If we look at the moon, it appears mostly white or yellow, sometimes blue and sometimes red. One might wonder. What color is the actual color of the moon? Does the moon really change colors, or does it have definite colors?

Color of the moon
Colors of the moon

What is the color of the moon?

Moon is grey because plenty of oxygen, silicon, magnesium, iron, calcium, and aluminum are on its surface. The color of other elements on the surface of the moon is not much in proportion and is not seen. Study says that the moon has various colors but the color that is more in proportion is grey, so it looks.

Moon from the Earth

Moon does not have its own light, it just reflects the sunlight. The moon is not a good reflector compared to the other planets or moons as it reflects only around 13 percent of the light that falls on it. We see it brighter than other planets because it is close to the Earth.

The color that we see is just a result of the scattering of light (Rayleigh scattering), the same reason why the sky is blue. The scattering of reflected sunlight can result in different colors of the moon.

As we see from Earth, the moon appears mostly yellow at night and white during the daytime. The yellow color is seen since yellow light is one of less scattered light as the light travels through the atmospheric particles. The red color though scattered least is not seen because yellow is relatively scattered more in proportion with greater abundance. During the day, the moon appears white due to excess sunlight (white light) coming directly from the Sun.

What is the cause of the blue and red moon?

The blue and red moon are seen in different circumstances. The blue color of the moon is exceptional, while the red texture on the yellow moon is often seen. As mentioned earlier, color is due to the scattering of light.

The moon appears blue when the atmospheric particles are of the right size (size close to the wavelength of blue light) to selectively scatter the blue light. This happens mostly in the regions where there is the availability of particles having such size. For instance, aerosols produced from coniferous plants can react with ozone to give such sized particles. A place with abundant coniferous plants is likely to visualize the blue moon.

Similarly, the smoke created by factories and fires can produce particles in the atmosphere with a size close to the wavelength of red light. This produces dispersion of red light, and we can see the red moon due to the abundance of red light. Also, during the rising and setting of the moon, the light coming from the moon has to travel a greater distance in the atmosphere. Due to this, the yellow light can get too much scattered from our line of sight with red light only remaining. So, the moon can appear red in such circumstances.

Blue Moon – Once in a blue moon

Blue moon, this phrase is often referred to as the moon, which is not actually blue to see but a rare moon. Each year usually offers 12 full moons, and each full moon occurs every 29 and half days. So in a year, there are approximately 11 more days. That means in three years; an extra moon can occur. This moon is called ‘the blue moon.’

The 12 full moons occur with 3 in each of four seasons in a year. But, during the occurrence of 13 full moons in a year, a season out of four has an extra full moon, i.e., a total of four full moons. So generally, one of the moons in a season with four moons is called a blue moon.

Moon from Space

Space does not have any particles to scatter the light coming from the moon, so we see only color, i.e., grey. The appearance of the moon is the representation of the minerals that make it up.

Also Read, Lesser Known Facts About the Moon

Ashwin Khadka is a PhD Scholar in Solar Cell and Aerosol Laboratory in Korea University, Republic of Korea under Korean Government Scholarship Program. He has a Masters Degree in Physics from Tribhuvan University, Kathmandu, Nepal. He is a science enthusiast, researcher and writer.