APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Comments and questions about the APOD on the main view screen.
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APOD Robot
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APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by APOD Robot » Wed Jul 18, 2018 4:11 am

Image Dark Slope Streaks Split on Mars

Explanation: What is creating these dark streaks on Mars? No one is sure. Candidates include dust avalanches, evaporating dry ice sleds, and liquid water flows. What is clear is that the streaks occur through light surface dust and expose a deeper dark layer. Similar streaks have been photographed on Mars for years and are one of the few surface features that change their appearance seasonally. Particularly interesting here is that larger streaks split into smaller streaks further down the slope. The featured image was taken by the HiRISE camera on board the Mars-orbiting Mars Reconnaissance Orbiter (MRO) several months ago. Currently, a global dust storm is encompassing much of Mars.

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gleeb

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by gleeb » Wed Jul 18, 2018 4:21 am

Looks to be not the first 'flow' in the area. Splitting may be due to dunes.?

randall.macdonald@rogers.com

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by randall.macdonald@rogers.com » Wed Jul 18, 2018 4:48 am

The dark streaks, to me, seem to be edited. I say this because the colour edges have no fading as would be seen in any flow where one medium affects another. Why is there no edge fading or bleeding of intensity or effect? The demarcation is abrupt in all the edges. I, thus, question it.

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by Chris Peterson » Wed Jul 18, 2018 6:02 am

randall.macdonald@rogers.com wrote:
Wed Jul 18, 2018 4:48 am
The dark streaks, to me, seem to be edited. I say this because the colour edges have no fading as would be seen in any flow where one medium affects another. Why is there no edge fading or bleeding of intensity or effect? The demarcation is abrupt in all the edges. I, thus, question it.
I think we can be safe in believing that none of the entities responsible for this image have fabricated any data.
Chris

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by Ann » Wed Jul 18, 2018 6:23 am

Chris Peterson wrote:
Wed Jul 18, 2018 6:02 am
randall.macdonald@rogers.com wrote:
Wed Jul 18, 2018 4:48 am
The dark streaks, to me, seem to be edited. I say this because the colour edges have no fading as would be seen in any flow where one medium affects another. Why is there no edge fading or bleeding of intensity or effect? The demarcation is abrupt in all the edges. I, thus, question it.
I think we can be safe in believing that none of the entities responsible for this image have fabricated any data.
:lol2:

Ann
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LMMT

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by LMMT » Wed Jul 18, 2018 7:23 am

Where is the tree?

alex944

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by alex944 » Wed Jul 18, 2018 7:33 am

"Candidates include dust avalanches, evaporating dry ice sleds, and liquid water flows". I doubt liquid water can be present on martian surface, because of too low pressure.

stargene

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by stargene » Wed Jul 18, 2018 7:42 am

I notice that this new flow and virtually all the older flows are sourced precisely at the top of the ridge
that transits from upper left, curving to lower right. FWIW. Does this imply something compacted at
the ridge top occasionally melts?

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by madtom1999 » Wed Jul 18, 2018 8:23 am

Having spent many happy hours playing with sand and dust in various forms I would put money on this being dry dust/sand. It would be nice to see the origin of the flow more clearly but the tendency to follow new paths suggests the flow settles on the surface like lava so forcing the later flows to follow a different downhill course.
Of course a liquid could do the same (like lava) by freezing on the surface but the flow lengths suggest an almost continuous flow of a very similar rate for which a liquid source is hard to concieve, whereas a ridge collapse of loose material would provide just that constant rate flow as it backs away from the precipitous area that started the flow.

emanueldewitt

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by emanueldewitt » Wed Jul 18, 2018 8:31 am

Not giving an idea of meters/kms is very unfriendly and makes the photo meaningless.

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by Boomer12k » Wed Jul 18, 2018 9:00 am

Solved.... Martian RAPUNZEL.... SOLVED....

took a few minutes...

OK...on a more serious note; It looks like it was done with a marker pen. There are 3 areas above it and slightly to the right, that look like cracks...they have nothing coming out of them. But this one has "a flow".

If you magnify, and check to the left...you see places that look like they might be deposits for a darker material...but no flows...waiting their turn? Still, "Frozen"...why so far off to OUR right of them, when they are on a cliff too? Why are they darker than the streaks on our right side? OK...more concentration of the material...why are they not flowing?
There are other "deposits" in the upper right of the photo? Why are they not flowing?
I wonder...since under the deposits on our left...there IS a slide area...that after a flow has been done, or a slide has happened, the material fades...dark material does not seem to be "blown around".
Why is it as "black as INK"???
If it is "Wind" and blown off dust...why is it not more consistent with the area? Is someone directing the winds only at one spot here?

Why does it appear to flow ACROSS the dunes...and not just in "valleys"...it is like someone took a marker, and stained the whole area of the photo...you can see places where it should have flowed into...but flows over and around an area... if it is a "flow", it should not have done that. It goes along the sides of "rumpled dunes"...not into lower areas. If blown then, it should have been more consistent to an area...my opinion...it is almost like OIL oozed up to the surface, even up the cliff...it is odd all-round...

OK...Rapunzel it is...

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Last edited by Boomer12k on Wed Jul 18, 2018 9:31 am, edited 3 times in total.

