Rather than having thin atmospheres around relatively large rocky bodies, the jovian planets have relatively small, dense cores surrounded by massive layers of gas. Made almost entirely of hydrogen and helium, these planets do not have solid surfaces.

Do gas planets have a solid core?

Astronomers have found a previously unseen type of object circling a distant star. It could be the core of a gas world like Jupiter, offering an unprecedented glimpse inside one of these giant planets. Giant planets like Jupiter and Saturn have a solid planetary core beneath a thick envelope of hydrogen and helium gas.

Do Jovian planets have a solid surface?

Unlike the terrestrial planets that make up our inner solar system — Mercury, Venus, Earth, and Mars — the Jovian planets do not have solid surfaces. Instead, they are composed primarily of hydrogen and helium, with traces of methane, ammonia, water, and other gases in their atmospheres.