Maurice Gray on Mars Series by Patrick Moore

Maurice Gray, a young recently-orphaned Englishman, arrives at the Woomera Rocket base in Australia to meet his only known relative, Leslie Yorke. He learns that Dr. Yorke, a scientist at the base, left on an expedition to Mars some time before and that nothing has been heard from them.

Some years after the events described in Mission to Mars, and The Domes of Mars, Maurice Gray and his friend Bruce Talbot are now permanent members of the research colony established on Mars. They learn from a new arrival that the United Nations, which funds the base, is having second thoughts about its viability.