Discussion: Mars Express' View of Olympus Mons

[Fraser]

SUMMARY: Now in orbit for more than a month, the European Space Agency's Mars Express spacecraft has been delivering mountains of data back to Earth. An image taken on January 21, 2004 is of the caldera of Olympus Mons, the largest known mountain in the Solar System. Olympus Mons is 22 km high and the caldera has a depth of 3 km.

What do you think about this story? Post your comments below.

[Chook]

I don't want to get into "The Electric Universe" thing - but what causes these surface features of Mars - shifting plates, cooling and shrinking of the surface crust, close collision with another body, (God help us) electricity from another body? What?

[Duane]

Most features seen on Mars are impact related. The large volcanos and the Valles (valleys)are likely a combination of shield volcanism combined with some crust deformation caused by a combination of planetary cooling and the weight of the shield volcanos.

Some of the features display evidence of possible water erosion.

[Nick4]

I will use this as my wallpaper mars has always bean one of my favoret sky objects thou i have never seen this valcano so much in detail.

[VanderL]

Most features seen on Mars are impact related. The large volcanos and the Valles (valleys)are likely a combination of shield volcanism combined with some crust deformation cause by a combination of planetary cooling and the weight of the shield volcanos.

What shield volcanoes can create something like Valles Marineris (which shield volcanoes exactly), planetary cooling shouldn't be visible in only one place and water erosion is also very unlikely (a 9 km deep valley?? and where did all the material go, there is no outflow), I saw some very strange features in the Valles, a furrow cut into one of the big mesas that is very shallow on the top of the mesa and very deep at the edge, and everything so sharp that it looks like it is cou out with hatchet.
I hope we get a lot more details, but my guess is that Valles Marineris wasn't created in any ordinary manner.
Cheers.

[Duane]

Sorry VanderL, I disagree. The explanation of crustal cooling and the resultant deformation of the lithosphere easily explains the Valles Marineris--similar processes are seen on Earth.

When you look at the position of Valles as compared to the main shield volcanoes (olympus and the Tharsis Montes) there seems to be a striking correlation. Considering the incredible weight of the outflows at this location, it almost seems inevitable that some degree of crack and stretch would occur.

That seems to be the most likely explanation for the Valles.

Furthermore, with this senerio, you would not see outflow, and depth would be simply a matter of how far the crust was forced to stretch before reaching equalibrium.

Finally, Valles Marineris is not the only example on Mars of rift valley like structure, it is just the most well known.

[VanderL]

Ok Duane, let me try to explain what I mean.
http://www.spaceref.com/news/viewsr.html?pid=11827
Here is the image I'm talking about, in the upper part you can see 2 big mesas. The upper one, if rifting is assumed, looks like the surroundings rifted away in all directions. The second mesa has the furrow feature I descrided earlier. How can this be caused by rifting, and when rifting is the mechanism, the material (that previously connected to the mesa) still has to go somewhere, just look at how sharply defined the cliffs are, some rubble must be visible, the canyons floors are wide, flat, and quite empty.
Cheers.

[Duane]

yes that is an excellent examle of a earth-like rift valley structure. The photo I have attached here is a shot of one on Earth, from space.

Look familiar? The same type of structure can be seen in the earth photo as the photo you have linked from Mars--the sharp cuts, the material (or lack thereof) left behind, etc.

There is no loss of material, VanderL, the ground has split. That very high-resolution photo makes it hard to see that split, but if you go to older photos of the Marineris, you can see the "rip" in the crust--good enough that you can almost sew it back togeather.

The tectonic plates of earth also show that same "ripped" type look, although the processes causing them are somewhat different. Look at the Atlantic plate between South America and Africa, for example.

Higher-resolution space photos of the Great Rift Valley of Earth also show the same sharply-defined cliffs with wide, flat, barren canyon floors.

[Chook]

Sorry fellows - but until Damienpaul created his course, us less informed amateurs need a little assistance with the nomenctature.

