The only thing I can add is the perspective of someone who has been alive long enough to remember every occasion when these brave souls, space explores, lost in their struggle against the harsh environment they dreamed of exploring. This is true of those who visit the deep, as well. Nothing about us indicates that we were 'made' to exist in these strange places. We need air to breath and a warmer, more inviting climate than the vacuum of space. We have to take our environment with us, in order to survive. And one of the things that make us humans special, as beings of the known universe, is our desire,or better yet, our need to know and explore that which we do not know. We want to 'know' for the sake of knowing, in most cases. Otherwise we would sit comfortable in our easy chairs and be spectators to the wonders around us and nothing more. Enjoying the bliss that is ignorance. I believe that is one of the reasons we mourn so deeply those who are brave enough to do our exploring for us, as we all can't directly participate in these great adventures.
As stated above, so well, we deeply mourn this loss and our thoughts and hearts go out to the families of these modern day hero's.