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This answer to Are there any photos of the Martian terminator from low Mars orbit? includes (without credit) what looks like an oft-repeated photo of Mars. A comment written from reverse image searching suggests it's from Viking-1 in 1976.

National Geographic says this is a Viking image and Universe Today says "...taken by the Viking 1 orbiter in June 1976." Forbes says "Image credit: NASA/Viking 1". While this is not really an image of the terminator, it's getting close; at the bottom right we see that the sides of tall features facing us are dark.

Since it's taken from orbit I've gone to https://photojournal.jpl.nasa.gov/Help/PIADetQuery.html and selected "Viking-1 orbiter" from the Search for Images by Spacecraft option. The resulting search query https://photojournal.jpl.nasa.gov/spacecraft/Viking%2BOrbiter%2B1 yields thumbnails of 87 images which doesn't seem include this one. Then again 87 sounds low.

Question: Which Viking-1 orbiter photo is this? When was it taken and what part of Mars is shown?

With the time and identity of (at least some of) the features in the image known, I'd like to try to figure out the foreground's proximity to the terminator, possibly using the reconstructed trajectory in JPL's Horizons as well since it includes a model for coordinates on planets and their rotation.


unidentified image presumably of Mars taken by the Viking-1 orbiter circa 1976 click for full size

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Viking Orbiter "violet-light" picture 34A13, it shows

the region east and northeast of the Argyre basin during winter in the southern hemisphere. (a) Most of the snow-covered Argyre basin is shown. This was taken just after the winter solstice when solar heating was minimal.

Further down it says the location is 47° S, 22° W

enter image description here

I found it in NASA-SP-441 Viking Orbiter Views of Mars p. 144 where it is shown in black & white. Some pictures in this document are in color. I suspect the linked image may have been re-processed more recently although I haven't found direct evidence of that. I read that this fellow was doing some of that work.

It's in the JPL PDS Image Atlas here. You can download a .img file but I don't know how to open that kind of file. The label there says the image time is 1976-07-24T10:35:26Z.

enter image description here

Just for fun, here's a similar view from Google Earth's Mars globe showing the chain of four large craters, which TIL are Lohse, Helmholtz, Wirtz, and Galle craters. At least one of those names resonates with me :)

enter image description here

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