Can you see Earth in this picture? What about the reddish speck of Mars?
Though dwarfed by the majesty and enormity of Saturn and its rings eclipsing the sun, this is also a picture of the inner solar system, taken by the Cassini spacecraft. Seemingly no bigger at this distance than the gas giant’s satellite moons, Earth, Venus, and Mars are a faint presence in the cosmic dark. (Mercury is obscured by Saturn.)
Launched in 1997, Cassini has shown us a variety of Saturn-related details, from liquid methane lakes on the moon Titan to turbulent storms on the planet’s surface. But Cassini team members also wanted a picture that included Earth — a challenge because our planet is close to the sun, and pointing Cassini’s cameras toward our star risks damaging their sensitive detectors.
On July 19, however, the sun slipped behind Saturn (from Cassini’s perspective), and the spacecraft took this portrait, capturing a swath more than 400,000 miles — greater than the distance from Earth to the moon. Exactly 141 separate images went into the final composite. (This closeup of Earth forms part of the complete picture.)
NASA first revealed the image this past Tuesday at the Newseum in Washington, D.C. On the same day, Carolyn Porco, an astronomer and the leader of the mission’s imaging team, personally dedicated the picture to legendary scientist and science communicator Carl Sagan at the opening of the Carl Sagan and Ann Druyen Archive at the Library of Congress.
The image recalls an earlier portrait of Earth taken by Voyager 1 in 1990, in which our planet appears as a “pale blue dot,” as Sagan described it. (See that picture and hear Sagan's observation.)
To raise awareness about the Cassini photo shoot in July, NASA also launched a campaign encouraging thousands of people to wave and say, “Cheese!” while the spacecraft was snapping pictures. During that time, said Porco, "the earth smiled in unison."