Launching of the beetles to Earth

After discovering that the Taumoeba-82.5 strain he had bred to save Earth could also penetrate xenonite—and that Rocky's ship, the Blip-A, was built almost entirely of that material—Grace faced an impossible choice. He could continue toward Earth, return a hero, and let Rocky and the entire Eridian species die. Or he could turn the Hail Mary around, find his friend, and accept that he would never see his homeworld again. He chose the latter. But before committing himself to a one-way rescue, he had to ensure that Earth would still receive the solution it needed.

The Decision to Launch the Beetles

Grace had spent weeks breeding Taumoeba-82.5, a strain of the Astrophage-eating microbe that could survive the nitrogen-rich upper atmospheres of Venus and Threeworld. But the same evolutionary pressure that gave it nitrogen resistance also gave it the ability to worm its way through xenonite—the very material of Rocky's fuel tanks. When Grace realized that Rocky's ship was almost certainly dead in space, its fuel devoured by the very organism meant to save both worlds, he knew he could not simply go home. He sat in the control room and sobbed, then made his calculation: he had enough food to reach Earth, or enough to reach Erid, but not both. The beetles—the four small, self-contained probes designed to carry data back to Earth—became his only way to save humanity without abandoning Rocky. Each beetle carried 120 kilograms of Astrophage fuel, a sealed computer, and a spin drive. Grace had already modified three of them—John, Paul, and Ringo—to serve as makeshift engines for the Hail Mary during the earlier crisis at Adrian. Now he would send all four, including the unmodified George, on their original mission.

Preparing the Mini-Farms

Rocky had built four miniature Taumoeba farms before they parted: small, steel-ish capsules, each containing a colony of Taumoeba-82.5, a Venus-like atmosphere, and a coil of Astrophage-filled tubing that would sustain the microbes for years. The capsules were made of Eridian steel—a dense alloy that Taumoeba could not penetrate. Grace epoxied one mini-farm to the undercarriage of each beetle, then spot-welded a small counterweight to the top to keep the probe's center of mass within its guidance computer's tolerances. The added weight meant the beetles would take slightly longer to reach Earth, but the computers were programmed to adjust acceleration accordingly. Grace also copied all his scientific findings—the data on Astrophage's life cycle, the discovery of Taumoeba, the breeding process, the nitrogen-resistance experiments—onto USB drives and placed one with each beetle. If even one probe survived the journey, Earth would have everything it needed.

The Launch

Grace had already used most of the beetles' fuel during the Adrian crisis, so he refueled each one from his own supply of Eridian-made Astrophage. The process was painstaking: he had to drill a six-millimeter hole into each beetle's sealed fuel bay, then use a syringe to inject a hundred milliliters of Astrophage at a time, repeating the operation two hundred times per probe. Once the mini-farms were attached and the fuel tanks were full, he sealed the beetles inside their launch cubbies in the Hail Mary's nose cone. He did not launch them immediately. Instead, he waited until he had made his final decision—until he had turned the ship around and begun the search for Rocky. Only then, with the Hail Mary accelerating away from Tau Ceti and toward the Blip-A's last known position, did he open the nose cone and release the four probes. He watched them on the Petrovascope: four tiny dots of Petrova-frequency light, growing fainter as they accelerated toward Earth at five hundred g's. "I know you'd love a beetle to take apart, but I couldn't spare one," he said to the absent Rocky. The beetles would experience about twenty months of subjective time during the thirteen-year journey; the Taumoeba inside their steel capsules would remain sealed and safe. Grace turned back to his own course, alone, with no guarantee that he would ever see Earth again—but with the knowledge that he had given his species its best chance to survive.