A new analysis of imagery from NASA’s NASA spacecraft provides the first evidence of recently flowing liquid on Pluto. Researchers have found patterns suggesting that liquid nitrogen is rising to the surface through cracks located at the northern edge of Sputnik Planitia, a massive nitrogen ice glacier that forms part of the dwarf planet’s famous heart-shaped feature.
Evidence of Subsurface Flow
The research, published July 31 in the Planetary Science Journal, indicates that dark streaks and diffuse features on the northern part of Sputnik Planitia may be temporarily and occasionally wetted by liquid nitrogen. According to the study, these surface patterns resemble glacial features on Earth that have been wetted by rain or the emergence of subsurface liquids.
Because Pluto’s thermal and atmospheric conditions make liquid nitrogen rain physically impossible, scientists concluded the liquid is flowing up from beneath the glacier. To achieve this, the base of the ice sheet must melt due to pressure before the nitrogen is pushed upward in liquid form and refreezes upon reaching the surface. This liquid may percolate through glacial ice and warm up before freezing again, potentially damming up in insulation spaces to create the dulled fronts observed by scientists.
Geological Activity on a Frozen World
Sputnik Planitia is a vast frozen nitrogen glacier larger than the U.S. states of Texas and Oklahoma combined. Images from the 2015 flyby revealed city-sized geologic convection cells in the northernmost regions, separated by diffuse and thin dark linear features. The absence of impact craters in this region indicates the surface is being continuously renewed.
Alan Stern, lead study author from the Southwest Research Institute in Boulder, Colorado, and principal investigator of New Horizons, stated that the results suggest a new kind of time-variable feature on Pluto
. Stern noted that Pluto never stops surprising us
and that the findings suggest liquids have recently expressed themselves on the surface.
Implications for the Solar System
The discovery that Pluto’s “heart” may hide flowing nitrogen indicates the dwarf planet is geologically active, a finding that contradicts earlier expectations that Pluto was a frozen, cratered relic that had been geologically dead for billions of years. Experts suggest that understanding this activity could provide insight into other icy worlds, such as Europa or Triton.
While the recent study focuses on nitrogen, other data from the New Horizons encounter has revealed a complex environment, including:
- Mountains kilometers high composed of water ice.
- A thin nitrogen atmosphere with a blue haze.
- Indirect evidence suggesting a liquid water ocean may exist beneath Pluto’s icy shell.
The New Horizons Mission
The New Horizons spacecraft launched in early 2006 and traveled roughly five billion kilometers over more than nine years to reach Pluto. The spacecraft performed a flyby on July 14, 2015, rather than entering orbit. While the close encounter lasted only hours, the data gathered continues to be analyzed by planetary science and terrestrial glaciology experts. Following its encounter with Pluto, the spacecraft flew past the distant object Arrokoth in 2019 and continues to travel outward through the Kuiper Belt.
