The Viking space probes visited the planet Mars
All of the eight planets have been visited or orbited by space probes.
All but Pluto, which is currently being visited.
April 2008 At present the only planet in our solar system that has not been visited (either by an orbiting spacecraft or flyby spacecraft) has been the recently planet downgraded body of Pluto. There is a mission currently in motion to visit this distant outpost.
The United States launched the Viking space probes. Viking 1 was launched on August 20, 1975, and Viking 2 was launched on September 9, 1975. These probes were part of NASA's Viking program to study Mars.
The Viking Space Probe was actually two different probes. Viking 1 and Viking 2 were used to explore Mars. The probes took photographs, did experiments and deployed instruments to the surface of Mars.
Humans have visited NO planet outside of Earth. Humans have visited the Moon, which is not normally considered a planet.Unmanned probes sent by humans, on the other hand, have already visited several planets.
viking 1
Some of the space probes that have visited Mars include Mariner 4, Viking 1 and 2, Pathfinder, Spirit and Opportunity rovers, Curiosity rover, MAVEN, and InSight. These missions have contributed valuable data and insights into the geology, atmosphere, and climate of Mars.
space probes
Space probes like New Horizons have only performed flybys of Pluto because it is very far away from Earth and the journey would require a significant amount of time and resources. Additionally, the spacecraft would need to carry enough fuel for the long journey and for entering Pluto's orbit, which adds complexity and cost to the mission.
Donkies
aside from earth, the planet that has been visisted by the most probes, is often said to be mars, however other scientific research has also proven that venus and Jupiter had also been visisted by several probes every 200 - 400 years. mars however is often visited by probes every 50 - 100 years.