New Martian "Gullies"

siriusmre · Mar 21, 2006

SPACE.com ran a story today that featured "images of a new gully that formed [on Mars] between July 2002 and April 2005." The text of the story, though, is mostly about a re-visioning of a hypothesis floated in 2000 to explain the "gullies" or rilles unexpectedly seen on the Martian surface (with the Mars Global Surveyor) by comparing the Martian formations to those seen on the Moon. The 200 MGS imgaes prompted speculation that there might actually be liquid water just below the Martian surface. [Gwendolyn Bart, a graduate student in planetary sciences at the University of Arizona, who presented her findings last week at the 37th Lunar and Planetary Science Conference in Houston] and other scientists are skeptical of the finding because Mars’ temperature and pressure are so low that liquid water can only exist for short periods of time before freezing or evaporating. "I would think that if there’s some non-water process that could form it, it would be more likely," Bart said in a telephone interview. Last year, Bart heard a talk by Allan Treiman, a senior scientist at the Lunar and Planetary Institute, who believes Martian gullies can be explained without resorting to explanations involving recent water. "It’s completely possible that there’s no water involved at all and that what we’re seeing are just dry flows of dust and sand," Treiman told SPACE.com. "You can get massive flows of material that’s completely dry and ends up having pretty much the same shape as if they were wet." [Emphasis added.] There is also another explanation that also does not require water--or any liquid, for that matter! Laboratory study of the way electric arcs affect surface materia <div class="Discussion_UserSignature"> </div>

JonClarke · Mar 21, 2006

On earth we know that gullies can be formed by rainfall runoff, spring sapping, spring discharge, snow and icemelt runoff, and particulate flows. We can also model these in the laboratory and simulate them with a computer. All except the first are processes consistent with what is known about more or less recent Martian conditions and the last can also operate on the Moon. The morphology Martian gullies vary significantly and individual gullies can be tied to specific processes, such as dry avalanches or spring activty. What is your evidence that: 1) An additional hypothesis for Martian gullies is necessary (in what way are current explanations inadequate)? 2) Electrical discharges can form gullies anywhere? 3) That they form gullies on Mars? 4) what specific features characterise gullies formed from discharges that allows them to be distinguished from gullies formed by other processes? Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

siriusmre · Mar 21, 2006

1), 4) The significant depth of the "gullies"--it appears to be at least several hundred meters deep; deep enough to be seen from space--in addition to the steep walls and flat bottoms of the channels leads me to question the dry avalanche or spring ideas. Besides, there is no currently accepted "theory" about all this. All reasonable hypotheses should be welcomed, no? 2) The "gully" in the image below was made by a "measly" lightning bolt strike from Earth's insulating atmosphere. Imagine the power and effect of a much larger or even planet-sized strike. 3) We have images of the electrical phenomenon, called Dust Devils, in action on the Martian surface. As you can see from the image, this relatively small discharge was able to "scratch" at least one mark into the Martian surface. It is coinceivable that a larger such event would make a larger mark. <div class="Discussion_UserSignature"> </div>

thepiper · Mar 21, 2006

Thanks for posting your take on this story. I would also add to 4) that an EDM (electrical discharge machining) created "gully" would show no signs of debris on its floor, and might possibly feature a small crater chain along the center of the channel. The resolution is unfortunately insufficient to make that determination. As a sign of recent massive electrical discharge phenomenon on Mars I don't think this is very conclusive, since it could be reasonably explained by other known geological activity. I do agree with you that there is still a large amount of electrical activity on Mars, such as the miles-high dust devils and massive globe-obscuring dust storms - all in an atmospheric pressure averaging 0.7% of Earth's - but I think Mars is relatively quiet in comparison to places like Io, where the "volcano" Prometheus is currently "etching" the surface through EDM and has been actively doing so every time it's been observed since 1979. Of course if we get a couple of new "martian meteorites" dropping in on us soon it would add to the odds that you're correct. <img src="/images/icons/smile.gif" />

