Self satisfied, content. Assured of our superiority and position in this world.
Of course, this couldn’t last forever. The first craft was almost sad, a little box with some frozen things in it. The Army moved to contain it, of course. They decided to put a couple samples in stasis, then sterilize the area. I guess that was our first mistake. Someone should have maybe let a scientist look at it before the fires started. I suppose there’s a small chance we would still be on top of the food chain. Self satisfied or content, anything but this.
Pinecones. That’s the closest analog we have. Once the heat from the fires hit the little organic husks, they exploded with life, microbial robots, converting this to that, changing oxygen to nitrogen. Another situation that might have clued a scientist in that the bigger mistakes were being made back in the labs, with the samples. Nobody knows if there were any survivors from the initial explosion of the craft. Nobody really cares.
The samples were put into basic stasis, deprived of oxygen, immersed in liquid nitrogen. Frozen beyond life, as we thought of it. They looked like slivers of gypsum, slightly opaque crystals. Didn’t even have a chance to get a good look at them under the microscope. The radiation of the x-rays was plenty to wake them up. They slid together without anyone noticing. The beginning of the end was a blob of chilly snot, sneaking out of a petri dish while some scientists watched the news of the explosion at the crash site, oblivious to anything. Even as the room was sealed, and the simple asphyxiant gas was released, they never suspected extra-terrestrial intelligence.
From what little we can gather now, they’re not really single organisms. More like colonies of simple machines. They get their energy through something like photosynthesis, they need hard UV radiation for the process, and instead of oxygen, they absorb nitrogen. The nitrogen levels in the atmosphere seem to be barely surviveable to them, in their strongholds, it is nearly 94% nitrogen atmosphere. Their destruction of the ozone layer is almost complete. The outside world is almost uninhabitable for Terran species.