What is Jupiter mostly made of?

Jupiter is mostly made of gas, primarily hydrogen and helium. By mass, its atmosphere is approximately 76% hydrogen and 24% helium, with only small amounts of compounds such as methane, ammonia, water vapor and hydrogen sulfide.

Jupiter is called a gas giant because hydrogen and helium dominate its composition, unlike the rocky planets Earth, Mars, Venus and Mercury. However, “gas” is a simplified quiz answer: deep inside Jupiter, increasing pressure transforms hydrogen into liquid and then electrically conducting metallic hydrogen.

The planet probably has a dense central region containing heavier elements, although its exact structure remains difficult to determine. Above that interior, the hydrogen-helium layers become progressively hotter and denser rather than ending at a sharply defined solid surface.

Jupiter’s colorful bands and enormous storms, including the Great Red Spot, occur in its atmosphere. The planet rotates once in about 10 hours, producing strong winds and helping stretch it into a visibly flattened shape at the poles.