Thus, "Life On Mars?" rocks out to the same chords as "My Way." The only differences are some chord inversions and the fact that "Life On Mars?" is in a different key. The chord progression is your classic descending jazz chord progression. But, you'll notice, this song is anything but classic jazz.
The song plays as a radio-friendly Broadway finale, not unlike songs featured in the 1973 rock musicals Godspell and Jesus Christ Superstar (disregarding the lyrics, of course). Two distinctive features of the song, the guitar solos and the string arrangement, are guitarist Mick Ronson's inventions. And then there's David Bowie's voice. Against the deeper orchestral hits in the chorus (on "Sailors," "lawman," and "Mars?"), Bowie belts out notes at the very edge of his vocal range. (They're B flats, if you wanted to know. As one's voice naturally deepens with age, Bowie no longer sings these notes quite so high.) The effect is that Bowie's voice harmonizes with the much lower notes of the orchestration to create a huge, full, and powerful chord on those notes.