Life on Enceladus?
Places to look for life in our Solar System
Places in the Solar System where life might exist (except the Moon and Ceres, which are just shown for scale).Credit: D. W. Hoard (2018), assembled form public domain NASA images
Saturn's small moon Enceladus – another ocean world?
Do underground oceans vent through the "tiger stripes" (at left) on Saturn's moon Enceladus?
Long features dubbed tiger stripes are known to be spewing water from the moon's icy interior into space, creating a cloud of fine ice particles over the moon's south pole and creating Saturn's mysterious E-ring. Evidence for this has come from the Cassini spacecraft that orbited Saturn from 2004 to 2017.
Why Enceladus has an active surface remains a mystery, as the neighboring moon Mimas, approximately the same size, appears quite dead. A recent spectroscopic analysis of ejected ice grains has yielded evidence that complex organic molecules exist inside Enceladus. These large, carbon-rich molecules bolster - but do not prove - the theory that liquid water oceans under Enceladus' surface could contain life.Credit (image and some text): NASA, ESA, JPL, SSI, Cassini Imaging Team [link]
Ice geyser curtains observed in tiger-striped region of Enceladus
Researchers modeled eruptions on Saturn's moon Enceladus as uniform curtains along prominent fractures that stretch across the icy moon's south pole. They found that brightness enhancements appear as optical illusions in places where the viewer is looking through a "fold" in the curtain (left image). The folds exist because the fractures in Enceladus' surface are more wavy than perfectly straight. The researchers think this optical illusion is responsible for most - but not all - of what appear to be individual jets. Some discrete jets ("cryogeysers") are still required to explain observations by the Cassini spacecraft.
Phantom jets in simulated images produced by the scientists (green overlays in right image) line up nicely with some of the features in real Cassini images that appear to be discrete columns of spray. The correspondence between simulation and spacecraft data suggests that much of the discrete jet structure is an illusion.
Curtain eruptions occur on Earth where molten rock, or magma, gushes out of a deep fracture. These eruptions, which often create spectacular curtains of fire, are seen in places like Hawaii, Iceland, and the Galapagos Islands. On Enceladus, the "lava" in these curtain eruptions is liquid water.Credit (image and some text): NASA/JPL-Caltech/SSI/PSI [link]
Structure of Enceladus
Thick ice crust.
Mostly shallow subsurface water ocean...
...except for an area around cryogeysers at the south pole, where local geothermal activity melts more of the ice crust.
Something about the internal structure of Enceladus localizes the tidal heating effect to this one area.
The appearance and evolution of life might also be confined to just this area.
This artist's rendering showing a cutaway view into the interior of Saturn's moon Enceladus. NASA's Cassini spacecraft discovered the moon has a global subsurface ocean and likely localized hydrothermal activity. A plume of ice particles, water vapor, and organic molecules sprays from fractures in the moon's south polar region.Credit: NASA/JPL-Caltech [link]