Life on Mars is named for a David Bowie song whose lyrics closely match the plot of the show.
Life on Mars would also be a reference to Sam waking up in 1973 and as he puts it, it's like "landing on another planet" and the series focuses on Sam's attempts to acclimatise to 1970s Britain whilst still trying to get back home; the show is all about Sam's Life on Mars.
Much of Life on Mars becomes Fridge Horror after the Ashes to Ashes finale. Gene's world is a copper's purgatory, they have to 'finish the job' to pass on, and Gene's role is to help them. It's implied that any copper who dies in that world without finishing the job goes to hell. Now watch the ending of the Life on Mars episode with Harry Woolf again. Fridge Brilliance if applied to Glen, but Harry is dying and has crossed the pavement. This man is Gene's mentor.
From the same episode, there's a throwaway line in which Gene claims part of his motivation for nabbing Harry's nemesis is that he's seen good coppers die trying to settle old scores. Presumably, he knows what he's trying to keep Harry out of.
Given the revelations of Ashes to Ashes, Sam did not prevent any future murders based on what he did to Tony Crane. Not only that, but his father did murder Annie Cartwright, and is the reason she is even in this world.