After completing Vetra's loyalty mission Vetra Nyx: Means and Ends, Hunting the Archon, and returning to the Tempest after landing on the planet, read her email titled "Kadara" on the pathfinder terminal.
Read Email From Vetra Edit
Go With Vetra To The Sulfur Springs On Kadara Edit
With Vetra in the active squad, travel to the navpoint located in the Sulfur Springs area on Kadara.
This is a short and peaceful mission; it contains only cutscenes and dialogue (and up to two interrupts; the interrupt while climbing has no influence on the mission or dialogue).