The Namib Desert is one of the oldest deserts and also one of the most diverse. With 50ºC (120ºF) temperatures and half a millimetre of rainfall annually, we see how this is possible. Half the size of Oklahoma, from its Skeleton Coast through the sea of sand to the haze of distant mountains this apparently forbidding desert hides secret water sources.

At the far tip of South America, lies a magical realm that seems frozen in time. Known as 'the end of the world', this is Patagonia. Vast glaciers shaped it into an Eden like no other. Adaptable and resilient creatures evolved unique survival strategies to flourish across its remarkable habitats. From precipitous mountain citadels and icy desert plateaus windswept steppe uplands through remote, primal forests to a mosaic of glacial valleys. To thrive here is to be as extreme as the land itself.

In Southeast Alaska, there's an ice-bound Eden that harbors possibly the richest temperate rainforests of all. Where the coastal mountains meet the Pacific, lays the Alexander Archipelago, a remote island chain running for almost 300 miles along the Alaskan Panhandle. This frozen frontier is one of the last great wildernesses of North America. And a stronghold for the country's highest diversity of megafauna, feasting on the abundance of fleeting summers to make it through relentless winters.

Principles of generosity and prosperity inform the selection of the last two crew members: Christopher Sembroski, a former member of the U.S. Air Force who served in Iraq and now works as a Lockheed Martin engineer, and Sian Proctor, a professor of geosciences and two-time NASA astronaut candidate. Excitement for the flight ramps up, but anxiety lingers.

As training begins, the crew members process the physical, mental and technical demands being placed on them. The group is going to be in some intentionally uncomfortable situations and, to see how they do as a team. A climb of Mt. Rainier puts them to the test.

A fighter jet ride prepares the crew for the G-forces of spaceflight. Haley, Sian and Chris relate the emotions they experience as launch approaches.