CometWatch – 17 August

Rosetta navigation camera (NAVCAM) image taken on 17 August 2014 at a distance of about 102 km from comet 67P/C-G.

Full-frame NAVCAM image taken on 17 August 2014 from a distance of about 102 km from comet 67P/Churyumov-Gerasimenko. Credits: ESA/Rosetta/NAVCAM

Full-frame NAVCAM image taken on 17 August 2014 from a distance of about 102 km from comet 67P/Churyumov-Gerasimenko. Credits: ESA/Rosetta/NAVCAM



  • Wes says:

    This is all very cool, I love it . But why don't ANY of our space probes/rovers have video and/or a microphone onboard? I would love to see video of the comet, or what sounds we could pick up . Oh well, I will still come to this site every day 🙂 . Good work !!!

    • Arnold Lopez-Cepero says:

      Wes - The cameras on Rosetta are, most likely, capable of taking many photo-images in rapid succession. When put together, they would constitute one or more videos of the comet. As for picking up sound, there's no air in space. It is simply dead silence.

    • Donald Q says:

      Well, there would be no audio, as we define it, in space. No atmosphere means no means of propagation of sound waves. They would need sensors that detect other parts of the electromagnetic spectrum.

    • Gary says:

      Sound doesn't propagate through vacuum...
      As for a mic on rovers, there is nothing to hear that's of scientific value. Wind is wind, here, or on Mars. It would be neat to hear the wind on another planet, sure, but it wouldn't add anything to the scientific collective.

      • Dave Robinson says:

        How can you say that the sound on another planet, such as Mars, "wouldn't add anything," unless you had listened to it and - as a result of evidence - found that to be true. On Earth, seismic activity, landslides and moving sand dunes all produce sound and listening to such sounds on Mars (for example) might produce new ideas.
        Many scientific discoveries have been made serendipitously (by accident).

    • David Sauvé says:

      @Wes: Given the distance the signal has to travel, I believe there is not enough bandwidth to send a video feed. I expect the scientists to model and map the comet nucleus in 3D instead rrom the multitude of photos. And sound does not travel in space for lack of air or water to propagate it, so audio recording would likely result in static due to various radiations...

    • Drav says:

      That's a good question Wes. I don't know if you did the experiment in Physics/Science class where you put a bell inside a glass jar and evacuate the air from the jar. It's well illustrated in this video on Youtube: Sound needs a medium (on Earth that can be solids, liquids or air) to propagate, and space is essentially a vacuum. Therefore microphones would on the whole be redundant (and seeing as payload weight of craft is a premium other instruments are preferred).

    • Nicholas T. says:

      Video would be good. But microphones would be useless for Rosetta. Sounds from the Mars rovers might be interesting, but I suspect it'd just be wind noise!

    • Mod says:

      No microphone because unless in physical direct contact to a body like this no vibrations or "sound" will travel in a vacuum. Video relies on a brief and very short frame rate, too short for instruments to pick up enough data in an image to do anything useful with. Instead a series of controlled exposures can be joined to form an animation of a body rotating or as we hope to see gaseous emissions. Hope this helps!

    • Zika says:

      It would not pickup ANY sound because there is no sound in vacuum of space.

    • Mikko says:

      A great question about the mic. When the comet approaches the Sun significant quantities of matter should evaporate from its surface, forming a suitable medium for sound to propagate in. I don't know if someone has already studied what is the sound a comet makes when passing around the Sun, but that surely is an interesting question.

  • logan says:


  • Ian Stirling says:

    There will be no sound in space - it's a hard vacuum.
    Video is really high bandwidth - and generally nothing moves.
    However - the lander has the CASSE instrument.
    It's not clear however if this can/will be configured to listen like a sweismometer on earth to sound from the comet, in real time, or only extracts small amounts of data from the signal.

  • Peter York says:

    Regarding the use of microphones, to quote from the tagline of the movie 'Alien' - in space no-one can hear you scream. Basic science - you need a medium to propogate sound waves hence, to quote Simon and Garfunkle, any spacecraft microphone would listen to the sound of silence. Video would be fine - but would require a very large bandwidth (that is, a lot of data would have to be sent in a very short time). But keep hoping - and learning - and enjoying!

    • Solon says:

      Technically there is sound in space, in the form of ion acoustic waves, but true that our ears could not hear anything out there. As for video, the light level is so low that no video camera could detect anything, unless perhaps the night vision devices like the BIPH (Binocular Photon Machine) might work, but nobody has ever tried night vision devices in space as far as I am aware.

  • Wes says:

    Aye, ok. No sound then, thanks for all the kind feedback.. So much to learn 🙂 .

  • Graham says:

    The other point about video - this comet is incredibly dark. The images are essentially false illumination because in reality the comet is about as black as a black t shirt. The data has to be processed or stretched to provide the images that are being shown. However Rosetta will be getting closer to the comet and taking ever more detailed images. Eventually a video will be produced from the accumulated stills - which essentially is what a movie or video really is.

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