M1011 Moray space mine
From Halopedia, the Halo wiki
Moray Space Mines are explosives built by the UNSC for use in deep-space combat.
Background
They are dropped from the bays of Longsword Interceptors to mine locations within space from incursion. They use both proximity and remote detonators and have very high explosive payloads. This may not be a regular armament as the Master Chief noticed that the Cryo-Tube had been removed to make way for this. During the Assault on Ascendant Justice these were used to destroy the ship's Seraph Fighters making way for a Longsword to land on the Covenant ship.