Pluto in a Minute: How Similar are Pluto and Charon to the Earth and the Moon?


By: NASA New Horizons

Originally published on Jul 8, 2015

What’s cool about Pluto? Get a quick peek at the latest science in this daily update from NASA’s New Horizons mission, on track for a flight past Pluto on July 14, 2015.The Pluto-Charon system is a lot more Earth-Mook-like than you’d think. This is Pluto in a Minute.

Let’s start with the similarities between the two planets first. They’re not that similar, but they do share some characteristics. Both Pluto and the Earth has nitrogen-based atmospheres, and both planets are also colored. Pluto has a reddish color, and the Earth, as we know, is green, brown, and predominantly blue.

Both planets also have relatively large moons. Our moon is a quarter of the size of the Earth and Charon is half the size of Pluto. And those two moons are similar as well. Our moon has an extremely tenuous atmosphere; whether or not Charon does have an atmosphere similar to our Moon’s is something New Horizons is going to check out. And both these moons are grey, though for different reasons. Our Moon is grey because of basalt or anorthosite, and Charon is grey from ice. And both these grey surfaces are heavily cratered, at least, we know that our own Moon’s is, though scientists suspect that Charon has its fair share of craters as well.

And, interestingly, both those moons were formed from impact events. Our own Moon was formed from debris after a Mars-sized planet smashed into the early Earth. Similarly, Charon was formed when a Pluto-sized body smashed into a young Pluto.
And one final commonality: both these moons are tidally locked to their home planets, which means they show the same face to the planet at all times.

For more on Pluto check out the New Horizons websites and tweet your question using the hashtag #PlutoFlyBy. And come back here tomorrow for more Pluto in a Minute.

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