Which planet is the smallest in the Solar System?

It is the closest planet to the Solar System, with a diameter just over one-third that of Earth.

Question

Question 1: Which planet is the smallest in the Solar System?

a. Mercury

b. Saturn

c. Uranus

Question 2: Mercury is the hottest planet in the Solar System, true or false?

a. True

b. False

Question 3: Which of the following sentences does not correctly describe Mercury?

a. Mercury has the highest average density in the Solar System.

b. Mercury has no natural satellites.

c. Mercury does not have seasonal weather changes.

Question 4: How many days (in Earth days) does it take for Mercury to complete its orbital period?

a. 68 days

b. 78 days

c. 88 days

Question 5: How many spacecraft have approached Mercury?

a. 2

b. 1

c. 0

Answer

Question 1: a - Mercury. Mercury is the closest planet to the Sun and the smallest in the Solar System. According to image data collected by the Messenger probe of the US National Aeronautics and Space Administration (NASA), the diameter of Mercury has narrowed by more than 13 km over the past 4 billion years. To date, the diameter of this planet is about 4,800 km, equal to 38% of the diameter of the Earth. Mercury is even smaller than Ganymede - the largest satellite of Jupiter and Titan - the largest satellite of Saturn.

Sentence 2: b - False. Closest to the Sun, Mercury is the second hottest planet in the Solar System. The temperature of Mercury's surface facing the Sun reaches 427 degrees Celsius, while the other side can be as low as -173 degrees Celsius. Meanwhile, Venus (the second planet from the Sun) has an average temperature of 462 degrees Celsius, is the hottest planet in the Solar System and holds the record for the most extreme weather in the universe.

Question 3: a - Mercury has a lower average density than Earth. Mercury is the second most dense planet in the Solar System (5.427 g/cm ³ ), after Earth (5.515 g/cm ³ ), despite its very small size. The reason is that Mercury's core accounts for about 42% of its volume and contains more iron than the other planets. Mercury and Venus are two planets in the Solar System that do not have natural satellites (also known as moons, only natural objects orbiting a planet or asteroid). With an extremely fragile atmosphere, Mercury does not have seasonal weather changes.

Mercury's core (right) makes up 42% of its volume and is rich in iron, giving the planet its average density, second only to Earth's (left). (Photo: Steemit)

Question 4: c - 88 days. Mercury takes only 88 days to complete its orbital period (the time it takes a planet or satellite to return to a fixed position in space), much faster than other planets. This speed of movement caused Mercury to be named after the Roman god Mercury, equivalent to the Greek god Hermes - the god of communication and messengers.

Question 5: a - 2. Because it is only about 58 million km from the Sun, Mercury is very difficult to reach. In 1974 and 1975, NASA sent the Mariner 10 spacecraft to visit Mercury three times and mapped less than half of the planet's surface. On August 3, 2004 , the Messenger probe was launched into space and entered Mercury's orbit on March 17, 2011. It carried out the mission of observing and researching historical and geological information about the smallest planet in the Solar System. Messenger ended its mission by crashing into Mercury at 3:30 p.m. on April 30, 2015. After more than 4 years of operation, Messenger provided valuable data and more than 100,000 photos of Mercury. One of the biggest discoveries was the giant ice block in the north polar region, where it is not illuminated by the Sun.