The planet was surrounded by some kind of time loop. That rocket with the dead body was shot up from the planet during global disaster event and landed on the same spot in the past and it will keep repeating. The planet probably will go through some kind of cosmic event that cause the planet itself to boil, hence observed as planet of flame, Red Cave. The crew probably entered during its calm state which will quickly turn heated in the next few moments/chapters.
Well...
I seem to remember that in Secret of Blue Water there was a character connected to a cord of sort...and then they used it in Evangelion as the cord that powers up the mechas.
I guess. 'been too long ago.