APOD: Seasonal Streaks Point to Recent on... (2015 Sep 30)

[APOD Robot]

Seasonal Streaks Point to Recent Flowing Water on Mars

Explanation: What creates these changing streaks on Mars? Called Recurring Slope Linea (RSL), these dark features start on the slopes of hills and craters but don't usually extend to the bottom. What's even more unusual is that these streaks appear to change with the season, appearing fresh and growing during warm weather and disappearing during the winter. After much study, including a recent chemical analyses, a leading hypothesis has emerged that these streaks are likely created by new occurrences of liquid salty water that evaporates as it flows. The source for the briny water is still unclear, with two possibilities being condensation from the Martian atmosphere and underground reservoirs. An exciting inference is that if these briny flows are not too salty, they may be able to support microbial life on Mars even today. The featured image of a hill inside Horowitz Crater was investigated by instruments aboard the robotic Mars Reconnaissance Orbiter that has been returning data from Mars since 2006.

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[Ann]

If not water, water, then at least there is liquid, liquid (almost) everywhere in the solar system. Apart from Mars and the Earth (of course!!!), there is Europa, moon of Jupiter, with its probable underground water ocean. Ganymede, too, shows signs of recent tectonic activity (water?), and I seem to remember that Callisto too may be liquid inside. Spectacular Enceladus sprays water-ice into space, drawing from its reservoir of a probable global underground ocean and creating a ring of its own in the Saturnian system. Triton, moon of Neptune, sports numerous cryovolcanoes, spraying ice and dust onto its surface. And Pluto has just been found to have a fantastic large region of extremely freshly deposited ice.

(And if we are not talking about liquid water and ices, there is of course Io, with its many active volcanoes. Personally I wonder if the thick atmosphere of Titan has been caused by some global upheaval on that large moon, which might perhaps have melted a thick layer of nitrogen ice, which then turned into an atmosphere. And what about the atmosphere of Venus? Is that, too, the product of volcanism?)

Our Solar system has proved to be fascinatingly dynamic. Suddenly those comets with their outbursts and tails don't seem so remarkable after all.

Ann

[Guest]

There are some grey linear features on the left slope of the hill in a grid-like pattern. Does anybody know what they are?

[FLPhotoCatcher]

There are some grey linear features on the left slope of the hill in a grid-like pattern. Does anybody know what they are?

Those are trails made by dust devils.

[GoJoe]

If not water, water, then at least there is liquid, liquid (almost) everywhere in the solar system. Apart from Mars and the Earth (of course!!!), there is Europa, moon of Jupiter, with its probable underground water ocean. Ganymede, too, shows signs of recent tectonic activity (water?), and I seem to remember that Callisto too may be liquid inside. Spectacular Enceladus sprays water-ice into space, drawing from its reservoir of a probable global underground ocean and creating a ring of its own in the Saturnian system. Triton, moon of Neptune, sports numerous cryovolcanoes, spraying ice and dust onto its surface. And Pluto has just been found to have a fantastic large region of extremely freshly deposited ice.

(And if we are not talking about liquid water and ices, there is of course Io, with its many active volcanoes. Personally I wonder if the thick atmosphere of Titan has been caused by some global upheaval on that large moon, which might perhaps have melted a thick layer of nitrogen ice, which then turned into an atmosphere. And what about the atmosphere of Venus? Is that, too, the product of volcanism?)

Our Solar system has proved to be fascinatingly dynamic. Suddenly those comets with their outbursts and tails don't seem so remarkable after all.

Ann

It looks to me like it could also be rocks crumbling and rolling down the side disturbing lighter colored dust on the surface. Since it is seasonal, perhaps the temperature change causes the rock to expand and contract which makes them crumble. Just a thought.

[De58te]

If this hill is on Mars where is the Martian Sky? The landscape seems to be taken in daylight, but the sky is as black as the airless moon. Pictures taken with the Curiosity or Opportunity rovers show a sky that is reddish brown, or gray if it is black and white picture.

[Boomer12k]

Mars is weeping, because we are looking it over....and it knows, someday, we will come...
Intriguing picture for sure.
Why no streaks on the left or right? Why no streaks on the foreground mounds? Why no Precipitated out Salt? If so salty, and the water evaporates...

Where does this picture come from, if the Orbiter is in Orbit?????

