Billions.
Strictly speaking, Saturn doesn't have a surface that can be landed on, so there have been no spacecraft landings on Saturn. Pioneer 11 and Voyagers 1 and 2 have done flybys of Saturn.
Saturn has not been found to have any comets orbiting around it. Comets are typically found in the outer reaches of the solar system in regions such as the Kuiper Belt or the Oort Cloud, rather than around gas giant planets like Saturn.
There have been no human explorations on Jupiter. All missions to Jupiter have been conducted using robotic spacecraft.
over 5,000
As of 2021, there have been over 20 spacecraft missions that have visited Venus, including flybys, orbiters, and landers. Some notable spacecraft include the Venera probes launched by the Soviet Union, the Magellan spacecraft by NASA, and the Akatsuki probe launched by JAXA.
Strictly speaking, Saturn doesn't have a surface that can be landed on, so there have been no spacecraft landings on Saturn. Pioneer 11 and Voyagers 1 and 2 have done flybys of Saturn.
Yes, there are many comets that have been seen by people.
There are so many fields that have not been studied in great depth. The least studied field is the one that hasn't been discovered yet.
There are many planets in our solar system that have not been visited by a spacecraft. As of now, the planet Uranus has not been visited by any spacecraft.
1 time Neptune has been vist
Comets have been in space since the start of time. In the 1800's there were many people who knew comets where a space phenomena, there were people who thought it was a message from the gods. What people thought of the comets depended on their cultural beliefs.
There are no comets on Neptune because Neptune is a planet and comets are, well, comets. They have nothing to do with each other.
Spacecraft is both singular and plural. You can have one spacecraft or many spacecraft.
In years past, there have been many spacecraft 'go missing' (Cosmos 1, Contour, Mars Polar Lander...), but I know of none that are currently missing.
Yes solar furnaces have been studied and many patents have bben placed on various designs that incorporate curved mirrors and an array of mirrors focused on a central point. -Hope this helps you!
Saturn has not been found to have any comets orbiting around it. Comets are typically found in the outer reaches of the solar system in regions such as the Kuiper Belt or the Oort Cloud, rather than around gas giant planets like Saturn.
There have been no human explorations on Jupiter. All missions to Jupiter have been conducted using robotic spacecraft.