APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

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APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by APOD Robot » Tue Oct 02, 2012 4:06 am

Image An Ancient Stream Bank on Mars

Explanation: Fresh evidence of an ancient stream has been found on Mars. The robotic rover Curiosity has run across unusual surface features that carry a strong resemblance to stream banks on Earth. Visible in the above image, for example, is a small overhanging rock ledge that was quite possibly created by water erosion beneath. The texture of the ledge appears to be a sedimentary conglomerate, the dried remains of many smaller rocks stuck together. Beneath the ledge are numerous small pebbles, possibly made smooth by tumbling in and around the once-flowing stream. Pebbles in the streambed likely fell there as the bank eroded. Circled at the upper right is a larger rock possibly also made smooth by stream erosion. Curiosity has now discovered several indications of dried streambeds on Mars on its way to its present location where it will be exploring the unusual conjunction of three different types of landscape.

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by bystander » Tue Oct 02, 2012 4:40 am

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by nstahl » Tue Oct 02, 2012 8:08 am

In the Viewtopic wrote:by JohnD » Sun Sep 30, 2012 9:06 pm

Thnaks, bystander, for posting that complete report. I need only quote the bits that puzzle me..

A Project Scientist is quoted, "Hottah looks like someone jack-hammered up a slab of city sidewalk, but it's really a tilted block of an ancient streambed" and it has water-worn, rounded pebbles in it to prove that. But the report then talks about an alluvial fan radiating from Pace Vallis, and implies, without actually saying so, that this was where the water came from to deposit this water-washed gravel.
But, this ancient stream bed is cemented into a slab, that is tilted to an extreme angle, in a way that only occurs in geologically aged strata on Earth. It must be very, very old, and must have been buried under many layers itself to be be so compacted. Is NASA getting the chronology wrong?
Which is older? This ancient stream bed or the alluvial fan? Or even Mount Sharp itself?
Is NASA's anxiety to show that water was there, which is proven now, making it minimise the risk that it all went long, long ago?
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Those seem like good questions to me. Any geologists here? Oh, and what could have caused that tilt? I thought Mars was geologically inactive; an impact?

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by Tszabeau » Tue Oct 02, 2012 1:12 pm

nstahl wrote:
In the Viewtopic wrote:by JohnD » Sun Sep 30, 2012 9:06 pm

Those seem like good questions to me. Any geologists here? Oh, and what could have caused that tilt? I thought Mars was geologically inactive; an impact?
I'm not a geologist but, I think water could erode cemented chunks from a strata and then push the chunks into tilted positions. I also think there are Marsquakes that could also contribute, despite the fact that there are no plate techtonics and/or other actions of a geological activity we associate with Earth's activeness driven by it's molten core. There are ancient volcanos on Mars which mean, in the past Mars had a molten core.

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by Psnarf » Tue Oct 02, 2012 2:33 pm

It is not difficult for me to imagine that Mars once had a hot core similar to Earth, which generated a magnetic field of sufficient strength to deflect most of what the Sun tossed at it. The origin of Phobos and Deimos remains a mystery, they look like captured asteroids, but could have been ejected when the surface of Mars was still pretty-much molten. However, the core cooled who-knows-when, shutting down the magnetic field, allowing CMEs, gamma rays and all to strip away much of the atmosphere. Today, the atmospheric pressure and temperature are such that frozen water relatively instantly sublimates. Space monkeys could be living in deep underground caverns, but that's idle speculation with nothing to support such a ludicrous notion.
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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by quigley » Tue Oct 02, 2012 5:36 pm

Has anyone read the John Carter of Mars series of books authored by Edgar Rice Burroughs? It makes for some interesting reading, especially about the ancient seas of Mars leaving their marks on the dying planet. Burroughs' insight is amazing for his works having been written just about one hundred years ago.

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by FloridaMike » Tue Oct 02, 2012 5:47 pm

nstahl wrote: Those seem like good questions to me. Any geologists here? Oh, and what could have caused that tilt? I thought Mars was geologically inactive; an impact?

I may be talking out of turn; but it seems to me we will need a real geologist up there to tease out the details of how / when things were laid down, bonded and finaly lifted up. A rover may be able to do it but it will require so much scouting around I doubt there will ever be the mission time for it.
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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by Chris Peterson » Tue Oct 02, 2012 6:37 pm

FloridaMike wrote:I may be talking out of turn; but it seems to me we will need a real geologist up there to tease out the details of how / when things were laid down, bonded and finaly lifted up. A rover may be able to do it but it will require so much scouting around I doubt there will ever be the mission time for it.
A real geologist would spend the vast majority of his time keeping the toilets running and just trying to survive. And of course, he'd only be as capable as the instruments he brought along.

No, rovers like this are much, much better than people at tasks like this. And we could send hundreds of them, with many different instruments (and even sample return missions) for the cost of a single manned mission.
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Capsaicin

Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by Capsaicin » Tue Oct 02, 2012 7:09 pm

Please no more "water on mars" photos. I'd like to think nasa is capable of spending $2.5 billion dollars on something other than "water existed here" photos. Just sayin...

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by cbritzman » Tue Oct 02, 2012 7:16 pm

I know a dry streambed is not an indication of the current or recent presence of water, but doesn't Curiosity have a mandate
to stay away from water, if detected ? I have read that someone directed it's drill chuck to be loaded with a drill, AFTER having been sterilized and sealed, while waiting for launch, due to a belatedly-developed paranoia that a rough landing could render it undable to access it's drill set.

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by Boomer12k » Tue Oct 02, 2012 9:18 pm

If Martian atmosphere is thin and has little effect on things....even with high velocities there is not much mass, so there is less effect than our winds on Earth....

Since Mars has less gravity, how much effect would water have as a stream???

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by Hehehe..you said.. » Wed Oct 03, 2012 1:04 am

That formation looks like... well, it's very organic looking...

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by neufer » Wed Oct 03, 2012 2:45 am

Boomer12k wrote:
Since Mars has less gravity, how much effect would water have as a stream???
Mars has a gravity of ~3/8 g such that the water flow is only about 3/8ths as strong/fast.

Martian water flow would probably be comparable if either:
  • 1) the Martian stream bed slope was 8/3's steeper or
    2) the Martian stream depth was 8/3's deeper.
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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by doribeans » Thu Oct 04, 2012 12:56 am

Not an astrophysicist or astrogeologist, but, could a deposit like this have been created without water by a atmospheric forces like loess?

It wouldn't need to be water, it could be that there was a thicker atmosphere during an earlier geologic period?

Realize the gravity and atmosphere today probably couldn't account for, but over millions of years you could get a lot of erosion and deposits.

Just asking?

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by neufer » Thu Oct 04, 2012 3:09 am

doribeans wrote:
Not an astrophysicist or astrogeologist, but, could a deposit like this have been created without water by a atmospheric forces like loess?

It wouldn't need to be water, it could be that there was a thicker atmosphere during an earlier geologic period?
How does loess make for so many round pebbles?
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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by trendyron » Thu Oct 04, 2012 7:01 pm

Gale Crater has no water outflow. Curiosity is not that far from the crater bottom. If water flowed eons ago past Curiosity's present position it would surely form a lake with Mount Sharp an island in the middle. That is assuming all hydrology reminants would be obliterated by the violent formation of Gale Crater and also assuming there are no deep aquifers in the area.

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by neufer » Thu Oct 04, 2012 7:44 pm


trendyron wrote:
Gale Crater has no water outflow. Curiosity is not that far from the crater bottom. If water flowed eons ago past Curiosity's present position it would surely form a lake with Mount Sharp an island in the middle. That is assuming all hydrology reminants would be obliterated by the violent formation of Gale Crater and also assuming there are no deep aquifers in the area.
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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by Save Earth Resources » Thu Oct 11, 2012 6:01 pm

No one mentions the possibility of wind erosion here? In a frenzy to prove life existed on this bleak planet, everyone is alive with wishy washy thoughts concerning water, streams and hills that are alive with the sound of music on this planet that couldn't possibly sustain our lives if we were all cockroaches basking in the windswept cosmic radiation on Pluto. :lol2:

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Re: APOD: An Ancient Stream Bank on Mars (2012 Oct 02)

Post by geckzilla » Thu Oct 11, 2012 8:37 pm

Save Earth Resources wrote:No one mentions the possibility of wind erosion here? In a frenzy to prove life existed on this bleak planet, everyone is alive with wishy washy thoughts concerning water, streams and hills that are alive with the sound of music on this planet that couldn't possibly sustain our lives if we were all cockroaches basking in the windswept cosmic radiation on Pluto. :lol2:
Of course wind has been considered, which you would know if you took just a few more minutes to read a little bit about the image. So far they think wind can be ruled out because the size of the rounded pebbles are too large to have been created by wind.
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