3
No human explorations has been nor can be on Mercury.
yes
There have been no human explorations on Jupiter. All missions to Jupiter have been conducted using robotic spacecraft.
only one: The voyager 2!
Leif Ericson's explorations ended in 1003 when he returned to Greenland. He had been to Greenland in 1002 and had converted many of the people to Christianity.
there were about 7 missions to mercury
No noone has ever been on neputune
Humans have sent space probes to take pictures of Mercury from orbit around the planet, but we have not sent a man to Mercury. Sending people to Mercury would be hard because it is so dangerously close to the sun.
2
So far, no explorations have been made on Jupiter. Not even the most sophisticated space programs in the world are able to make that kind of voyage at this time.
Eric the Red led many viking explorations throughout the north Atlantic.
Previous manned spaceflight missions included the Mercury Program and the Gemini Program.