Snowman in space? Saturn's moons line up to create odd optical illusion



It looks rather like some surreal snowman, floating in the blackness of space.

But this odd image is actually just an optical illusion created as two of Saturn's moons pass in front of one another.

The moon Dione, at the top in the image, is actually closer to the spacecraft here.

The striking picture was taken by Nasa's Cassini spacecraft as it orbits Saturn.



Looking like half of a figure eight, two of Saturn's moons appear conjoined in this Cassini spacecraft image

However, because of the similar 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 to blend seamlessly with Rhea.

Rhea is 1,530km in diameter whereas Dione is smaller at only 1,120km in diameter, or 32 per cent the size of Earth's Moon.

The two moons are actually around 500,000 kilometers apart.



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

Cassini completed its initial four-year mission to explore the Saturn System in June 2008 and the first extended mission, called the Cassini Equinox Mission, this month.

Now it is seeking to make exciting new discoveries in a second extended mission called the Cassini Solstice Mission.

The mission’s extension, which expected to last until September 2017, is named after the Saturnian summer solstice occurring in May 2017.

The northern summer solstice marks the beginning of summer in the northern hemisphere and winter in the southern hemisphere.

Since Cassini arrived at Saturn just after the planet's northern winter solstice, the extension will allow for the first study of a complete seasonal period.

Cassini launched in October 1997 with the European Space Agency's Huygens probe. The probe was equipped with six instruments to study Titan, Saturn's largest moon.