What is the purpose of the visits Marley describes in a Christmas carol?

Jacob Marley was doomed to wander the earth for eternity as "pennance" for his evil treatment of humankind while he lived. Charles Dickens describes his punishment by providing the visual context of the great chain Marley wears when he appears to Ebeneezer Scrooge. The chain has many items attached, including money boxes, to symbolize those things that were most important to Marley. Marley declares that Scrooge's own chain was every bit as "long and ponderous" as Marley's a full seven years previously when Marley died.

Scrooge's only chance for redemption, then, appears to be a full repentance from the greed and avarice of his life's work, and a new and honest interest in the affairs of others.