Martian Geology - Olivines, andesites, faults etc

dickbill · 2003-07-29 13:08:52

This is hot topic, martian geology, it deserves a specific thread no ?

As I read some basic geologic school books to refresh my old memory, some questions came to my mind:

1) I've read before that there is no plaque tectonic on Mars, Mars is a single plaque, is it still valid assumption ?

2) I've also read that Valles Marineris is a fault. It's not an "oceanic" rift where the crust is continually repleted while the margins diverge. During cooling of martian crust, the crust shrunk and the reduced surface was compensated, which resulted in the Valles Marineris Fault. It is supposed to be an old event and knowing Mars today, we would expect this fault to be filled with sediment. But it's not the case, the VAlles is empty. Where are all the sediments gone ? Why Valles Marineris is so empty ?

3) How to explain the alignement of the big Volcanoes if there is no tectonic rift ?

4) How to explain the north lowland/south highland dichotomy of Mars. Is it a tidal bulge (in the hypothesis that Mars was one day tidally locked to a giant planet in the past) or the result of a giant impact?. For some reason, the giant impact theory is rarely mentioned, why's that ? Otherwise, what could explain that an hemisphere is 8 km higher than the other ?
Do we consider the highland a continental crust and the lowland an oceanic crust ? this contradict the single plaque theory and we should expect some plaque subduction...among other questions.

Shaun Barrett · 2003-07-29 21:04:09

I agree with you 100%, Dickbill. The geology of Mars is absolutely fascinating!
All the news items I've read over the years tell me that even the experts are amazed and perplexed at the sheer complexity of Martian geology. There seems to be no single hypothesis which explains all the data we've accumulated so far.
If your list of important questions could be answered, we would probably be at least 90% of the way to a basic understanding of Mars' history.

I, too, have always wondered about those three enormous volcanoes, Ascraeus, Pavonis and Arsia. Why are they on an almost straight line hundreds of kilometres long? Why do they sit atop the anomalous Tharsis bulge? Is it just a coincidence that Tharsis is almost exactly opposite the vast Hellas impact basin on the other side of the planet?

What if our dating of Martian surface features is completely wrong? What if there have been more recent episodes of impact events on Mars, not manifested to the same extent in other regions of the solar system? What if our usual method of crater counting on Mars is therefore leading us astray? Could the fringe theory you mentioned, that Mars was once a moon of a larger rocky planet between Earth and Jupiter, actually have any basis in fact?

And that question about plate tectonics is a tantalising one. As I'm sure you know, there is actually quite good evidence of tectonic activity in Mars' early days. Or at least the remnant crustal magnetism in the southern highlands seems to indicate this.
Just in case you, Dickbill, or some others here at New Mars haven't seen the colour-coded map of the remnant Martian magnetic fields yet, have a look at this site.
The striped pattern of magnetic reversals is almost exactly like the ones found either side of the Mid-Atlantic Ridge here on Earth. This terrestrial ridge is recognised as a region of crustal spreading at the junction of two plates. The big difference, of course, is that here the process is continuing today, while on Mars it appears to have stopped billions of years ago.
How to reconcile what looks like early tectonic plate movement on a planet with no evidence anywhere else of the existence of tectonic plates is a puzzle! Perhaps there were originally several mobile plates on Mars but evidence of them has since been obscured by impacts and volcanic resurfacing of much of the planet's surface.

One of the many enigmas Mars has presented us with in recent years involves sand dunes. I can't find the article right now (I'll look harder if anyone's interested? ) but it seems there are quite newly formed wind-blown sand dunes in the caldera of Olympus Mons, 27 kms above datum where the air pressure is about 2 millibars!
Geologists cannot explain how sand could have been blown into characteristic dune shapes at such an altitude. The air is too thin to lift the sand grains. The almost complete lack of impact craters suggests the dunes are very young.
The obvious implication here is that the Martian atmosphere must have been substantially denser, even 27 kms up, in the very recent past - perhaps only centuries or a few thousand years ago, who knows?!
I speculate that, if the air was dense enough to blow sand around on top of Olympus, the atmospheric pressure at datum may have been as high as 30 or 40 millibars (high enough to greatly expand and extend the opportunities for liquid water at the surface). And this kind of pressure elevation may be a fairly frequent and regular occurrence on Mars, helping to explain what looks like very recent fluvial activity(? ).

There are many more questions than answers, of course, at this stage! But I'm hoping to live long enough to see some of these mysteries solved.
To my way of thinking, only sending humans to Mars will do the trick ... I wish they'd get on with it!!!
???

Do others here have any pet theories about how Mars has developed geologically, either in the distant past or more recently? I'm sure you, Dickbill, must have one or two thoughts yourself?!

dickbill · 2003-07-30 09:28:05

Hi Shaun

I, too, have always wondered about those three enormous volcanoes, Ascraeus, Pavonis and Arsia. Why are they on an almost straight line hundreds of kilometres long? Why do they sit atop the anomalous Tharsis bulge? Is it just a coincidence that Tharsis is almost exactly opposite the vast Hellas impact basin on the other side of the planet?

This is consistant with an early plaque movement, but maybe not necesseraly of tectonic origin. Would it be possible that a giant impact, such as the one that created the Hellas bassin, could fracture the crust and move the pieces in such a way that the underjacent ascending magma pockets would create a serie of aligned volcanoes on these moving broken pieces or between them ?
I guess that future geologues on Mars will be able to prove this hypothesis by drilling carrots to detect putative impact-associated fractures. If this is an impact that had fractured the martian crust, versus a plaque tectonic, perhaps a radial shape pattern of fractures could be detected.

What if our usual method of crater counting on Mars is therefore leading us astray? Could the fringe theory you mentioned, that Mars was once a moon of a larger rocky planet between Earth and Jupiter, actually have any basis in fact?

I 've read about this theory on a web site 2 or 3 years ago and I've lost the link. But at one moment the Mars-planet X theory diverged a little bit in science fiction, because by the time MArs was freed of his giant mother planet by a cataclysmic event, a civilization had time to develop. If somebody has a link to this theory, welcome to post.

this site.
The striped pattern of magnetic reversals is almost exactly like the ones found either side of the Mid-Atlantic Ridge here on Earth. This terrestrial ridge is recognised as a region of crustal spreading at the junction of two plates.

And Mars core has recently been shown "partially melted". This adds again to an early magnetism hypothesis and maybe an early plates movement, whatever its origin.

One of the many enigmas Mars has presented us with in recent years involves sand dunes. I can't find the article right now (I'll look harder if anyone's interested? ) but it seems there are quite newly formed wind-blown sand dunes in the caldera of Olympus Mons, 27 kms above datum where the air pressure is about 2 millibars!

I'm sure you, Dickbill, must have one or two thoughts yourself?!

I am a partisan of an early wet Mars, but a boreal ocean I am not sure. I think that Mars has enjoyed several episodes of warm climates and floods. This is inescapable because the flooding patterns on Mars are so widespread. But at the same time, the early "faint sun" doesn't explain how water could have been liquid on Mars for a long time. So either the internal planet heat and volcanism, and/or the episodic meteoritic bombardment were the source of that warming. I also believe, like you, that the early atmosphere was denser and could have sustain liquid water on the surface given a source of heating. What was that early atmosphere ? I don't know.
The proximity of the Evil Jupiter has certainly affected Mars history and it is difficult to explain Mars evolution without Jupiter. The rate of fall of comets (water and ammoniac rich) is an important parameter of an early planet atmosphere and Jupiter probably dictate how much of the comets will fall on Mars. Ammoniac is a green housing gas that could have been absent on Mars. Early earth was supposed to contained a lot of that, in addition to methane, it was one of the key element of the Miller experiment. Miller put ammoniac, methane water and hydrogen in a flask with UV and electric discharges, and after a time he obtained an organic soup containing amino acids. The basic for a biochemistry. Nothing of that on Mars probably, so I am not so sure that Mars is or was "alive". The only microbes Mars has seen, might have been Terran, but to be frank, I really don't know. I am waiting to see.

rgcarnes · 2003-08-07 20:59:50

Shaun,

This is in reference to your recent comments on 'sand dunes' inside the cauldera of a high volcano on Mars.

