This mosaic view of Saturn was taken while Cassini was about 500,000 miles away from the planet. Images shot on October 17, 2012. Credit: NASA/JPL-Caltech/SSI.

In her 2007 TED Talk, “This is Saturn,” planetary scientist Carolyn Porco blew some minds with images taken by Cassini, the robot spaceship launched in October 1997 to study and photograph Saturn and its accompanying moons. Carolyn Porco: This is Saturn Gleaning “oohs” and “aahs” from the assembled TED audience, she concluded with a stunning shot of a backlit picture of Saturn and its rings — with Earth in the background. It was quite a moment.

“People erupted to their feet. Obviously we Earthlings resonate with seeing ourselves as this dot in the distance,” Porco remembered of the moment in a recent telephone call. “And then I realized it was such a wasted opportunity. If people had known in advance that their picture was being taken, there would be an opportunity for high-fiving all over the planet!”

That time is now. Between 9:27 pm and 9:42 pm GMT on July 19th, Cassini will again be positioned to take another photograph of Saturn and its entire ring system during a total eclipse of the Sun. Once again, Earth will show up in the background. And this time, Porco is calling for everyone to take 15 minutes to step outside, gaze up into the blackness of space, be grateful for our existence, and maybe even wave. “Take a moment to reflect on our cosmic whereabouts and the significance of the accomplishments that allow this interplanetary photo session to happen,” she urges. “Think about how precious life is, about our place in the cosmos. Look up and smile.”

Porco is dubbing this “The Day The Earth Smiled,” and there are ways to get involved beyond waving and smiling. With an advisory board including many other TEDsters — like physicist Brian Cox and the so-called “Father of SETI,” Frank Drake — Porco is also organizing two contests calling for Earthling participation. Check them out — and get involved:

Message to the Milky Way: On July 19th, create an original image that best represents Earth. Porco explains: “If you were to sit down with an alien and you wanted to show him/her/it one picture that says it all about what is unique about your home planet, what would that picture have in it?” The winning image will be included in a message broadcast to the Milky Way using a large radio telescope (likely, the Arecibo telescope.)

A Musical Celebration: Are you a composer? Create an uplifting composition to celebrate The Day The Earth Smiled.

Porco hopes to raise funding that will allow winning sounds and images to be composited and released in a multimedia presentation that  will celebrate the “gasp-worthy, goosebump-raising day Earthlings knew their picture was being taken from a billion miles away.” She adds: “It will be a splendid interplanetary moment of cosmic self-awareness.”

Are you in?