditions of Mars are far different, and so achieved entirely different end-result conditions)

I'd think that exposed ice must sublimate away over time rather than dissasociate, as photodissociation of ice is an entirely different matter than a vapor or a gas.

Another mechanism I don't hear too often (though you did mention it, excellent) is the seasonal melting of the polar caps (South much more than North, if I remember correctly from dim memories of college). Each time they do, it releases H2O and CO2 into the atmosphere, increasing the rate of photodissociation seasonally. So each time the caps re-freeze, they are diminished. Some day, they will likely cease to exist.

 

[cloud018]

yes , When they confirmed that water was present then definately the lake is there ...

/*Edited to remove advertizement*/

 

[terranoid]

I've seen enough images of Venus losing atmosphere to the solar wind to know that it is likely that Mars can and does probably lose a portion of it's atmosphere to solar storms and such. It has a much weaker magnetic field as well. Your question about where the water goes is valid, but the answer (and options) may not be limited to Mars.

True, but Venus does not have water vapor in it's athmosphere. Water molecules are heavy and Mars has enough gravity to hold heavy molecules down. Mars gets much less solar wind than Venus also, because intensity drops in the square of distance.

Water molecules are not heavy, they are very light. Humid air is lighter than dry air. Hydrogen atoms consist of a single proton and one electron, they are significantly lighter than any other atom. Two hydrogen atoms combined with only one oxygen atom (H2O) is even lighter than a single oxygen (O2) molecule. Carbon dioxide (CO2) molecules are much heavier than that and Mars can just barely hold them.

 

[InfoSpong]

Could it be possible the asteroid belt outwards from mars was once a planet or moon etc?? This planet could have exploded or similar and caused a mass radiation to hit Mars to evaporate the water. As radical it may sound but the direction the radiation from the outer pushed towards the inner towards Earth as Earth could have been in the right place at the right time. If mars dont hold the water, well it should be somewhere.

BTW, does anyone know what is the cause of the asteroid belt outside Mars ?

 

[MeteorWayne]

There's nowhere near enough mass in the asteroid belt to make a planet.

As for why it's there, the gravitational disruption from Jupiter (and Saturn to a much less extent) prevented the planetesmals in that region from accumulating in one spot and therefore accrete into one object.

 

[RyanFrey52]

Well meteor wayne answered my question. I was wondering if the belt could coalesce into a planet or micro planet similar to pluto. to answer the question about the where the belt came from...4.5 billion years ago a massive star went supernova. the matter and particles then began to come back together and form the sun. after our sun was created there was still massive amounts of matter left over. The matter started come together in ever increasing bundles to form the planets. but, with what was stated in an earlier post, the gravity from the gas giant jupiter kept a firm gravitation grip on the chunks of rock that now form the asteroid belt outside of mars. something else i feel i should mention but someone please correct me if I'm wrong, the outer planets of the solar system are mostly gas, it seems that the rocky material, iron, nickel, etc., stayed in the inner part of the system. which raises a question...is it like that in other solar systems as well? Rocky planets closer to their sun and gasious ones farther away?

 

[MeteorWayne]

That's a tricky question to answer. So far we have found a lot of gas giants VERY close to the star. But that is an artifact of the detection methods we've used so far. The easiest to detect are giant planets, close to the star; in fact most of the first 300 or so fell into that category. Up until now, we have not had the ability to detect an earth like rocky planet at an earth like distance from a star.

That is beginning to change with the COROT and Kepler missions currently underway. Some COROT results have come in; the first Kepler results should come out in a bt less than a year. Such rocky planets, being smaller are much harder to find, and we are just getting to the point of being able to detect them.

The next year or two should be very interesting

 

[Astrotiser]

MeteorWayne, this may seem a little bit off topic, but I am impressed by your wealth of knowledge on the topic of astronomy, and your confidence in answering questions. I am curious where you find so much information about the field. I am conducting a project at my University in which I am trying to raise enthusiasm for astronomy in people who know very little about it, and it seems that you could help me narrow down some astronomy research and findings to those that people may be interested in in a general sense? Thanx for your time either way!

 

[MeteorWayne]

This is a little off topic for this thread, so I'll send you a PM. Wayne