Is Pluto a planet? The debate has been raging since 2006 when it was demoted after a vote by members of the International Astronomical Union. What most forget is that the root cause for the discussion was the discovery in 2003 of a Pluto-like object slightly farther out in the solar system. It was nicknamed Xena and then later renamed Eris. Another world, Makemake, soon joined it. Then Haumea and Sedna.
The IAU classified all of them as dwarf planets—including Pluto—though their distant locations mean they’re often called Kuiper Belt objects (KBOs). The Kuiper Belt is a vast donut-shaped region of icy bodies beyond the orbit of Neptune at the edge of the solar system, and until recently, they were thought of as cold, dead places. It’s increasingly being recognized that they may be warm at heart—and now evidence has just emerged.
Living Worlds
Just as NASA’s New Horizons revealed it to be geologically active in 2017—imaging its nitrogen-ice plains, mountain ranges, dunes and ice volcanoes—both Eris and Makemake have now been confirmed to be alive.
A paper published today in the journal Icarus using observations from the James Webb Space Telescope reveals evidence for hydrothermal or metamorphic activity within both icy dwarf planets. Methane detected on their surfaces suggests hot geochemistry in their rocky cores.
Thermal Processes
“We see some interesting signs of hot times in cool places,” said SwRI’s Dr. Christopher Glein, an expert in planetary geochemistry and lead author. “I came into this project thinking that large KBOs should have ancient surfaces populated by materials inherited from the primordial solar nebula, as their cold surfaces can preserve volatiles like methane.”
The primordial solar nebula refers to the cloud of dust, ice and gas that the solar system was born within. “Instead, JWST gave us a surprise [and] we found evidence pointing to thermal processes producing methane from within Eris and Makemake,” said Glein.
Geologically Active
These distant, icy worlds may contain water if they are geologically active. There’s evidence of subsurface oceans at several icy moons in the solar system, including Jupiter’s moon Europa, Saturn’s moon Enceladus and, suggested just last week, its small moon Mimas. Whether water oceans exist on Eris and Makemake is unknown, but it will surely be something that planetary scientists will now study. The prize is significant because if either has a habitable environment, it will become the most distant world in the solar system that could support life.
Dynamic Worlds
“After the New Horizons flyby of the Pluto system, and with this discovery, the Kuiper Belt is turning out to be much more alive in terms of hosting dynamic worlds than we would have imagined,” said Glein. “It’s not too early to start thinking about sending a spacecraft to fly by another one of these bodies to place the JWST data into a geologic context … I believe that we will be stunned by the wonders that await!”
Wishing you clear skies and wide eyes
