A team co-led by Southwest Research Institute found evidence for hydrothermal or metamorphic activity throughout the icy dwarf planets Eris and Makemake, situated within the Kuiper Belt. Methane detected on their surfaces has the tell-tale signs of warm and even hot geochemistry of their rocky cores, which is markedly different than the signature of methane from a comet.
“We see some interesting signs of hot times in cool places,” said SwRI’s Dr. Christopher Glein, an authority in planetary geochemistry and lead writer of a paper about this discovery. “I got here into this project considering that enormous Kuiper Belt objects (KBOs) must have ancient surfaces populated by materials inherited from the primordial solar nebula, as their cold surfaces can preserve volatiles like methane. As an alternative, the James Webb Space Telescope (JWST) gave us a surprise! We found evidence pointing to thermal processes producing methane from inside Eris and Makemake.
The Kuiper Belt is an unlimited donut-shaped region of icy bodies beyond the orbit of Neptune at the sting of the solar system. Eris and Makemake are comparable in size to Pluto and its moon Charon. These bodies likely formed early within the history of our solar system, about 4.5 billion years ago. Removed from the warmth of our Sun, KBOs were believed to be cold, dead objects. Newly published work from JWST studies made the primary observations of isotopic molecules on the surfaces of Eris and Makemake. These so-called isotopologues are molecules that contain atoms having a distinct variety of neutrons. They supply data which might be useful in understanding planetary evolution.
The JWST team measured the composition of the dwarf planets’ surfaces, particularly the deuterium (heavy hydrogen, D) to hydrogen (H) ratio in methane. Deuterium is believed to have formed within the Big Bang, and hydrogen is essentially the most abundant nucleus within the universe. The D/H ratio on a planetary body yields information concerning the origin, geologic history and formation pathways of compounds containing hydrogen.
“The moderate D/H ratio we observed with JWST belies the presence of primordial methane on an ancient surface. Primordial methane would have a much higher D/H ratio,” Glein said. “As an alternative, the D/H ratio points to geochemical origins for methane produced within the deep interior. The D/H ratio is sort of a window. We are able to use it in a way to look into the subsurface. Our data suggest elevated temperatures within the rocky cores of those worlds in order that methane may be cooked up. Molecular nitrogen (N2) could possibly be produced as well, and we see it on Eris. Hot cores could also point to potential sources of liquid water beneath their icy surfaces.”
Over the past twenty years, scientists have learned that icy worlds may be way more internally evolved than once believed. Evidence for subsurface oceans has been found at several icy moons similar to Saturn’s moon Enceladus and Jupiter’s moon Europa. Liquid water is one in all the important thing ingredients in determining potential planetary habitability. The potential for water oceans inside Eris and Makemake is something that scientists are going to review within the years ahead. If either of them is habitable, then it could turn out to be essentially the most distant world within the solar system that would possibly support life. Finding chemical indicators of internally driven processes takes them a step on this direction.
“If Eris and Makemake hosted, or perhaps could still host warm, and even hot, geochemistry of their rocky cores, cryovolcanic processes could then deliver methane to the surfaces of those planets, perhaps in geologically recent times,” said Dr. Will Grundy, an astronomer at Lowell Observatory, one in all Glein’s co-authors and lead writer of a companion paper. “We found a carbon isotope ratio (13C/12C) that means relatively recent resurfacing.”
This work is a component of a paradigm shift in planetary science. It’s increasingly being recognized that cold, icy worlds could also be warm at heart. Models developed for this study moreover point to the formation of geothermal gases on Saturn’s moon Titan, which also has abundant methane. Moreover, the inference of unexpected activity on Eris and Makemake underscores the importance of internal processes in shaping what we see on large KBOs and is consistent with findings at Pluto.
“After the Latest Horizons flyby of the Pluto system, and with this discovery, the Kuiper Belt is popping out to be way more alive by way of hosting dynamic worlds than we might have imagined,” said Glein. “It is not too early to begin desirous about sending a spacecraft to fly by one other one in all these bodies to put the JWST data right into a geologic context. I imagine that we might be stunned by the wonders that await!”
