Lisa volunteers for a future one-way journey to Mars, much to Marge's chagrin. As she searches for a way to convince Lisa not to go, Marge hits upon the most devious strategy of all, and volunteers to go along for the ride. Will the Simpsons girls be mankind's first residents of the Red Planet?
Homer was using the Flanders' leaf blower when it ran out of gas, so Homer decided to complain to him, only to discover that Ned got a chicken coop to get fresh eggs. He also discovered that his neighbour's eggs are much better than the ones consumed by the Simpsons, so Homer teams up with Bart to steal eggs from him. But Ned discovered their plan and managed to catch them stealing, so Homer decided to create his own chicken coop to get his own eggs.
However, Homer and Bart realized that the stolen eggs taste much better than theirs, so they decide to get rid of their chickens and keep stealing Flanders' eggs. The family donates their chickens to Exploration Incorporated, a company that wants to make a Mars colony by the year 2026. After visiting their facilities, Lisa is interested in the project and decides to sign up. The family is highly against Lisa's choice, but Homer convinces Marge to pretend they support Lisa, so this way she will lose interest in going to Mars.
However, this proves to be inefficient, so the whole family signs up on the project to force Lisa to give up. During one of the tests, everyone failed, except for Marge and Lisa. However, Paul and Barry, the project's ideologists announced that a rival project is almost in completion, so instead of 2026, the launch would be on Thursday. Most of the participants give up immediatelly, but Marge and Lisa decide to stay on the project, much to Homer and Bart's dismay.
During the launch, Marge and Lisa reconcile and decide that they do not want to go to Mars anymore, but they make their decision too late as the countdown just started. However, when the countdown reached zero, the rocket didn't move an inch. Paul and Barry reveal that their spaceship was only the outside of a rocket and they did that only to inspire the next generation, and to provide a distraction as they drove away, which failed because their car wouldn't start.
At home, Lisa comments to Marge that they almost went to Mars out of sheer stubbornness, to which Marge explains that this is what a mother-daughter relationship is. A fast-foward 35 years into the future (2051) is shown, with Marge and Lisa living on Mars, as Lisa says that she wants to leave Mars and move to Venus. The episode ends with Paul and Barry driving away from the fake launching site, planning their future business.