The desert world

Intro This planet in the future is a sand covered desert with the largest forms of life are the giant cacti that pepper the surface. Its dry surface and scorched rocks are hot enough to cook eggs on in the day yet freezing cold at night with the only sources of water being ether the large oasis on the north and south pole, the huge cacti or deep under the sand. Theres a human walking around this planet... Who are they. Are they you? If not do you know them? Are you even a human or a alien from this planet?