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A Martian avalanche: before and after

A Martian avalanche: before and after
Click for full resolution animation.

Cool image time! The science team for the high resolution camera of Mars Reconnaissance Orbiter (MRO) today released a beautiful blink animation showing the before and after terrain at an avalanche site along the scarp of Mars’s north pole ice cap.

The animation is very cool, but it is also helpful to align the two images next to each other to carefully study what actually changed. The image to the right, cropped and reduced here, shows both photos. (Thank you to planetary scientist Shane Byrne for splitting the animation for me.). I have added the white bars to indicate the cliff section that broke off during the avalanche. That section was made of water ice, with probably some dust and rocks mixed in, and broke into the blocks that are now scattered on the ground below.

This avalanche itself is actually not unusual and as I noted in an earlier post, is part of an annual season of numerous avalanches that occur on this northern scarp of the polar ice cap each spring. As written by Dr. Candice Hansen of the Planetary Science Institute in Tucson, Arizona,

Every spring the sun shines on the side of the stack of layers at the North Pole of Mars known as the north polar layered deposits. The warmth destabilizes the ice and blocks break loose. When they reach the bottom of the more than 500 meter tall cliff face [about 1,600 feet], the blocks kick up a cloud of dust.

And as Byrne noted to me in an interview when I asked him how it was possible for MRO to image so many avalanches, as they occur,

“It is incredible. I think this is the most incredible thing about the whole process.” said Byrne. “If you fly over a mountain range on the Earth and take a picture, the chances catching an avalanche in progress are almost zero. But on Mars half of the images we take in the right season contain an avalanche. There’s one image that has four avalanches going off simultaneously at different parts of the scarp. There must be hundreds to thousands of these events each day.”

In an email exchange with him today, he also added that this is not the first before and after comparison images obtained. “We’ve been seeing these blockfalls for several years now. That’s partly why these scarps are being so intensively monitored by HiRISE.”

Do these avalanches mean that the Martian northern polar ice cap is shrinking? Maybe, maybe not. Right now scientists think the cap is in a steady state, neither growing or shrinking. These events are thus more likely comparable to the routine calving of ice sections from the foots of glaciers here on Earth, a common tourist destination in the waters of western Alaskan coast.

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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.

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"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


  • Steve Kasian

    “If you fly over a mountain range on the Earth and take a picture, the chances catching an avalanche in progress are almost zero. But on Mars half of the images we take in the right season contain an avalanche. There’s one image that has four avalanches going off simultaneously at different parts of the scarp. There must be hundreds to thousands of these events each day.”

    What does the first sentence have to do with anything? These images were taken a half-decade apart; What does catching an avalanche in the act on Earth have to do with discovering evidence of avalanches on Mars such imagery?? It’s like comparing apples to oranges and remarking about how similar they are to one another. ?? And what is this mention of “simultaneous” avalanche activity going on in such images?? The images are 5 years apart! I don’t know what planet he’s from, but on Earth, simultaneous means “at the same time.”

  • Steve Kasian: You should have read my earlier post on BtB: Avalanche season at the Martian north pole, which I clearly linked to and referenced. They routinely catch avalanches as they happen, without even trying, sometimes with multiple avalanches in the same image.

    Moreover, you didn’t read very closely before blasting your criticism. I think I was very clear. The quote is from that earlier post, and was referring to other images. I also made it clear those images referred to the remarkable fact that images of the northern scarp of the north pole ice cap in the spring routinely catch avalanches in progress Look at the images in that earlier post.

    And please read things before criticizing in the future. You will look better.

  • citizen

    Robert, nice push-back to quick-draw Steve!
    I enjoy listening to your reports on the John Batchelor podcasts. You are a welcome trustworthy source for we who lack scientific credentials to keep abreast of space developments and NASA achievements as well as their lack thereof. I’m contributing to your BtB today. Thank you.

  • philip lee horner

    Someday men will die there in a rockfall.

  • wayne

    –that, is a very deep statement! (no pun intended)

    Do we know the concentration of this ice or the depth? and what is the typical temperature range this area experiences? (being lazy here, just thinking out loud.)
    (and on a more general line of inquiry — ‘water-ice’—are we talking about frozen perchlorates, or what? How much actual water is present? )

  • wayne: Do I have to browbeat you like I did with Lee S in the comment thread for the crested saguaro? :)

    The link in the last paragraph of this post will answer some of your questions, plus provide links to others that will like likely answer them all.

  • Star Bird

    Could there be the possibility of Mars Quakes on the red planet is that all possible?

  • Star Bird: We will have a better idea of whether there are quakes on Mars when the InSight science team releases their results from the seismograph, probably this coming March.

    However, in this case, the avalanches are merely a natural occurrence caused by seasonal temperature changes. When the Sun finally hits this cold scarp after months of arctic darkness, the heat causes expansion and sublimation of the carbon dioxide frost that layers the ice, and that causes disturbances in the ice blocks, causing avalanches.

    We see this same process on Earth, though not quite as dramatically as the avalanche season on Mars.

  • wayne

    Thank you, and acutely aware of the beat-down you delivered to Lee!

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