:---[===] *

[Guest]

If not water, water, then at least there is liquid, liquid (almost) everywhere in the solar system. Apart from Mars and the Earth (of course!!!), there is Europa, moon of Jupiter, with its probable underground water ocean. Ganymede, too, shows signs of recent tectonic activity (water?), and I seem to remember that Callisto too may be liquid inside. Spectacular Enceladus sprays water-ice into space, drawing from its reservoir of a probable global underground ocean and creating a ring of its own in the Saturnian system. Triton, moon of Neptune, sports numerous cryovolcanoes, spraying ice and dust onto its surface. And Pluto has just been found to have a fantastic large region of extremely freshly deposited ice.

(And if we are not talking about liquid water and ices, there is of course Io, with its many active volcanoes. Personally I wonder if the thick atmosphere of Titan has been caused by some global upheaval on that large moon, which might perhaps have melted a thick layer of nitrogen ice, which then turned into an atmosphere. And what about the atmosphere of Venus? Is that, too, the product of volcanism?)

Our Solar system has proved to be fascinatingly dynamic. Suddenly those comets with their outbursts and tails don't seem so remarkable after all.

Ann

We find it truly amazing, and a little incomprehensible, that so may bodies in the solar system, presumably made from the same fundamental raw materials and resources, can be so vastly different and unique.

Also... it looks as though the slope is too steep for a rover (not the current ones on the planet) to get up and sample the outflow or the stream beds. How else could we get a sample for study? You want your sample in a in a liquid/moist state to see what is there, right? Or will any live organism be dormant in the surrounding soils?

[neufer]

If this hill is on Mars where is the Martian Sky? The landscape seems to be taken in daylight, but the sky is as black as the airless moon. Pictures taken with the Curiosity or Opportunity rovers show a sky that is reddish brown, or gray if it is black and white picture.

• It is a NASA "composite" picture:

<<The image was produced by first creating a 3-D computer model (a digital terrain map) of the area based on stereo information from two HiRISE observations, and then draping an image over the land-shape model. The vertical dimension is exaggerated by a factor of 1.5 compared to horizontal dimensions.>>

[Chris Peterson]

It looks to me like it could also be rocks crumbling and rolling down the side disturbing lighter colored dust on the surface. Since it is seasonal, perhaps the temperature change causes the rock to expand and contract which makes them crumble. Just a thought.

To be clear, the hypothesis that this involves liquid water is only partly based on the morphological evidence. The strongest part of the argument comes from the chemical analysis, not the visual appearance.

[neufer]

[size=150][color=#0000FF]Perchlorate is often written with the formula ClO[sub]4[/sub][sup]−[/sup][/color][/size]

---

<<In May 2008, the Wet Chemistry Laboratory (WCL) on board the 2007 Phoenix Mars Lander performed the first wet chemical analysis of martian soil. The analyses on three samples, two from the surface and one from depth of 5 cm, revealed a slightly alkaline soil and low levels of salts typically found on Earth. Unexpected though was the presence of ~ 0.6% by weight perchlorate (ClO₄⁻), most likely as a Ca(ClO₄)₂ phase. These salts, formed from perchlorates discovered at the Phoenix landing site, act as "anti-freeze" and will substantially lower the freezing point of water. Based on the temperature and pressure conditions on present-day Mars at the Phoenix lander site, conditions would allow a perchlorate salt solution to be stable in liquid form for a few hours each day during the summer.

The possibility that the perchlorate was a contaminant brought from Earth has been eliminated by several lines of evidence. The Phoenix retro-rockets used ultra pure hydrazine and launch propellants consisted of ammonium perchlorate. Sensors on board Phoenix found no traces of ammonium, and thus the perchlorate in the quantities present in all three soil samples is indigenous to the martian soil.

In 2006, a mechanism was proposed for the formation of perchlorates that is particularly relevant to the discovery of perchlorate at the Mars Phoenix lander site. It was shown that soils with high concentrations of chloride converted to perchlorate in the presence of sunlight and/or ultraviolet light. The conversion was reproduced in the lab using chloride-rich soils from Death Valley. Other experiments have demonstrated the formation of perchlorate is associated with wide band gap semiconducting oxides. In 2014 it was shown that perchlorate and chlorate can be produced from chloride minerals under martian conditions.

Further findings by the Mars Curiosity rover in 2012-2013 support perchlorates as being widespread, and even inspired a Science article titled "Pesky Perchlorates All Over Mars". At half-a-percentage of the component of Martian soil ("a fair amount"), Martian perchlorates present a serious challenge to human settlement.

On September 28, 2015 NASA announced that they had found liquid water on Mars with a significant quantity of various perchlorates.>>

[Gary S]

It looks to me like it could also be rocks crumbling and rolling down the side disturbing lighter colored dust on the surface. Since it is seasonal, perhaps the temperature change causes the rock to expand and contract which makes them crumble. Just a thought.

