* Mars: Though we haven't sent humans to Mars yet, we have sent numerous robotic spacecraft to explore its surface, atmosphere, and geology.

We have also landed spacecraft on the following moons:

* The Moon: We have sent multiple missions to the Moon, including the Apollo missions, which landed astronauts on its surface.

* Titan (Saturn's moon): The Huygens probe landed on Titan in 2005, providing the first close-up images of its surface.

However, it's important to note that no human has ever set foot on any other celestial body other than the Moon.

We are currently working towards sending humans to Mars in the future, but it remains a challenging and complex endeavor.