 Why did Gwayne decide that they all had to stay?
Captain Gwayne cursed and rolled over, reaching for his boots. The starlanes between Earth and her potential colonies were rough on the men who traveled them now. Gwayne swore softly to himself. The two he'd drawn, Kaufman and Pinelli, seemed to be totally devoid of any sense of caution. But something had happened to the exploration party fifteen years back, and to the more recent ship under Hennessy that was sent to check up. Earth had ordered him to detour here, after leaving his load of deep-sleep stored colonists on Official World 71, to check on any sign of Hennessy. One, at the front, was stuttering into life, and Gwayne dashed for it as the exit port slid back. Then Gwayne spotted them; surrounded by the menacing horde.
 because it was the best chance at human survival
 to discover all of the secrets on the planet  because it was the best chance at human survival  because everyone outside the hull is beyond saving  to try to save Hennessy and his crew