Gully erosion in a Martian dune field
Click for original image.
Today’s cool image is another example of how little we really understand the geology of Mars. The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on February 22, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
The focus of the image is the eastern end of a large and very distinct dune field inside 31-mile-wide Matera Crater, as shown by the white rectangle in the overview map above. The field fills an area 10 by 11 miles inside the floor of the crater. On that eastern end is a very pronounced drainage gully dropping downhill about 2,000 feet to the east.
Gullies on Martian slopes, especially on the interior rims of craters, are not unusual. Though their true cause is not yet confirmed, the theories behind their existence all relate to some form of water/ice process, mostly relating to the seasonal freeze-thaw cycle.
This picture was taken in the spring, exactly when seasonal changes might be spotted. In fact, scientists have been taking regular MRO images of this gully since 2007, when it was featured image. From that 2007 caption:
Gullies are features found on slopes and dunes in the mid-latitudes of both hemispheres. Both slope and dune gullies were initially suggested to be a result of liquid water from the surface or subsurface. Slope and dune gullies usually have different morphologies: dune gullies are more linear and have levees bordering their channels. They typically have no distinguishable, or very small, alcove and debris aprons. Slope gullies, on the other hand, often have deeply incised alcoves and channels that exhibit fluvial characteristics such as streamlined islands.
What is highly unusual about this dune field is that one of its gullies has the morphology of a slope gully.
In 2020 that monitoring paid off, when a new picture detected a major change near the bottom of this gully.
The sand divided into many small toes near its end, or perhaps many individual flows descended near the same spot. Additionally, a long sinuous ridge of sand was deposited. This could be a “levee” that formed along one side of a flow, but there is not much sand past the end of the ridge, so it might also be the main body of a flow.
A very quick comparison of the 2020 image with this new 2024 picture suggests more changes have occurred since 2020.
Why these changes occur on this dune slope and not many others is a mystery. Another mystery is the presence of dune fields inside most of the craters in this region. Those fields do not fill the entire crater floor, but tend to be concentrated in only one area, usually in the northern half but not always.
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 print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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
Click for original image.
Today’s cool image is another example of how little we really understand the geology of Mars. The picture to the right, rotated, cropped, reduced, and enhanced to post here, was taken on February 22, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO).
The focus of the image is the eastern end of a large and very distinct dune field inside 31-mile-wide Matera Crater, as shown by the white rectangle in the overview map above. The field fills an area 10 by 11 miles inside the floor of the crater. On that eastern end is a very pronounced drainage gully dropping downhill about 2,000 feet to the east.
Gullies on Martian slopes, especially on the interior rims of craters, are not unusual. Though their true cause is not yet confirmed, the theories behind their existence all relate to some form of water/ice process, mostly relating to the seasonal freeze-thaw cycle.
This picture was taken in the spring, exactly when seasonal changes might be spotted. In fact, scientists have been taking regular MRO images of this gully since 2007, when it was featured image. From that 2007 caption:
Gullies are features found on slopes and dunes in the mid-latitudes of both hemispheres. Both slope and dune gullies were initially suggested to be a result of liquid water from the surface or subsurface. Slope and dune gullies usually have different morphologies: dune gullies are more linear and have levees bordering their channels. They typically have no distinguishable, or very small, alcove and debris aprons. Slope gullies, on the other hand, often have deeply incised alcoves and channels that exhibit fluvial characteristics such as streamlined islands.
What is highly unusual about this dune field is that one of its gullies has the morphology of a slope gully.
In 2020 that monitoring paid off, when a new picture detected a major change near the bottom of this gully.
The sand divided into many small toes near its end, or perhaps many individual flows descended near the same spot. Additionally, a long sinuous ridge of sand was deposited. This could be a “levee” that formed along one side of a flow, but there is not much sand past the end of the ridge, so it might also be the main body of a flow.
A very quick comparison of the 2020 image with this new 2024 picture suggests more changes have occurred since 2020.
Why these changes occur on this dune slope and not many others is a mystery. Another mystery is the presence of dune fields inside most of the craters in this region. Those fields do not fill the entire crater floor, but tend to be concentrated in only one area, usually in the northern half but not always.
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 print edition can be purchased at Amazon or from any other book seller. If you want an autographed copy the price is $60 for the hardback and $45 for the paperback, plus $8 shipping for each. Go here for purchasing details. 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