<P> Jupiter is composed primarily of gaseous and liquid matter . It is the largest of the four giant planets in the Solar System and hence its largest planet . It has a diameter of 142,984 km (88,846 mi) at its equator . The average density of Jupiter, 1.326 g / cm, is the second highest of the giant planets, but lower than those of the four terrestrial planets . </P> <P> Jupiter's upper atmosphere is about 88--92% hydrogen and 8--12% helium by percent volume of gas molecules . A helium atom has about four times as much mass as a hydrogen atom, so the composition changes when described as the proportion of mass contributed by different atoms . Thus, Jupiter's atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements . The atmosphere contains trace amounts of methane, water vapor, ammonia, and silicon - based compounds . There are also traces of carbon, ethane, hydrogen sulfide, neon, oxygen, phosphine, and sulfur . The outermost layer of the atmosphere contains crystals of frozen ammonia . The interior contains denser materials - by mass it is roughly 71% hydrogen, 24% helium, and 5% other elements . Through infrared and ultraviolet measurements, trace amounts of benzene and other hydrocarbons have also been found . </P> <P> The atmospheric proportions of hydrogen and helium are close to the theoretical composition of the primordial solar nebula . Neon in the upper atmosphere only consists of 20 parts per million by mass, which is about a tenth as abundant as in the Sun . Helium is also depleted to about 80% of the Sun's helium composition . This depletion is a result of precipitation of these elements into the interior of the planet . </P> <P> Based on spectroscopy, Saturn is thought to be similar in composition to Jupiter, but the other giant planets Uranus and Neptune have relatively less hydrogen and helium and relatively more ices and are thus now termed ice giants . </P>

What is the ratio of jupiter's diameter relative to that of earth