An examination of possible encounters humans could have once colonies are established beyond Earth.
| Name | Type | Role | |
|---|---|---|---|
| Kevin Burns | Writer | ||
| Max Thompson | Writer | ||
| Lennox Wiseley | Writer | ||
| Sue Ann Pien | Guest Star | Self - Candidate, Mars One | |
| Jason Martell | Guest Star | Self - Author, Knowledge Apocalypse | |
| John Brandenburg | Guest Star | Self - Plasma Physicist, Orbital Technologies | |
| Seth Shostak | Guest Star | Self - Senior Astronomer, SETI Institute | |
| Peter Diamandis | Guest Star | Self - Chairman and CEO, X Prize Foundation | |
| Paul Valle | Guest Star | Self - Argos Project Manager, NASA | |
| Josh Richards | Guest Star | Self - Candidate, Mars One | |
| George Noory | Guest Star | Self - Radio Host, Coast to Coast AM | |
| Lewis Dartnell | Guest Star | Self - Professor of Science Communication, University of Westminster | |
| William Henry | Guest Star | Self - Author/Investigative Mythologist | |
| Nick Pope | Guest Star | Self - U.K. Ministry of Defense (1985-2006) | |
| Stephen Petranek | Guest Star | Self - Author, How We'll Live on Mars | |
| Elizabeth Rampe | Guest Star | Self - Exploration Mission Scientist, NASA | |
| Linda Moulton Howe | Guest Star | Self - Investigative Journalist, Earthfiles | |
| Giorgio A. Tsoukalos | Guest Star | Self - Publisher, Legendary Times Magazine | |
| Dr. Travis Taylor | Guest Star | Self - Aerospace Engineer | |
| John Gruener | Guest Star | Self - Space Scientist, NASA | |
| Jonathan Young | Guest Star | Self - Founding Curator, Joseph Campbell Archives | |
| Chandra Wickramasinghe | Guest Star | Self - Director, Buckingham Centre for Astrobiology | |
| Michael 'Mike' Bara | Guest Star | Self - Author, Hidden Agenda | |
| Jim Green | Guest Star | Self - Chief Scientist, NASA | |
| Paul Davies | Guest Star | Self - Astrobiologist, Arizona State University | |
| Erich von Däniken | Guest Star | Self - Author, Chariots of the Gods | |
| David Childress | Guest Star | Self - Author, Technology of the Gods | |
| Andrew Collins | Guest Star | Self - Author, The Cygnus Key | |
| Lucien Junkin | Guest Star | Self - Robotics Engineer, NASA | |
| John Connolly | Guest Star | Self - Human Mars Study Lead, NASA | |
| Michio Kaku | Guest Star | Self - Author, The Future of Humanity | |
| Julie Badger | Guest Star | Self - Robonaut Project Manager, NASA | |
| Susan E. Leventhal | Executive Producer | for HISTORY | |
| David Silver | Executive Producer | ||
| Max Thompson | Executive Producer | ||
| Kevin Burns | Executive Producer | ||
| Scott Hartford | Executive Producer | ||
| Kim Sheerin | Executive Producer | ||
| Giorgio A. Tsoukalos | Executive Producer | Co-Executive Producer |