After graduation he began acting in the early 1960s, then did small roles in theatre followed by TV and film. In 1977, he married Barbara Newborn. They had two daughters, Susannah and Rebecca, and six grandchildren. The marriage lasted until his death in 2011.
Pancreatic cancer diagnosis and retirement from acting
In 2008, Mars was diagnosed with pancreatic cancer which had already spread beyond his pancreas. His cancer made him so ill that he could not reprise his role as King Triton for The Little Mermaid: Ariel's Beginning, so Jim Cummings took over the role. As well as not being able to voice Triton, he could not voice Grandpa Longneck in The Land Before Time.
Mars died from pancreatic cancer on February 12, 2011, at the age of 75, after suffering from the disease for three years (normally, pancreatic cancer kills its victims six months after they have been diagnosed). He is survived by his wife, Barbara Newborn Mars, to whom he had been married for 34 years, his two daughters Susan and Rebecca, and his six grandchildren.