Get your Pluto trivia down cold

It has been eight months since the New Horizons spacecraft flew past Pluto (SN Online: 7/15/15), but the discoveries keep trickling in. Mission scientists have now recapped the latest findings in five papers published online March 17 in Science. Science News has previously reported on many of these findings, but to mark those months of discovery, here are nine newsy nuggets about our favorite dwarf planet:

1. Ice is king. Frozen nitrogen, methane and carbon monoxide blanket the landscape and help shape mountains, plains and a cornucopia of alien landforms (SN: 8/8/15, p. 6). Frozen water, in fact, is what passes for bedrock on this frigid world.

2. The left ventricle of Pluto’s famous heart (informally named Sputnik Planum) might be a basin carved by an incoming space rock (SN Online: 11/10/15). The surface of this pristine ice field that’s sunken several meters below the surrounding terrain is less than 10 million years old, quite young by solar system standards.

3. Many heavily cratered regions on Pluto and all its five moons are ancient, dating back 4 billion years — not long after the formation of the sun and planets.

4. Stretching for hundreds of kilometers along the western edge of Sputnik Planum lies a jumble of mountainous cubes of water ice roughly 5 kilometers high (SN Online: 9/10/15). This rugged terrain floats on a frozen sea of nitrogen and carbon monoxide.

5. Pluto’s largest moon, Charon, is a world divided. An east-to-west gash separates two very different hemispheres. To the north the ground is heavily cratered; to the south lie smooth plains and rolling hills. Chasms might have formed when a subsurface ocean froze long ago and burst apart the moon’s surface (SN Online: 2/25/16).

6. Charon’s north pole (dubbed Mordor Macula) is red, a pole feature not found on any other planet or moon. The pole has just come out of a decades-long winter, making it cold enough to trap methane that has either escaped from Pluto or leaked out of Charon. Ultraviolet light from the sun could rework the methane into a tarry reddish blend of hydrocarbons known as tholins, which are also found at low latitudes on Pluto.

7. The chaotic dance of the other tiny moons — Nix, Styx, Kerberos and Hydra — has no equal in the solar system. All are tipped on their side and twirl feverishly (SN: 12/12/15, p. 10); Hydra spins 89 times during each 38-day trek around Pluto and Charon.

8. While Pluto’s small satellites are pretty uniformly gray, a slight red hue stains Nix’s largest crater. That could be left behind by whatever hit the moon, or it could be material excavated from underground.

9. Pluto has blue skies with about 20 sharply defined layers of haze (SN: 8/22/15, p. 7). Bring a space suit when you visit, though: The surface air pressure is about 1/100,000 that of Earth and the temperature is a brisk ‒228° Celsius.