A fresh Martian impact

By Phil Plait | August 16, 2012 7:10 am

Because the planets are so terribly old, and impacts so rare, I still have this (very slight) prejudice that craters are old too. The Moon was bombarded billions of years ago, and the craters on Earth are mostly so old that they’ve eroded away. Heck, even a "new" crater like the one in Arizona is tens of thousands of years old.

Getting the age of a crater can be tricky. But sometimes it’s so easy it’s literally a matter of keeping your eyes on one spot. Like this spot on Mars:

That image (highly color enhanced; click here for a grayscale version) shows a crater seen by a camera on the Mars Reconnaissance Orbiter in 2011. We can tell it’s young because it’s still surrounded by the ejecta blanket; material that blasted out of the crater and settled around it. That stuff tends to erode away (or get covered in dust and sand by Martian winds) relatively quickly.

But in this case, we know just how young it is: it wasn’t seen in images taken of the same spot by a camera on board the Odyssey Mars probe… in 2009! In other words, this crater is less than three years old!

That’s so cool. And it speaks to the power of having multiple, sustained missions to other worlds. Things change. If we take one picture and then walk away, we’ll miss a lot.

Image credit: NASA/JPL/University of Arizona


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MORE ABOUT: craters, Mars, MRO, Odyssey

Comments (44)

  1. Chris

    Another alien probe landed there! So how big is that splotch?

  2. Phil

    Got any stats on how big the crater is and how big the impactor may have been?

  3. Mejilan

    I realize that isn’t the actual color… but the blue blast is really quite beautiful.

  4. Dean

    Do we have any idea of the mass of the impactor? I wonder what an equivalent strike on Earth would have been like.

  5. Other Paul

    It’ll’ve knocked Mars out of orbit and so Mars will come and kill us all!
    Oh Noes! Death from the Skies! Flee!

  6. Levi in NY

    That’s really awesome! Yet another reminder that nothing in this universe stays the same.

  7. XRBfan

    Hi Phil,

    Do you have a link to the 2009 image? I’d like to see a side-by-side of this. Thanks!

    Amanda

  8. Yeeeeeh NASA!

    http://www.neatorama.com/2012/08/15/Were-NASA-and-We-Know-It/

    BTW I wonder how long it will take before the open sore community/conspiracy lovers come up with a chemtrail-esque solution for the blue color.

  9. Actually, that’s the real color. The meteorite landed on a Smurf.

  10. squawky

    @XRBfan (#6)

    The caption on the HiRISE image site says that the intersecting image is from THEMIS, not from HiRISE, so a side by side might be hard. Unfortunately, the images are very different scale (the HiRISE image has a resolution of 30 cm/pixel at full resolution, the THEMIS image 18m/pixel).

    Best guess, the crater looks to be 20-25m in diameter (too small to see in the THEMIS image), but the large dark ejecta blanket is 200-300 m in diameter and should be visible to THEMIS if it was there in 2009.

    The image in question is THEMIS VIS image V31279001 – you can browse it online at http://themis-data.asu.edu/#/planetview/inst/themis/V31279001 . The crater would be located near the top of the full image strip.

  11. That’s very cool. I would expect that Mars gets hit more often because it’s closer to the asteroid belt.

  12. Paul

    I am terrified! Let’s see, fresh huge crator caused just down the street! That is my cue scream an pack, not stand in bewilderment of the carnage!

  13. Keith Hearn

    It really looks like there are two ray patterns. The blue rays all point to the visible crater, but the bigger black rays all seem to point to a spot below and to the right of the crater. Any idea what would cause this? It almost looks like there were two impactors, but there is no sign of a crater from the one that caused the black rays.

  14. Stop saying “rays”, or the tinfoilhats will have a meltdown otherwise.

  15. Craig

    Needs a “click to ensplatenate”

  16. Chris

    @11 Larian
    I would think it would get hit more often since it has much less atmosphere, so what does hit doesn’t break up as much. But it does have a much smaller cross section than the Earth. I wonder if there is a rate comparison between the two planets.

  17. Scott Halls

    I would be intrigued to know the answer to Keith Hearn’s question. Why do the outer rays all seem to point back to a different centre to the inner rays? hmm……

  18. Because a splat isn´t even?

    and stop staying “rays”

  19. Wzrd1

    @11 Larian, even worse, it’s between the asteroid belt and Jupiter AND has a thin atmosphere.

  20. Daniel

    @ 11 Keith – I’m wondering the same thing. Would an angled-impact cause this? Say, if the impactor came in at a low angle and tossed ejecta to the lower part of the image? The blanket is somewhat of a fan shape, but i’m not sure the rays would radiate from a point downrange (vs radiating from crater) if that’s the case.

  21. oldebabe

    Okay, but do we know what the size of the hit/crater is, and what does it signify?

  22. Wayne Conrad

    I printed it out and extended each dark ray (SkyGazer, hehe!) with a sharpie. They don’t all intersect at the same point, or even two pointss. Most of the intersections are scattered about a broad region near the bottom of the impacted area; a few intersect in a small region near what looks like a fresh crater. I’m intrigued as well.

    Was the object broken up when it hit? Was one part small enough to scatter the dust but not large enough to leave a visible crater? Did the fast moving object carry with it, comic book style, some wind which scattered the dust when it splatted? I don’t know enough about the science of it to even guess what’s plausible.

  23. Keith Bowden

    @kuhnigget
    No, no, it hit Dr. Manhattan! :)

  24. Scott Halls

    The majority of the outer “rays” really do seem to intersect way off from the actual crater.

    I can understand the pattern being lop-sided if the impactor came in on a low angle, but this seems to be something different as the origin of the majority of the rays is away from the impactor crater.

