Fountains caught against the darkness
Event image. Visible-light photograph from the 10 May 2015 plume sequence, originally about 2 kilometres per pixel. Over 6.5 hours, the phase angle changed from 149 to 155 degrees; most of the brightening comes from stronger forward scattering. E-ring viewing depth also alters the background. This still and its linked recording show the same observation.
NASA/JPL image-use policy · credited mission imagery, resized to WebP
· Original image source · Image licenceBacklighting turns escaping material into a luminous veil above the icy surface of a small Saturnian moon.
- World
- Enceladus
- Case date or period
- Observations · 2005–2015
Look closer
Cassini observed material rising from Enceladus under carefully chosen illumination. Images that initially look nearly blank can reveal structures when the viewing conditions favour scattered light.
Follow the evidence
Compare the plume’s changing appearance across viewpoints. Brightness differences alone do not give a simple measure of how much material is escaping, because the lighting geometry also changes.
The ice behind the glow
The spectral graphic records more than the plume’s outline. Cassini’s infrared spectrometer detected a signature of small ice particles, and a similar signature in surrounding E-ring material. Those measurements connected the visible plume with the ring, adding compositional evidence to the photographs.
An orbital rhythm in the scattered light
Matthew Hedman and colleagues analysed 252 VIMS plume images, accounting for viewing geometry. The integrated brightness was several times greater near Enceladus’s farthest orbital point from Saturn than near its closest point. This correlation supports tidal control of the erupting fractures. The measurement follows sunlight scattered by ice particles; it is not a direct reading of total gas flow, and particle properties affect the signal. An orbital trend provides stronger evidence than comparing two differently illuminated photographs alone.
Sources & further reading
- Enceladus Plume — NASA Image and Video Library / JPL
- Changing View of the Enceladus Plume — NASA Image and Video Library / JPL
- Out of the Noise — NASA Image and Video Library / JPL
- Enceladus plume spectrum — NASA / Cassini VIMS team
- An observed correlation between plume activity and tidal stresses — Hedman and colleagues — Original investigator research / author archive
- Enceladus plume exposures — 2005 — NASA / JPL / mission imaging team