ESA Science & Technology - S/2005 S1

Cassini's confirmation that a small moon orbits within the Keeler gap in Saturn's rings is made all the more exciting by this image, in which the disk of the 7 kilometre-wide body is resolved for the first time.

The new body, provisionally named S/2005 S1, was first seen in a time-lapse sequence of images taken on 1 May 2005, as Cassini began its climb to higher elevations in orbit around Saturn. This view was acquired one day after the discovery sequence of images and has allowed scientists to measure the moon's size and brightness.

In the vicinity of the little moon, the Keeler gap edges bear striking similarities to the scalloped edges of the 322 kilometre-wide Encke gap, where the small moon Pan (25 kilometres across) resides. From the size of the waves seen in the scalloped edges of the Encke gap, imaging scientists were able to estimate the mass of Pan. They expect to do the same eventually with S/2005 S1.

This image was obtained with the Cassini spacecraft narrow-angle camera on 2 May 2005, at a distance of about 594 000 kilometres from Saturn. Cassini was about 525 000 kilometres above the ringplane when the image was taken. Resolution in the original image was 3 kilometres per pixel. The image has been magnified by a factor of two, and contrast has been enhanced, to aid visibility of the small moonlet.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency.