The two planets are gas giant – they are not a rocky planet like Earth -. They are basically made up of gas and has no surface where you can for example put down your leg and stand on.
The two planets are made of Helium and Hydrogen with the Hydrogen being prominent. The reason according to scientist is that both planets formed earlier in the Solar System and this made them accumulate lots of the two gases.
Jupiter is made of of 90% Hydrogen and 10% Helium. It is a huge planets with the size of two combination of all planets in the Solar System. Saturn has 96% Hydrogen and 3% Helium. Because of the composition of these planets, they are lighter in mass even though they are bigger in size than the rocky planets.
Saturn for example is 95 times bigger than Earth but only 12% of the Earth’s mass.
Because of their nature, they are almost a Star in composition, Jupiter for example will be called a small star if it were 80 times as large. Even though they are not stars, their proximity has made the planets one of the most hostile in the solar system.
Jupiter has the strongest magnetic field in the Solar System with a strong radiation belt that can destroy any object that comes within 300,000 km of the planet. Saturn has a weaker radiation belt. Though with a hostile atmosphere of Ammonia Ice and winds of up to 1600 KPH and bolts of lightning that is a million times as strong as that on Earth.
The only probe ever sent to explore Jupiter;’s atmosphere is Galileo. It took 14 years to get to Jupiter after and spent Eight years orbiting around the planet at a safe distance. On September 21, 2003 it probe was deployed to land on Jupiter. It wasn’t equipped with a camera but has other scientific instrument. The probe reached 150 km Below Jupiter’s Sea Level. It reported wind of 700 KPH and air pressure of 22 BARS and a temperature of 151 C.
Jupiter has the shortest day in the Solar System completing one rotation every 9.9 hours. This is due to the strong magnetic field.