A Martian crater with a straight edge


Genesis cover

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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A mis-shapened crater on Mars
Click for full image.

Cool image time! The image to the right, cropped and reduced to post here, was released today by the science team of the high resolution camera on Mars Reconnaissance Orbiter (MRO). It shows a small Martian crater whose northern rim for some reason is flattened into a straight line. Such a crater is rare, since almost all craters rims are round, even in the case of a low angle impact. The cause is unknown, though there are theories. From the caption, written by Ingrid Daubar of the Lunar and Planetary Laboratory in Arizona:

One possibility is that there was a zone of joints or faults in the crust that existed before the impact. When the impact happened, the crater formed along the straight line of these faults. Something similar happened to Meteor Crater in Arizona. Our image doesn’t show any faults, but they could be beneath the surface.

Perhaps some sort of uneven collapse changed the shape of the crater. There are piles of material on the crater’s floor, especially in the northwest and northeast corners. If those piles fell down from the rim, why did it happen there and not in other places? This crater is near the size where larger craters start to show wall slumping and terraces, so this type of collapse could be occurring unevenly.

The crater is located in the southern cratered highlands of Mars, at about 32 degrees latitude. At that latitude, it is also possible that some past glacial activity could have misshapen this crater, though I have no idea how. The crater itself does not appear to have any glacial material in it.

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3 comments

  • It looks like the sides of a round crater fell in; if you use the circumference of the bottom of the crater and follow that around. It looks like it would fit right inside with a small section of the straight wall being curved also.

  • Max

    I agree with Charles.
    The rim on the left remained intact as it fell to the bottom pushing material in front of it to the center. The collapsed rim on the right closely matches the missing material from the crater wall and also pushed “run out” before it filling the center of the crater with a loose bulge.
    Just below the cliffs of the top straight line you can see the circular original wall of the crater protruding in the way you would expect it.
    Such a collapse could’ve been triggered by a meteor impact on the crater wall similar to the one that came later in the center of the pit.

  • Mike

    Could it possibly be caused my say 3 meteors? 2 smaller ones causing the top left and right rounded edges. Then another, the last one, toward the bottom. Top right could almost be a circle if you look at it. Then the bottom one even shows slight striations suggesting a ring. I am no astronomer or astrophysicist though so I apologize if this sounds absurd.

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