Question 1

Still booming

Accepted Answer

Our solar system comprises eight planets. Earth, Mars, Venus and Mercury are telluric planets, small, dense and generally made up of  three layers  of metals and silicates. Jupiter, Saturn, Uranus and  Neptune are gas giants, which do not have solid surfaces and are more distant from the Sun. All four of them  do have a ring sytem –  Saturn's is the most visible one  – and atmospheres churned by huge storms. Jupiter and  Saturn consist mostly  of hydrogen and helium, whereas Uranus and  Neptune also contain water, ammonia and methane coming in the form of ice.It used to be believed that the planets had formed at the very same place where they have been to this day.. But the dicovery of exoplanets has turned this vision around from 1995. Since 2005, the Nice model – developed by an  international team – provides one of the most convincing explanations for the Solar system's current organisation. It suggests that the planets were born in a cloud of gas and dust surrounding the then young Sun, but the gas  giants, through gravitational interaction with a plethora of  smaller bodies, migrated. This «cosmic snooker game » effectively pushed them away and outwards.This migration, spread over several hundreds of millions of years, caused a massive  redistribution  of matter : asteroids and  comets rained down in droves on  internal planets, among which the Earth and the Moon. This is referred to as the Late Heavy Bombardment.

Question 2

Funfact | Adress: Extra-solar system

Accepted Answer

Two Swiss astronomists from Geneva University discovered the first exoplanet orbiting around a solar-like star (51 Pegasi b) : Michel Mayor and Didier Queloz. They were both awarded the Nobel Prize for Physics in 2019 (shared with astrophysicist James Peebles).

Question 3

Funfact | My Very Excellent Mother Just Served Us Nachos.

Accepted Answer

This excellent planetary mnemonic will help you  remember the order of the eight planets from the Sun : My Very Excellent Mother Just Served Us Nachos.(M,V,E,M,J,S,U,N) for Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune.

Question 4

Funfact | The other planets

Accepted Answer

While the other planets of our solar system have been known since Ancient times, Uranus was not discovered until 1781 and Neptune in 1846.

Question 5

Funfact | 76 years later

Accepted Answer

After 76 years and a revisitation of the definition of  what a planet is, Pluto was demoted from its planetary status and  recategorised in 2006 as a dwarf planet by the International  Astronomical  Union (IAU) (We still love you, Pluto !)

Question 6

The twelfth man was a geologist

Accepted Answer

Of the twelve individuals who walked on the Moon,  all were American men and only one of them was a scientist  : Harrison Schmitt. Until then, the  NASA would train their pilots in geology ; after intense lobbying from the science community,  a geologist was eventually trained in piloting.Schmitt spent three days on the Moon during the  Apollo 17 mission, in December 1971. Despite he was the last astronaut  to have walked on the Moon, he was not  the last one to leave it : his crewmate and misson commander Eugene Cernan holds the symbolic title of the last man to have walked on the Moon. Thanks to his expertise, Schmitt was able to identify interesting geological contexts on site and select the most relevant samples. Apollo 17 brought back 110 kilos of  lunar rocks, that are still studied nowadays.

It is raining meteorites

Tracing back the thread of Earth's history, we arrive at a period called the Hadean, in reference to the god of the underworld. This era is apocalyptic and mysterious.

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