Terra spots an impact on, um, Terra

By Phil Plait | February 1, 2010 7:00 am

While high over the grasslands of Kazakhstan, the Terra Earth-observing satellite saw something interesting… can you spot it in this image?


Not so easy, is it? But if you look just left of center you’ll see this:


See it there, right in the center? It’s the Chiyli impact crater, an ancient scar from a cosmic collision. The crater is roughly 1.5 km across (about a mile) — about the same size as Meteor Crater in Arizona — meaning the object that created it was something smaller than a football field, moving at perhaps 30 km/sec (20 miles/sec). It hit about 46 million years ago, give or take. Long after the dinosaurs, but long before us, too. Note that it’s a double-rimmed crater too, which sometimes form in large impacts depending on the conditions of the impactor and the ground.

This is a false-color image, at least part of which is in the infrared; vegetation appears red, water blue, and bare land is "earth tones" (browns and tans). This sort of imagery allows scientists to investigate how vegetation, land, and water change over time.

terra_chiyli_flippedWhen I first saw this image, I didn’t see it as a crater, but more as a raised annulus, a ring in the ground. I knew immediately that this meant that in the picture, the sunlight was coming up from the bottom, and it turns out that’s correct. It’s a cool and optical illusion; when we see craters illuminated from below, they look like domes, and vice-versa. In the picture here, I flipped the image and now, to me at least, it looks more like the depression that it really is. The wide inner rim is more obvious, too.

Here’s an even better example:

Is it a dome… … or a crater?

It just goes to show you that finding evidence of extra-terrestrial events on Earth can be tough, and even when you find them you can’t rest easy. They’re apt to fool you one way or another.

CATEGORIZED UNDER: Astronomy, DeathfromtheSkies!

Comments (16)

  1. Plutonium being from Pluto

    Yup. Cool optical illusion & demonstration of how easily our brains & eyes can be fooled. :-)

    Well done to the Terrans running the Terra mission. Nicely spotted :-)

    That would a third of a trio along with Aqua and Atmos right? 😉

    (But watch out for their evil hidden rivals the sub-terra-ien team! 😉 )

  2. Pi-needles

    high over the grasslands of Kazakhstan

    Kazakhstan eh? Did they spot Borat? 😉

  3. too much compression in the first image… almost impossible to see anything :)),

    Anyway nice image (and optical illusion) from one of the very few satellite systems (together with Aqua and Aura) that provides free daily coverage of the earth in a very good resolution for amateur forecasters (250m).

    What about the new vision for space exploration? Is the US going to scrap Ares 1 and 5?
    I would prefer to see the shuttle derived Jupiter rocket to be developed as soon as possible…, and more emphasis on private rockets doing the (hopefully) routine business of getting humans to LEO

  4. Plutonium being from Pluto

    @ 3. danezia :

    What about the new vision for space exploration? Is the US going to scrap Ares 1 and 5?

    It would seem so, yes. Looks like the rumours are now being officially confirmed. The Australian ABC news on-line site – complete with an ironic “Apollo 11 : Special Coverage – 40th anniversary of the Moon landing” banner at the top – says :

    US President Barack Obama has abandoned plans to return US astronauts to the moon by ending the costly Constellation next-generation rocket program. … “We are cancelling the program, not delaying it,” Mr Obama’s budget chief Peter Orszag said. The decision means NASA will be constrained to low-earth orbits for years to come, and transforms the aspirations of the US space program.

    See : http://www.abc.net.au/news/stories/2010/02/01/2807263.htm

    I am personally saddened & angered by this. A lot has been spent developing it already and Ares was just getting going in my view and to cut it short now seems very wasteful and short-sighted. To me it looks a bit like changing racehorses in mid-race only jumping from a thorough-bred that was already running strong onto a half-dead miniature pony. :-(

    But that’s all getting a bit far off-topic – I imagine the BA will be posting on that matter specifically soon enough anyhow.

