From Halopedia, the Halo wiki
All that is known about the Daedalus is that sometime around the start of the Human-Covenant War, the Daedalus went down in-atmosphere over the planet Galgalia. The planet's high gravity and harsh conditions, as well as the circumstances of the atmospheric insertion, made any chance of this ship's crew or cargo surviving improbable. However, a group of four marines had endured the crash, each having buckled themselves into an M12 Force Application Vehicle and braced themselves for impact. Remarkably, all four of the vehicles survived the crash intact. Once on the surface, the marines innovatively relied upon the possible uses of the vehicles for survival. Having set their transmitters to broadcast a distress signal, they were eventually rescued from the planet's surface. The ship's molten wreckage was supposedly scattered miles across the surface of the planet and the ruins were later scavenged thoroughly.