Five-time Oscar nominee Adams will play a linguist hired by the army to translate aliens in Story of Your Life.
Paramount paid a hefty $20m (Â£12m) for the rights to distribute the movie in North America and China.
Based on a short story by science-fiction writer Ted Chiang, it is due for release in 2016. Prisoners film maker Denis Villeneuve will director.
Meanwhile Michael: The Last Photo Shoots takes a behind-the-scenes look at the pop star's final days.
Directed by Craig J Williams, the documentary is billed as an intimate, unique story told through the eyes of friends, photographers and stylists who helped Jackson prepare for his ill-fated comeback, after several years living in seclusion overseas.
Lightning Entertainment has acquired the international sale rights.
"We see Michael Jackson as influential and powerful today, nearly five years after his death, as ever before," said the company's vice president, Ken DuBow.
With much of the film world present in the South of France for the next fortnight, the business of buying and selling films is an important counterpart to the glamour of the red carpet.
But sales meetings are often star-studded affairs in their own right.
Last year Justin Timberlake held a VIP party to drum up interest in Spinning Gold, his biopic of Neil Bogart who helped popularise disco acts like Donna Summer and the Village People on his Casablanca Records label.
Russell Crowe, Jason Statham and the cast of The Hunger Games are all rumoured to be putting in appearances at this year's festival.
A new sci-fi starring Amy Adams is among the first big films to find buyers at the Cannes Film Festival.