50 Interesting Facts About Planets and their Moons – Part 2

A day on Venus is longer than a year on Venus. It takes Venus longer to rotate once on its axis than to complete one orbit of the Sun. That's 243 Earth days to rotate once, and 225 Earth days to complete one orbit of the Sun.

2. In 1977, Jupiter, Saturn, Uranus, and Neptune were entering a rare alignment that occurs once every 175 years. This happened to be when humans were first attempting space exploration so we were coincidentally able to send Voyager 2 on a flyby of all four planets on its way out of the solar system.

3. There are locations on planet Mercury where certain times during the day the sun will appear to pause, reverse direction, then continue forward again as it moves across the sky. This happens as the planet's angular orbital velocity and angular rotational velocity flip as it crosses perihelion.

4. Jupiter's moon Amalthea is extremely irregular in shape and was the last moon in the solar system to be discovered through direct visual observation. It was discovered in 1892 by the American astronomer Edward Emerson Barnard from the Lick Observatory with a 36-inch refractory telescope.

5. The length of a day on Mars has been known (accurate to within 3 minutes) since 1666 but the length of a day on Saturn was a mystery until 2019. A Saturnian day is now known (with a reasonable degree of certainty) to be 10 hours, 33 minutes, and 38 seconds.

Saturns' rings are, cosmically speaking, a very brief event. We are about halfway through their 200 million year lifespan and are very lucky as a species to be alive to witness them. Any velociraptor with a telescope looking at Saturn would not have seen rings.

7. The planet Uranus was discovered before the continent of Antarctica.

8. The surface of Enceladus, the sixth major moon of Saturn, reflects 90% of the light that hits it, essentially making it a giant mirror.

9. Mercury is the closest planet to Earth (not Venus) and every other planet in the solar system most of the time.

10. Jupiter is a "cosmic vacuum cleaner." Its gravitational influence causes comets and asteroids to collide with it. The rate of impacts on Jupiter is about 2000-8000X higher than the rate on Earth. Without Jupiter, the probability of asteroid impacts with the inner planets would be much greater.

Uranus and Neptune are easy to spot in binoculars. Uranus might even look greenish, thanks to methane in the planet's atmosphere. Once a year, Uranus is barely bright enough to glimpse with the unaided eye.

12. "Pan" the second moon of Saturn, is irregularly shaped because it has accidentally captured some of Saturn's ring material.

13. You would weigh the same on Mercury as you would on Mars. Due to the much higher density of Mercury, the smaller planet has almost identical surface gravity to Mars.

14. Even though Jupiter is a massive planet, a day on Jupiter only lasts about 5 hours because it's rotating at 28,000 mph. By comparison, Earth rotates at around 1,000 mph.

15. The A and B rings of Saturn (the most visually prominent rings) are hundreds of thousands of kilometers wide, but only 5-15 and 10-30 meters thick, respectively.

One major concern of establishing human settlements on Mars is pregnancy. Members of the craft may likely not engage in sex due to their stressful and isolated environment, and it is still not fully known how the environment in a spacecraft would affect the development of a child aboard.

17. The planet Mercury, the closest planet to the sun, has a nighttime temperature of -280°F as it has no atmosphere to retain the 800°F temperature it reaches during the day.

18. Jupiter's Great Red Spot is so loud, that its acoustic sound waves heat the surrounding atmosphere to almost 2400 degrees Fahrenheit.

19. If you were to jump off the tallest cliff in the Solar System, Verona Rupes on Uranus's moon Miranda, you would fall for 12 minutes before hitting the ground a good 20 km below.

20. Almost all pictures we see of Venus are filtered for more cloud detail, or remove all clouds completely. Viewed naturally the planet appears bright white and nearly featureless due to the complete cloud cover.

Jupiter has a layer of liquid metallic hydrogen underneath all the layer of gasses that we see meaning that it has a huge magnetic field and very bright and large auroras at its poles.

22. The orbit of Mercury follows a unique pattern different from other planets which remained unexplained until Einstein’s theory of bending space-time due to large nearby gravitation. The previous theory was there was another planet between mercury and the sun, which they named Vulcan.

23. The sky on Mars is red and its sunsets are blue, which is exactly the opposite of Earth's.

24. Uranus has a magnetic field that "flickers" because its magnetic field is so off-kilter with its rotational axis that magnetic lines will snap apart and reconnect as it rotates. According to one astronomer, "Uranus is a geometric mess."

25. The magnetosphere of Jupiter, extends up to seven million kilometers in the Sun's direction and almost to the orbit of Saturn in the opposite direction. If it was visible from Earth, in the night sky, it would be roughly 4 to 5 times bigger than our moon.