Earthlings are being asked to smile to the heavens tonight, in order to make history.

At about 10.30pm the Cassini probe spacecraft will turn around in its current orbit around Saturn and take a picture of the Earth.

It will be the first time that Earth's inhabitants will know in advance that their picture is being taken from over a billion kilometres away.

Those behind the event, The Day the Earth Smiled, said "it will be a day to revel in the extraordinary achievements in the exploration of our solar system that have made such an interplanetary photo session possible”.

They added “it will be a day for all of us to smile and celebrate life on the Pale Blue Dot”.