Planets: a. Which planet in our solar system has the shortest day - making one rotation about its axis every 10 hours or so? Is it Mercury, Jupiter, or Pluto? b. How many planets have no moons? c. Which planet has the tallest mountain - Earth, Mars, or U

The colossal gas giant Jupiter boasts the shortest day in our solar system, completing a full spin in just under 10 hours. This incredible speed is even more remarkable given Jupiter's immense size—it's more than 11 times the diameter of Earth. While one might guess a small planet like Mercury would spin quickly, it actually has a very long day. Jupiter's rapid rotation is a common trait among the gas giants and contributes to the powerful jet streams and distinct, stormy bands we see in its atmosphere.

Closer to the sun, the terrestrial planets offer their own unique superlatives. Mercury and Venus are the only two planets in our solar system completely devoid of moons. Their proximity to the Sun's immense gravitational pull makes it very difficult for them to capture and hold onto a natural satellite. Farther out, Mars is home to the tallest known mountain, Olympus Mons. This massive shield volcano towers nearly three times the height of Mount Everest. Its colossal size is possible thanks to Mars's lower surface gravity and lack of plate tectonics, which allowed lava to build up in the same spot for millions of years.