The Chronicles Of Pern: First Fall

Benden cocked his head, his expression rueful. "A fighter to the last… and it took a wretched planet to defeat him."

"Poor planet Pern," Saraidh said sadly. "Not its fault, but I'm recommending that this system be interdicted. I did some calculations—which I'll verify on the Amherst computers—and rechecked the original EFC report. That wasn't the first time the Oort organism fell on the planet. Nor will it be the last. It'll happen every two hundred and fifty years, give or take a decade. Furthermore, we don't want any ship blundering into that Oort cloud and transporting that organism to other systems."

She gave a shudder at the thought.

"There she is," Benden said with a sense of relief as the viewport filled with the perceptibly nearing haven of the Amherst. "And, all things considered, a successful rescue run."