.jpg "Sky Colours on Other Planets: What Would You See on Mars or Venus?")
Table of Contents
Sky Colours on Other Planets: What Would You See on Mars or Venus?
The Science Earth’s Blue Skies
Conclusion: The Beauty of Extraterrestrial Skies
The one enduring occurrence we witness throughout the world is the sunrise and sunset. Depending on the season and the location, the effects of the sun’s movement may vary. However, one common association we all have is that the sky turns blue when the sunrises, and black after sunset. The exposure to the sun has a varied effect on all the planets. What colours the sky blue? The colour of a planet’s sky is determined by its chemical composition and the angle at which sunlight hits the atmosphere.
| Planet | Sky Colour | Reason |
| Mercury | Black | Although Mercury is closest to the sun, its low surface gravity and proximity to the sun make it nearly impossible to hold onto a significant atmosphere. Thus, there are no chemicals to capture and spread the sunlight. Hence, Mercury’s skies have no distinct colour and simply appear black. |
| Venus | Orange | Venus is the closest planet to Earth and the second closest planet to the sun, but it receives far less sunlight than Earth. This is because the Venusian atmosphere is around 90 times denser than Earth’s. Sunlight cannot easily penetrate Venus’s atmosphere, and this makes it look like Venus is drenched in the eternal orange colour that we associate with sunrise and sunset. |
| Earth | Blue | Earth has earned the moniker of the “Blue Planet” because its water bodies reflect a blue colour and make the entire planet look blue from space. Earth’s skies appear blue because they scatter blue light in the atmosphere which is caused by the combination of chemicals and the angle at which sunlight hits the atmosphere. |
| Mars | Red | The sky and the surface of Mars are red, hence the name – Red Planet. Due to a combination of factors such as oxidation of Martian rocks, frequent dust storms that spread the dust particles across Mars’ atmosphere, and low surface gravity, the red dust particles settled in the atmosphere. Hence, Mars has a red sky. |
| Jupiter | Dim Blue | Jupiter is also believed to have blue skies, though it is much dimmer than Earth. This is because Jupiter receives less sunlight than Earth. The exact cause of Jupiter’s blue skies is unknown, but it is assumed to be similar to what happens on Earth. |
| Saturn | Yellow | Though Jupiter and Saturn have many common aspects, they both have different coloured skies. The yellow colour of Saturn is attributed to the presence of ammonia crystals in the upper atmosphere which scatters the incoming yellow light across the sky. |
| Uranus | Cyan | Uranus’ upper atmosphere is covered in a permanent haze that obscures any details on the planet. Its sky colour is believed to be cyan due to the presence of methane in its atmosphere that scatters both green and blue light. |
| Neptune | Blue | Neptune has a very similar composition to Uranus, and methane is believed to be the common factor behind the colour of both their skies Yet, Neptune has a blue sky, similar to Earth. Though the exact reason is not known, it is mostly believed that this may be due to the extreme storms on Neptune. |
When the sunlight reaches the atmosphere, it is scattered in all directions by the gases and particles in the air. Light energy travels in waves. Some light travels in short, choppy waves, others in long lazy waves. Blue light is scattered more than the other colours because it travels as shorter and smaller waves. Hence, the sky looks blue most of the time.
On the horizon, the sky fades from light blue to white colour. The sunlight that reaches us from low skies passes through more air than the sunlight from above. Thus, passing through all the air, the air molecules and particles scatter and re-scatter the blue light many times and in many directions. In the Earth’s atmosphere, these particles are primarily nitrogen and oxygen molecules.
The phenomenon that gives us our blue sky was first explained by British scientist Lord Rayleigh. Hence, it is named after him and known as Rayleigh scattering.
Other planets and moons in the solar system have unique atmospheres that result in different sky colours. Saturn’s largest moon, Titan, has a thick nitrogen-rich atmosphere that scatters sunlight and gives it a hazy orange sky. Exploring extraterrestrial skies gives us an idea of the composition of its atmosphere and potential for life on the planet.
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