APOD: Layered Rocks near Mount Sharp on Mars (2015 Feb 09)

[APOD Robot]

Layered Rocks near Mount Sharp on Mars

Explanation: What caused these Martian rocks to be layered? The leading hypothesis is an ancient Martian lake that kept evaporating and refilling over 10 million years -- but has now remained dry and empty of water for billions of years. The featured image, taken last November by the robotic Curiosity rover, shows one-meter wide Whale Rock which is part of the Pahrump Hills outcrop at the base of Mount Sharp. Also evident in the image is cross-bedding -- rock with angled layers -- which were likely facilitated by waves of sand. Curiosity continues to find many layered rocks like this as it continues to roll around and up 5.5-km high Mount Sharp.

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[madtom1999]

This can also be achieved by windblown sand and soils. I'm not saying there wasn't water on Mars but there are many features attributed to water that can as easily be explained by dry geology, and in many cases the 'dry' solution (???) seems more applicable.

[Boomer12k]

For this to have occurred over and over again, that suggests Rain...or melt off of ice at least in Martian Summer... This would be like what would happen in Crater Lake, Oregon, if all the water evaporated...you would have Wizard Island...now Wizard Mountain, in Crater Lake...or...that would be...um...Crater Caldera..

:---[===] *

[r9brown]

These Martian rocks strikingly resemble Earth shales that have been fractured by repeated freeze and thaw. The Earthly effect, however, requires the presence of water in the rocks. I wonder what the Martian mechanism is?

[bactame]

The layering is obvious and the thickness of the layers is pretty uniform suggesting many years of an annual cycle. The cross-bedding though is pretty weak so this particular lake bed doesn't appear to have been changing all that much. The layering itself consists of fairly thin layers suggesting hundreds of years going perhaps to a thousand but millions i don't see in this image. Show me cliff of this stuff and then millions might make sense.

[TheSylphOfBlood]

This can also be achieved by windblown sand and soils. I'm not saying there wasn't water on Mars but there are many features attributed to water that can as easily be explained by dry geology, and in many cases the 'dry' solution (???) seems more applicable.

Well there is also the fact that they found solid water ice just below the surface and on the poles (I'm pretty sure it's water (as opposed to CO2) anyway, though my memory is a little fuzzy)

[TheSylphOfBlood]

These Martian rocks strikingly resemble Earth shales that have been fractured by repeated freeze and thaw. The Earthly effect, however, requires the presence of water in the rocks. I wonder what the Martian mechanism is?

There was water found on Mars. The reason its no longer liquid is because Mars lost it's atmosphere and got very cold very fast, so what didn't evaporate and get sucked into the void of space froze.

[TheSylphOfBlood]

For this to have occurred over and over again, that suggests Rain...or melt off of ice at least in Martian Summer... This would be like what would happen in Crater Lake, Oregon, if all the water evaporated...you would have Wizard Island...now Wizard Mountain, in Crater Lake...or...that would be...um...Crater Caldera..

:---[===] *

I'm thinking run off from Mount Sharp. It would be similar to any other mountain here on Earth when it had an atmosphere. I bet when Curiosity gets to Mount Sharp we're gonna be getting pictures of obvious streams/ rivers and probably some deltas from the runoff.

[rocks&beer]

Bottom right of image shows planar fracture-fill veins indicative of groundwater flowing through the sediment/rock following deposition.

The cross-beds do look alluvial to me. Of course, that proves nothing.

[Chris Peterson]

The layering is obvious and the thickness of the layers is pretty uniform suggesting many years of an annual cycle. The cross-bedding though is pretty weak so this particular lake bed doesn't appear to have been changing all that much. The layering itself consists of fairly thin layers suggesting hundreds of years going perhaps to a thousand but millions i don't see in this image. Show me cliff of this stuff and then millions might make sense.

This image is a ~1 meter section of a sedimentary zone some 150 meters high.

The approximately 1 cm thick layers are probably far too large to reflect an annual cycle. More likely is repeated periods of liquid water related to a longer period cycle such as Milankovich or its martian equivalent.

[Chris Peterson]

This can also be achieved by windblown sand and soils. I'm not saying there wasn't water on Mars but there are many features attributed to water that can as easily be explained by dry geology, and in many cases the 'dry' solution (???) seems more applicable.

But the mineralogy is consistent with water-based chemistries. We don't just have visual imagery to work with.

[Chris Peterson]

There was water found on Mars. The reason its no longer liquid is because Mars lost it's atmosphere and got very cold very fast, so what didn't evaporate and get sucked into the void of space froze.

