Carnil, known as the red star, was actually the Name the Sindar and Dúnedain applied to the planet Mars.It was also known as Gormok, possibly a Name from Westron, Old Mago or one of the Languages of the Men of the East.In the Sixth Age members of the Notion Club had lucid dreams about space travel and Mars as a place that is a barren and horrible network of deserts and chasms.
The stars were created by Varda, but given that Mars is a planet, she most likely had help from other Valar or perhaps she put down the framework for Eru to finish the planet. It is conceivable that Carnil had actual life on it. Though Tolkien never wrote about Martians, his best friend C.S. Lewis did and both considered working together , although a true crossover of each others fictional universes never really happened .In Lewis's Universe Mars was also known as "Malacandra" and is inhabited by three native species/sentient races.