JonClarke · Mar 22, 2006

"1), 4) The significant depth of the "gullies"--it appears to be at least several hundred meters deep; deep enough to be seen from space--in addition to the steep walls and flat bottoms of the channels leads me to question the dry avalanche or spring ideas. Besides, there is no currently accepted "theory" about all this. All reasonable hypotheses should be welcomed, no? The gullies are not "several hundreds of metres deep". Martian gullies are at most 100 or so metres wide and therefore only a could of 10's of metres deep. Many are much smaller than that, those in S05-01721 are ~20 m across. So you have not shown that current explanations are inadequate. The fact there are several different explanations for the gullies is not because the explanations are inadequate, but because they are likely to be the result of several different processes, just like terrestrial gullies. Some look like melting snow or ice, others look like springs from an aquifer. this is where planetary geology is different from (say) physics or chemistry, you don't look for one unified explanation for classes of features (there may not be one), but rather for the explanations that best fit the observations. All reasonable hypotheses should be welcomed, but they should be necessary hypotheses. Occam's razor says you don't postulate explanations without need. So, for example lava flows can form gully-like features but this does not mean that lava flows should be postulated unless there is specific evidence in favour of a lava flow origin and other explanations (snow melt, sapping, springs etc.) are indaequate in that case. And you have not answered 4), which asked you to identify "what specific features characterise gullies formed from discharges that allows them to be distinguished from gullies formed by other processes?". 2) Thank you for a most interesting photo. Assuming that it has been correctly <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

thepiper · Mar 22, 2006

The dust devils cannot be the result of convection unless you can provide the mechanism that can life the larger grains of sand miles into the sky in the near vacuum of Mars’ atmosphere. The trails are dark because the soil has been burned, as shown in laboratory experiments with electrical discharges here on Earth.

siriusmre · Mar 22, 2006

That's a good point, Piper, about the channel morphology. It would be instructive to see higher resolution images of these "gullies" to see if there are in fact crater chains or secondary rilles within the channels themselves. If these were made electrically, then I would expect to see those elements in better images, in addition to the sheer sides and flat bottoms that we already see. <blockquote>In reply to:<hr />As a sign of recent massive electrical discharge phenomenon on Mars I don't think this is very conclusive, since it could be reasonably explained by other known geological activity.<hr /></blockquote> Certainly, it is not conclusive. We would, of course, need to see the actual strike for it to be difinitive. Given the obviously highly charged nature of the Martian atmosphere it it would not be unreasonable to consider that there was some sort of discharge event that caused these features, in addition to considering other more orthodox agents. I would think, though, that you more than most here would realize that some of what passes for "known geolgical activity" may not have happened the way that most people think. And right, Mars is relatively quiet when compared to a place like Io. Indeed we should be looking differently at the Prometheus phenomenon on Io. It may finally lead to a whole new understanding of what is happening everywhere. Welcome to the party! <div class="Discussion_UserSignature"> </div>

siriusmre · Mar 22, 2006

<blockquote>In reply to:<hr />1) [Why is] an additional hypothesis for Martian gullies...necessary (in what way are current explanations inadequate)? [...] The fact there are several different explanations for the gullies is not because the explanations are inadequate, but because they are likely to be the result of several different processes, just like terrestrial gullies. Some look like melting snow or ice, others look like springs from an aquifer.<hr /></blockquote> You seem to have answered your own question there. I would add, also, that I never said that the current hypotheses were inadequate; indeed, according to you, existing hypotheses need not at all be viewed as inadequate in order for other hypotheses to be formed. I merely suggested that there may be yet another way to look at this--another hypothesis, if you will. Again, assuming that the global dust storms that engulf Mars periodically are due to an electrical effect, it follows that the atmosphere would be highly charged. If that is the case, then it is possible that these features were made by electrical means. Again, this is a HYPOTHESIS based on a set of assumptions that you may not accept--just as some may not accept the HYPOTHESIS that these were made by some form of flowing liquid--but it remains a valid consideration, admittedly among many. That's the point of a hypothesis, it has to be tested. Right now, none of these is tested, and so it hurts nothing or no one simply to brain-storm to come up with as many plausible, testable ideas as possible. Isn't that the most "scientific" way? <blockquote>In reply to:<hr />2) Electrical discharges can form gullies anywhere? [...] Thank you for a most interesting photo.<hr /></blockquote> You're welcome. If something is shown to be true once, then it is true. <blockquote>In reply to:<hr />3) That th</blockquote> <div class="Discussion_UserSignature"> </div>