To be clear, the hypothesis that this involves liquid water is only partly based on the morphological evidence. The strongest part of the argument comes from the chemical analysis, not the visual appearance.

I thought of crumbling darker sediments too - they could contain water ice as a matrix glue. Then the summer "heat" would sublimate some ice away, releasing small rock fragments to roll down the slope to create the linear features(?) This process would not require any liquid water. I don't see any eroded gullies in the image.

[Sawngrighter]

Why should snowfall and snowmelt on Mars NOT be normal? We've known for a long time there is lots of water on Mars, and new evidence suggests a historical planet wide ocean.
https://www.newscientist.com/article/dn ... n-on-mars/

Sublimation could put water into the atmosphere, water which could fall as snow in proper season. Martian spring and summer temperatures would allow the snow to melt. I really don't see any big mystery.

But if that idea is not acceptable, then how about the possibility that eruptions from superhuge Olympus Mons simply covered the seas/oceans/ocean on Mars with minerals, with water seeping upwards to the surface? https://www.physicsforums.com/threads/w ... rd.309946/

Size of Olympus Mons. http://www.bing.com/images/search?q=oly ... ORM=IQFRBA

[Ron-Astro Pharmacist]

Bacteria on Mars would have a unique composition from anything that Earth may have evolved. I would think we would be able to tell a Mars bacterium from an Earth bacterium easily once returned to Earth. Colonizing Mars with Earth bacteria is an ethical dilemma which will need debated prior to human colonization but I don't think it would confuse us long if we accidentally discovered a contaminant.

Of course bringing Mars bacteria back to Earth would constitute another debate. Looks like another slippery slope is likely to develop.

[ThePiper]

There are some grey linear features on the left slope of the hill in a grid-like pattern. Does anybody know what they are?

There is no doubt: Ski trails...

[bystander]

http://asterisk.apod.com/viewtopic.php?t=35217

[Ron-Astro Pharmacist]

I had no idea that slippery slopes themselves were so controversial. Let alone the other ethical metaphors listed on the link. Maybe I'd better stick with attempts at a humorous approach like, "Yea. They are ski trails. Just look at the jump on the left..." Are they really dust devil trails? I don't suppose they are animal trails.

Probably not.

[neufer]

Why should snowfall and snowmelt on Mars NOT be normal?

Sublimation could put water into the atmosphere, water which could fall as snow in proper season. Martian spring and summer temperatures would allow the snow to melt. I really don't see any big mystery.

• Martian snow pack is only observed at the poles... where snow does fall "in the proper season".

Click to play embedded YouTube video.

<<The Phoenix lander descended on Mars [68°N 234°E] on May 25, 2008. Snow was observed to fall from cirrus clouds. The clouds formed at a level in the atmosphere that was around −65 °C, so the clouds would have to be composed of water-ice, rather than carbon dioxide-ice (dry ice) because, at the low pressure of the martian atmosphere, the temperature for forming carbon dioxide ice is much lower—less than −120 °C. As a result of the mission, it is now believed that water ice (snow) would have accumulated later in the year at this location. This represents a milestone in understanding Martian weather. Wind speeds ranged from 11 to 58 km per hour. The usual average speed was 36 km per hour. These speeds seem high, but the atmosphere of Mars is very thin—less than 1% of the Earth's—and so did not exert much force on the spacecraft. The highest temperature measured during the mission was −19.6 °C, while the coldest was −97.7 °C.>>

<<In meteorology, virga is an observable streak or shaft of precipitation that falls from a cloud but evaporates or sublimes before reaching the ground. At high altitudes the precipitation falls mainly as ice crystals before melting and finally evaporating; this is often due to compressional heating, because the air pressure increases closer to the ground. In September 2008 NASA's Phoenix lander discovered a snow variety of virga falling from Martian clouds.>>

Snow on Mars: NASA Spacecraft Spots 'Dry Ice' Snowflakes
by SPACE.com Staff | September 14, 2012 07:30am ET

<<A spacecraft orbiting Mars has detected carbon dioxide snow falling on the Red Planet, making Mars the only body in the solar system known to host this weird weather phenomenon. Researchers have calculated that carbon dioxide snow particles on Mars are roughly the size of a human red blood cell.

