Prerequisites:
You’ll first hear about the Turian ark in the angaran forest world of Havarl. After completing the sidequest “Helping Havarl’s Scientists”, talk to the angara Kirran Dals. Next, you have to speak with Tovar about the turians. Their locations will be marked in the southeastern corner of the map. Follow the waypoint to reach them.
The turians belonging to the turian ark Natanus will be under attack from the Roekaar once you find them in Havarl. Conveniently, their camp has a memory trigger so you’ll find them anyway sooner or later. Take out the initial wave of attackers as well as the enemy reinforcements that will arrive via dropship. After defeating them all, talk to the turian leader named Avitus Rex to update this task.
You’ll learn that the ark hit the Scourge and this group is one of the many scattered survivors of the ark. This is a long quest so it will be put on hold for the meantime.
Note: While the mission status is “On Hold”, this is not entirely true. The objectives related to this mission ends here. Continue with the story until you reach Kadara. Here, this mission ends automatically and will be continued as “Turian Ark: Lost But Not Forgotten”. This is triggered by receiving an email from Avitus Rex about the reported turian ark debris found in Elaaden.