Bright Messengers (Rama, #1.5)

As civilization on earth faces destruction, two vastly different people share a vision both hopeful and tinged with danger. They also share a life on Mars, as a priestess acting on faith and an engineer focused on surviving the harsh red planet. The mystery spawned by a cloud of white particles holds them and Raman society spellbound in the debut novel of the co-author of such bestsellers as Rama II and Garden of Rama.