I didn't really intend to suggest that anyybody try to use the MGS map directly in Celestia. And you're right that the colors may not be quite true. But the MGS images do give a good indication of the clouds, haze, dust storms, etc., which are quite common on the real Mars.
- Hank
New colored Mars with clouds
HankR wrote:Here's a map of Mars with clouds from NASA's Mars Global Surveyor spacecraft. It's low-res and would need to be resized to use with Celestia, but it gives an idea of how Mars actually looked in April, 1999.
http://photojournal.jpl.nasa.gov/catalog/PIA02066
- Hank
Hi Hank,
Thanks for this info maybe I will once revise my cloud map.
Bye Jens
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HankR
HankR wrote:...it gives an idea of how Mars actually looked in April, 1999.
Actually, I think this isn't quite true. I believe the MGS global maps are built up over the course of a Martian day and at each location show the conditions at the time the spacecraft passed overhead. Since the orbit is sun-synchronous, the local time is the same at each location. (Mid-afternoon, I think.) So the planet as a whole would never actually look like this at any given instant.
A problem with modeling Martian clouds is than in many cases they are sensitive to the time of day. Perhaps there might be some way to use a custom shader to modulate the alpha blend based on the solar phase angle?
- Hank
Hi folks:
Don asked me to contact my contacts at NASA and try to resolve the Mars color issue. I did that but did not get a good reply. The response stated that the "true" color images of Mars from spacecraft were the Viking landers, which had color charts to compare to and filters designed to produce an accurate color. Unfortunately, I think Viking only took its pictures while on the surface. I have not had the time to check, but I suspect that the Viking mission did not snap photos from space as it approached Mars, since the spacecraft were not fully deployed until landing. Does anyone know for sure? If that's the case, then extrapolating from the surface to a full globe image would not be very accurate.
Frank
Don asked me to contact my contacts at NASA and try to resolve the Mars color issue. I did that but did not get a good reply. The response stated that the "true" color images of Mars from spacecraft were the Viking landers, which had color charts to compare to and filters designed to produce an accurate color. Unfortunately, I think Viking only took its pictures while on the surface. I have not had the time to check, but I suspect that the Viking mission did not snap photos from space as it approached Mars, since the spacecraft were not fully deployed until landing. Does anyone know for sure? If that's the case, then extrapolating from the surface to a full globe image would not be very accurate.
Frank