Planetary Cores Measure Up

“How big is Jupiter’s moon Io? The most volcanic body in the Solar System, Io (usually pronounced “EYE-oh”) is 3,600 kilometers in diameter.”

“Galileo spacecraft found Jupiter’s volcanic moon Io has a huge iron core that takes up half its diameter.”

[Io] “The explosive plumes demonstrates that some volatile species remain; the most likely candidate are sulphur and its compounds. Sulphur is a cosmetically abundant element but one that does not play a prominent role in terrestrial volcanism because, it is believed, most of the Earth’s sulphur is in its core.”

Source: The Cambridge Photographic Guide to the Planets [page 216]

Earth’s inner core  1,250km + outer core 2,200km =  3,450km (radius)

Jupiter’s natural satellite Io entire diameter = 3,600km


“Triton has a diameter of 2,700 km (1,680 miles). Spacecraft images show the moon has a sparsely cratered surface with smooth volcanic plains, mounds and round pits formed by icy lava flows. Triton consists of a crust of frozen nitrogen over an icy mantle believed to cover a core of rock and metal”
Earth’s inner core diameter is 2,500km

“Many of the features on the surface of Mars resemble features on the Earth; there are great dusty plains, there are large volcanoes, and there is a large rift valley along the equator. Similar to the Earth, Mars has ice caps at the poles which grow and shrink with the seasons. There are surface features which suggest that liquid water once flowed across the surface of Mars, but there are no current lakes or rivers of liquid water on the surface. As on Earth, water or water ice may be present underground. The mass of Mars is approximately 7.1 x 10^20 tons (6.4 x 10^23 kg or .11 x Earth mass). The mean diameter of Mars is 4,217 miles (6,785 km or .53 x Earth diameter).”
The diameter of Earth’s entire core is 6900 km

“Mars is a cold desert world. It is half the diameter of Earth and has the same amount of dry land. Like Earth, Mars has seasons, polar ice caps, volcanoes, canyons and weather, but its atmosphere is too thin for liquid water to exist for long on the surface. There are signs of ancient floods on Mars, but evidence for water now exists mainly in icy soil and thin clouds.”

“Two hundred and fifty million years ago the landmasses of Earth were clustered into one (hypothesized) supercontinent dubbed Pangaea.”


Newest Evidence: Diameter of Mercury’s Iron Core = 3,600km

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