NASA Probes Photograph Earth from Saturn and Mercury on the Same Day

NASA probes Cassini and MESSENGER each pointed their cameras at Earth July 19 to capture images of our planet from the distant reaches of our solar system.

When Cassini snapped Earth's picture from the Saturn system there was plenty of advanced notice of the event, and NASA's public relations machine was in high gear, highly publicizing the event and encouraging people to "smile and wave" as they looked towards Saturn in the sky.

But the photo taken by MESSENGER as it probes Mercury in a campaign to find natural satellites around the planet closest to the Sun, was not made widely known.

MESSENGER's photo of Earth was at a distance of 61 million miles away, a huge distance, but compared to the 900-million-mile-away image of our planet taken by Cassini from Saturn, MESSENGER seems like it's just next door.

In both images Earth appears to be nothing more than a speck of light in the dark background of space.

Capturing an image of Earth from the outer solar system is difficult because pointing a camera toward Earth also means pointing the camera toward the Sun. Aiming a highly sensitive camera directly at the Sun can be just as damaging as looking right at it with your naked eyes. The Cassini image was made possible because the probe was behind Saturn as it passed in front of the Sun, providing a temporary shade from the star's light.

The full-color Cassini image reveals Earth and the Moon, the first time the probe captured an image of the pair as two distinct objects. Earth appears pale blue and the Moon stark white, visible between Saturn's rings. The image was a small portion of a larger mosaic image of Saturn and its rings. Cassini team members are currently assembling the image, but it will be weeks before it's made available.

In the MESSENGER image, Earth and the Moon are less than one pixel, but they appear larger because the image is overexposed, NASA said.

"That images of our planet have been acquired on a single day from two distant solar system outposts reminds us of this nation's stunning technical accomplishments in planetary exploration," said MESSENGER Principal Investigator Sean Solomon.

"And because Mercury and Saturn are such different outcomes of planetary formation and evolution, these two images also highlight what is special about Earth. There's no place like home."

Click here for more information about the MESSENGER photo and here for more information about the Cassini image.