Scientists: Mars’ mysterious slope streaks and seasonal recurring lineae are caused by dust
A typical Martian slope streak.
On Mars there are two mysterious features that are somewhat similar but entirely unique to the Red Planet, and for years have baffled planetary geologists as to their origins.
One feature is called slope streaks, which appear randomly year-round as either dark or bright streaks on slopes. They resemble avalanches, except that they do not change the topography, have no debris piles at their base, and sometimes travel along that topography, sometimes even going uphill for short distances. Over time these streaks then fade.
The other feature is called recurring slope lineae, because though they look like slope streaks, they are not random but appear seasonally at the same places each year. Lineae are also always dark.
Scientists have proposed many theories to explain both, with most theories involving some form of water process, either the seepage of brine from below or water vapor causing the Martian surface dust to flow, like droplets on a car windshield. None of these theories has been confirmed, or entirely accepted.
Two studies at this week’s 55th annual Lunar and Planetary Science Conference in Texas have both concluded that water is not a factor in the formation of either phenomenon. Instead, both papers propose a much simpler explanation: Wind and blowing dust interact to cause small dust avalanches.
From the conclusion of the paper [pdf] looking at slope streaks:
Overall, our findings strongly support a wind-triggered dry avalanche hypothesis of [slope streak] formation that is recharged due to dust accumulation and transport.
During dust storm season, the wind causes dust to accumulate on slopes. Eventually, and randomly, that accumulation causes a dust avalanche, which though an actual landslide is only made up of that surface dust, so it only stains the surface going downhill.
The paper [pdf] looking at recurring slope lineae came to a similar conclusion:
These results support the idea that dust could be the main material mobilized, and that the dust deposition and winds seem to be somehow involved in the formation and disappearance mechanisms.
The data suggests that the seasonality of lineae is due to the annual dust storm season. The data from both papers suggest that the specific topography of every location, combined with the prevailing winds, determines whether the streaks will be randomly located, or seasonal at the same place.
None of this is as yet proven, but these new theories are especially appealing because of their simplicity. That these features are unique to Mars is likely because of its one-third Earth gravity and very thin atmosphere. On Earth conditions won’t allow dust to behave in this manner.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
A typical Martian slope streak.
On Mars there are two mysterious features that are somewhat similar but entirely unique to the Red Planet, and for years have baffled planetary geologists as to their origins.
One feature is called slope streaks, which appear randomly year-round as either dark or bright streaks on slopes. They resemble avalanches, except that they do not change the topography, have no debris piles at their base, and sometimes travel along that topography, sometimes even going uphill for short distances. Over time these streaks then fade.
The other feature is called recurring slope lineae, because though they look like slope streaks, they are not random but appear seasonally at the same places each year. Lineae are also always dark.
Scientists have proposed many theories to explain both, with most theories involving some form of water process, either the seepage of brine from below or water vapor causing the Martian surface dust to flow, like droplets on a car windshield. None of these theories has been confirmed, or entirely accepted.
Two studies at this week’s 55th annual Lunar and Planetary Science Conference in Texas have both concluded that water is not a factor in the formation of either phenomenon. Instead, both papers propose a much simpler explanation: Wind and blowing dust interact to cause small dust avalanches.
From the conclusion of the paper [pdf] looking at slope streaks:
Overall, our findings strongly support a wind-triggered dry avalanche hypothesis of [slope streak] formation that is recharged due to dust accumulation and transport.
During dust storm season, the wind causes dust to accumulate on slopes. Eventually, and randomly, that accumulation causes a dust avalanche, which though an actual landslide is only made up of that surface dust, so it only stains the surface going downhill.
The paper [pdf] looking at recurring slope lineae came to a similar conclusion:
These results support the idea that dust could be the main material mobilized, and that the dust deposition and winds seem to be somehow involved in the formation and disappearance mechanisms.
The data suggests that the seasonality of lineae is due to the annual dust storm season. The data from both papers suggest that the specific topography of every location, combined with the prevailing winds, determines whether the streaks will be randomly located, or seasonal at the same place.
None of this is as yet proven, but these new theories are especially appealing because of their simplicity. That these features are unique to Mars is likely because of its one-third Earth gravity and very thin atmosphere. On Earth conditions won’t allow dust to behave in this manner.
On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.
The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.
The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.
"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News
This is such a strange sight as always.
Having worked in dust capturing systems of very fine particulate, dust flows in the lowest crevices and pools at the base of the slope just like water… But when extremely dry, it has a static electrical charge which allows it to spread out and even float in the air settling slowly or being attracted to opposite charges. (The sun‘s UV does to the Martian surface what your old cathode ray TV did to dust particles in the air causing them to be attracted to the TV set, the way some good air filtration system‘s operate efficiently)
So little dust starting from such a narrow point and spreading to cover such a large area doesn’t seem possible. (hence the mystery) The slope streak just below the big one seems to be flowing uphill? Or instead of spreading out it got more narrow as it flows down… can’t explain it. Perhaps it’s related to carbon dioxide venting similar to the black streaks coming from the ice cap? oxygen free carbon like graphene or graphite?
Here’s a new mystery that I didn’t see coming, a new volcano discovered on Mars… Junk science? Geologist using their imagination to explain the largest canyon in the solar system?
https://newatlas.com/space/martian-volcano-ice/
Max: This volcano paper was presented this week at the Lunar and Planetary conference. New Atlas is overstating its significance. The volcano remnant is real, but the story here is not its discovery but its context in the overall geological history of Mars. It is very old, and appears to have occurred in some relation to the theorized catastrophic floods that created Valles Marineris.