APOD: Layered Hills in Arabia Terra on Mars (2010 Aug 15)

[APOD Robot]

Layered Hills in Arabia Terra on Mars

Explanation: Why are some hills on Mars so layered? The answer is still under investigation. Clearly, dark windblown sand surrounds outcropping of light sedimentary rock across the floor of crater Arabia Terra. The light rock clearly appears structured into many layers, the lowest of which is likely very old. Although the dark sand forms dunes, rippled dunes of lighter colored sand are easier to see surrounding the stepped mesas. Blown sand possibly itself eroded once-larger mesas into the layered hills. Most of the layered shelves are wide enough to drive a truck around. The above image, showing an area about 3 kilometers across, was taken in 2003 October by the now defunct Mars Global Surveyor spacecraft orbiting Mars.

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[popmueller@hotmaikl.com]

They look like strip mines.

[XACULEATUS at comcast]

The more evenly formed ones bear an UNCANNY resemblance to Scale Insects (Family Coccidae), many of which are perfectly flat underneath and adhere to the flat or smoothly and gently curved surfaces of plants and use a beak to penetrate and suck the tasty juices of their host plant. They form a protective covering over their body in the form of sequentially secreted layers of hard chiten (but sometimes just wax instead!), and therefore look like scales on trees or herbaceous plants. Looking down at them from above looks almost exactly like some of this hills featured in today's APOD. Perhaps those aren't hills at all, and life has truly been found on Mars in the form of giant Scale Coccids!!

[ficheye]

I think everyone knows what Richard C. Hoagland is going to say. These were built by an intelligent race millions of years ago... and NASA is covering it up! But one of the posters below has an interesting thought about the features looking like strip mines. And Hoagland will say "Yes, of course, because the ancient Martians used slave labor to build their fabulous monuments"! I digress.

[FrogSplash]

I wonder what these would look like in color. Come on NASA color photography isn't that expensive. Not false color either I want the real thing. I do see the bug representation here though. Doctor Who once found life on Mars. They were the Frozen Warriors.

FS

[orin stepanek]

http://www.msss.com/mars_images/moc/200 ... index.html Looks to me like Mars went through a similar erosion process to that of Earth.

[biddie67]

Amazing - they look like huge slices of onions! Could these formations be the result of some kind of series of successive volcanic eruptions over time that each layer, in its own time frame, then eroded away?

Has there been any analysis as to what type of rock they are made of?


P.S. I just went back and read the information found at the "Sedimentary rock" link above (I apologize - I should have read it first). Since I'm not trained in sedimentology, I have to assume that there are all different kinds of sedimtary rocks with different erosion properties. Could there be any volcanic/lava eruptions that subsequently behave like eroding sedimentary rocks?

[StarstruckKid]

Some of these images are just too cool to be real.

Erosion of multiple sedimentary layers? Gigantic Busby Berkely dance number set with thousands of (yes) dancing Martians arranged around each ring, doing 8-legged high kicks? Martian rice farms? Planetary zits?

I'd guess the eery perfection of the terraces is evidence of no rain in a very long time.

[neufer]

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[Case]

Martians ate rice perhaps?

[León]

The mention of the trucks is related to open pit mines, like the image below

But they are (transcribe) Eastern Arabia Terra is mantled in a layer of dust a few centimeters to a meter thick, yet contains morphologic features that suggest a history of multiple events of deposition and consolidation of fine-grained material and a significant amount of erosion. Early in Martian history, this region was affected by volcanic and fluvial activity but has since been dominated by aeolian processes. Five craters in this region contain interior mound material that ranges in height from 1600 to 2100 m above the crater floor. The fluted erosional pattern and the thermal inertia are suggestive of a weakly indurated material, and the extensive layering implies that these mounds were formed by a repeated process or processes. Although these materials primarily occur within craters, there are materials outside craters that have similar erosional features and fine laminations, suggesting a more extensive deposit. The most likely process to form this material is the deposition and cementation of air fall dust and is potentially related to Martian obliquity changes. The significant amount of erosion of the intracrater mounds unit indicates a dramatic change from a depositional environment to an erosional regime over the past 106-108 years. Currently dust is accumulating in this region in years with planet-encircling dust events, but global circulation model results indicate that dust devils may be removing slight amounts of dust from Arabia Terra. These observations suggest that the thickness of the dust mantle may not be currently increasing and may instead be in equilibrium. http://adsabs.harvard.edu/abs/2008JGRE..11312001F

Layers in crater found within the Schiaparelli crater basin as seen by Mars Global Surveyor

[Raum]

They look like the result of a very strong or long-period erosion cycle generated by a prevailing wind or current. Most of the hills are now teardrop or pointed to the upper right of the photo. It would be fascinating to determine how long each period was and how long ago they stopped. The weather that did this must have stopped or the hills would be completely gone. The most aerodynamic hills on the right show the most layers because the tops did not wear away as fast as the more blunt hills. This may point to more than just weather patterns on Mars.

[Chris Peterson]

I wonder what these would look like in color. Come on NASA color photography isn't that expensive. Not false color either I want the real thing.

