Ocean salinity

In a paper published in the journal Icarus, Alex Nguyen, a graduate student at Washington University in St. Louis, used mathematical models and images from the New Horizons spacecraft to take a closer look at the ocean that he says likely covers Pluto beneath a thick layer of nitrogen, methane and water ice. (Image: NASA)

Surprise: an ocean of liquid water on Pluto

They estimate that Pluto's ocean is, at most, about 8% denser than seawater on Earth, or about the same as the Great Salt Lake in Utah (but much less salty than the Dead Sea.