The First is set in the near-future and will chronicle the first human mission to Mars and the challenges of interplanetary colonization. The series will not only focus on the astronauts and scientists on the mission in space, but also the ground team on Earth and the crew's family and loved ones.
Details about Penn's character have not been released, but Deadline reports he's playing a former NASA astronaut named Tom Haggerty.
"I have such deep admiration for Sean's immense talent and extraordinary body of work," said Willimon, who also created House of Cards. "I feel very lucky to be collaborating with an artist of his caliber."
The First will premiere on Hulu and Channel 4 in the UK in 2018.