Conjoined Moons

By Nancy Atkinson - September 24, 2010 06:31 AM UTC | Planetary Science

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This latest image from the Cassini spacecraft will make you do a double-take! It is an optical illusion, but the two moons appear like conjoined, identical twins! The two moons are fairly close in size, but Dione, the smaller of the two at the top in the image, is actually closer to the spacecraft, making the two look almost identical. And because of the similar albedo, or reflectivity, of the two moons and because of the location of a particularly large crater near the south polar region of Dione, the moon appears blended seamlessly with Rhea. Double your pleasure!

Dione is 1123 kilometers (698 miles) across and Rhea is 1528 kilometers (949 miles) across.

The image was taken in visible light with the Cassini spacecraft narrow-angle camera on July 27, 2010.

See more about the image at the CICLOPS website.

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com