While the dunes may have the classic dune shape, perhaps they are not the typical silica sand. Condensed sulphur vapor might, by some stretch of the imagination, deposit itself in the same form on being propelled from within the cauldera from a directional source. Sulfur is called brimstone for the reason that it has been found condensed in deposits at the cooler rim or brim of some volcanos here on earth. The thought of sodium nitrate or other salts as possibilities has also come to mind.

Its relatively easy to make sulphur into microsphere form providing a smooth flowing 'sand' that is less dense than silica sand. I've forgotten the density of sulphur, but Ill check on it as soon as I send this.

Palomar · 2003-08-08 09:59:26

*Excuse the interruption, but I have a question (and I admit the topic material thus far is a bit beyond my current working knowledge):

If there are no tectonic plates on Mars -and- if the volcanoes thereon are dormant, there will be no Marsquakes...right?

Just curious.

Also, does anyone have any estimates of approximately how long Marsian volcanoes have been dormant? And if for a long time, why so long?

Perhaps these issues have been discussed and detailed previously, but I don't recall (and what with my brain being in the 18th century 3/4 of the day, every day...)....

Thanks in advance!

--Cindy

dickbill · 2003-08-08 10:59:33

*Excuse the interruption, but I have a question (and I admit the topic material thus far is a bit beyond my current working knowledge):

don't worry, it's not a scientific board with reviewers ready to jump at your throat if you say something wrong, it's a free forum where people have more or less knowledge of the topic but ask questions. All what people need to enjoy the topic is an open mind and some curiosity. Of course if a geologist could post here that would be great too.

If there are no tectonic plates on Mars -and- if the volcanoes thereon are dormant, there will be no Marsquakes...right?

If the volcanoes are dormants....meaning that there is no pockets of magma under the volcanoes, ready to ascent to the surface and erupt, I don't know. I would guess that microgravity variations would be able to detect magma pockets ?
MArsquakes are probably rare in abscence of volcanism or tectonism but they could still be present, caused by other mecanisms: faults readjusting in the crust and other out of equilibrium crust phenomena. On earth you know the example of the icebergs recession: once covering the northen hemisphere, the icebergs added weight to some part of the continental plates which then tended to ploy under the weight, but after the iceberg melted, these continental plates were now trying to get back to their original level, possibly causing some quakes.
There are some instances on MArs where we could imagine such crust readjustment: the caps of Mars, which add weight to the crust, the extraordinarly low Hellas bassin, the valles marineris fault, the weight of the giant volcanoes on the crust.

I am sure Marsquakes exist and could be detected. So, let's fustigate the absurd decision of the europeans, the french in this case I have to say, to eliminate the netlander mission, it was a collaboration with NASA by the way. The mission consisted in part to land a network of small seismic stations on MArs. They canceled supposedly to save a little bit of money...how short sighted this is. Yes, they saved a couple of millions, but by the time, the scientists involved are probably disgusted and discouraged. I would be. And the cancelation of the comet mission after the crash of arianeV-extended while a safer arianeV-standard could have been used. What is the message sent to the enthousiastic scientists ? The time of hard work, the experience acquired, this has no price but still worth nothing for the politicians.

Palomar · 2003-08-08 11:36:40

The mission consisted in part to land a network of small seismic stations on MArs. They canceled supposedly to save a little bit of money...how short sighted this is. Yes, they saved a couple of millions, but by the time, the scientists involved are probably disgusted and discouraged. I would be.

*I'm disgusted and discouraged by that mission being canceled. Damn them! Want to bet the "money saved" from canceling that mission was "better spent" on $500.00 toilet seats for some governmental body?...or some such...grumble, grumble.

Would it have been possible to rig up the robots either now on Mars or currently on their way to Mars with seismographic sensors before they were launched? If so, are there seismographic sensors built into the robots? You'd think if the ground were shaking, the robots would/could somehow transmit that information...but how I don't know.

