• 
  Rob Nelson

   Himself - Host (4 episodes, 2017)
• 
  Adam Cho

  Roboticist
• 
  Brad Aagaard

  Self - USGS
• 
  Griffin Alberti

  Self - Tech Advisor
• 
  Kenneth Bader

  Self - Paleontologist
• 
  Hank Bailey

  Self - Odawa Elder
• 
  Tracy Beach

  Self - Colorado Historian
• 
  Brent Breithaupt

  Self - Paleontologist

• 
  Jarrod Burks

  Self - Archaelogist
• 
  Jennifer Burnham

  Self - Soil Scientist
• 
  Rufus Catchings

  Self - Geologist
• 
  Nigel Crook

  Self - Geophysicist
• 
  Mike Feves

  Self - Geophysicist, Earth Dynamics
• 
  Peter Gavette

  Self - Archaelogist
• 
  Mark W. Holley

  Self - Underwater Archaelogist

• 
  Aubri Jenson

  Self - Guide
• 
  Stefan Burns

  Self - Geophysicist
• 
  Tim Bechtel

  Self - Geophysicist
• 
  Valerie Van Heest

  Self - Historian
• 
  Frank Watson

  Self - Bill's Borther
• 
  John Martini

  Self - Alcatraz Historian
• 
  Tom Parsons

  Self - USGS
• 
  Doug Platt

  Self - Capitol Spokesman
• 
  Ron Oremland

  Self - Geomicrobiologist
• 
  Bradley T. Lepper

  Self - Archaeologist
• 
  Gretchen Schmauder

  Self - Geologist
• 
  Larry Johnson

  Self - Seelbach Historian
• 
  George 'Paki' Stephenson

  Self - Geologist
• 
  Luther Strayer

  Self - Lead Scientist
• 
  William Watson

  Self - Historian