— There is a scene in the movie "Apollo 13," inspired by the events of the real mission, where Ed Harris, portraying flight director Gene Kranz, takes to a blackboard to draw the path of the crippled spacecraft from where it is to where it needs to be in order to return the astronauts home.

"I want this mark all the way back to Earth with time to spare," says Kranz (Harris) to a group of flight controllers.

Though not a direct parallel, this clip, an exclusive sneak peek from this week's episode of "For All Mankind," outlines the trajectories for what could be the "failure is not an option" moment for Season 4 of the alternate space history drama. Only in this case, it is not one group all working to solve the same problem, but three teams not yet aware of the division between them.

To set up this scene from "Legacy" (Episode 8), premiering on Friday (Dec. 29), there are three people in the Kranz role: Dev Ayesa (Edi Gathegi), the founder of Helios, a commercial spaceflight company running the operations at the Happy Valley Mars base; Margo Madison (Wrenn Schmidt), the Soviet Union's lead engineer for the asteroid redirect program, who previously served as the chief of NASA (it's a long story); and Danielle Poole (Krys Marshall), NASA astronaut and the commanding officer on the red planet.

Each are addressing their respective teams as to what Ranger, an asteroid capture spaceship, needs to do to put a mineral-rich asteroid onto their desired new path.

"Ranger's engines can only affect small changes to the asteroid's trajectory, just enough to bring it near Mars," says Madison (Schmidt) as she draws its path as a dotted line on a whiteboard in NASA's headquarters building on Earth. "Once it is there, Ranger will again burn..."

"...for exactly 20 minutes," says Poole (Marshall), picking up the conversation but to her international team of scientists and engineers on Mars. "When the time comes, we will slow the asteroid down just enough for the gravity of Mars to bend its trajectory to speed it towards Earth."

But there is a third meeting going on, one unknown to both Madison and Poole. And what they have planned could not only change the course of the asteroid, but the direction of humanity in space going forward.

Watch the exclusive clip below and then tune into "Legacy," Season 4, Episode 8 of "For All Mankind," on Friday (Dec. 27) only on Apple TV+.