Escape Velocity by Charles L. Fontenay

Murdering Stein was easy. Kraag waited until Jonner donned his spacesuit and went out to have a personal look at the asteroid. Even then Kraag held his patience, because he wanted Jonner to come back to the ship unsuspecting.
Kraag sat tensely at the back of the control room while Stein, the navigator and communications man, operated the radio. There was a brief period when Stein talked with Marsport, then he got in touch with Jonner. Until Jonner got some distance from the wrecked ship, most of their conversation was an argument.