Tag Archives: Dione

Dione’s global geology


Cool image time! The picture of Saturn’s moon Dione, taken by Cassini in April 2015 and reduced in size to show here, shows a range of global tectonic geological features. The impact craters we of course understand, but the white linear features are more puzzling. They are probably related to a heating and cooling process, but the full nature of that process is at present not fully understood. Tidal effects and the planet’s cooling over time both contributed, but to what extent is not yet known. Add on top of that the violent effect of impact and the process gets even more complicated. Moreover, do the linear features suggest present geological activity, or are they evidence of past events? Your guess is as good as mine.

Enceladus rises over Dione

Enceladus rising behind Dione

Cool image time! The image on the right was taken by Cassini in September 2015, and shows two Saturn moons, bright Enceladus partly blocked by darker and nearer Dione.

Although Dione (near) and Enceladus (far) are composed of nearly the same materials, Enceladus has a considerably higher reflectivity than Dione. As a result, it appears brighter against the dark night sky.

The surface of Enceladus (313 miles or 504 kilometers across) endures a constant rain of ice grains from its south polar jets. As a result, its surface is more like fresh, bright, snow than Dione’s (698 miles or 1123 kilometers across) older, weathered surface. As clean, fresh surfaces are left exposed in space, they slowly gather dust and radiation damage and darken in a process known as “space weathering.”

The image doesn’t contain any earth-shattering discoveries. It is simply beautiful. And in these dark times, seeing beauty is sometimes the most important thing one can do.

Cassini has found hints of activity coming from the Saturn moon Dione.

Cassini has found hints of activity coming from the Saturn moon Dione.

The spacecraft’s magnetometer has detected a faint particle stream coming from the moon, and images showed evidence for a possible liquid or slushy layer under its rock-hard ice crust. Other Cassini images have also revealed ancient, inactive fractures at Dione similar to those seen at Enceladus that currently spray water ice and organic particles.

Cassini looks past one Saturn moon to another

The image below was taken on January 11, 2011 by the space probe Cassini, in orbit around Saturn. First we see the southern polar regions of the moon Rhea, 949 miles in diameter. Beyond is the moon Dione, 698 miles across, appearing to sit on the rings of Saturn.

As far as I am concerned, this image, as well as almost every other image from Cassini, proves that any hotel built in orbit around Saturn is unquestionably going to be one of the hottest tourist spots in the solar system.

Looking past Rhea to Dione and Saturn's rings