--Cindy

Josh Cryer · 2003-08-08 12:46:09

Hmm, I heard about this before, but didin't see anything new about it. I didn't know it was canceled. What a shame. But going to the website, it wasn't to even happen until 2008. A long way away. Maybe we'd have men on Mars by then. According to clark we should be getting that idea!

It probably would've been a good idea, actually, to have rigged a seismograph to the rovers. The rovers batteries (and panels) would eventually deterioriate beyond the ablity to continue moving about, but probably not so bad as to run a seismograph. So you just put'er in park mode, and there ya go. Neat idea Cindy, too bad it didn't happen.

dickbill · 2003-08-08 13:07:27

canceled. Damn them! Want to bet the "money saved" from canceling that mission was "better spent" on $500.00 toilet seats for some governmental body?...or some such...grumble,

The french CNES was in deficit of 35 millions euros , and some cuts were decided. The NASA also canceled the mission, supposedly before the CNES according to an article of LE Monde, so the blame is not only to the CNRS, but it looks like everybody was happy to cancel this franco/american project and some people said it was actually a political decision.
But what I am sure is that the money saved now will be wasted anyway later.

quote from Nature:

France purges space programme in bid to survive budget crisis DECLAN BUTLER
In the red: falling funds have led the French space agency to cancel its NetLander Mars mission.
In a dramatic bid to address its long-running financial problems, the CNES, France's national space agency, has cut or frozen 10 of its 44 missions ? including an ambitious effort to send four landers to Mars.
link at:
http://www.nature.com/cgi-taf...._r.html

Shaun Barrett · 2003-08-10 01:27:27

Rex, I've been thinking about your comments regarding the dunes in the Olympus caldera.
Maybe you're right that extremely fine particulates could be shifted into dune shapes by the thin air at those altitudes. I don't know enough about the mechanics of the situation to give a sensible opinion.

But these dunes weren't reported as being anything other than normal in texture or colour. In other words, they were apparently indistinguishable from dunes you might find anywhere on Mars.
Surely sulphur, even in microsphere form, would be yellow? And sodium nitrate is white.

Does this colour your judgment somewhat??!!! [Groan!!]

sethmckiness · 2003-08-10 02:14:24

If there are no tectonic plates on Mars -and- if the volcanoes thereon are dormant, there will be no Marsquakes...right?
Just curious.

I don't remember how many years the qualifier is to be able to labe a volcano or caldera as dormant. I believe it is 1000-10,000 years of no activity. I believe that it could be more accurately said as extinct. Also, if you were to say that it was dormant that would mean there had been recent volcanic activiyt in geological terms at least.

Also. Due to the lack of what we know of Erosion on Mars, accurate dating of geological structures becomes more of a S.W.A.G. (Scientific Wild Ass Guess). This can only be truely solved by one of two things. One, a research station on Mars, or a much larger effort with probes, due to the contrast of martian geology compared to terran geology.

Also, am I the only one that thinks geology is a poor word to describe the Study of Mars and how it was created?

RobertDyck · 2003-08-10 09:01:21

am I the only one that thinks geology is a poor word to describe the Study of Mars and how it was created?

Am I the only one who is tired of different words invented to say the same thing? Geology is the study of rocks. (and larger geological structures, but there is that word "geo" again. You can't define a word by itself.) Don't fall into the trap that Kim Stanley Robinson did. He used the word Areology in his Red/Green/Blue Mars novels. I found that so annoying. Geology is geology no matter which planet it is on. On Venus would you call geology aphrology? On the moon would you call it lunology? What about the Jovian moon Ganymede? Or Callisto, or Europa, or Io, or Amalthea? There are over a dozen moons around Jupiter alone. This reminds me of the names of groups of animals; a different name for each species. Did you know there is one name for a group of geese on the ground, and another for the same geese in the air? Let's not create the same mess with a branch of science. Geology is geology no matter what planet it is on.

