Using the NASA/ESA/CSA James Webb Space Telescope, astronomers have found evidence for gaseous methane on the distant dwarf planet Makemake. Reported in a paper in the Astrophysical Journal Letters, this discovery challenges the traditional view of Makemake as a quiescent, frozen body and makes it only the second trans-Neptunian object, after Pluto, where the presence of gas has been confirmed.
Protopapa et al. used Webb observations (white) to detect methane gas on Makemake; sharp emission peaks near 3.3 microns reveal methane in the gas phase above Makemake’s surface; a continuum model (cyan) is overlaid for comparison; the gas emission peaks are identified where the observed spectrum rises above the continuum. Image credit: S. Protopapa / I. Wong / SwRI / STScI / NASA / ESA / CSA / Webb.
Makemake, also known as 2005 FY9 and (136472), was discovered in 2005 by a team of astronomers from the California Institute of Technology led by Mike Brown.
This dwarf planet is located in a region beyond Neptune that is populated with small Solar System bodies.
It has a radius of approximately 715 km (444 miles) — just slightly smaller and dimmer than Pluto.
It takes about 305 Earth years for this dwarf planet to make one trip around the Sun.
Previously observed stellar occultations suggested that Makemake lacked a substantial global atmosphere, though a thin one could not be ruled out.
Meanwhile, infrared data of the dwarf planet hinted at puzzling thermal anomalies and unusual characteristics of its methane ice, which raised the possibility of localized hot spots across its surface and potential outgassing.
“Makemake is one of the largest and brightest icy worlds beyond Neptune, and its surface is dominated by frozen methane,” said Dr. Silvia Protopapa, an astronomer at the Southwest Research Institute.
“Webb revealed that methane is also present in the gas phase above the surface, a finding that makes Makemake even more fascinating.”
“It shows that Makemake is not an inactive remnant of the outer Solar System, but a dynamic body where methane ice is still evolving.”
The observed methane spectral emission is interpreted as solar-excited fluorescence, which is the re-emission of sunlight absorbed by methane molecules.
According to the team, this could indicate either a tenuous atmosphere in equilibrium with surface ices — similar to Pluto — or more transient activity, such as cometary-like sublimation or cryovolcanic plumes.
Both scenarios are physically plausible and consistent with the current data, given the level of noise and limited spectral resolution of the measurements.
“While the temptation to link Makemake’s various spectral and thermal anomalies is strong, establishing the mechanism driving the volatile activity remains a necessary step toward interpreting these observations within a unified framework,” said Dr. Ian Wong, an astronomer at the Space Telescope Science Institute.
“Future Webb observations at higher spectral resolution will help determine whether the methane arises from a thin bound atmosphere or from plume-like outgassing.”
“This discovery raises the possibility that Makemake has a very tenuous atmosphere sustained by methane sublimation,” said Dr. Emmanuel Lellouch, an astronomer at the Paris Observatory.
“Our best models point to a gas temperature around 40 K (minus 233 degrees Celsius) and a surface pressure of only about 10 picobars — that is, 100 billion times below Earth’s atmospheric pressure, and a million times more tenuous than Pluto’s.”
“If this scenario is confirmed, Makemake would join the small handful of outer solar system bodies where surface-atmosphere exchanges are still active today.”
“Another possibility is that the methane is being released in plume-like outbursts,” Dr. Protopapa said.
“In this scenario, our models suggest that methane could be released at a rate of a few hundred kilograms per second, comparable to the vigorous water plumes on Saturn’s moon Enceladus and far greater than the faint vapor seen at Ceres.”
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Silvia Protopapa et al. 2025. JWST Detection of Hydrocarbon Ices and Methane Gas on Makemake. ApJL, in press; arXiv: 2509.06772