I read this book when I was a teenager, I think it was one of a series. All I can remember is that the main character grew up alone on Mercury when all of the settlers were killed. Ring a bell for anyone?
Might that be one of the Eric John Stark stories by Leigh Brackett? Stark was raised by Mercurians after his parents died in a mining accident.
Stark was born on Mercury. His parents were employees of the mineral extraction company Mercury Metals and Mining. After his parents died in a cave-in caused by a quake, Stark was adopted by a tribe of Mercurian aborigines who are described as hairy and possessing snouts. They gave him the name N'Chaka, meaning "the man without a tribe". He believed himself to be one of them, rather than a human, and endured their rigorous way of life in the Mercurian Twilight Belt, surviving by hunting rock-lizards.