Pluto in true colors

The Truth About Pluto Colors – Four Shades of a Planet

What Does Pluto Look Like?

Like a planet, indeed! But what are the real Pluto colors?

In astronomy, most of the images do not essentially reflect what astronomic objects would really appear to our eyes.

But relax! This is not for fooling us. Those images are for us to envy, but mostly for scientists to explore and understand celestial objects’ behaviours.

New Horizons Spacecraft arrived and immediately skipped its primary mission target: Pluto in July 2015. Than the team started to collect data from the cameras onboard and initiated publishing the best Pluto and Charon pictures.

On 14 July 2015, New Horizons Team published the clearest, global and best picture of Pluto we have ever had in history. And we were absolutely thrilled.

Pluto
Beautiful Planet Pluto. Source: NASA

However that image was a combination of real visible and infrared images and was slightly deceiving in terms of color. And 3 years after the Pluto flyby, the team decided to prepare and publish a more realistic picture of Pluto with the proper and actual Pluto colors for public.

Below image was released on 23 July 2018.

Pluto in true colors
Real Colors of Pluto! Credit: NASA/JHUAPL/SWRI/Alex Parker

True Pluto Colors – What Do We Actually See Here?

Simply A Calibrated Image

This is a color-calibrated version of the original image from 2015. The original picture was captured via Ralph Multispectral Visual Imaging Camera (MVIC), 35.445 kilometers away from Pluto surface with surface details as small as 1.3 kilometers. Same properties are valid for the calibrated version as well.

Why Does Pluto Appear In Red Color On The Original Image?

Instead of a red-dominant surface color of Pluto on the original image, this image mostly reflects shades of brown, yellow and light blue together with white. But why does this image include different colors than the original?

The reason is the way MVIC creates images.

Neural combination of our eyes and brain is capable of processing and interpreting images with a limited interval of light in terms of wavelength. And this interval does not include infrared. However infrared wavelength is extremely useful when it comes to astronomy.

So in our case, the MVIC uses and combines both infrared and visible images. And the majority of Pluto’s surface particles reflect in dark red colors on infrared.

Pluto colorized
Another false color image of Pluto. This image was prepared for crystallizing the surface features. Credit: NASA/JHUAPL/SWRI/ Z.L. Doyle

What Are The Sources of Different Colors on Pluto Surface?

Generally speaking; brown and white are the dominant colors of Pluto. But you can also see the tints of yellow and blue. Did you ever wonder why? We did!

The surface composition of Pluto includes nitrogen ice together with water, methane, carbon monoxide and ethane ices. And the heavy and bright white color on surface is the direct reflection of those ices. Sounds simple, white means ice.

The white color is dominant and smooth especially on Tombaugh Regio and gets more brighter in carbonmonoxide, methane and nitrogen rich Sputnik Planitia area.
White also seems to be apportioned to rest of the surface. However there is one region with minimum signs of white color. This area is informally named Cthulhu Regio where light brown is the dominant color.

Tholins Acquire The Painting Job

The brown color is very common all over the planet surface and it feels like the white ices were distributed on top of it with different densities on different locations. However, the truth is quite opposite!

Cthulhu Regio
The brown-dominant Cthulhu Regio. Blurred part on this image belongs to Pluto’s non-encountered hemiphere. Credit:NASA/JPL

Researches show that the source of this brown color (which looks more reddish in infrared) is the tholins on Pluto surface. And tholins are formed when nitrogen and methane molecules interact with solar radiation. The tholins, complex organic molecules, are either formed on surface or (most likely) in the atmosphere, raining to the surface over time. This means the tholin layers covered the nitrogen and methane dominant surfaces, not the reverse way.

So the overall landscape color of Pluto is a result of the contest between those materials. And the white areas hint the surface and atmospheric activities where the ice molecules overcome tholins.

When it comes to variations of blue and yellow colors on northern hemisphere, scientists believe the reason is the dominance of methane ices. While the blue parts are estimated to be younger, the coloring agent of yellow zones might be the old deposits of methane ice.

Atmospheric Color of Pluto

Pluto has a weak, unstable and seasonal atmosphere. During New Horizons’ Pluto flyby, Pluto’s atmosphere was luckily available and it was glowing in blue shades similar to Earth’s (except Earth’s atmosphere might include red colors on the edge).

Pluto atmosphere
Pluto’s beautiful atmospheric haze. Credit: NASA/JHUAPL/SWRI

While the tholins on surface provide a brown color, they strangely help the atmosphere to glow in blue!

When it comes to the view of sky from the surface, Pluto differs from Earth. If you were standing on Plutoland, you’d most likely observe a dark grey or black colored sky on a sunny Pluto day, instead of a blue one. Because unlike Earth, Pluto is extremely far from her light source: The Sun.

How Would Pluto Look Like If you Were Onboard New Horizons Spacecraft?

In relation to above mentioned distance to Sun, this question frequently pops up. Would you see Pluto like it appears on this color calibrated image?

Although Pluto is far away from Sun, there is enough sunlight to enlight Pluto surface over there. Plus, Pluto has a high surface albedo (more than 1.4 times of Earth in average).

In addition, this image was captured from 35.000 kilometers away and Pluto’s diameter is roughly 2/3 of our Moons’. Considering the Moon is 384.000 kilometers away from us in average, Pluto would seem like a magnified version of Moon seen by you now: Approximately 7.3 times bigger.

So if you were staring from one of New Horizons Spacecraft‘s windows (if there were any!) during the closest flyby, that’s how you would see her. However, for being able to see more surface details with your bare eyes; you have to ask spacecraft operators for a closer and slower flyby!

References

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