bonzelite · Mar 22, 2006

i will repost a recent entry in the SS&A forum about martian gullys, as this is nearly the same thread. quoting myself from this thread: click here for SS&A i am of a similar mindset and assessment as JohnClarke. in many cases where sand or wind is declared a culprit, the trace signature of the flow pattern resembles a fluvial mechanism. i do not rule out sand or wind, but the gully carved in the photograph is very, very deep and crisp, terminating in fan structures as you would see in water erosion --sculpted by something of a dynamic fluid (this is but one of many, many pictures of gullying and/or sediment carrying). being that mars is replete with terrain softening, as the surface appears (at least in part based upon mounting data), to be a vast desert tundra, melting of pack ice is the most, as of yet, viable explanation. i am inferring at this point in the game that much of the martian regolith is an aggregate of ice, snow, and dirt. this further takes my mindset far and away from a recent press release that the gullying on mars is created by sand, as is seen on the moon. furthermore, the pictures of said moon strutures, in my professional assessment as a visual artist, do not template the martian structures. if anything, the martian structures should template the lunar structures. furthermore, being that the highly softened and eroded lunar gullies are of sufficient age, who is to say that fluvial dynamics were not also a culprit? shattering the idea that liquid is impossible on the moon, as well? we do not know about the lunar past as it may have really unfolded. but that is another topic entirely... /safety_wrapper>

siriusmre · Mar 22, 2006

Yeah, I saw that thread in SS&A. This is essentially the same thread; I started this one here because I did not want to offend anyone's delicate scientific sensibilities by posting a link to site that discusses you-know-what in the sacrosanct SS&A forum. That said, I have to disagree with you and JonClarke about the "most likely" culprit for this phenomenon. From a certain way of thinking, wind, water, or ice are the "most likely" causes, but this seems to fall flat given the purported atmospheric conditions on Mars. If "the Martian regolith is an aggregate of ice, snow, and dirt" how does the ice melt? As relates to this case, why did it preferentially melt where it did, if indeed this was caused by the "melting of pack ice?" I predict that one day we will find that, despite "mainstream" planet scientists' aversion to assigning responsibility for similar structures in disparate environments to similar or the same processes, these structures may in fact have been created by the same process: electric arcing. It may be the way that things are, but it seems counterintuitive to me that "mainstream" planet scientists would NOT seek to find a common explanation for phenomena that appear identical. <div class="Discussion_UserSignature"> </div>

JonClarke · Mar 23, 2006

What is your evidence that the dust devils list sand miles into the sky on Mars? All the evidence is they list only dust. How can trails be burned into the soil when there is no free oxygen? We know what the trails look like because the Spirit rover has driven over them. There is no sign of burning or any other change except that the surface dust is thinner. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Mar 23, 2006

"I would also add to 4) that an EDM (electrical discharge machining) created "gully" would show no signs of debris on its floor, and might possibly feature a small crater chain along the center of the channel. The resolution is unfortunately insufficient to make that determination. " It would be nice to have evidence of this but it sounds reasonable. Lighting strikes do produce small craters on earth from boiling soil moisture. Lack of debris makes sense if there is no transport along the channel. I suggest two more criteria: Small size (the only example anyone has tendered for discussion is about 30 cm across and 5-6 m long) and the presence of fused material (fulgurite), which is very commonly associated with lighting strikes to soil on earth. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Mar 23, 2006

"If these were made electrically, then I would expect to see those elements in better images, in addition to the sheer sides and flat bottoms that we already see." Yes, good observation. The problem is that vertical sides and flat floors are common in water cut gullies too. Our difficulty is that we are arguing from a case study of 1. I did some seraching on databases at work and found only one other reference (out of several hundred on the effects of flightning strikes) to any kind of trough. This was to small radial cracks, a metre or so long and a few cm across. We need more examples, otherwise yours is a very unusual and thus possibly atypical event. Do you have a source and location for that image? "Given the obviously highly charged nature of the Martian atmosphere it it would not be unreasonable to consider that there was some sort of discharge event that caused these features, in addition to considering other more orthodox agents." I don't think there is any evidence that the atmosphere of Mars is highly charged. None of the successful missions to date have encountered any unusual electrostatic effects, despite mission times totalling over 14 years (with the possible and doubtful exception of Mars-3). "I would think, though, that you more than most here would realize that some of what passes for "known geolgical activity" may not have happened the way that most people think". Quite possibly, but you have to have reasons and evidence in specific cases. This is what we are trying to determine here. Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

