Unidentified alien vessel

A spacefaring vessel, belonging to an unknown species, crash landed on Halo Installation 04 around 40,000 BCE.

History
Around 60,000 years after the firing of the Halo Array, this vessel crash landed on Installation 04 in Sector 1215. Twenty-six hours later, monitor 343 Guilty Spark arrived at the crash site and noted the crew had not attempted to exit the vessel. He marked seventeen atmosphere leaks along the hull of the ship that had been caused prior to the crash. An analysis showed these gases to be similar to those that comprised Installation 04's atmosphere. Guilty Spark hoped to get answers from these lifeforms, since he had many questions.

Sometime prior to the crash, the ship started broadcasting a distress signal repeated every 72.83 seconds. After attempting to translate it, Guilty Spark blocked the signal, as no communication revealing the location of any of the Halos was allowed. As the ship appeared to be a short-range vessel, Guilty Spark believed there may have been more like it somewhere in the vicinity and so could not take the chance of more lifeforms discovering the ring and possibly breaching Flood containment. In accordance with procedure, 343 Guilty Spark did not attempt to make physical or remote contact with the possible occupants of the ship. Eventually, the atmosphere stopped leaking from the ship and two weeks later, the distress signal terminated. After the distress signal terminated, the monitor had a massive sarcophagus constructed around the remains of the vessel over the course of the next week. Guilty Spark would then lament a missed chance to learn more about the rest of the galaxy and decide to relax his protocols somewhat the next time an alien vessel arrived so as not to miss another such opportunity.

Trivia

 * This ship's crash landing may have been previously alluded to in Conversations from the Universe, in which Guilty Spark states that other species had visited the installation prior to the Covenant's arrival. However, it is unlikely that he refers to this incident specifically, as the other races recorded what they encountered on the Halo and then left.
 * After a Halo Waypoint forum user joked that the vessel's slipspace capabilities indicate that it was not built by "dogs, cats, [or] certain bears", the administrator known as Catalog facetiously replied, "Query Answer: No known Tier 2 species matching suggested morphology [re: ursus sapiens]." Ursus sapiens is a hypothetical binomial nomenclature meaning "wise bear". The joke was later referenced in the name of the achievement—Bearly Contained—from Halo: The Master Chief Collection that requires the player to activate Terminal 6 on 343 Guilty Spark.
 * Catalog also stated that the ship's hull pattern bears similarity to the designs used by seven distinct species.
 * The overhead view of the crashed ship closely resembles a Reaper (particularly of the Sovereign class) from the Mass Effect universe.

List of appearances

 * Halo: Combat Evolved Anniversary
 * Terminals