"Impact-related" - assume it relates to hits from asteroids;
"shield volcanism" - ?
"mesa" - it that the surface feature that looks like a flat-bottomed lake with steep sides but no water?
"lithosphere" - ?
"valles" - valleys?
"rift-valles" - ?
"rifting" - ?

Sorry about this but if we are to try to intelligently follow the conversation of you experts then we have to know what the words mean.

Many thanks

[Duane]

Chook, I have added links in my posts to most of the words on your list.

[VanderL]

Thanks for the links Duane, but they don't help me understand what i think I see on Mars. Of course on Earth every feature undergoes significant erosion, while on Mars only wind (sand) erosion is working. Questions
1. Rifting on Mars is not due to plate tectonics?
2. An isolated mesa in Valles Marineris with extremly steep cliffs on all sides can be formed by rifting?
3. Circular cliffs can be formed by rifting?
4. Is rifting is an ongoing process on Mars or is it an ancient process (planetary cooling?) that has stopped long ago, because erosion must be stronger I think.
I'll think of more questions later, again thanks Duane.
Cheers.

[johnm]

How about the effects of the huge temperature swings on Mars? Over millions of years this could also generate some erosion.

[damienpaul]

perhaps the circular shaped mesas are from diapiric domal uplift similar to salt deposits on earth?

[VanderL]

diapiric domal uplift

Don't you need a lot of water to do that kind of uplifting?
And it's the form of the edges of the mesas, the cliffs that I'm referring to.
And could you maybe also link an example? That way Chook (and me too) can still follow the discussion without having to google constantly
Cheers.

[Chook]

Thanks for the help, not.
I'll go back to the "Unrelated to Space" topics.

[VanderL]

Sorry Chook, there isn't any such topic.
Keep it up, just get used to the jargon and there is always someone willing to explain to us how the Universe works.
Cheers.

[Duane]

damionpaul--interesting question, but on first blush I would say unlikely. Not impossible, but unlikely. The thing is, the process arising from the crustal cracking would be sufficient to explain the raised mesas, especially those which are located in the floor of the valley.

With our current understanding of the processes that gave rise to the Valles, the involvement of diapars is not necessary. While certainly some degree of lift, especially in other parts of Mars, could have arisen as a result of this process, the Marinaris actually shows more signs of shrinkage than lifting. This is partially why it is thought the trench opened for as long and as deep as it did--the shrinkage of the lithosphere combined with the deformation which arose during the formation of the Tharsis Montes and Tharsis Plateau.

Frankly, the final answer will probably have to wait until the area is visited

VanderL--

1) No the rift-like processes on Mars do not appear to be caused by tectonics. There is some certainty here given the lack of subduction zones combined with the stable formation of the Tharsis complex. If there had been tectonic activity, the lithosphere would likely have "drifted" as the plates on Earth do, thereby preventing the formation of the gigantic volcanoes evident on Mars.

Note I call them "rift-like". The process is quite different from the rift processes of Earth.

2) Yes, the process allows for the formation of mesas. An anology might be the way that concrete sidewalks crack as a result of frost. The cracking can split, leaving islands or "mesas" between the halves.

In the case of Mars, the formation of the trench occurred over the course of eons, with there likely being stops and starts, espcially during the initial formation. Add in the the possible erosion from flood water, and the mesas seem to be a reasonable consequence.

3) Yes for the same reasons.

4) It appears the the rifting has stopped, and that most, if not all, of the processes which lead to the lithospheric splitting occurred in the ancient past-- ~ 3 Billion yrs ago. Since then, the dominant process appears to be wind erosion. There is some disagreement here though, as some scientists have postulated that the volcanic process has occurred recently (well geologically speaking, 500 million yrs ago or so) and might even be active today.