JonClarke · Mar 23, 2006

"You seem to have answered your own question there. I would add, also, that I never said that the current hypotheses were inadequate; indeed, according to you, existing hypotheses need not at all be viewed as inadequate in order for other hypotheses to be formed. I merely suggested that there may be yet another way to look at this--another hypothesis, if you will. " It's no point proposing additional hypotheses unless you have evidence that current ones are inadequate. Are they inadequate or not? " Again, assuming that the global dust storms that engulf Mars periodically are due to an electrical effect, it follows that the atmosphere would be highly charged.' There is not evidence that dust storms on Mars - or anywhere else for that matter - are an electrical effect. So the assumption is unwarrented. Dust storms may cause in electrical phemena, but to say that they are electrical in nature is to reverse cause and effect. "If that is the case, then it is possible that these features were made by electrical means. Again, this is a HYPOTHESIS based on a set of assumptions that you may not accept--just as some may not accept the HYPOTHESIS that these were made by some form of flowing liquid--but it remains a valid consideration, admittedly among many. That's the point of a hypothesis, it has to be tested. Right now, none of these is tested, and so it hurts nothing or no one simply to brain-storm to come up with as many plausible, testable ideas as possible. Isn't that the most "scientific" way?" Since the basic assumptions are baseless there no point to the hypotheses. It's not scientific to deal with baseless hypothesis. Also, we are not discussing dust storms, we are looking at the issue of gullies. It's not the scientific way to bring in extraneous issues. "If something is shown to be true once, then it is true. " That's not a good way to put it. A better way would be " If s <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

bonzelite · Mar 23, 2006

If "the Martian regolith is an aggregate of ice, snow, and dirt" how does the ice melt? possibly summertime UV. surface temps on mars, in temperate zones in summer, can reach around 60F+ (15.5C+). excerpt: http://www.geocities.com/tdl.geo/mars.html New maps of Mars combine images from the Mars Orbiter Laser Altimeter (MOLA) on the Mars Global Surveyor with Mars Odyssey spectrometer data through more than half a Martian year of 687 Earth days. From about 55 degrees latitude to the poles, Mars boasts extensive deposits of soils that are rich in water-ice, bearing an average of 50 percent water by mass. A typical pound of soil scooped up in those polar regions would yield an average of half a pound of water if it were heated in an oven. The tell-tale traces of hydrogen, and therefore the presence of hydrated minerals, also are found in lower concentrations closer to Mars' equator, ranging from two to 10 percent water by mass. Surprisingly, two large areas, one within Arabia Terra, the 1,900-mile-wide Martian desert, and another on the opposite side of the planet, show indications of relatively large concentrations of sub-surface hydrogen. Scientists advanced two possible theories of how all that water got into the Martian soils and rocks. First the vast water icecaps at the poles may be the source. The thickness of the icecaps themselves may be enough to bottle up geothermal heat from below, increasing the temperature at the bottom and melting the bottom layer of the icecaps, which then could feed a global water table. The second hypothesis is based on evidence that about a million years or so ago, Mars' axis was tilted about 35 degrees, which might have caused the polar icecaps to evaporate and briefly create enough water in the atmosphere to make ice stable planet-wide. The resu

siriusmre · Mar 23, 2006

<blockquote>In reply to:<hr />It's no point proposing additional hypotheses unless you have evidence that current ones are inadequate. Are they inadequate or not?<hr /></blockquote> Again, based on your own statement, this is a strawman argument. Quoting YOU now: "The fact there are several different explanations for the gullies is not because the explanations are inadequate, but because they are likely to be the result of several different processes, just like terrestrial gullies." Right. I don't know how to say it any more clearly. <blockquote>In reply to:<hr />There is not evidence that dust storms on Mars - or anywhere else for that matter - are an electrical effect. So the assumption is unwarrented. Dust storms may cause in electrical phemena, but to say that they are electrical in nature is to reverse cause and effect.<hr /></blockquote> Maybe. I would just ask you to explain--as I think also ThePiper has done--how you think the Martian atmosphere is able to hold enough dust aloft to cause a global dust storm. The fact that the Martian atmosphere is pretty well confirmed to be extremely thin, combined with the fact that these dust storms do seem to have elecrical effects associated with them leads one to ask obvious questions about the relationship between the two phenomena,. including whether the storms could actually be an effect of the electricity. This might be one of those cases where a current hypothesis (i.e., Martian "winds" are responsible for global dust storms that exhibit electrical characteristics) is showing its obvious inadequacy. <blockquote>In reply to:<hr />Since the basic assumptions are baseless there no point to the hypotheses. It's not scientific to deal with baseless hypothesis.<hr /></blockquote> Baseless? You mean like assuming that the ultra-thin Martian atmosphere is capable of mechanically stirring eve <div class="Discussion_UserSignature"> </div>

bonzelite · Mar 23, 2006

they need video surveillance 24/7 of "hot" areas of activity, with sensors and live feeds from the chosen areas. that would instantly prove something.