Palomar · 2003-08-10 09:49:30

[Don't fall into the trap that Kim Stanley Robinson did. He used the word Areology in his Red/Green/Blue Mars novels. I found that so annoying. Geology is geology no matter which planet it is on. On Venus would you call geology aphrology? On the moon would you call it lunology? What about the Jovian moon Ganymede? Or Callisto, or Europa, or Amalthea? There are over a dozen moons around Jupiter alone. This reminds me of the names of groups of animals; a different name for each species. Did you know there is one name for a group of geese on the ground, and another for the same geese in the air? Let's not create the same mess with a branch of science. Geology is geology no matter what planet it is on.

*Agreed; I'm a fan of the K-I-S-S method myself. As you so adroitly point out, it would become very confusing very quickly. One gripe I've had against certain sci-fi writers are when they create an extensive new vocabulary; trying to keep up with it all can get very tedious. I understand a certain level of lingo alteration, what with slang and colloquialisms changing over the years...but enough's enough. I really never could "get into" _The Moon is a Harsh Mistress_ by Heinlein; the syntax style in the book grates on my brain.

But "uh-oh", Robert: It doesn't take much to incite my ever-present curiosity: What are the names for geese on the ground and the same geese in the air? I'm unfamiliar with it. You can send me a private message if you want; I don't want to "derail" the topic.

Geology is geology...agreed.

--Cindy

RobertDyck · 2003-08-10 10:16:41

But "uh-oh", Robert: It doesn't take much to incite my ever-present curiosity: What are the names for geese on the ground and the same geese in the air? I'm unfamiliar with it.

On the ground a group of geese is a gaggle, in the air they are a flock. On the water a group of ducks is a paddling, in the air they are a team. However, mallard ducks on the ground are a sorde, if they are taking off into the air they are a flushe. Why one term for mallard ducks and another for other ducks? I think the hunters of old had too much time on their hands.

Shaun Barrett · 2003-08-10 18:37:54

I suppose it all depends how small your world is.
If your world revolves around hunting geese and ducks, you will tend to describe things very precisely and other hunters will know exactly what it is you're referring to with a minimum of explanation.
I believe eskimos have many adjectives for 'white' and dozens of names for ice of different consistencies. It's not hard to see why, given their environment, but it looks like overkill from our perspective!

But, putting all that aside, I do agree with Robert and Cindy.

Josh Cryer · 2003-08-10 20:41:20

There was a small discussion about this very thing over at the Wiki

NASA does exhibit a trend of prefixing things with astro- when it relates to space, but this is probably more meant to relate to astronomy- which is basically looking at things which are far away!

?Geology? is fine and dandy for general language, but if I were to say, ?Hmm, this geologic formation is over 5 miles deep!? You might wonder where in the heck I was talking about! I could be referring to Earth's Mariana Trench.

Martian geology and Earth geology are going to be different fields.

rgcarnes · 2003-08-10 22:38:14

I think I was party to the wiki discussion, but back to the dunes in Olympus Mons: 1. Sulphur, salts, or other volcanic emissions would be accompanied by concurrent emission of gasses perhaps including water vapor (steam) in a transient situation so that they might provide their own wind when they are released.

The steep temperature and/or pressure gradient which could exist within the cauldera walls up to its rim could even give the local atmosphere enough stability temporarily to suspend and move things about before dissipating.

An additional possibility is that the dunes are made up of particles similar to the hollow microspheres formed in the process of burning coal in electrical power plants. These are hollow aluminosilicate glass spheres typically containing some percentage of iron and which have an effective density less than water. They are, in fact, collected for use in various applications by skimming them from the surface of settling ponds.

One should also keep in mind that dust can be suspended and moved by electrostatic forces even without an atmosphere.

dickbill · 2003-08-11 07:12:30

I prefer the gaz and fumaroles hypothesis but I am not convinced, (btw would it be possible to have a link to that picture of sand dunes on Olympus caldera ? I think I remember it but I've seen so many sand dunes pictures of Mars that maybe I'm wrong.) The fact is that even if the volcanoe produced a lot of gas, at that altitude and in the quasi vacuum, I would expect the gas to go straight in space, and not horizontally to form the dunes.

