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For several decades, scientists have gradually become aware of the geological activity of the small icy bodies in our solar system. Evidence for the presence of inner oceans has been found, for example, on Jupiter's moon Europa and Saturn's moon Enceladus, which consist of water kept liquid by internal heat. In a new study, a team of planetologists shows that Eris and Makémake, two dwarf planets in the Kuiper Belt and supposedly “icy,” may actually be showing geological activity because their surfaces have recently been renewed.

While many scientists focus on a star's habitable zone, where water can exist in a liquid state on a planet's surface, to search for worlds where life is possible, a lot of work has been done in recent decades showing that Liquid water this could exist beneath the surface of icy moons in the outer solar system, such as Europa, a moon of JupiterJupiter, or Enceladus, a moon of SaturnSaturn. If the latter have a cold surface due to their great distance from the Sun, planetary scientists suspect internal geological activity there, allowing sufficient heat production for a layer of liquid water (and other elements in still small concentrations) to persist beneath their frozen crust.

Are the icy worlds in the farthest reaches of the solar system dormant?

There are even more distant ice worlds, such as the dwarf planets Eris or Makemake, which orbit in the Kuiper Belt and beyond. The latter is located well outside the orbit of NeptuneNeptune, at a distance from the Sun that varies between 30 and 55 astronomical units. With a diameter of 2,326 kilometers, ErisEris is the most massive of the dwarf planets discovered to date, with a mass almost 27% greater than that of PlutoPluto (which is, however, slightly larger). Due to its high mass, scientists suspect that it consists mostly of rock covered by a thin layer of ice. Makémake is about 1,430 kilometers in diameter, making it the third largest known trans-Neptunian object.

Because they are so far from the Sun's heat, astronomers have long viewed these worlds as cold and inactive. But based on observations from the James Webb Space Telescope, a team of scientists suspects that the two dwarf planets are actually geologically active. The isotopic composition of its surface actually appears to indicate relatively recent renewal on the geologic time scale of geological time. They present their results in the magazine Icarus.

Icy oceans beneath the surface of trans-Neptunian dwarf planets?

The team of scientists analyzed data collected by the James Webb Space Telescope as it analyzed the frozen surfaces of the two dwarf planets. More specifically, his instruments determined the isotopic composition of the methane molecules present on the surface. Methane consists of one atom of carboncarbon and four atoms of hydrogenhydrogen, the most abundant element in the universeuniverse. However, certain methane molecules can contain deuterium instead of hydrogen: it is a stable isotope of hydrogen that, unlike it, contains a neutron neutron. According to scientists, deuterium likely formed during the Big Bang; Determining the relative concentrations of deuterium and hydrogen in methane molecules can thus allow an estimate of their origin and the conditions under which they were formed.

And the team's results are clear: the D/H ratio (which quantifies the relative concentrations of deuterium and hydrogen in methane molecules) observed in the methane molecules on the surface of icy dwarf planets is weaker than those discovered inside comets, for example unchanged since its creation. According to scientists, this is evidence that the methane present on the surfaces of Eris and Makemaké was generated and released to the surface by internal geological processes after their formation. According to their data, they therefore have a relatively hot rocky core, which probably derives its energy from the decay of radioactive elements and enables the formation of methane molecules. Their results also suggest that if these two planets had high concentrations of methane during their formation, it has likely been emitted since then. So if their rocky cores produce enough heat, could these two dwarf planets harbor an ocean of liquid water? Although more work is needed to solve this mystery, we now know that trans-Neptunian objects are not as inert as we thought…