Cassini Finds Warm Cracks on Enceladus
Scientists working jointly with Cassini’s composite infrared spectrometer and its high- resolution imaging camera have constructed the highest-resolution heat intensity maps yet of the hottest part of a region of long fissures spraying water vapor and icy particles from Enceladus. These fissures have been nicknamed “tiger stripes.” Additional high-resolution spectrometer maps of one end of the tiger stripes Alexandria Sulcus and Cairo Sulcus reveal never-before-seen warm fractures that branch off like split ends from the main tiger stripe trenches. They also show an intriguing warm spot isolated from other active surface fissures.
“The ends of the tiger stripes may be the places where the activity is just getting started, or is winding down, so the complex patterns of heat we see there may give us clues to the life cycle of tiger stripes,” said John Spencer, a Cassini team scientist based at Southwest Research Institute in Boulder, Colo.
The highest-resolution spectrometer scan examined the hottest part of the entire tiger stripe system, part of the fracture called Damascus Sulcus. Scientists used the scan to measure fracture temperatures up to 190 Kelvin (minus 120 degrees Fahrenheit). This temperature appears slightly higher than previously measured temperatures at Damascus, which were around 170 Kelvin (minus 150 degrees Fahrenheit).
Spencer said he isn’t sure if this tiger stripe is just more active than it was the last time Cassini’s spectrometer scanned it, in 2008, or if the hottest part of the tiger stripe is so narrow that previous scans averaged its temperature out over a larger area. In any case, the new scan had such good resolution, showing details as small as 800 meters (2,600 feet), that scientists could see for the first time warm material flanking the central trench of Damascus, cooling off quickly away from the trench. The Damascus thermal scan also shows large variations in heat output within a few kilometers along the length of the fracture. This unprecedented resolution will help scientists understand how the tiger stripes deliver heat to the surface of Enceladus.
“Our high-resolution images show that this section of Damascus Sulcus is among the most structurally complex and tectonically dynamic of the tiger stripes,” said imaging science team associate Paul Helfenstein of Cornell University, Ithaca, N.Y. Some details in the appearance of the landforms, such as a peculiar pattern of curving striations along the flanks of Damascus, had not previously been noticed in ordinary sunlit images.
The day after the Enceladus flyby, Cassini swooped by the icy moon Tethys, collecting images that helped fill in gaps in the Tethys global map. Cassini’s new views of the heavily cratered moon will help scientists understand how tectonic forces, impact cratering, and perhaps even ancient resurfacing events have shaped the moon’s appearance.
Enceladus is too far from the Sun to have oceans of liquid water - a necessary ingredient life as we know it - on its surface. However, Cassini's discovery of geysers erupting from the moon has raised questions about a possible subsurface ocean. If liquid water persists beneath the surface of Enceladus, some scientists believe that habitable environments could exist as well.