So, what about a simple ice cloud: we know that Mars has ice clouds at high altitude, maybe high enough to pass oven the Olympus Caldera and sometimes creates a local wind there.

sethmckiness · 2003-08-11 08:03:08

Sulphur, salts, or other volcanic emissions would be accompanied by concurrent emission of gasses perhaps including water vapor (steam)

Water Vapor will be only present if there is water in the Magma.

Also.. what is the barometric pressure and the gravity at Olympus Mons. Also, what is the Depth of the Caldera and the width. With that information, one could calculate the possibily of sand dunes. Also, In the Southern United States they have Salt Domes. Is it possible that Olympus Mons never erupted. If the Caldera collapsed from a magma reservoir draing back to the Mantle, or some other loss of support, it would collapse to form what we see today, what if the sand dunes where in existance before the area was elevated and then that particular are collapsed. It could be some crazy synclinal deformity. I personnaly don't think that sand dunes could form on their own at that barometric pressure even in the martian G. with the possible exception of some massive storm going over.. Speaking of which what height does the dust reach during a global storm on Mars?

Also. On Mars there will be its own names to d

sethmckiness · 2003-08-11 08:12:59

Oops.. damn mouse on laptops.. anyway..

For Geological Epoch/eons ages periods etc etc, there will be Mars specific names due to different events as there will be on any 'body' we study. Just like different types of biology are subdivided into different areas. People have spent their whole lives studying the Laramide Orogeny (mountain building process that led to the Rocky Mountains) which was a very complex event. So the Study of Mars and how it was formed may take on a science of its own.. While I haven't poured over the maps of Mars, I know much of the things I learned about Structual Geology still work, will others are simply out the window. It's a different field of , study with some similiarities, dictated by Age, Makeup of the Core, mantle and crust. The Atmosphere(we need some core samples to verify the stability of the atmosphere.) and how it varies. Etc. The one area of geology I still know fairly well is structure. On Mars, you don't so the Syncline/Anticline deformities so much, or the definitive evidence for faulting to support an active plate tectonic system. But it's hard to say. depending on the wind erosion, the hardness of the rock, and the abrasiveness of the sand in the storms, the whole planet could be like Arches National Park.. Who knows...

dickbill · 2003-08-11 09:20:57

Water Vapor will be only present if there is water in the Magma.

which might be the case on Mars. Several martian meteorites found on Earth have cristals and composition that belongs to a magma containing water.

http://www.nirgal.net/meteori_table.html

click on NWA1669 (number 22 of the list). It is said that the composition of the meteorite corresponds to a magma possibly containing 3 to 4% water.

dickbill · 2003-08-11 12:08:42

Shaun, it's difficult to see any sand dunes here:

"MOC narrow-angle image E08-00004
Traverse in Olympus Mons summit caldera"

That's in the middle of the crater, but then
I watched another traverse pictures in the caldera in
"MOC narrow-angle image E07-00958
High resolution traverse across Olympus Mons west calderae"

I don't see much sand dunes except at the immediate proximity of the west wall of the caldera, at the bottom of the wall, it looks like wind pattern.

prometheusunbound · 2003-08-11 12:46:16

I, too love the KISS methood. . . .but isn't geology the study of earth? Geo-earth logy-study of

I don't want to confuse anyone but unless Earth is earth then our working definations will have to change.

sethmckiness · 2003-08-12 21:51:29

In all reality Martian magma probably did contain H20, but it's hard to say if the Mantle is even Active now, or if it has cooled. With now Magnetosphere, It would be hard pushed to prove a molten magnetic Core. Also, is there a link where the MOC pictures have been parsed together? Or do you have to go through each individual picture?

sethmckiness · 2003-08-13 04:30:35

Wind blown snow erosion.Snow Erosion

wind blown erosion on Mars?
Mars

Looks like eroded cratering, possibly mistaken for Karst Topography.

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Re: Martian Geology - Olivines, andesites, faults etc

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