Jonas told Fallon on Tuesday that he started writing the album in July while his wife Priyanka Chopra was in Germany filming the newest Matrix film. The singer said he felt disconnected from the world and Chopra at the time.
"Within a couple of days I was like, 'Oh, this is a solo album.' Then a few days later I was like, 'This is a kind of like themed album,'" Jonas said.
"This idea that we've all had this year now...this year of being sort of disconnected from reality, disconnected from the world and feeling like we're on our own planet. And you know, also, obviously, missing her at that time as well and then reconnecting with her," he continued about the themes behind the album.
Jonas debuted two new songs from the album, including the title track and "This is Heaven," while he hosted and performed on Saturday Night Live. Spaceman will be released on March 12.
"The main theme from this album, I think, is more than anything is just about hopefulness for the future and seeing a brighter day ahead," Jonas said.
Jonas also took on the Singing Whisper Challenge with Fallon. The duo took turns guessing what song the other was singing while wearing noise-canceling headphones.