  25. Chris

    Somebody get our their BB gun and a sandbox, we’re gonna have to solve the mystery of the “rays”.

  26. you guys kill me, or rather “them”

  27. Arthur Maruyama

    @ XRBfan:

    I think I have a good candidate for a THEMIS image of the same region here:
    http://viewer.mars.asu.edu//planetview/inst/themis/V11063001#start
    Note the narrow valleys to the left of the pair of large craters near the bottom of the image at my link. If you click on the image on the page to blow up the image, you can see a smaller pair of craters and a hill roughly in a line overlapping the valleys which I think are those that you can see near the top of the greyscale image linked by Phil.

  28. Steven

    Don’t forget Mars has an atmosphere. It’s possible the impactor was coming apart before it hit the ground, and while still in the atmosphere caused a blast wave that created rays by say, blowing away surface dust and exposing bedrock. That could explain the asymmetry we’re seeing.

  29. Arthur Maruyama

    I should note that the save date for that THEMIS image was January 9, 2006, and I do not know how much earlier the image was actually taken.

  30. Keith Hearn

    Ok, here is some speculation: We know that wind on Mars blows away the omnipresent red dust, exposing darker rock below. So my guess is that the black rays are where the dust has been blown away, and the blue rays are the actual ejecta blanket. This makes sense because the blue seems to be (a) centered on the crater, and (b) be on top of the black as we would expect ejecta to be on top of the exposed rock.

    So now we just need to explain why the wind pattern was offset from the actual impact. The object appears to have come from the top of the image, based in the ejecta pattern. Maybe the wind pattern for an angled impact is actually centered downrange from the impact? It’s not like we have much data on wind patterns from impacts, they don’t leave much long-lasting evidence.

    The object will be curving downward at the end of its fall, due to gravity, but wouldn’t the wind continue in a straight line, and thus hit downrange from the object?

    Disclaimers: The above is pure speculation. I am not a rocket scientist, I am a software engineer. Anyone with more experience or knowledge of wind patterns associated with impacts is free to correct me (please do so, I want to know what happened, even if it turns out my speculation is wrong).

  31. amphiox

    But this means we could have had actual video of the impact and we missed it!

    Damnitdamnitdamnitdamnitdamnit…..

  32. amphiox

    I would think it would get hit more often since it has much less atmosphere, so what does hit doesn’t break up as much. But it does have a much smaller cross section than the Earth. I wonder if there is a rate comparison between the two planets.

    But it also has much lower gravity to draw in impactors, so there’s that.

    But couldn’t we just count total craters on Mars, and then compare that to total craters on the moon (using that as proxy for total craters on Earth scaled down by the appropriate size/gravity factor), do an adjustment to however much you think the thin atmosphere and wind-blown dust on Mars will cover up or erode away craters, and settle the question?

  33. @27
    yup, space sucks

  34. @18 Wzrd1 – I believe that the more widely accepted view is that the order, going outwards from the Sun, is Mars, asteroid belt, Jupiter.

  35. tim Rowledge

    @kuhnigget: Actually, that’s the real color. The meteorite landed on a Smurf

    Actually it was a Smurf-ship that crashed. There’s way to much blue material to be less than a dozen Smurfonauts, making it likely it was a Smoogle class interplanetary chemtrail disperser vessel. It was in fact one of these that crashed into the WTC, following a failed attempt to divert the planes. The chemtrail fluid is what burned with enough heat to melt the steel. Truth. Wake Up Sheeple!

  36. W Sanders

    There are blue rocks on Earth, why not on Mars? One of my favorite mountain bike trails (in My Diablo State Park, California) passes through a patch of blue rocks. I think they are travertine or travertine-like, but I’m not much of a geologist.

  37. Maybe I’m just pissing into the wind here, but the rays could have been affected by the atmosphere and the same wind that blows the dust around. Blowing wind and air resistance would have different affects on differently sized particles.

    And I totally though Phil was doing a joke here and the reveal was going to be that the impact was from part of the Curiosity landing (heat shield, etc.).

  38. Chris

    @28 amphiox
    But it also has much lower gravity to draw in impactors, so there’s that.

    Actually gravity doesn’t draw in impactors like you think, it’ll just change their velocity. Consider all the asteroids which pass by the Earth. None of them actually hit unless the Earth is actually in the way. All the others just speed on by. Orbits severely perturbed and sometimes may hit in the future, but most of the time nothing happens. Gravity doesn’t suck. If the object wasn’t gravitationally bound in the first place, it won’t be drawn in.

  39. Robert

    Perhaps the impactor split: One exploded near the surface, tunisia-style, causing the black lines, and another impacted, causing the blue ones?
    I, too would be interested in the before picture, to see exactly what was there. Something interesting happened here, that I know!

  40. CR

    A hundred years from now, Martian colonists studying history will marvel at how we were amazed by this photo, when they likely will be observing similar impacts live and in person.

    I can dream, can’t I?

  41. Nigel Depledge

    Robert (35) said:

    One exploded near the surface, tunisia-style. . .

    Wait, when did Tunisia explode?

  42. amphiox

    Chris @39;

    I was thinking about Shoemaker-Levy 9, which was captured by Jupiter into a decaying orbit that lead to impact. Earth’s greater gravity should mean a higher likelihood of that impact mechanism. And a deeper gravity well means greater velocity change for incoming objects and a sharper deflection angles, which means that an approach that is a near-miss for a smaller gravity well becomes an impact for a larger one.

  43. XRBfan

    @squawky & @ Arthur Maruyama, Thanks for the THEMIS images! The valleys are a good guess Arthur. I think I agree with you. Cheers, Amanda

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