From Earth’s surface, it’s very hard to visualize how much empty space surrounds us. If we could capture photos of Earth from a distant vantage point – say, the outer solar system – we could perhaps begin to picture it, but those opportunities are rare. We humans have acquired only two images of Earth from the outer solar system – ever. The first and most distant was taken 23 years ago by NASA’s Voyager 1 spacecraft from 4 billion miles (6 billion kilometers) away, showing Earth as a pale blue dot . The other opportunity was Cassini’s image in 2006 from 926 million miles (1.49 billion kilometers). But today another opportunity will occur. On July 19, 2013, NASA’s Cassini spacecraft, now orbiting Saturn and weaving in and among its moons, will be aligned in such a way that Saturn will eclipse the sun as seen from the spacecraft. With the sun’s light blocked, space scientists will capture the third-ever picture of Earth from the outer solar system, hundreds of millions of miles away.
Earth will appear as a small, pale blue dot between the rings of Saturn in the image, which will be part of a mosaic, or multi-image portrait, of the Saturn system Cassini is composing, NASA says.
Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California said:
While Earth will be only about a pixel in size from Cassini’s vantage point 898 million [1.44 billion kilometers] away, the team is looking forward to giving the world a chance to see what their home looks like from Saturn.
Cassini will start obtaining the Earth part of the mosaic at 2:27 p.m. PDT (5:27 p.m. EDT or 21:27 UTC) on July 19 and end about 15 minutes later, all while Saturn is eclipsing the sun from Cassini’s point of view. The spacecraft’s unique vantage point in Saturn’s shadow will provide a special scientific opportunity to look at the planet’s rings. At the time of the photo, North America and part of the Atlantic Ocean will be in sunlight.
Carolyn Porco, Cassini imaging team lead at the Space Science Institute in Boulder, Colorado said:
Ever since we caught sight of the Earth among the rings of Saturn in September 2006 in a mosaic that has become one of Cassini’s most beloved images, I have wanted to do it all over again, only better. This time, I wanted to turn the entire event into an opportunity for everyone around the globe to savor the uniqueness of our planet and the preciousness of the life on it.
Porco and her imaging team associates examined Cassini’s planned flight path for the remainder of its Saturn mission in search of a time when Earth would not be obstructed by Saturn or its rings. Working with other Cassini team members, they found the July 19 opportunity would permit the spacecraft to spend time in Saturn’s shadow to duplicate the views from earlier in the mission to collect both visible and infrared imagery of the planet and its ring system.
Matt Hedman, a Cassini science team member based at Cornell University in Ithaca, N.Y., and a member of the rings working group, said:
Looking back towards the sun through the rings highlights the tiniest of ring particles, whose width is comparable to the thickness of hair and which are difficult to see from ground-based telescopes. We’re particularly interested in seeing the structures within Saturn’s dusty E ring, which is sculpted by the activity of the geysers on the moon Enceladus, Saturn’s magnetic field and even solar radiation pressure.
Bottom line: NASA’s Cassini spacecraft, now orbiting Saturn, will take a third picture of Earth from the outer solar system on July 19, 2013. The other two pictures were taken in 1990 and 2006.