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JohnD
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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by JohnD » Wed Jul 18, 2018 9:19 am

Any 'mystery' or lack of scale is resolved by the merest, most trivial click on a link in the caption. It takes you to the NASA site with a wide view of the streak and this caption:
"This image from NASA's Mars Reconnaissance Orbiter (MRO) shows streaks forming on slopes when dust cascades downhill. The dark streak is an area of less dust compared to the brighter and reddish surroundings. What triggers these avalanches is not known, but might be related to sudden warming of the surface.
These streaks are often diverted by the terrain they flow down. This one has split into many smaller streaks where it encountered minor obstacles.
These streaks fade away over decades as more dust slowly settles out of the Martian sky.
The map is projected here at a scale of 25 centimeters (9.8 inches) per pixel. [The original image scale is 28.1 centimeters (11.1 inches) per pixel (with 1 x 1 binning); objects on the order of 84 centimeters (33.1 inches) across are resolved.] North is up."

So NASA seem certain that this is dust, contradicting the mysterioso "No one is sure" of the APOD caption. What I'd like to know is, why is this dust flow so dark?

John

DomeLord

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by DomeLord » Wed Jul 18, 2018 10:54 am

Scale?

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by JohnD » Wed Jul 18, 2018 12:34 pm

Domelord,
You can write (type) but can you read? The text I copied from the NASA site and included in the point you skimmed, includes the words "The original image scale is 28.1 centimeters (11.1 inches) per pixel (with 1 x 1 binning); objects on the order of 84 centimeters (33.1 inches) across are resolved"

John

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by bls0326 » Wed Jul 18, 2018 1:07 pm

JohnD: Do you know the pixel size of the "original image" ? On the featured image page there are two size choices for the "projected image", then at least three size choices for the selected flow image. Scaling the image off my computer screen and using the original image scale does not seem to result in any reasonable scale for the image.

I see that the original picture shows several more streaks. This APOD is just showing a piece of the picture with the more interesting streak.

Brian

Blank_dan

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by Blank_dan » Wed Jul 18, 2018 1:14 pm

The streaks appear to me to be analogous to “snow rollers”. Through wind and gravity the lighter layer of “snow” is rolled up by cohesion at a point on the precipice where it collects and is subject to a steady wind. As they roll they peel up the entire depth of the “snow” deposit. Revealing the darker dirt beneath.

They increase in size, diameter and length, as they are blown down the slope. They follow a random distribution as they roll out over the shallower grade. Enventually breaking into smaller (shorter) “logs”. These fragments then sublimate away.

In this particular case the rollers are all generated in the same cleft.

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by neufer » Wed Jul 18, 2018 1:20 pm

Click to play embedded YouTube video.
APOD Robot wrote:
Wed Jul 18, 2018 4:11 am
Image Dark Slope Streaks Split on Mars

Explanation: What is creating these dark streaks on Mars? No one is sure. Candidates include dust avalanches, evaporating dry ice sleds, and liquid water flows. What is clear is that the streaks occur through light surface dust and expose a deeper dark layer. Similar streaks have been photographed on Mars for years and are one of the few surface features that change their appearance seasonally. Particularly interesting here is that larger streaks split into smaller streaks further down the slope. The featured image was taken by the HiRISE camera on board the Mars-orbiting Mars Reconnaissance Orbiter (MRO) several months ago. Currently, a global dust storm is encompassing much of Mars.
Art Neuendorffer

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by Bellerophon » Wed Jul 18, 2018 2:20 pm

I'm just surprised no one has suggested that it's the famous Mutagenic Black Goo (and that once there's a sample return mission, we're all done for. We'll all turn green and have arms growing out of our backs). https://tvtropes.org/pmwiki/pmwiki.php/ ... tagenicGoo

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by JShepp64 » Wed Jul 18, 2018 4:31 pm

LMMT wrote:
Wed Jul 18, 2018 7:23 am
Where is the tree?
Ha! Ha! My thoughts exactly! :lol2: It must be transparent and very large....

Guest

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by Guest » Wed Jul 18, 2018 4:38 pm

Diana has dropped her chapel veil....

zendae1

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by zendae1 » Wed Jul 18, 2018 5:29 pm

It looks like a delta.

Czerno O

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by Czerno O » Wed Jul 18, 2018 6:10 pm

Re : linear scale.... For someone like me who can't see individual "pixles" nor count them pixels ;=) ... can someone at last provide a significant idea of the size of the featured martian streaks - in feet, meters, kilometers, miles,... whatever appropriate units of length ! TIA !
An intriguing picture anyway that is.

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by JohnD » Wed Jul 18, 2018 8:24 pm

The TINIEST bit of additional "research" , button-clicking really, finds "Original image scale range 28.1 cm/pixel (with 1 x 1 binning) so objects ~84 cm across are resolved" and " Black & white is 5 km across; enhanced color about 1 km For scale, use JPEG/JP2 black & white map-projected images (See: https://hirise.lpl.arizona.edu/ESP_053518_1955) It's not rocket science!

John

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Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by bls0326 » Wed Jul 18, 2018 8:45 pm

Czerno O: The streak is somewhere in the range of 2100 feet long and 1050 feet wide at the widest point. I downloaded the JPEG/JP2 black and white map-projected from the site listed in JohnD's post. That map is apparently 5 km across, but it shows more than today's APOD. Scaling the streak based on the 5 km across info results in the length width above.
Of course I may have a mistake in here somewhere.

Brian

GoshOGeeOGolly

Re: APOD: Dark Slope Streaks Split on Mars (2018 Jul 18)

Post by GoshOGeeOGolly » Thu Jul 19, 2018 3:47 pm

Top left of the photo .. there is dark stuff in the cavities .. the dark stuff appears to be the same dark stuff as the flow. What flows when it is dry? Would powdered carbon flow like that? Where might that powdered carbon come from? The stuff seems to flow without causing erosion as liquid would. Buckeyball stuff?