The crew failed.
The supervolcano on 83 Leonis II erupted ahead of its predicted time. Away teams from the Mercury determined, before this eruption, that Starfleet’s presence on the world had not been limited to secret observation but had instead been much more involved: Captain Kells’s team discovered evidence of biotampering, while Commander Ross’s found a remaining researcher who admitted that the rest of his team had geoengineered the eruption, apparently to eradicate the pre-warp population. Captain Kells determined that this degree of tampering nullified the Prime Directive’s order of non-involvement, and the crew of the Mercury and the Aquitania began beaming up refugees. However, the civilian Dr. Saveron also beamed down without authorization, ostensibly to expedite the evacuation, but the distress call he sent from the surface attracted the attention of a Cardassian warship, which arrived and chased away the two Starfleet vessels despite their pleas of humanitarian assistance. As the ships left, the Mercury crew gathered on the bridge to pay respect and tribute to the unknown race that was likely to perish thanks to the eruption and the climactic changes it would cause.
But life went on. The Aquitania, with Ambassador Ventu and all the alien refugees, departed Deep Space 10 after it and the Mercury had returned, and the Mercury crew turned its attention to recreation and the remaining problems of the previous mission: Dr. Saveron was arrested for his unauthorized beam-down, Ensign Alora DeVeau continued to search for the DNA fingerprints of the missing researchers, and Captain Reynolds and Dr. Hawkeye revealed that the last researcher had been intentionally poisoned — and genetically manipulated. Though the mission had ended, the repercussions for the Mercury crew will continue to accrue….