You are mistaken. Color photography can be very expensive. A color camera might be of very little scientific value, and would displace an instrument capable of producing useful data. High quality imaging involves taking multiple images through different filters. This allows details about composition to be worked out. When a camera is stationary, or moving slowly with respect to its target, multiple images through different filters can be combined to reproduce color. But when everything is moving, as here with a low orbit camera, combining images becomes difficult. This image was made with very specific science goals in mind, and producing a color image to please the crowds was apparently not one of them.

This is an old image. The newer MRO probe has the HiRISE camera. It is, in fact, a sort of color camera, although the three bands are not intended to provide true color. However, the data can be transformed to provide a reasonable approximation of color as we would see it. But again, that isn't the primary goal.

False color images are generally much more useful.

[owlice]

Darn you, neufer! Now I want a 24-layer Chocolate Cake for my next birthday cake; yellow cake with chocolate frosting just might not cut it next time!

(But since I'm old and have a pea-brain, I will not remember this by the time my birthday rolls around, so yellow cake with chocolate frosting will work just fine!)

[Peter Eckhoff]

Did anyone notice the boulder that rolled down one of the terraces? It started near the top of the terrace and rolled in the 300 degree direction and now rest slightly away from the terrace just offshore in one of the "lakes". Might be of interest to a geologist investigating the geology of the terraces and "lakes".

[Ann]

I wonder what these would look like in color. Come on NASA color photography isn't that expensive. Not false color either I want the real thing.

Hmmm, I'm glad that someone sees it my way!

Color or no color, some of those layered hills look just eerily perfect.

Ann

[rstevenson]

Here's a 3D image of part of Arabia Terra, as referenced on this page, about 1/3 of the way down.

Rob

[thearborist]

Since these are formed in what is apparently sedimentary rock layers, could they be sink holes? Put a layer of sand on a cardboard, then punch a hole it it. The effect looks about the same, especially if the sand is compacted in layers. Maybe a bubble formed the hills and left a void below that later collapsed. Or to carry it to the bizzare/extreme, may it was giant Martian ‘ants’ whose nest collapsed.

[rstevenson]

Since these are formed in what is apparently sedimentary rock layers, could they be sink holes? Put a layer of sand on a cardboard, then punch a hole it it. The effect looks about the same, especially if the sand is compacted in layers. Maybe a bubble formed the hills and left a void below that later collapsed. Or to carry it to the bizzare/extreme, may it was giant Martian ‘ants’ whose nest collapsed.

I think you may be picturing these inside out. They're hills, not pits. Aerial photos (or orbital, in this case) can be tricky to properly orient yourself as to in/out, but these are definitely outies, not innies.

Rob

[Beyond]

To me, it is quite evident that water flowed through there at some time in the past.

Also - if you frost a two layer cake, you still have a two layer cake.
Frosting neufer's 12 layer cake all of a sudden turns it into a 24 layer cake. No wonder no-one understands the new math

[keshlam]

I tend to agree that what I'd suspect if I saw this on earth -- ignoring human activity -- is sedimentary layers being eroded away by slowly receding water, perhaps with harder and softer layers alternating (which tends to result in undercutting and collapse, thus leaving relatively sharp-edged plateaus). If the water is going down at a relatively steady rate, that could account for the thresholds being fairly evenly spaced, as they fall below the threshold for each new undermining sequence...

Yeah, I'm stretching a bit. But given some of the "impossibly" flat-topped and steep-sided structures on Earth which were created by a weather-resistant capstone over softer rock... and given that Earth has had periods where inland seas either gradually receded or broke free and drained away...

I have to admit that it does look a lot like terracing or mountaintop-removal, though your mention of "wide enough to drive a truck around" may be biasing that perception.

[keshlam]

Actually, there's a simple initial test: Do all the hills in the same area have steps at about the same heights (allowing, if necessary, for some possible distortion by uneven uplift)? Or, if they're uneven, is the bias minor and consistently in a particular direction? Either would tend to confirm the progressively-receding-shoreline idea, since one would expect liquid to seek roughly the same height across an area (modulo local masscons and persistent currents).

If the heights, and heights of the steps, are irregular that would tend to argue against this theory.


I think there's consensus that Mars did once have significant amounts surface water, right?

[JR in WV]

I'm with the Strip Mining post! Bolt Mountain in SW WV looked just like this until the trees began to grow on the flat benches.

So now we know that the Martians didn't care for their environment any better than we are, with the result that their planet became uninhabitable! Curses, they're ahead of us again!!

;-)

Wonderful images, all! Thanks!

[B]

would it be possible to generate a 3D computer image of the region?? an artist could then work out scenes of the topography as human eyes would see it..

[Chappy]

What a fascinating image!
The detail is spectacular, and I disagree with some other posters...the contrast in this image is far superior to what a color image would show.

@Peter Eckhoff - Do you mean this one?



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I don't think this is a boulder from this mound, although it's very probable that many pieces do break away and roll down at times.
Similar striations can be seen on other mounds as well, with no associated boulder visible. I don't even think such a boulder would even be visible at this resolution, I think what you see as a boulder is actually a small mound itself. Looking at it really closely also revealed (to me) that what appears to be a single striation from a possible boulder rolling down, is more likely 2 separate ones.
There are also other similar small mounds scattered around that look exactly like this one, that aren't close to larger mounds that they may have broken away from, so this leads me to believe that it's just a separate small mound itself, that just kinda lines up with the striations in the big mound.