The Martian Sky |
The Martian Sky |
Oct 11 2009, 06:41 PM
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IMG to PNG GOD Group: Moderator Posts: 2254 Joined: 19-February 04 From: Near fire and ice Member No.: 38 |
I have been attempting to make computer generated images of the Martian atmosphere, both as seen from the surface and from space. To check the results I have been looking for spacecraft images to use as ground truth. I have found lots of images - by far the best ones I have found are from UMSF in this thread: http://www.unmannedspaceflight.com/index.php?showtopic=3324
However, I'm always looking for more ;-). So if anyone knows of more and/or better images I'm interested in them. What would be best are mosaics showing the sky from the horizon (with the horizon/surface visible) and towards the zenith. The sky varies a lot because of variable amount of dust but the general impression I get is that the sky is bright near the horizon (usually brighter than the surface) but gets much darker higher in the sky. There is probably a fairly large, bright area in the sky near the sun, possibly less reddish (lower R/B ratio) than parts of the sky farther from the sun. I'm already getting fairly interesting results, this one has a field of view of 90 degrees: (needless to say this one is 'overexposed' near the horizon; dynamic range is sometimes a problem) The problem is that even though this may not be bad the limb currently appears far too bright as seen from space : This shows that my atmospheric model is erroneous in some way - I suspect that as seen from the surface the Martian sky is darker high above the horizon than I have been assuming. |
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Sep 15 2022, 10:32 PM
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Senior Member Group: Members Posts: 4256 Joined: 17-January 05 Member No.: 152 |
This MSL navcam image:
https://mars.nasa.gov/msl-raw-images/proj/m...NCAM00558M_.JPG was taken at around 20:24 LMST, when the sun was around 23 deg below the horizon according to http://www.greuti.ch/msl/clock_and_filenames.htm. You can still see some twilight glow in the sky, as this low-pass filtered (and half-sized) version shows: This view is towards azimuth 140 deg, and the sun was at azimuth 242 deg, so the brightening of the sky towards the right of the frame is consistent with a twilight glow. On earth, twilight would be completely over well before this, when the sun is around 18 deg below the horizon. Do we expect martian twilight to last longer than earth's, given the dominance of dust scattering? The length of twilight will presumably depend on the atmospheric tau, though judging from the daylight images tau was fairly average on that sol. |
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