LRO hit by meteoriod in 2014


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LRO as it was hit by a meteor

While taking an image in October 2014, Lunar Reconnaissance Orbiter had apparently been hit by some small object, causing it to vibrate and create the zig-zag distortions seen on the image, a cropped section of which is shown on the right.

Clearly there was a brief violent movement of the left NAC [Narrow Angle Camera]. The only logical explanation is that the NAC was hit by a meteoroid! How big was the meteoroid, and where did it hit? The physical properties and vibration modes of the NAC are very well known – during development a detailed computer model was made to ensure the NAC would not fail during the vibrations caused by the launch, which are severe. The computer model was tested before launch by attaching the NAC to a vibration table that simulates launch. The model was solid, both NACs survived the test, and launch.

Most of each NAC is sequestered inside the spacecraft structure, so only the leading edge of the baffle and the radiator are exposed to space, and thus are potential targets for impactors. From the detailed computer model, the LROC team ran simulations to see if we could reproduce the distortions seen the image. Assuming an impact velocity of 7 kilometers per second and a density 2.7 g/cm3, an impacting particle would have been 0.8 mm in diameter (~half the size of a pinhead). If the velocity was faster, then the particle would have been smaller, and if slower then larger.

For comparison, the muzzle velocity of a bullet fired from a rifle is typically 0.5 to 1.0 kilometers per second. So the meteoroid was traveling much faster than a speeding bullet. In this case LROC did not dodge a speeding bullet, but rather survived a speeding bullet!

The image is fascinating because you can see the vibrations slowly disappear as the zig-zags shrink and fade.

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14 comments

  • Dick Eagleson

    Boi-oi-oi-oi-oing!

    As the old saying goes, “Wow! I bet that left a mark!”

    It would be interesting if LRO could be retrieved at some point and a detailed forensic examination made of the pit caused by this impactor. It might have been a micrometeorite – most probably was, in fact. But there’s a non-zero chance it might also have been some sand grain-size bit of detritus whose origin was in one of the Apollo missions.

  • Dick Eagleson

    Off topic, but still – IMHO – germane:

    reCAPTCHA is getting more and more onerous to use. When you first added it to your site, I was generally only presented with one of those little picture puzzles to solve. Now, it’s averaging closer to three. The comment I just left wouldn’t post until I had “solved” six of the things. One of them not only contained none of the designated target objects, it also had no “Skip” button. I think the folks at reCAPTCHA must be suffering an epidemic of retinal decay as the only reason I can see for this recent weirditude is that many of their little puzzles are incorrectly coded.

    I like your site and like commenting here, but if it starts taking me longer to get past your robot Cerberus than it does to actually compose a comment, I’ll have to content myself with just reverting to lurker status, I guess.

  • Dick Eagleson: Thank you for the feedback on reCAPTCHA. I will consult with my software guy.

  • Alex

    Mr. Zimmerman: I agree to Dick Eagleson. I am making same observation with reCAPTCHA. It feels more and more as penalty.

  • wayne

    Dick– Your comments are always well informed, hoping you don’t bail completely!

    Ref reCAPTCHA–‘
    There is a definite trend, in my anecdotal experience, for longer & more obscure challenges. Not all the time, but enough to notice.

  • eddie willers

    “Whoa….steady old girl!”

  • Mitch S.

    Hmm, I haven’t been harassed by captcha, just check a box that “I’m not a robot”.
    Let’s see what happens this time.
    Hopefully it will be easier than the German sobriety test…

    https://www.youtube.com/watch?v=unseSFWjuqs

    Looks like LRO would have had trouble passing that test – but I’d be in worse shape if I got whacked by a micro-meteor!

  • Jor

    Dick Eagleson, I enjoy your comments, I agree that the captcha thing can be a pain sometimes, but I wouldn’t go any where.

  • eddie willers

    Hmm, I haven’t been harassed by captcha, just check a box that “I’m not a robot”.

    Me neither. I’m using the Chrome browser running on a Chromebox.

    But I always come here on the same machine. Maybe if you come here on various different devices, it wants to check you more thoroughly?

  • Mitch S

    I usually use the chrome browser on a Win 10 or a Linux (openSUSE) machine but I’m posting this on a Kindle with the Silk browser.

  • Mitch S

    On the Kindle it made me go through the reCaptcha trial.
    Never saw a captcha require so many pages of correctly answered image sets.
    Kinda felt like that German sobriety test!

  • Dick Eagleson

    Thank you all for the kind words.

    For a long time, I rarely got hit with even one reCAPTCHA picture puzzle, just click the “I’m not a robot” box and that was that. But I’ve not changed machines or my OS. My browser is Firefox, which seems to have been updating itself once or twice a month for some time now, so that may conceivably be an issue. I don’t reboot my machine very often so my IP address, even given that it is assigned via DHCP by my ISP, tends to be stable over fairly long intervals. All the updates aren’t making Firefox more stable, unfortunately. Perhaps when I kill and restart it something funny happens to cookies or something else associated with this site that makes reCAPTCHA look sideways at my sessions. Whatever is goingon,the feeling I’m getting is that the more I comment here, the more I’m grilled by reCAPTCHA – not the sort of “incentive plan” Mr. Zimmerman intends, I dare say.

  • Alex

    @Dick Eagleson & Mr. Zimmerman:

    My problem (and cause of reCAPTCHA’s overreaction) seems to be that my telecom provider changes my IP adress automatically, everytimes if I reboot my computer. Often, I need up two two minutes to come trough the significant numbers of picture puzzles that arise, esp. if had make an error.

  • wayne

    Interesting tidbits from all.

    I’m on Windows 10 pro with Internet Explorer v. 11 (also have Edge and Chrome but I’m locked into I.E. to access my work and by inertia I’m often on I.E. here. )

    –I use CCleaner, literally every 15 minutes throughout the day, and often find my I.E. browser is open & running in the deep background, phoning the Mother Ship, constantly, among other things…
    [CCleaner is free, highly recommend. Helps me cut down on “personalized search results,” and confuses YouTube over “suggested videos.”]
    (Tangentially– one needs to very careful about allowing YouTube to “access your clipboard,” I’m a big video-clip poster, but if you don’t kill these persistent cookies from Youtube–they are busily accessing anything/everything on your clipboard, until you overtly deny them permission.)

    I have always been challenged at least 1X and lately that has increased to multiple challenges, the longest being about 7-8 different screens.
    (Usually involving street-signs, cars, and business storefronts– few of which are ever in English.)

    Wikipedia says Google is rolling out “noCAPTCHA” more and more, which does utilize your IP address and mouse movements within the CAPTCHA box to determine if you are a bot or not, without additional challenges.

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