On 19 July 2013, as part of the Wave at Saturn event celebrated the world over, Nasa’s Cassini spacecraft slipped into Saturn’s shadow and turned to image the planet, seven of its moons, its inner rings – and, in the background, our home planet, Earth.
With the Sun’s powerful and potentially damaging rays eclipsed by Saturn itself, Cassini’s onboard cameras were able to take advantage of this unique viewing geometry. They acquired a panoramic mosaic of the Saturn system that allows scientists to see details in the rings and throughout the system as they are backlit by the Sun. This mosaic is special as it marks the third time our home planet was imaged from the outer solar system; the second time it was imaged by Cassini from Saturn’s orbit; and the first time ever that inhabitants of Earth were made aware in advance that their photo would be taken from such a great distance.
With both Cassini’s wide-angle and narrow-angle cameras aimed at Saturn, Cassini was able to capture 323 images in just over four hours. This final mosaic uses 141 of those wide-angle images. The image sweeps 651 591 kilometres across Saturn and its inner ring system, including all of Saturn’s rings out to the E ring, which is Saturn’s second outermost ring. For perspective, the distance between Earth and our Moon would fit comfortably inside the span of the E ring.
Earth is a bright blue dot to the lower right of Saturn. Venus is a bright dot to Saturn’s upper left. Mars also appears, as a faint red dot, above and to the left of Venus. Seven Saturnian moons are visible, including Enceladus on the left side of the image. Zooming into the image reveals the moon and the icy plume emanating from its south pole, supplying fine, powder-sized icy particles that make up the E ring. (See Annotated version of the image.)
Image credit: Nasa/JPL-Caltech/SSI