Frozen Cliffs

The icy cliffs of Dione

One of the newest raw images from Cassini’s latest flyby shows the icy terrain of Saturn’s moon Dione, with steep hills, ridges and the bright face of one of the many deep canyons that meander across its surface. Known as “wispy lines”, these canyon walls expose bright water ice (that makes up about a quarter of the 700-mile-wide moon) since darker surface coatings can’t stick to their steep cliff sides. The most reflective deposits appear white in the image above, which I have level-adjusted to enhance detail.

Dione's wispy lines

Based on the original image scale of 50 feet per pixel (the Cassini spacecraft was about 1600 miles above Dione ย when this was taken…that’s about 7 times the max altitude of the ISS) the canyon wall is over a mile high! Standing on the edge would be like standing on the rim of the Grand Canyon…except that the sky would be filled with Saturn! Cool.

It’s been suggested that the canyons on Dione are a mature stage of the “tiger stripe” features found on nearby Enceladus, which are the source of ice geysers that supply material to the diffuse E-ring that ultimately ends up coating the surface of Dione. The Saturnian family is a very interconnected one.

See more images of Dione from the April 7th flyby as well as some bonus ones of Janus, Epimetheus and Enceladus on the Cassini imaging lab site here.

Image: NASA/JPL/Space Science Institute

4 Comments

  1. Terry says:

    “mature stage of Tiger Stripe” as in… less active/non-active geologically? As in, it is theorized that what we are seeing on Enceladus is temporary or “youthful” and unlikely to continue?

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    1. J. Major says:

      Yes. As in. I guess some think that Dione’s features might be similar to Enceladus’ grooves, only cold and geologically dead. Based on the idea that they are both caused by tectonic activity.

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  2. Terry says:

    So why might there be such a disparity in geologic/tectonic activity? Is there a significant difference in size or proximity to Saturn? They “should” be about the same age and composition…

    Is Enceladus sufficiently closer to the Mother Ship to be subject to the same tidal forces that Io is with Jupiter, with just a different composition – hence geyser vs lava

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    1. J. Major says:

      Dione is a bit farther out than Enceladus (check out this scale chart) and is twice as large, but just how that affects the tidal forces felt by the two moons in comparison to each other is beyond me. I would have to assume that any distance closer to Saturn would greatly increase the tidal effects. As to why Enceladus has jets and other nearby moons don’t (as far as we know now…there’s speculation that more could yet be found) it would have to depend on very specific factors of each moon’s composition. Saturn’s family of moons has a lot of variation, this is what makes the Cassini mission so fascinating!

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