The strange beginning of a 300-mile-long meandering canyon on Mars
Today’s cool image will be unlike most cool images, in that we will begin not with the image but with the overview map to the right. The long meandering canyon at the center of this map is Nirgal Vallis, a 300-mile long canyon on Mars that eventually drains to the east into a much larger drainage system that runs south-to-north several thousand miles into the Martian northern lowland plains.
At first glance Nirgal Vallis invokes a river system. It starts in the west as several branches that combine to form a single major canyon meandering eastward until it enters that south-to-north system. To our Earth eyes, this canyon suggests it was carved by water flowing eastward, the many drainage routes combining as they flowed downhill.
Today’s the cool image, its location indicated by the white dot, tells us however that liquid water might not have been what created this canyon.
Click for original image.
The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 28, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The different colors in the color strip probably represent different types of rock and sand, with the orange in the canyon dust and fine sand (thus the dunes), and the green on the plateau coarser rocks and bedrock.
The science team labels this “Nirgal Vallis Headwaters.” We are looking at the very start of a long 300-mile-long canyon. It however is very unlike the headwaters of a river system, which is usually a very small creek or stream or even a simple trickle coming out of the ground. With water-formed systems the channel grows slowly from that trickle to a wider river.
Here however Nirgal begins suddenly, in a wide canyon. As noted by Mars Express image release from 2019,
Nirgal Vallis is a typical example of a feature known as an amphitheatre-headed valley. As the name suggests, rather than ending bluntly or sharply, the ends of these tributaries have the characteristic semi-circular, rounded shape of an Ancient Greek amphitheatre. Such valleys also typically have steep walls, smooth floors, and, if sliced through at a cross-section, adopt a ‘U’ shape.
All of these geological features suggest the slow carving of the canyon by glaciers, not liquid water. Moreover, the orbital images suggest that some of that carving might have occurred underground. Though this image captures the beginning of Nirgal Vallis, the overview map shows further canyons to the west that are aligned with it. It is as if the ice flowed underground, and eventually pulled the surface away to reveal that underground canyon along most of its length. Only in the west, where the ice flow was smaller does some of that roof remain.
Where this ice came from remains a mystery. This location is mostly in the dry equatorial regions of Mars, though its southern edge slips into the mid-latitude regions where many glaciers are still found. The possibility that water ice was once prevalent here suggests once again that Mars has undergone many significant changes in climate.
Readers!
Every February I run a fund-raising drive during my birthday month. This year I celebrate my 72nd birthday, and hope and plan to continue writing and posting on Behind the Black for as long as I am able.
I hope my readers will support this effort. As I did in my November fund-raising drive, I am offering autographed copies of my books for large donations. Donate $250 and you can have a choice of the hardback of either Genesis: the Story of Apollo 8 or Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space. Donate $200 and you can get an autographed paperback copy of either. IMPORTANT! If you donate enough to get a book, please email me separately to tell me which book you want and the address to mail it to.
Please consider supporting my work here at Behind the Black. My analysis of space, politics, and culture, taken from the perspective of an historian, is almost always on the money and ahead of the game. For example, in 2020 I correctly predicted that the COVID panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Every one of those 2020 conclusions has turned out right.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
Today’s cool image will be unlike most cool images, in that we will begin not with the image but with the overview map to the right. The long meandering canyon at the center of this map is Nirgal Vallis, a 300-mile long canyon on Mars that eventually drains to the east into a much larger drainage system that runs south-to-north several thousand miles into the Martian northern lowland plains.
At first glance Nirgal Vallis invokes a river system. It starts in the west as several branches that combine to form a single major canyon meandering eastward until it enters that south-to-north system. To our Earth eyes, this canyon suggests it was carved by water flowing eastward, the many drainage routes combining as they flowed downhill.
Today’s the cool image, its location indicated by the white dot, tells us however that liquid water might not have been what created this canyon.
Click for original image.
The picture to the right, rotated, cropped, reduced, and sharpened to post here, was taken on September 28, 2024 by the high resolution camera on Mars Reconnaissance Orbiter (MRO). The different colors in the color strip probably represent different types of rock and sand, with the orange in the canyon dust and fine sand (thus the dunes), and the green on the plateau coarser rocks and bedrock.
The science team labels this “Nirgal Vallis Headwaters.” We are looking at the very start of a long 300-mile-long canyon. It however is very unlike the headwaters of a river system, which is usually a very small creek or stream or even a simple trickle coming out of the ground. With water-formed systems the channel grows slowly from that trickle to a wider river.
Here however Nirgal begins suddenly, in a wide canyon. As noted by Mars Express image release from 2019,
Nirgal Vallis is a typical example of a feature known as an amphitheatre-headed valley. As the name suggests, rather than ending bluntly or sharply, the ends of these tributaries have the characteristic semi-circular, rounded shape of an Ancient Greek amphitheatre. Such valleys also typically have steep walls, smooth floors, and, if sliced through at a cross-section, adopt a ‘U’ shape.
All of these geological features suggest the slow carving of the canyon by glaciers, not liquid water. Moreover, the orbital images suggest that some of that carving might have occurred underground. Though this image captures the beginning of Nirgal Vallis, the overview map shows further canyons to the west that are aligned with it. It is as if the ice flowed underground, and eventually pulled the surface away to reveal that underground canyon along most of its length. Only in the west, where the ice flow was smaller does some of that roof remain.
Where this ice came from remains a mystery. This location is mostly in the dry equatorial regions of Mars, though its southern edge slips into the mid-latitude regions where many glaciers are still found. The possibility that water ice was once prevalent here suggests once again that Mars has undergone many significant changes in climate.
Readers!
Every February I run a fund-raising drive during my birthday month. This year I celebrate my 72nd birthday, and hope and plan to continue writing and posting on Behind the Black for as long as I am able.
I hope my readers will support this effort. As I did in my November fund-raising drive, I am offering autographed copies of my books for large donations. Donate $250 and you can have a choice of the hardback of either Genesis: the Story of Apollo 8 or Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space. Donate $200 and you can get an autographed paperback copy of either. IMPORTANT! If you donate enough to get a book, please email me separately to tell me which book you want and the address to mail it to.
Please consider supporting my work here at Behind the Black. My analysis of space, politics, and culture, taken from the perspective of an historian, is almost always on the money and ahead of the game. For example, in 2020 I correctly predicted that the COVID panic was unnecessary, that the virus was apparently simply a variation of the flu, that masks were not simply pointless but if worn incorrectly were a health threat, that the lockdowns were a disaster and did nothing to stop the spread of COVID. Every one of those 2020 conclusions has turned out right.
Your help allows me to do this kind of intelligent analysis. I take no advertising or sponsors, so my reporting isn't influenced by donations by established space or drug companies. Instead, I rely entirely on donations and subscriptions from my readers, which gives me the freedom to write what I think, unencumbered by outside influences.
You can support me either by giving a one-time contribution or a regular subscription. There are four ways of doing so:
1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.
2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.
3. A Paypal Donation or subscription:
4. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652
You can also support me by buying one of my books, as noted in the boxes interspersed throughout the webpage or shown in the menu above.
Thanks for keeping the mystery alive Bob. What a crazy place
It’s almost like Mars serves some kind of purpose.