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Criss-crossing Martian ridges hit by new impacts

Criss-crossing Martian ridges hit by new impacts
Click for full image.

The image to the right, cropped to post here, is a captioned photo from the high resolution camera on Mars Reconnaissance orbiter and released today. From the caption:

The black spots [recent impacts] form because the craters exposed cleaner materials in the subsurface beneath the bright, dusty surface.

Our image is also interesting because the surface has a criss-cross pattern formed by wind activity. Bright ripples that are oriented from the upper right to the lower left are perpendicular to the wind flow. In contrast, outcrops that have been eroded by the wind are oriented perpendicular to the ripples to produce the criss-cross pattern we now observe.

The overview map below might also help explain this criss-cross pattern.

Overview map

The caption notes that this image, indicated by the red cross, is located near the large meandering canyon dubbed Mangala Valles. What must also be realized is its proximity to both Mars’ giant volcanoes as well as the planet’s largest volcanic ash deposit, dubbed the Medusae Fossae Formation.

The darker northwest-to-southeast ridges appear to be ash deposits that are being eroded away by the wind, thus explaining their orientation parallel to the prevailing wind direction. If you go the Medusae Fossae link above, you will see from the cool image there the resemblance these ridges have to that eroding ash deposit.

The lighter northeast-to-southwest ridges appear to be the underlying bedrock, their orientation caused not by wind but by a more fundamental geological process related to the complex formation of Mangala Valles itself, as discussed in this paper [pdf]

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Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
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  • pawn

    What is with the parabolic looking line at the foci?

  • pawn: That’s a great question. I hadn’t noticed it until you pointed it out.

    I suspect that this double impact occurred at the same moment, probably because the asteroid broke in two as it barreled though Mars’ atmosphere. That line is probably the result of the collision of the blast waves from the two impacts, laying down a line on the ground. If the left impact was slightly larger it would explain the slight push towards the right.

  • Diane Wilson

    Parabola could indicate direction of impact? This looks like a double impact (meteor brought a friend?) and possible interference between impact shock waves?

    Is there possibly an earlier photo of the same spot? Occasionally they have caught really recent impacts, proven by earlier photos without impact scars. This looks very recent.

  • pawn

    Robert, I agree. They might have been additive and disturbed the lighter shaded soil to a higher degree where they met. The additive condition of the shocks was at a single location (considering a hemisphere) that moved outwards as time went on resulting in a continuous “curve”.

    Kinda weird (but Mars……)

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