|Io, the volcanic hate-pizza world. I mean, look at it: It makes Deadpools fave look nice. Every swirl is a lava flow, every black spot an active volcano. It hates everyone. £30 says that someone tries to land there before 2100AD|
...but Saturn is yellow, Uranus and Neptune are blue, and that's it, right?
Well of course not, or that'd be the end of this article.
The thing about other worlds is that they are, well, worlds. There's a lot of room on each for lots of different colours. Lets take a look at the Moon, our nearest neighbour: Since it's so conveniently close you may actually be able to stick your head out the window and do this, and it probably looks a silvery white colour.
But, if you land on it, you see a landscape like this:
|The Moon: A smorgasboard of grey|
|Turquoise particles of lunar soil, courtesy fo JPL.|
|Green and yellow lunar soil, courtesy of JP..|
|Red and plum coloured soil particles, courtesy of JPL.|
|Above: Orange lunar soil, near 'Shorty' crater. Courtesy of JPL/ NASA.|
Patches of oddly coloured soil can be found all across the Moon, where one impurity or another has come to dominate for some reason.
So, the colour of the Moon depends on how closely, and where, you look at it.
How about Mars? It's red, right?
Uh-uh. To keep this manageable, let's just focus on the Martian sky:
No human has ever been to Mars, so what we know of the colours there comes from cameras. And a lot depends on how your calibrate your camera: Even a fairly small change can turn an alien sky....
....into an Earth like one:
That's caused a lot of 'NASA is hiding the truth about Mars!*' stories over the years. But, even when you get the colour balance right, the Martian sky really does change colour from hour to hour. During the day the sky is technically a faint blue**, but endless dust in the atmosphere changes it to a light pink or butterscotch:
|Above: The view from Opportunity rover. Courtesy of JPL/ Cumbrian sky.|
When it's cloudy the sky can appear white, or grey:
|Above: A winters day at the landing site of the Viking spacecraft. Courtesy of NASA|
|A Martian sunset, captured by the Curiosity rover. Courtesy of JPL.|
Mars actually gives pretty good value for money when it comes to spectacular skies.....
|I don't remember where on Mars this is, possibly the arctic plain where the Phoenix lander explored? But look at that sky....|
|Above: Mercury with the colour vaiations exaggerated enough to see.|
We could keep going all day with examples of how colour is a complicated question on other worlds: There's 'enhanced colour' where a computer program brings out colour differences too subtle for the human eye to detect. Then there're colours beyond the range of a human eye, like infrared and ultraviolet, which are very important on worlds like Titan: There the sky is opaque orange in visible light, but clear in the infrared - so when you see maps like these, taken from space, of Titan's methane/ethane lakes you're actually looking at infra red colours no normal eye can see.
|Above: Titan's lakes, easily visible in these infra-red colours, but obscured by orage smog in visible light. Courtesy of JPL/ NASA.|
Elsewhere in the Universe:
China plans a dockable space telescope
Blue Orgin opens its doors to reporters
ESA probe find vast 'magnetic void' around comet
* I'm not saying they aren't hiding the truth about Mars, just that if they got the colour wrong it's more likely they just ballsed up the color balance.
** The process that makes Earth's sk blue, Rayleigh scattering, also works on Mars. But the yellow/pink colur of alll the dust in the air overpowers it on all bu the calmest days.