What are those big noisy towers on Eos' plain?

There's a really big Kett Base on the edge of a cliff, where you will come by very close to get to the lower dunes area. If you walk about the place, the local leader, one called Invictor, will speak about you or to you. The Quest with the Massani guy is basically about going there and taking that base down.

The second time you touch down Eos and activate a forward post, the first thing Sam will explain is that Kett base on the planet overview. On the map, you'll find it on the central area, a bit to the West, on a plateau.

Yes investigating the kett fortress is apparently the only thing left to do on Eos. The quest says 'investigate the fortress' and 'find way to get through the shield'. My question was about these 3 terminals I found and disabled all around the big Dune plain. Are those terminals part of the fortress quest? They're not mentioned

iirc Zaeed's son did say to cut the power to the barracks. You can see a turret there that doesn't work anymore.

Ok then. I just don't understand why they are not mentioned in any quest like 'disable the 3 terminals'. Maybe because I had all of them already disabled before meeting massani? idk

You get XP for turning them off, but I don't think they're tied to any specific quest, unless this is another instance of the pertaining quest script not correctly firing like what happened pre-1.05 with the malfunctioning probes on Eos.

Your squad should be talking about a kett outpost in smokes, turns out massani did it. Once you talk to him he says to pick the smaller targets, the barracks, by first disabling the power to it (the terminals). This is probably to avoid reinforcements in the kett's main base.

They possibly optional, given some things in this game trigger due your own exploration, instead of laid bare and explained all the time. The first time I played, I went to that fortress before doing anything else for Massani, so his conversation was already fixed for that situation.

Actually Massani's dialogue is bugged in that convo. On my first playthrough, I killed Invictor before speaking to Massani and his dialogue still pointed out that I hadn't taken the "crown jewel."