Markus,
I too have thought about this. I did think that it could be the Martian atmosphere, and while it is a factor, it really is not a major one.
Since reading your original post yesterday, my brain has been "number crunching" for possible reasons. And I think I've come up with the main reason - resolution!
And it was thinking about the New Horizon's approach images of Pluto that cemented this thinking for me.
If you think about all the bodies in our solar system, they all have a lot of surface detail. However, from Earth, this detail is modest at best (Jupiter), or the vaguest of shades (Ganymede). Of course Jupiter is larger,
but when you look at the resolution per square minute of arc, or better still per square second of arc, the amount of actual detail is exactly the same between Jupiter and Ganymede. Same with Mars. The tyranny of distance is the killer as all these details get all mashed up and merged into one blurry blob.
Remember the images from Pluto as New Horizons approached? The first pics that showed a disk showed bugger all detail (nil resolution really). As the probe got closer and closer, the resolution of the cameras was able to finally begin to distinguish the details until we were able to get the details that blew our socks off!
The Moon is much the same. From Earth, we just cannot make out the Apollo landing sites - distance means we don't have the resolution capacity to do so. Not even the HST can see the Apollo landing sites.
Add to Mars its surface compositions, and all we get at the dark and light patches, with the curiosity of these dark patches appearing "green", which I think is a curiosity of light with red and green being complimentary colours - there is nothing green on Mars... The over all red colouration of Mars, this goes a long way to reducing contrast and hence lower resolution as well.
If you were on Mars looking back at Earth, you would also have the same problem resolving detail. Of course there are some differences between Earth and Mars, but the same resolution issues apply, and this would also mean that you would also encounter the same blurring and merging of details so that you would not see the same surface detail that is even visible from the Moon, littlelone the ISS.
Alex.
