The captain of the science vessel USS Grissom, studying the Genesis Planet when it was destroyed by Kruge's Bird-of-Prey.
Esteban commands the USS Grissom, sent to survey the Genesis Planet with Saavik and David Marcus aboard. Wary of the planet's quarantine, he is reluctant to permit a landing, and he reports the strange findings that lead Saavik and David to discover a young Spock.
When Kruge's Bird-of-Prey attacks without warning, a single shot destroys the Grissom with all hands, leaving Saavik and David stranded on the planet. He was played by Phillip R. Allen.