The secret to all of that activity is Pluto’s probable underground ocean. The water ice on the surface of the world suggests ...

Why was Pluto reclassified as a dwarf planet? One might think that it’s purely a matter of size. Mercury, the smallest of the ...

But instead of surface water being evaporated by the Sun and falling as rain, Pluto experiences a daily nitrogen cycle. Nitrogen is heated and cooled as Pluto rotates. A New Horizons image of ...

Why was Pluto reclassified as a dwarf planet? One might think that it’s purely a matter of size. Mercury, the smallest of the ...