Tom Cullen (“Weekend”), Elias Koteas (“Shutter Island”) and Johnny Harris (“Snow White and the Huntsman”) have all been added to the cast of sci-fi horror “Last Days on Mars.”

Thesps join previously announced Liev Schreiber, Olivia Williams and Romola Garai in the pic, which Focus Features Intl. is shopping to buyers at the Cannes Film Festival.

Ruairi Robinson (“Fifty Percent Grey”) helms the pic, based on a short story by Sydney J. Bounds.

Script is adapted by Clive Dawson while Qwerty Films’ Michael Kuhn and Andrea Cornwell produce.

“Last Days” centers on a group of astronauts on an exploratory mission to Mars who, on the eve of their return to Earth, discover colonies of bacteria living deep within the permafrost which infects them.

Pic will lense in Jordan and Blighty’s Elstree Studios.

Universal Pictures will release the pic in the U.K.