Because the Sun was the first to form from the solar nebula, it preserved the chemical composition of this cloud of gas and dust. Comets came later, so their compositions reflect the chemistry and environment of the period after the sun already formed. By measuring the compositions of comets, scientists can then better understand what was happening in the solar system during this chapter of the solar system's history. Comparing the chemistry of the early solar system with Juno's measurements of Jupiter's chemical composition—and its water content in particular—will help scientists determine when and where Jupiter formed.