AP
John H. Glenn Jr. dons his silver Mercury pressure suit in preparation for launch on Feb. 20, 1962
John Glenn, who was the first American to orbit Earth, has passed away at the age of 95 in Columbus, Ohio.
Glenn was also a decorated war hero, former senator, educator, husband, father of two, and defender of humanity who worked against the proliferation of nuclear weapons.
In the wake of the news, scientists and space luminaries have taken to Twitter with an outpouring of condolences, memories, and love.
We'll update the list here as more space-related celebrities chime in, but below are some of the more notable tweets we've seen: