who discovered the first one?
It was first observed by Galileo Galilei.
Io (moon)
The first reported observation of Io was made by Galileo Galilei on 7 January 1610 using a 20x-power, refracting telescope at the University of Padua. 
where are jet streams located in the atmosphere On earth, near the altitude of the tropopause what are they? Jet streams are fast flowing, narrow, meandering air currents in the atmospheres of some planets. what are the applications of these fast flowing air currents? On Earth, the northern polar jet stream is the most important one for aviation and weather forecasting. these air currents form in any other planets? Yes, on Jupiter for instance how they are formed there? On Jupiter, they are caused by the convection cells that form the familiar banded colour structure and are driven by internal heating. what is the above mentioned planet composed of? Primarily composed of hydrogen with a quarter of its mass being helium. It may also have a rocky core of heavier elements. how is the atmosphere there? It has the largest planetary atmosphere in the Solar System. what time it takes to complete one revolution around the sun? 11.86 years what is flyby mission? Operations where spacecrafts are brought within observation range to closely monitor and study astronomical objects. has any flyby mission carried out for this planet? Yes, the Pioneer and Voyager missions to name two of them. when was the first one carried out? 1973 how many natural satellites does this planet have? 79 can you mention some of them? Io, Europa, Ganymede, and Callisto to name a few
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Io (moon) [SEP] Observational history
The first reported observation of Io was made by Galileo Galilei on 7 January 1610 using a 20x-power, refracting telescope at the University of Padua. However, in that observation, Galileo could not separate Io and Europa due to the low power of his telescope, so the two were recorded as a single point of light. Io and Europa were seen for the first time as separate bodies during Galileo's observations of the Jovian system the following day, 8 January 1610 (used as the discovery date for Io by the IAU). The discovery of Io and the other Galilean satellites of Jupiter was published in Galileo's "Sidereus Nuncius" in March 1610.