As the mission launches, Emma's mettle as commander is tested by an onboard accident, a divided crew and a family emergency back on Earth.
After a ship malfunction threatens the voyage, Emma works with Misha on a high-risk repair operation.
A staff change at Mission Control unsettles the unflappable Lu, and the fallout undermines Emma's command; Matt encourages Lex to return to school.
Ram endangers the lives of everyone on the Atlas, causing Emma to put herself in harms way; Matt must make a life-changing decision.
As Christmas approaches, crew members prepare to make their final calls home before communication grows spotty; Matt and Lex adjust to their new normal.
Tempers flare on the Atlas over a water-system glitch and an act of betrayal; Matt meets Lex's new friend while working on the ship's issues.
Emma's behavior causes concern; Kwesi and Lu team up on a plant mystery; Lex makes an impulsive decision with far-reaching consequences.
A problem with the supply ship jeopardizes the Atlas' mission and calls into question Emma's commitment to landing on Mars.
Emotions run high as rapidly dwindling water rations leave the crew and Mission Control scrambling to find a fix before time runs out.
With only hours to go before Atlas' planned touchdown on Mars, Emma is faced with everything that could go wrong; Lu receives new orders.