  5. Petrolonfire

    It’s the Chiyli impact crater

    Chiyli? Chilly as in cold or chili as in hot? 😉

    It’s a cool and optical illusion; when we see craters illuminated from below, they look like domes,

    How can a hole in the ground be illuminated from below? Either the Earth is transparent (goes outside & looks down at feet – nope) or that “crater” is really a glowing volcano! 😉

  6. Plutonium being from Pluto

    PS. Too late to add via ‘edit’ & noticed this on re-reading that news item more closely :

    Getting the cancellation through Congress will be a tough mission for the administration, as MPs from Florida and other states with close ties to the space program are likely to oppose moves that could threaten local jobs.

    Here’s hoping Congress does the right thing & blocks Obama on this.

    If Americans here want to keep their manned space program going somewhere other than Low Earth Orbit anytime soon then I urge them to write to their congresscritters & tell ’em to keep Ares-Constellation alive.

    I, for one, would really love to see humans return to the Moon in my lifetime – to see the first woman step onto the regolith of that magnificent desolation & to see the first astronomer land there too!

  7. Mchl

    @Plutonum being from Pluto:

    Even if the astronomer in question is a bad one 😛

  8. Doc

    It looks like there are some other circular forms in the same image, further to the left of Chiyli, approximately above the two red-brown spots. Are these also impact craters, image artifacts, or something else?

  9. Thanny

    The direction of illumination in a 2D image doesn’t matter. Both crater pictures flip between bubble and crater for me, because both interpretations are valid, as with a Necker Cube.

    What’s relevant is that we’re looking straight down. If the image were taken at just a slight angle, the demarcation between ground and sky would suddenly exist, and the true terrain would be steadily perceived.

  10. Nuno Lucas

    Programmers for a very long time use that optical illusion to make the 3D effect of a pressed/released button on the screen. The border of the button can be nothing more that two parallel lines, one much darker than the other. By changing which one is darker you either get a pressed or raised effect.

    I’ve been told there are some people that see the inverse of the effect than the rest of us, so they can get confused if a button is pressed or released.

  11. Chanelle

    Interestingly, in the original photo, I see it as a crater. In your “flipped” image, I see it as a raised plateau type structure.

    And, being the strange creature that I am, I turned my head upside down to look at your final two photos, and try as I might, the dome still looks like a dome, and the crater looks like a crater.

  12. Brian

    Chanelle: I also couldn’t get the two images to flip when I turned my head upside-down. Apparently the brain takes the position of your head into consideration when it considers the shadows. I had to copy the images to my computer and flip them over in software in order to change them. (Which worked, of course, since both photos are otherwise the same.)

  13. AJ

    @ no. 1, Plutonium: “That would be a third of a trio along with Aqua and Atmos right? ;-)”

    Atmos? Bad idea, if you ask me… http://tardis.wikia.com/wiki/ATMOS

  14. Plutonium being from Pluto

    @ AJ Ah yes, I’d forgotten about *that* ATMOS. 😉

    Inspired by the alliterative repetition in the BA’s title here, I’ve come up with this little bit of …


    Doggrel for the day :

    Terra Afirma!
    By Stevo Raine “PlbfPL” , 2010 -Feb.-2nd

    On Terra was spied
    By the Terrans keen eyed
    A crater found by Terra sat high.
    Now Terra’s crater is quite tough to find
    But tougher for Terrans to abide
    If at terra-crater impact there then you’d be in quite a bind
    At the time that it hit you’d be Terra-fied!
    (& fried!)
    But a terran reflecting on the Terra-found crater descending
    Can be glad that it ain’t Terra-sized!


    Hope y’all like it! :-)

    Hmm … Is there a ‘Guinness Book of Records entry for getting the word “Terra” or variants thereof (sensibly) into every line of doggrel enough times? 😉

    If so, then I challenge y’all to beat that! 😉

  15. Plutonium being from Pluto

    @ 7. Mchl Says:

    @Plutonium being from Pluto: Even if the astronomer in question is a bad one?

    Oh *especially* then! 😉

  16. dcsohl

    The crater shows up pretty well on Google Maps, too. Here it is, just north of Dimitriyevskiy.


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