The UIA’s now formally known as the Thargoid Maelstroms have begun taking up residence in the bubble around ammonia worlds. As everything is ramping up in the thargoid war, it seems there is a lot to look at in and around the maelstroms themselves. These curious biological plant like creatures/ships known as Caustic generators float around the maelstrom pumping out caustic gasses that will start damaging your ship until you either use a decontamination limpet or burn it off by exceeding 200% heat, however, if you get above 20% heat they will start dumping more and more caustic gasses in a never ending cycle. Through testing, it seems staying under 20% heat and using a very small ship (IE Dolphin) without a shield will allow you to stay almost invisible, and they will not produce caustic gasses. Seemingly the higher your heat or the more they notice your presence, they pulse red lights faster and faster. The caustic generators do seem to use this same gas as a propulsion system and you can still be affected if you run into it. These caustic generators seem to be the main line of defense in the maelstrom aside from the blast the maelstrom uses when you are too close.
Caustic Tissue Samples can be obtained from the generator by using Research Limpets (also available as part of the Xeno Multi Limpet controller). You will also need a Xeno Scanner. Approach the generator until you can scan it with the Xeno Scanner, then after the scan the left nav panel will allow access to the fourth tab (similar to scanning limpet points on megaships) where you can select the limpet point and fire off the research limpet.
Thanks to CMDR Bearded Devil for help putting together this information.