Pluto might have an underground ocean

Artistic concept of the New Horizons space probe near Pluto and its satellite Charon (Image Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Artistic concept of the New Horizons space probe near Pluto and its satellite Charon (Image Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)

The New Horizons space probe was launched on January 19, 2006 and should reach Pluto in the summer of 2015. It should fly within 10,000 km (6,200 miles) of the dwarf planet to map its surface and that of its satellite Charon.

In the meantime, planetary scientists Guillaume Robuchon and Francis Nimmo of the University of California at Santa Cruz are examining the possibility that Pluto has an underground ocean analyzing the possible signs of its existence. The idea may seem absurd but it’s possible that Pluto contains a sufficient quantity of radioactive material, especially potassium, that it can generate with their decay the heat necessary to maintain a layer of liquid water.

Radioactive potassium is found in abundance in meteorites created in the early solar system and it would be enough that Pluto had a tenth of the amount found in meteorites to generate enough heat to have an ocean of liquid water.

Guillaume Robuchon and Francis Nimmo are therefore focusing on the possible signs that an ocean would produce on the surface of Pluto, composed of a layer of nitrogen ice on a layer of water ice. This way, when the New Horizons space probe reaches the dwarf planet and transmits its images, they can begin immediately to look for these signs.

When a planet spins, its angular momentum tends to push the material towards the equator, forming a bulge. But if Pluto had an ocean underneath the surface the ice would flow, reducing the bulge. According to calculations, if there’s liquid water the bulge should be about 10 km high (6 miles), enough to be detected by the New Horizon probe.

Another element to be studied is given by Pluto’s surface characteristics. The presence of fractures on the surface layer of nitrogen ice and in that case their characteristics may be another indicator of the existence, or nonexistence, of a layer of liquid water.

Inevitably, if they find that there’s actually liquid water on Pluto, scientists will start wondering if there’s a possibility that some form of life has developed there. To our knowledge, on this dwarf planet the chemical elements necessary for life are too scarce but at this point we must expect any surprises.

In recent decades many discoveries have enabled us to expand the theoretical habitable zone to places that were once considered completely dead. Continuing discoveries about Europa, one of the major Jupiter’s satellites, now raise a limited surprise. Titan and Enceladus, two of Saturn’s satellites, are also possible candidates as hosts of life forms. However, nobody would have thought of Pluto in those terms.

Obviously the theory of Pluto’s underground ocean is still to be verified, but the important thing is that at this point scientists consider the possibility that other dwarf planets in the Kuiper Belt have liquid water and the elements needed to develop the life. Our horizons keep on expanding!

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