On Earth, the sky is blue.
What color would the sky be on other planets in our solar system? What about outside the solar system? Are there planets with purple skies, or green skies? Or are the all just blue?
$\begingroup$
$\endgroup$
5
-
$\begingroup$ We have seen pictures from Mars and Venus. They aren't blue:-) $\endgroup$– Rory AlsopCommented Jan 19, 2019 at 21:32
-
3$\begingroup$ On Mars, the sky is red and the sunset is blue $\endgroup$– pelaCommented Jan 19, 2019 at 21:39
-
1$\begingroup$ Terrestrial Exoplanet Skies – I've Built a Visual Sky Chart. Is it Accurate? $\endgroup$– uhohCommented Jan 20, 2019 at 2:09
-
$\begingroup$ Also astronomy.stackexchange.com/questions/24804/… $\endgroup$– AlchimistaCommented Jan 21, 2019 at 11:00
-
1$\begingroup$ space.stackexchange.com/questions/24108/… $\endgroup$– AlchimistaCommented Jan 21, 2019 at 11:02
Add a comment
|
3 Answers
$\begingroup$
$\endgroup$
On Mars, it's pink because of the rust in the air. But it's blue near the sunset, where light doesn't get to bounce off the iron and be reflected red.
On Venus, it's yellow because of sulfuric acid gas. Note the white object on the ground:
Titan sky is blue with yellow sunsets, according to this rigorous simulation:
All other planets either
Only have a hard surface thousands of mles deep, or
Have no atmosphere, and a black sky.
$\begingroup$
$\endgroup$
2
The color you can see in the sky depends on two things, first the color (if you want to be more specific, the emission spectra of the light of the star) of the light shining, this is the Sun in our case (but may be another star in order to answer your question about outside the solar system), and second depends on the chemical components of the atmosphere of the planet in question, because this atmosphere is the reason for what is called the absorption lines.
Absorption light is something like that, if you have white light and a gas with green absorption lines, then after crossing the gas the light will turn the opposite of green, I don't know what color that is.
In conclusion if our atmosphere changes (for some unknown reason) here on planet Earth, then the color of the sky is going to change.
-
1$\begingroup$ Absorption plus scattering of different types plus refraction. Based on absorption only we would have a sun white sky dome here on earth. But correct is with a change in atmosphere we might see change in colours. $\endgroup$ Commented Jan 21, 2019 at 11:07
-
$\begingroup$ I have to comment that the sky on Earth varies considerably in color. It can change with season, time of day, atmospheric contaminants, etc. However, I guess that most people would consider the sky to be blue. $\endgroup$ Commented Feb 12, 2019 at 3:09
$\begingroup$
$\endgroup$
9
Atmospheric color has to do mainly with how the elements that make up the atmosphere scatter light. On Earth, the atmosphere of around 20% $\require{mhchem}\ce{O2}$ scatters higher-frequency wavelengths such as the blues and ultraviolets, which gives it its blue hue. On Luna there is an extremely sparse exosphere which does not noticeably scatter light, which in turn causes the sky to be black even though it receives the exact same amount of solar radiation as the top of Earth's atmosphere.
Same story with Mercury as Luna: an extremely thin exosphere causes the sky to be black. Venus is cloaked in a thick atmosphere of carbon dioxide, both the thickness and composition of which is responsible for the orange atmosphere you would see on the surface (if you survived long enough to see the surface). Mars has a thin $\ce{CO2}$ atmosphere, which gives an orangish-brown sky.
As for the gas giants I don't know off the top of my head, though there is a NASA simulation that shows sunset colors on some of the gas/ice giants if you can find that.
-
1$\begingroup$ I've edited your answer, but as a new contributor it might be worth reviewing the help center topics and looking at how other answers are written so you get a better idea of our site's expectations. The How to Answer page notes that "We don't expect every answer to be perfect, but answers with correct spelling, punctuation, and grammar are easier to read. They also tend to get upvoted more frequently." $\endgroup$ Commented Jun 18 at 3:30
-
1$\begingroup$ @ChappoHasn'tForgotten you have put superscript instead of subscript for the chemical formulas :) $\endgroup$ Commented Jun 18 at 4:41
-
1$\begingroup$ Thanks @ChappoHasn'tForgotten, ill remember that next time! Though it does look like you switched O2 to CO2 when describing Earth's atmosphere, I'll go fix that though. $\endgroup$ Commented Jun 19 at 19:50
-
1$\begingroup$ Never mind, looking at the edit log it looks like it was @uhoh who changed o2 to co2, no worries though $\endgroup$ Commented Jun 19 at 19:57
-
1$\begingroup$ The image in this answer suggests Titan has a blue sky from Raleigh scattering (like Earth) but the Sun appears red/orange/yellow on the horizon because of absorption of shorter frequencies (like Earth). However, this might be the basis for a good question about the difference in Raleigh scattering in N$_2$-rich atmospheres when O$_2$ is present. And/or: when we analyse a star's light through the atmosphere of its exoplanet, is Raleigh scattering a factor or is that only observed from "beneath" the sky (i.e. on the planet's surface)? $\endgroup$ Commented Jun 21 at 5:01