APOD: Fresh Tiger Stripes on Saturn's... (2018 Jul 01)

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Fresh Tiger Stripes on Saturn's Enceladus

Explanation: Do underground oceans vent through the tiger stripes on Saturn's moon Enceladus? Long features dubbed tiger stripes are known to be spewing ice 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 robot Cassini spacecraft that orbited Saturn from 2004 to 2017. Pictured here, a high resolution image of Enceladus is shown from a close flyby. The unusual surface features dubbed tiger stripes are visible in false-color blue. Why Enceladus is active remains a mystery, as the neighboring moon Mimas,approximately the same size, appears quite dead. A recent 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 -- that oceans under Enceladus' surface could contain life.

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<<Stardust was a 390 kilogram robotic space probe launched by NASA on 7 February 1999. Its primary mission was to collect dust samples from the coma of comet Wild 2, as well as samples of cosmic dust, and return these to Earth for analysis. The flyby of Wild 2 was at a sufficiently low velocity (less than 6.5 km/s) such that non-destructive capture of comet dust is possible using an aerogel collector.>>

A "Stardust" sample return mission involving an energy efficient long elliptical [Saturn] orbit with the center of the E ring at perikrone would result in sufficiently low intercept velocities (less than 5.25 km/s) to non-destructively capture Enceladus geyser material using aerogel collection.

The backlit E ring, with Enceladus silhouetted against it. The moon's south polar jets erupt brightly below it.

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<<The E Ring is the second outermost ring and is extremely wide; it consists of many tiny (micron and sub-micron) particles of water ice with silicates, carbon dioxide and ammonia. The E Ring is distributed between the orbits of Mimas and Titan. Unlike the other rings, it is composed of microscopic particles rather than macroscopic ice chunks. In 2005, the source of the E Ring's material was determined to be cryovolcanic plumes emanating from the "tiger stripes" of the south polar region of the moon Enceladus. Unlike the main rings, the E Ring is more than 2,000 km thick and increases with its distance from Enceladus. Tendril-like structures observed within the E Ring can be related to the emissions of the most active south polar jets of Enceladus. Particles of the E Ring tend to accumulate on moons that orbit within it. The equator of the leading hemisphere of Tethys is tinted slightly blue due to infalling material. The trojan moons Telesto, Calypso, Helene and Polydeuces are particularly affected as their orbits move up and down the ring plane. This results in their surfaces being coated with bright material that smooths out features.>>