Every so often, an astronomical artist gets lucky. As the New Horizons space probe closes on minor planet Pluto after its nine-year voyage, I'm astounded by how close I came to accurately depicting Pluto in 1979.
I'd like to claim prophetic powers, but the painting was guided by the reasonable assumption that Pluto likely has a periodically active atmosphere that distributes powdery exotic frosts into lowland areas. The reddish color of the higher features is caused by tholins – hydrocarbons common in the outer solar system. The partial circular arcs would be caused by flooding of craters by slushy exotic ices. Pluto is apparently more orange than I painted it, however; I assumed the exotic ices would push colors more into the whites and grays.
This page went viral during the week of the New Horizons encounter. Some commenters on blog sites such as Daily Kos and Slate took me to task for neglecting to paint Pluto's iconic "Heart," while others pointed out that there is indeed a vaguely heart-shaped squiggle at the upper left of the painting! ("Conspiracy theorists, start your engines," joked a writer on Yahoo News). A few people noted that the NASA image was rather different than the later images, but the July 7 photo was one of the last showing the hemisphere of Pluto that is turned eternally toward the moon Charon and was one of the first to show features of scale comparable to those depicted in the artwork.
The theory behind the painting turns out to be more or less correct: exotic ices, such as frozen nitrogen and methane, fill lowland basins and form glacier-like features in the heart-shaped feature unofficially named Tombaugh Regio. Pluto's tenuous nitrogen atmosphere was revealed as a ghostly halo surrounding the planet. Higher surface features are indeed generally darker, but I did not anticipate Pluto's 2-mile-high mountains of water ice, assuming such features would have been worn down by eons of meteoritic bombardment and mountains would be more modest. Instead, it seems new water ice is continually exposed as the more volatile ices escape to space at a rate of perhaps 500 tons per hour.
Enhanced color mosaic of New Horizons images of Pluto (NASA/JPL)
Nitrogen glacier flows on Pluto; Charon in distance; oil painting by Don Dixon, 2016