Personally, I would tend to doubt those claims, given the cratering count of even the "youngest" areas of Mars, but again we really won't know for sure until measurements are taken on Mars itself.

johnm--Yes that could cause some minor erosion, but it certainly doesn't account for the types of terrain seen on Mars today. Temperature swings are not, in and of themselves, erosional in the absence of something that can melt and refreeze (like water).

Chook--keep pluggin lad, it's not that hard! :P

[Chook]

Quote Duane:
"Chook--keep pluggin lad, it's not that hard!"

Thanks for the encouragement ... it REALLY sounds interesting and I'd love to know what you are talking about but I'm not understanding the key words.

Look - it really would be valuable for all us amateurs, like myself, if there was a reference page here where we could look up specialised words like "valles, lithosphere, diapars (is that the same as nappies?lol), tectonics, subduction zones, mesas, diapiric domal uplifts" etc. etc.

I am quite happy to "Google" these words, as VanderL has suggested - but a resourse such as a Technical Dictionary would be added value to this wondeful forum.

Especially to Beginners, like myself.

[VanderL]

Ok Chook, point taken I'll try to give some links once in a while, and don't think I'm an expert, cause I'm not.

Now this
http://www.spaceref.com/news/viewsr.html?pid=11852
What do the planetary geologists think how these features were created?
Cheers.

[Duane]

VanderL, planetary geologsts think this:

The somewhat concentric bands in this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image may be an expression of eroded layered material.

Says that right in the article. Now because that might make me sound like a smart-alec, which I am not trying to be, let me paraphrase.

The picture might show layered material within the crater that has undergone some form of erosion. Because it is Mars, probably wind erosion.

By the way, you'll notice a lot of "mights" and "could be" and "its thought" in posts regarding this type of discussion. The reason for that, is that you cannot be absolutely sure until you have actually stood on the spot and looked really carefully at it. While the formations appear to be similar looking to formations on Earth that were caused by certain processes on Earth, it is not Earth. As such, we can only hypothesize until we get there to look.

[VanderL]

Thanks Duane, that's exactly what I want to hear; the "mights" and "possibly's" I mean, because I think we are projecting too much Earth processes onto Mars and we need a lot more data to be sure.

Btw I heard there's a (Barbie) doll named after you!
Cheers.

[Duane]

Really?!? A Duane doll?

[VanderL]

Yeah, apparently a Ken replacement!
Cheers.

[damienpaul]

because I think we are projecting too much Earth processes onto Mars and we need a lot more data to be sure.

I agree wholeheartedly, but it is hard not to be earth centred in our thinking.

Maybe there aren't any Ken and Duane Martian dolls on Mars...

[Algenon the mouse]

I am not ready to rule out convections or plate tectonics on Mars. I have heard all the theories before, but I still think that there might be plates on Mars, just fewer of them. Mars is smaller. We actually have no idea what state the lithosphere is in, it is all just guess work and theory. The Volcanos might just be dormant. Their cycle of eruption might be longer than earth volcanos due to fewer plates. Shield volcanos tend to get big, btw. and if it is just a few plates that are seperating...

Until we REALLY look at the geology (marsology?) of Mars, we will not really know.

[VanderL]

Has anyone tried to explain what the sequence of events were that can explain the shape of the Olympus Mons caldera? There are several circles visible, is it possible to deduce which is the oldest eruption (if it erupted at all) and which one is the freshest?

[damienpaul]

And as an extension to your question VanderL perhaps, add in when asteroidal impacts occured.

[VanderL]

You're referring to the small impacts in the sides of Olympus Mons and the caldera I presume?
Those would be the latest addition, because old impacts are presumably covered by lava flows. Btw where are the outflows of lava?
Cheers.

[Tinaa]

Since Mars has an atmosphere, wind erosion would have turned much of that lava to dust after a couple of billion years.

[Guest]

You mean that the last eruption of Olympus is billions of years ago? Wouldn't there be layers visible then, where the erosion exposes the different lava flows, and with a volcanos this size there would be an awful lot of lava to erode, I think.
Cheers.