Water isn't lost to space, but hydrogen is. That leaves the need for an oxygen sink. Some of that is easily seen in the highly oxidized surface, but not enough has been firmly identified yet to balance the amount of hydrogen assumed lost (based on D-H ratios). Much water is still present. The water in the southern ice cap alone is enough to cover the entire surface of Mars 10 meters deep (assuming a smooth surface), and the total water is believed to be enough to cover the planet 30 meters deep. Based on hydrogen loss, that amount was about 90 meters when this lake was formed.

So yes, lots of water was available to create these structures. All that was needed was enough heat to keep it liquid for periods of time. Not a lot is known about that, but there are certainly very plausible theories which are being tested by this probe and others.

[owlice]

What an amazing and beautiful image this is!

[Ron-Astro Pharmacist]

The "dry and empty of water for billions of years" comment made me curious if we have ever dated Martian rocks? Cal Tech was up to the task.

http://www.caltech.edu/news/first-rock- ... mars-41496

Since the Earth is 4.5 billion years old, Cal Tech estimate of 3.86 to 4.56 billion years was, as commented, "an utterly unsurprising result." I suppose they will keep trying on the various landscapes encountered to pin down the water's "coming and going" dates. Love to be driving Curiosity anytime but especially when it -makes a splash.

http://science.nasa.gov/science-news/sciencecasts/

[Chris Peterson]

The "dry and empty of water for billions of years" comment made me curious if we have ever dated Martian rocks? Cal Tech was up to the task.

Caltech.

[FloridaMike]

The "dry and empty of water for billions of years" comment made me curious if we have ever dated Martian rocks? Cal Tech was up to the task.

Caltech.

[Ron-Astro Pharmacist]

Thanks. That - I should have known. It's one of the few campuses, devoted to astronomy and physics, I've actually visited. Besides that "SLAC'ing Stanford place. Both of my daughters spend plenty of time looking for tee-shirts and sweatshirts. Alex Filippenko would have surely flunked me for the day if he saw this. He does seem to like his T's too. I attribute some bad puns and my awareness of APOD to watching his Astronomy lectures. "Cal Tech" I partially blame on spell check.

Mostly me.

[APODFORIST]

This is a wonderful picture. Looks like 10 meters away but it's millions of kilometers.

[ShadeofGray]

Looks like some of those overhangs broke yesterday, or the week before - months at most. There is no or little dust on some of the exposed broken interiors of these jagged formations. Rates of dust deposition and removal on Spirit/Oppy solar panels (no reason to think these rates are different on Curiosity and its locale) are on the scale of days, weeks or months, so if this formation was there for years we would not expect an exposed broken surface to look different from the unbroken surfaces. Perhaps Mars is a bit more dynamic than we thought? Question is, what broke them? The minuscule wind? A dust devil? Marsquake? Rough handling?

[geckzilla]

Rates of dust deposition and removal on Spirit/Oppy solar panels (no reason to think these rates are different on Curiosity and its locale) are on the scale of days, weeks or months,

Why not? Different locations may have different wind patterns, sand deposits, and geography which could alter the rates.

[ShadeofGray]

Geck- I can't find more frequently sampled rate info for Curiosity- however it accumulated significant dust over a two year period. http://www.planetary.org/blogs/emily-la ... after.html

Pathfinder rates are comparable to the MERs. http://onlinelibrary.wiley.com/doi/10.1 ... 9/abstract

It's possible what we are looking at is a random distribution, but some of the broken pieces seem to have a very clear delineation of dust on the outside vs little or none on the newly exposed part.

Thanks for your response.

[geckzilla]

It's possible what we are looking at is a random distribution, but some of the broken pieces seem to have a very clear delineation of dust on the outside vs little or none on the newly exposed part.

Well, I guess I can't say Mars having a uniform dusting over its surface would really be the most unbelievable thing I've ever heard about it, so I'm just going to say this is one more reason I don't want to go to Mars.

[loquin]

Any theories as the the source of the light colored 'worm-tracks' near the crevice at the center of the image? (section below, w markup)


Lou

[rstevenson]

Any theories as the the source of the light colored 'worm-tracks' near the crevice at the center of the image?

Hi Lou,

I think the clue lies in the bottom-right of the main picture. (See my closeup crop.) There's been some vertical cracking through the sedimentary layers - a very common occurance. These cracks can fill up, perhaps with magma if there's nearby volcanism or maybe with very mineral-rich water, which deposits salts in the cracks. In any case, these cracks can contain material harder than the sedimentary layers, and can then become prominent when the sedimentary layers are eroded - very prominent in that area I show here, where the entire sedimentary layer has disappeared, leaving only the filled cracks. So I think we're seeing the edges of these vertical cracks in the areas you asked about, and other spots, as you can see just above this undercut.

Hope this helps.

Rob