enter image description here

I was looking at the Cassini raw images taken from Apr. 26, 2017 4:45 AM to 9:09 AM, and I noticed that some of them show a lot of white specks. Sometimes the specks appear to be streaks. What are these things?

I know the spacecraft was "diving" through the gap between Saturn and its rings; are these "ring particles" (whatever those are)? If so, then why are some of them streaking and others not?

I considered perhaps they were digital noise of some kind, but that would not explain the streaks and the random appearance of al this stuff. If they are particles, why are they so well-lit? Is it ice reflecting the sun or something?

  • 2
    $\begingroup$ Those are likely traces after cosmic rays, high energy ions arriving at very high speed from interstellar or intergalactic distances, hitting the CCD at random angle. Most of it is blocked by Earth's atmosphere, but in space they are a common noise in photography. $\endgroup$ – LocalFluff May 3 '17 at 6:30
  • $\begingroup$ Then why is it only on some of the images, whilst others are completely free of these artifacts? And, why does it leave directional streaks? These lenses have shielding (a hood), so the rays would be coming in at a sharp angle. Therefore they would not leave streaks across the surface of the image sensor. I've never seen digital noise caused by high energy particles that goes across multiple pixels in an arcing streak pattern, except inside a particle accelerator where that's the intent. $\endgroup$ – CommaToast May 3 '17 at 6:39
  • 2
    $\begingroup$ Alot of shielding is required to stop them. They have so much energy that if they hit an atom in the metal hood, it is split into a cascade of multiple secondary particles. The two main traces in this image could come from the same primary impact. A certain fraction of the time an ion comes in at oblique angle to the CCD and makes long traces that we easily notice in some of the images. $\endgroup$ – LocalFluff May 3 '17 at 6:53
  • 1
    $\begingroup$ @LocalFluff there's this question and answer for example. $\endgroup$ – uhoh May 3 '17 at 13:47
  • $\begingroup$ Some of this may also be dust impacting the shroud/telescope causing a shower of ionized gas and nanometer-sized grains. The Kronian system is very dusty ;) $\endgroup$ – honeste_vivere Aug 21 '17 at 15:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Browse other questions tagged or ask your own question.