tomnackid · Mar 23, 2006

Sigh, again with "Tom Swift and His Electric Universe"? A gully can't just be a gully? It looks like a sand flow at the top of a dune. Something I've seen many times on Earth. Why invoke magic lightning bolts?

yevaud · Mar 23, 2006

The curious thing is, for all of this electric sculpting going on, no one's ever actually seen it? <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

JonClarke · Mar 23, 2006

That would be nice! But It's going to be a while before it happens, unfortunately :-( Jon <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

siriusmre · Mar 23, 2006

<blockquote>In reply to:<hr />The curious thing is, for all of this electric sculpting going on, no one's ever actually seen it<hr /></blockquote> Maybe. EU theorists point to the mysterious "bright spots" evident on images from comets such as Tempel 1 and Wild 2. They would draw your attention to the fact that these "bright spots" appear to prefer high points on the comet surface, and they might suggest that perhaps these "bright spots" are in fact the electrical discharges that are sputtering the surface of the comets, producing the minerals and "volatiles" that we see. <div class="Discussion_UserSignature"> </div>

yevaud · Mar 23, 2006

Perhaps. I was thinking more along the lines of the sheer size of such an electrical discharge needed to sculpt entire gullies, Wadis, etc. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

JonClarke · Mar 23, 2006

"Again, based on your own statement, this is a strawman argument. Quoting YOU now: "The fact there are several different explanations for the gullies is not because the explanations are inadequate, but because they are likely to be the result of several different processes, just like terrestrial gullies." Right. I don't know how to say it any more clearly. " You are missing my point. The reason that there are several different hypothesis is that the evidence shows that no single hypothesis is correct. Hypotheses are not invented willy nilly, for the fun of it. So, in the case of the gullies, springs are proposed because many gullies appear to originate in a particular stratum (or even muitple strata, as in this image. Others are associated with a layer of apparentrly plastered on material, which may be snow, melt water seems likely explanation. In cases where such plastered on material is absent but there is no obvious source stratum, former snow banks can be reasonably invoked. Some gullies, with simple straight morphologies, no obviously water-laid features like meanders or levees, are most parsimoniously explain by dry flows. New hypotheses must address an apparent problem in the ability of current ones to address observations. Nick Hoffman's CO2 flows one one such, and attempted to circumvent the perceived issues of low temperatures and low pressures for liquid water. Since his solution required rather special and unlikely circumstances to work and was not required anyway, it has not gained general acceptance. "I would just ask you to explain--as I think also ThePiper has done--how you think the Martian atmosphere is able to hold enough dust aloft to cause a global dust storm. The fact that the Martian atmosphere is pretty well confirmed to be extremely thin, combined with the fact that these dust storms do seem to have elecrical eff <div class="Discussion_UserSignature"> Whether we become a multi-planet species with unlimited horizons, or are forever confined to Earth will be decided in the twenty-first century amid the vast plains, rugged canyons and lofty mountains of Mars Arthur Clarke </div>

tomnackid · Mar 23, 2006

Maybe. EU theorists point to the mysterious "bright spots" evident on images from comets such as Tempel 1 and Wild 2. They would draw your attention to the fact that these "bright spots" appear to prefer high points on the comet surface, and they might suggest that perhaps these "bright spots" are in fact the electrical discharges that are sputtering the surface of the comets, producing the minerals and "volatiles" that we see. ---------------------------------------------------------------------------------- I did some research on the Stardust results. It turns out that the minerals found in the samples have PREVIOUSLY been detected in the outer reaches of dust clouds surrounding young stars. This seems to indicate that the minerals existed PRIOR to forming comets and where not created in comets. Why minerals created at high temperatures would be found in dust clouds far from a star is still a matter of conjecture. The most popular hypothesis so far is that they were originally much closer the the center of the primordial cloud that formed the star and where pushed out by light pressure and solar wind when the sun "turned on". Another idea is that collisions generated the heat necesary to create the minerals. I suppose electrical discharges could also do it but there is no evidence yet of wide scale electrical discharges in dust clouds surounding young stars. Either way, the minerals existed BEFOR the comets.

yevaud · Mar 23, 2006

Exactly correct, and thank you for pointing that out. T. Tauri stars clear a large amount of material out from around the star, pushing it via light pressure towards the rim. We know this from observations of T. Tauri's in various stages of development. <div class="Discussion_UserSignature"> Differential Diagnosis: "I am both amused and annoyed that you think I should be less stubborn than you are." </div>

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