The snow on Mars fell from clouds around the planet's south pole during the Martian winter spanning 2006 and 2007, with scientists discovering it only after sifting through observations by NASA's Mars Reconnaissance Orbiter (MRO). The Martian south pole hosts a frozen carbon dioxide — or "dry ice" — cap year-round, and the new discovery may help explain how it formed and persists, researchers said. "These are the first definitive detections of carbon-dioxide snow clouds," lead author Paul Hayne, of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, Calif., said in a statement. "We firmly establish the clouds are composed of carbon dioxide — flakes of Martian air — and they are thick enough to result in snowfall accumulation at the surface." "The infrared spectra signature of the clouds viewed from this angle is clearly carbon-dioxide ice particles, and they extend to the surface," Kass added. "By observing this way, the Mars Climate Sounder is able to distinguish the particles in the atmosphere from the dry ice on the surface."

Astronomers still aren't entirely sure how the dry ice sustaining Mars' south polar cap — the only place where frozen carbon dioxide exists year-round on the planet's surface — is deposited. It could come from snowfall, or the stuff may freeze out of the air at ground level, researchers said.>>

[jandomc]

Regarding perchlorate salts deposited on Mars, two small observations further to those above are pertinent. Conversion of chloride to chlorate requires UV as stated but also an oxidant. This can't surely be oxygen. Can you enlighten us further? Secondly, chlorate is mono-ionic - i.e. ClO4- not double minus as written above.

[BMAONE23]

It looks to me like it could also be rocks crumbling and rolling down the side disturbing lighter colored dust on the surface. Since it is seasonal, perhaps the temperature change causes the rock to expand and contract which makes them crumble. Just a thought.

To be clear, the hypothesis that this involves liquid water is only partly based on the morphological evidence. The strongest part of the argument comes from the chemical analysis, not the visual appearance.

I thought of crumbling darker sediments too - they could contain water ice as a matrix glue. Then the summer "heat" would sublimate some ice away, releasing small rock fragments to roll down the slope to create the linear features(?) This process would not require any liquid water. I don't see any eroded gullies in the image.

With the exception that the Proposed "Crumbling Dark Sediments" would remain dark for far longer than a couple of months. The only mechanisms that could lighten the soil appearance over the course of a couple months time is:
Drying damp soil (damp soil is almost always darker than it's dry counterpart)
Being overlain by dust (would require Dust transport of sufficient quantity in the region at that specific time)
Reaction to fairly strong radiation source can also affect soil solor

[daddyo]

It looks to me like it could also be rocks crumbling and rolling down the side disturbing lighter colored dust on the surface. Since it is seasonal, perhaps the temperature change causes the rock to expand and contract which makes them crumble. Just a thought.

I thought of crumbling darker sediments too - they could contain water ice as a matrix glue. Then the summer "heat" would sublimate some ice away, releasing small rock fragments to roll down the slope to create the linear features(?) This process would not require any liquid water. I don't see any eroded gullies in the image.

With the exception that the Proposed "Crumbling Dark Sediments" would remain dark for far longer than a couple of months. The only mechanisms that could lighten the soil appearance over the course of a couple months time is:
Drying damp soil (damp soil is almost always darker than it's dry counterpart)
Being overlain by dust (would require Dust transport of sufficient quantity in the region at that specific time)
Reaction to fairly strong radiation source can also affect soil solor

I like your ideas of crumbling & rolling material causing the streaks, it has more of that appearance to me. The boulders would clear topsoil too and perhaps what lay underneath is slightly damp, causing the hydrated signature. Maybe it's this warming hydrated material that freed the boulders in the first place. The teltale signature of boulders rolling/sliding is the fixed width of the paths. Someone needs to build a physical model and try to match what's seen.

[Steve Dutch]

Forget the water. Who's making all those dune buggy tracks on the left side of the hill?

[hoohaw]

Is the vertical scale in the photo exaggerated?

[Ron-Astro Pharmacist]

In September 2008 NASA's Phoenix lander discovered a snow variety of virga falling from Martian clouds.>>

I wished they'd spell "virga" as "verga". Some might misread it and think Phoenix had a really unexpected scoop. (Of course those bacteria might need some help on those really cold Martian nights)

Sorry. I bet I'm getting as annoying as those commercials. I'll put myself in the corner for a time out. Actually I will be gone for a while. As soon as I thought I read there was Viagra on Mars I suited up to head out.

So what if it doesn't fit – it's the only one I could find on short notice. Maybe Andy Weir will write a sequel - "The Viagrian" The story of another intrepid astronaut who mistakenly went to Mars to find Viagra only to be stranded when the rest of the female crew left him – on purpose - when he somehow found some! This story doesn't have a happy ending though it could be modified in a different genre.

[BMAONE23]

Is the vertical scale in the photo exaggerated?

Yes, by a scale of 1.5. It would be nice to have roll overs on these displaying an actual vertical height image as well as the exaggerated height images.