3

This may be a trivial question, but why did the amount of dirt on the ICC lens cover change so much between the two exposures? How much time elapsed between the two images? When will it be safe to remove the lens cover? Is the same cover used to protect against dust storms later on?

Image 1 is the later one, taken at 13:59 on the same day:

enter image description here

image 2 taken at 13:34: enter image description here

Hobbes
  • 127,529
  • 4
  • 396
  • 565
Bruce G
  • 41
  • 3
  • https://mars.nasa.gov/insight/multimedia/raw-images/?order=sol+desc%2Cdate_taken+desc&per_page=50&page=0&mission=insight

    The two on the right. NASA specifically said that the junk in the image was dirt on a lens cover

     – Bruce G Nov 27 '18 at 18:02
  • Sorry. It's the ICC, not the IDC – Bruce G Nov 27 '18 at 18:04
  • 1
    I edited the question to avoid further confusion – Bruce G Nov 27 '18 at 18:16
  • I've added the images. Timestamps are visible on the page you linked, so that answers that part of the question. – Hobbes Nov 27 '18 at 18:45

3 Answers3

3

It appears that the question was actually about the two pictures taken by the ICC immediately after landing (I was under the impression that the second version was just a digitally processed version of the first image when I was watching the live event, but it turns out that they are two separate images).

So here is the first image, with the time stamp 13:34:21.

InSight photo 1

Here is the second image, with the time stamp 13:59:31, taken approximately 25 min after the first image.

InSight photo 2

In order to compare the two images, I made a GIF animation:

InSight GIF

The first image is the one with more dense black spots in the upper right corner.

From here at least two things clearly stand out:

  • Overall, the black spots are moving downward. This is most probably due to gravity.
  • Especially towards the middle, many black spots are disappearing.

I am not an authority on InSight, and I can only conjecture here that the black spots are some sort of condensate (possibly water), and sublimation is responsible for the disappearance of the spots.

timur
  • 157
  • 1
  • 5
  • 1
    Yes. Thank you. Those are the two images I was referring to. Sorry for the confusion on the camera.

    I later did see the time stamps in NASA's comments, so it does appear that in many cases dirt is dropping off, but also note the rock ini the foreground that loses several spots, but also picks up new ones. Likewise, throughout the image, there are places were more spots have appeared on the second image.

    I noticed this as I was attempting to combine the two images in Photoshop, using clear areas from one image to fill in obscured areas on the other.

     – Bruce G Nov 27 '18 at 18:33
  • 1
    And thanks for the conjecture about condensation. I hadn't considered that – Bruce G Nov 27 '18 at 18:34
  • 1
    What about wind? – timur Nov 27 '18 at 18:35
  • @BruceG: What you say "more spots appeared" may be the result of the spots moving along the surface of the lens. If you look at the animation, you will see what I mean. – timur Nov 27 '18 at 18:38
1

This is the first image:

enter image description here

Here is the second image:

enter image description here

In the first image, beyond the dust particles, there is an almost unobstructed view of the surrounding and the horizon. In the second image, we see that there are obstructions, and it is obvious that the camera is placed somewhere on top of the main body of the craft.

Now, here is a schematics of the craft:

enter image description here

This shows that there are two cameras, one attached to the Instrument Deployment Arm (Instrument Deployment Camera), and one on the side, below the deck (Instrument Context Camera). All of the above lead to the conjecture that the first picture was taken by the ICC, while the second one was taken by IDC.

Finally, it is nice to see that my conjecture is confirmed by NASA here and here.

timur
  • 157
  • 1
  • 5
  • There are two images covered with dust specks. See https://mars.nasa.gov/insight/multimedia/raw-images/?order=sol+desc%2Cdate_taken+desc&per_page=50&page=0&mission=insight The amount of dirt and the placement of some of the dirt changes between the two views. What accounts for this? Unfortunately I don't see a time stamp on the images so it's hard to know which one was actually taken first.

    I don't know how to

     – Bruce G Nov 27 '18 at 18:01
1

The images are taken half an hour apart, I suspect the first image was taken shortly after landing. That would mean the dust that was sent flying when the spacecraft landed has had time to settle in the second image.

Hobbes
  • 127,529
  • 4
  • 396
  • 565