Dark trails above an icy moon
Processed image. Three successive Voyager 2 views, top to bottom, about 45 minutes apart, presented together in one photographic sequence plate. The publisher dates it 26 August 1989. The plume rises roughly eight kilometres before trailing downwind for about 150 kilometres. Apparent thickening may reflect changing viewing angles, so it is not a measured increase in eruption rate. This is a still sequence, not a film.
NASA/JPL image-use policy · credited mission imagery, resized to WebP
· Original image source · Image licenceVoyager’s brief encounter captured signs of active plumes.
- World
- Triton
- Case date or period
- Voyager encounter · August 1989
Look closer
Triton’s south polar terrain includes dark streaks and plume structures. Images and annotations from Voyager help distinguish material above the surface from deposits lying on it.
Follow the evidence
The encounter offers a limited set of geometries and times. Trace plume direction and surface markings separately; a persistent dark streak need not mean a plume is active in every frame.
Future measurements can separate plume engines
Jason Hofgartner and colleagues reassessed Triton’s active plumes and dark fans, comparing solar-heating and internal-heat explanations. They proposed tests involving surface composition and thickness, fan deposits, plume and fan distributions, and local temperatures. Those measurements could distinguish a nitrogen-ice greenhouse mechanism from eruptions powered deeper inside. Voyager established airborne structures, but a dark surface fan preserves a deposit rather than the activity itself. The limited encounter cannot uniquely determine the energy source, and a proposed subsurface ocean is not established by the plume photograph alone.
Follow the airborne cloud and its shadow
The three-view plate follows an airborne plume from top to bottom at roughly forty-five-minute intervals. The separate annotated plate repeats one image to identify the cloud and its shadow; it does not double the observations. Viewing angle can alter apparent cloud density, so compare geometry before inferring a stronger eruption. In the south-polar photograph, dark fans lie on the surface and preserve earlier transport. They can remain after a vent stops, unlike material visibly suspended above the terrain.
Sources & further reading
- Triton Volcanic Plumes — NASA Image and Video Library / JPL
- Triton Dark Plume — NASA Image and Video Library / JPL
- Triton South Polar Terrain — NASA Image and Video Library / JPL
- Hypotheses for Triton’s plumes: New analyses and future remote sensing tests — Hofgartner and colleagues — Original author research paper