The MU-TH-UR 6000, known simply as "MOTHER" was a 182 model 2.1 terabyte AI Mainframe that served as the computer mainframe for the Nostromo, Mother auto-piloted the ship while the crew were in hypersleep and monitored their activities. Mother communicated with the crew through the intercom system or a special interface room only accessible to officer at the top of the chain of command.
"MOTHER" collaborated with Science Officer Ash to implement Special Order 937 and ensure the survival of the Xenomorph specimen collected on LV-426. "MOTHER" also monitored the activities of the crew of the Nostromo for Weyland-Yutani.
When the nuclear reactor was overheated, the Nostromo's self-destruct sequence was activated. Ripley tried to delay it by activating the cooling system, however though Ripley succeeded in activating the cooling system, she was unable to turn off the self-destruct because she was unable to complete the sequence before the option to override the self-destruct expired. "MOTHER" was destroyed along with the Nostromo when it exploded.