Heavy Turret

Heavy Turrets are turrets that are more heavily armored than their more common counterparts. This makes them more capable of defending positions.

During Balak's raid to Asteroid X57 for a slave grab, he instead saw potential and ordered the asteroid's three fusion torches lit and accelerate the asteroid to collide with the Alliance colony of Terra Nova. He had turrets deployed around the torch stations to defend them against anyone that may interfere with his plans, and then had additional turrets deployed at the entrance to the main facility. Shepard must get past these turrets to stop the asteroid and save the colony.

Tactics
Unlike every other Turret that is encountered in Mass Effect, these turrets are 'sheathed' and their protection will not drop until you get close enough. This unfortunately foils any attempt to snipe them from a distance, so you will have to adjust your normal tactics for dealing with them. This means the Mako has to be very close to attack, and since they are placed in groups, dodging the rockets becomes more difficult. However, 'reclaiming' each fusion torch station from the batarians will render the turrets harmless, so it's also possible to endure the rockets until you can park close enough to the station to get inside.

Outside of the Main Facility, there are two turrets that are on rails, making aiming at them much more difficult. A better solution is to use AI Hacking on those turrets – as the other turrets won't be able to hit them either – or wait until they have moved to one end of the rail and attack them then.

Another good tactic is to try and isolate one, deal with it, then move on to the rest. This is possible at the Fusion Torch Stations, but not at the main facility as they will all emerge at once.