by Two dwarf planets within our solar system, named Eris and Makemake, may exhibit enough geothermal activity to hold oceans of liquid water inside, according to modeling that describes new observations made with the James Webb Space Telescope.
“We see some interesting signs of warm times in cool places,” said Christopher Glen, a planetary geochemist from the Southwest Texas Research Institute, in statement.
Found deep in the Kuiper beltEris is the icy world, when it was discovered in January 2005, spent Pluto‘status in the Solar system into a crisis. Only 44 kilometers (27 miles) smaller than Pluto but 25% larger in length due to a greater concentration of rock in its core, Eris became the prototype dwarf planet. Pluto had to follow suit. Makemake (pronounced “Mah-kay-Mah-kay“) two months after Eris, and at 1430 km (888 miles) across it is about 1000 km (about 600 miles) smaller than Eris and Pluto.
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The great distance they have from the sun —– Eris is currently 14.4 billion kilometers (8.9 billion miles) away and Makemake is 7.7 billion kilometers (4.8 billion miles) away – little is known about the distant ones dwarf planets.
However, recent observations with the James Webb Space Telescope have shed new light on life, discovering a surprising origin for the frozen methane ice on their surface.
“We found evidence that points to thermal processes that produce methane from within Eris and Makemake,” said Glen.
Methane is called a hydrocarbon, in that it is made from a mixture of hydrogen and carbon atoms (specifically, one carbon atom and four hydrogen atoms.) Those atoms can come in different flavors, or “isotopes,” containing the same number protons but different numbers of it neutron.
If the methane on the surfaces of these dwarf planets had accreted from the initial planet-forming disk around the young sun 4.5 billion years ago, they would have a certain isotopic ratio between two isotopes of hydrogen — regular hydrogen, with one proton and zero neutrons. , and deuterium, with one proton and one neutron. The hydrogen isotope ratio measured by the JWST is, however, different from the ratio that would be expected if methane were primordial, as we see most of it. Comets.
“The deuterium/hydrogen ratio points to a geochemical basis for methane produced in the inner world,” Glen said. “Our data suggests that the rocky cores of these worlds have elevated temperatures so that methane can be cooked. Molecular nitrogen could also be produced, and we see it on Eris.”
That is, hydrothermal reactions, or metamorphic activity that refers to heat and pressure acting on rocks, must have produced the deep methane in Eris and Makemake. Then, that methane must have made its way to the surface through gasification, or even volcanism.
To form methane in this way, temperatures above 150 degrees Celsius (about 300 degrees Fahrenheit) are required. These temperatures could only come from radioactive isotopes present within the rocky cores of each dwarf planet releasing heat as the isotopes decay.
“Hot cores could also indicate that there may be sources of liquid water beneath their icy surface,” Glen said, raising the possibility that Eris and Makemake might have habitable oceans.
Methane outgassing on the surface may have been occurring until recently (geologically) according to another isotope ratio, between carbon-12, which has 6 protons and 6 neutrons, and carbon-13, which has 6 protons and 7 neutrons there.)
“If Eris and Makemake hosted, or perhaps could still host, hot, or even hot, geochemistry in their rocky cores, cryovolcanic processes could deliver methane to the surfaces of these planets, perhaps in a few decades down geologically,” said Will Grundy from Lowell Observatory, who led the initial JWST observations. “We found a carbon isotope ratio that suggests relatively recent resurfacing.”
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Interestingly, the models developed to describe the formation and gasification of methane on Eris and Makemake could also be applied. Saturn‘ moon Titan. Research published earlier this month suggests that methane and other carbon-based molecules important to life may not be able to reach Titan’s subsurface ocean after it has hung around the surface for a while, where hydrocarbons are abundant. This called into question the possible habitability of Titan’s ocean hypothesis. However, if methane and other gases can form geothermally within Titan’s rocky core, as they do on Eris and Makemake, then Titan’s oceans could provide a source of carbon chemistry from within the planet rather than from its surface.
The results of the methane observations on Eris and Makemake are described in a paper published in the April 2024 issue of the journal. Icarus.
