50 Interesting Facts About Planets and their Moons – Part 2

Jupiter's moon Io is surrounded by a cloud of neutral Sodium (Na) gas which changes shape in response to variations of Jupiter's magnetic field.

27. Saturn has a very well-defined hexagon at its north pole that can fit up to four piles of earth inside of it.

28. All of Jupiter's moons are named after the extramarital lovers and children of the mythical Roman god Jupiter. NASA’s probe to Jupiter, Juno, was named after his wife flying in to "check up on her husband's mischief."

29. Five planets visible to the naked eye, Mercury, Venus, Mars, Jupiter, and Saturn, have been known since ancient times. They can easily be seen with the naked eye if one knows when and where to look.

30. Uranus smells like farts because its atmosphere consists largely of hydrogen sulfide.

The co-orbital Saturn moons Epimetheus and Janus avoid collision by mutual acceleration, deceleration, and an eventual orbit "trading" every four years.

32. Triton, the largest moon of Neptune, is the only moon in our solar system with a retrograde orbit - an orbit in the opposite direction of its planet and is thus thought to be a dwarf planet that Neptune caught from the Kuiper belt.

33. Rhea, a moon of Saturn, is showing signs of a breathable atmosphere and is a good canidate for an oxygen and water refill station for future missions.

34. The moons of Uranus are the only moons in the universe not given Roman/Greek names, they are given names from Shakespeare's characters.

35. Phobos, Mars's largest moon, is set to collide with Mars or break up into a ring in 50 million years due to tidal forces.

One of Jupiter's moons, Callisto, has about 99% of the diameter of the planet Mercury, but only about a third of its mass.

37. It is Venus, not Earth, that has the least orbital eccentricity or most circular orbit in the solar system.

38. Neso, one of the moons of Neptune, is the farthest moon from its planet in the Solar System. It takes 26 Earth years to orbit Neptune planet once and it is as far away from the planet as the Earth is to Venus.

39. Because of Uranus' axial tilt, it "rolls" around the sun like a marble. Its poles each experience 42 years of light and 42 years of darkness during the summer and winter solstices.

40. Raindrops on Saturn's largest moon, Titan (the only other known world with seasonal rainfall) would be twice as big as raindrops on Earth and would fall as slow as snowflakes. Also, they're made of liquid methane, not water.

The atmosphere of Venus is so thick that it has 4 times more Nitrogen than Earth even though its Nitrogen only makes up 3.5% of its atmosphere, compared to 78% of Earth's atmosphere.

42. Venus could have had habitable conditions for billions of years in the past, long enough for life to have developed.

43. Mercury's diameter is only 1/194th of that of the sun, as seen from Earth. A telescope with a magnification of 50 to 100x shows Mercury as a small black dot crossing the sun's face during a transit, which will happen again in 2032.

44. The planet Uranus was originally named "George" after the British King George III.

45. Saturn's moon Iapetus was discovered in 2007 to have a unique equatorial ridge that has peaks up to 8 mi (13 km) high and only exists in the dark region of the moon. There is no definitive explanation for how it formed.

Mars' moons, Phobos, and Deimos orbit in opposite directions along the equator. At certain longitudes, you wouldn't be able to see them at all.

47. Saturn's largest ring, the Phoebe ring, is so big that if it were visible to the naked eye, it would span the width of two full moons in our sky.

48. Saturn’s moon Mimas is the smallest known astronomical body to still have a round shape due to self-gravitation. Its total surface area is approximately the same as Spain.

49. Jupiter's moon Ganymede has a thin oxygen atmosphere and also likely has a saltwater ocean 200 km below the surface.

50. Europa's (Jupiter's moons) ocean is 62 miles deep meaning you could fit seven Mount Everest one on top of the other inside it. The deepest part of our ocean, Marianas Trench, could only fit one with 2 miles to spare.