10 most difficult planets riddles

The ridge is 13 km high, 20 km wide and 1300 km long. Its origin is not known, but considering the amount of craters, it's safe to assume that it is a very old geological feature.

The diameters of Uranus and Neptune are respectively 25 362 km and 24 622 km - the difference is only 2.92%.

Caloris Planitia is a plain within a large impact basin on Mercury, informally named Caloris, about 1,550 km in diameter. It is one of the largest impact basins in the Solar System. The crater, discovered in 1974, is surrounded by a ring of mountains approximately 2 km (1.2 mi) tall.

The Martian year is almost twice longer than Earth's year.

Neptune was the first planet to be discovered by using mathematics. After the discovery of Uranus in 1781, astronomers noticed that the planet was being pulled slightly out of its normal orbit. John Adams of Britain, and Joseph Leverrier, of France, used mathematics to predict that the gravity from another planet beyond Uranus was affecting the orbit of Uranus. A young astronomer, Johann Gottfried Galle, decided to search for the predicted planet and observed Neptune for the first time in 1846.

Jupiter's moons, especially Io (spot on the left), are powerful sources of auroras on Jupiter. These arise from electric currents along field lines, generated by a dynamo mechanism due to the relative motion between the rotating planet and the moving moon.

Like the classical planets, Uranus is visible to the naked eye, but it was never recognised as a planet by ancient observers because of its dimness and slow orbit. Sir William Herschel announced its discovery on 13 March 1781, expanding the known boundaries of the Solar System for the first time in history and making Uranus the first planet discovered with a telescope.

The dwarf planet Pluto has five moons down to a detection limit of about 1 km in diameter. In order of distance from Pluto, they are Charon, Styx, Nix, Kerberos, and Hydra. Charon, the largest of the five moons, is mutually tidally locked with Pluto, and is massive enough that Pluto–Charon is sometimes considered a double dwarf planet.

Henry Cavendish, british physicist (1731-1810) was the first scientist to calculate mass of the Earth. Greater accuracy has not been achieved for nearly 100 years. He only made a mistake about 1% compared to today's calculations. Cavendish estimated the mass of the Earth to be 6 billion trillion tons. Modern calculations say about 5.9725 billion trillion tons. (5,97219×10^24 kg)

Discovered craters on Mercury are named after outstanding artists. In addition to the above, there are also craters on the Mercury map named after: A. Mickiewicz, L. van Beethoven, F. Goya and C. Monet.