The hypothesis of an underground ocean on the dwarf planet Pluto was revived by some research based on data collected by NASA’s New Horizons space probe during its July 14, 2015 flyby. Generally the hypothesis concerns an ocean of water but William McKinnon, professor of earth and planetary sciences in Arts & Sciences at Washington University in St. Louis and one of the authors of some studies on Pluto, suggested that the ocean contains a lot of ammonia.

William McKinnon was also among the authors of the research on the reorientation of Pluto caused by the weight of the ice in the Sputnik Planitia basin in the heart-shaped region. Right there under according to the hypothesis there is or at least there was in the past an ocean. Various teams of researchers conducted computer simulations to create models of the area in order to try to understand what lies underground.

The available data are far from exhaustive so various models can fit them and among them there’s one that includes the presence of an ocean in which there is a remarkable component of ammonia. The color-coded topographic image of Pluto shows in yellow and red the elevations and in blue and purple the depressions, in particular that of Sputnik Planitia, where there may be the underground ocean.

According to William McKinnon and a number of his colleagues, there’s almost certainly ammonia somewhere inside Pluto because it was detected on Charon, the largest of its moons, and on one of its small moons. McKinnon thinks it’s under Sputnik Planitia, where it forms an ocean quite noxious, very cold and salty, almost a syrup. The presence of an antifreeze such as ammonia would allow to have a liquid ocean at temperatures significantly lower than one formed almost only of water.

William McKinnon’s hypotheses go beyond trying to imagine exotic life forms that could live in such an environment. Life forms similar to the Earth’s ones can tolerate only a limited amount of ammonia so to live in an ocean scuh as that hypothesized should be very different.

In recent decades, many scientists tried to imagine life forms based on a biochemistry different from ours that could live in the methane seas of Saturn’s moon Titan or in the atmospheres of gas giant planets. Now we can expect speculations about life forms that can live in the presence of a lot of ammonia.

All this is very intriguing but also based on inferences and speculations, not on direct detections, and William McKinnon is the first to say it. It’s for this reason that he’s among the scientists who want another mission to better study Pluto and its moons. The idea would be to send a space probe built to enter the dwarf planet’s orbit with instruments that can better study its geology.

Don’t hold your breath because even if such a mission was approved today it would take a few years just to design and build the space probe. Above all, the journey would be extremely long: New Horizons took almost ten years to reach Pluto for a flyby at very high speed. Meanwhile, scientists keep on studying the available data.