Mercury could unlock secrets to how our moon formed: Scientists find striking similarities between two cosmic bodies Just like the moon, a part of Mercury's surface is relatively smooth Its cratered land also has a similar topography and age to that of the moon Scientists propose that Mercury and the moon may be chemically similar This provides evidence in support of popular theory on how moon formed Mercury, the closest planet to our sun, may hold the key to understanding how the Earth's moon formed. Nasa scientists have highlighted how Mercury has some striking similarities to Earth's satellite, particularly in relation to its geological history. At the recent Origin of the Moon conference held at the Royal Society, London, scientists said that the finding could shed light on a popular theory on how the moon was created. Mercury (pictured), the closest planet to our sun, may hold the key to understanding how the Earth's moon was formed Sean Solomon, the principal investigator for Nasa's Messenger mission to Mercury, told Space.com that the similarities show that Earth and the moon are not unique in having a similar isotopic composition. He said, "aspects of the moon are common to rocky bodies that are similar in size despite being different in bulk composition." There is currently no theory that can fully answer all the questions about how the moon formed. The most popular theory is that the moon formed when a planet, around the size of Mars, collided with Earth around 4.56 billion years ago. The most popular theory is that the moon formed when a planet, around the size of Mars, collided with Earth around 4.56 billion years ago This collision divided Earth into two unequal parts. The smaller of these condensed into the moon. The best simulations of this process suggest that about 80 per cent of moon ought to have come from the impactor and 20 per cent from the Earth. The hypothesis, however, has been called into question by measurements that find that the Earth and Moon have the same isotopic composition. In March this year, the Messenger spacecraft finished mapping the Mercury's entire surface, and scientists are now ploughing through the data that was beamed back. One of the most significant findings is the similarities in geological history of both the moon and Mercury. Just like the moon, a part of Mercury's surface is relatively smooth. On Mercury, the smooth area covers 27 per cent of the surface; on the moon this is around 16 per cent. The surface of Mercury (left) and Mars (right) has some striking similarities. Mercury's ancient cratered land has a very similar topography and age to that of the moon Scientists believe these areas were formed billions of years ago from volcanic eruptions that covered the surface with lava. Mercury's ancient cratered land also has a very similar topography and age to that of the moon. Both bodies have polar ice deposits and also have two sides that are strikingly different from each other. Solomon believes to get a better understanding of how the moon formed we need to get a sample from Mercury. If Mercury happens to be isotopically similar, it could suggest that the objects that collided to grow the final stages of the Earth and created the moon were made out of similar material. "If there was [such a process]," said Solomon, "all our puzzles about why the Moon and Earth are so similar isotopically then evaporate." A controversial theory has been proposed that a giant explosion equivalent to 40 billion atomic bombs originating from the Earth's core somehow led to the formation of the moon. Planetary scientist Wim van Westrenen believes this violent event took place approximately four-and-a-half billion years ago and could answer the hotly contested question of where our moon comes from. The scientist, from VU University in Amsterdam, told New Scientist magazine that previous explanations about how the moon came to be simply do not add up. Chemical analysis of the rocks last year by the University of Chicago found that they shared identical oxygen, silicon and potassium isotopes with Earth, hinting that the Moon shares its origin with the Earth. Van Westeren said that taken at face value, the findings suggest that the moon was once part of the Earth that was blasted into space by an enormous explosion from the Earth's fiery core. To do this, he believes that there must have been a 'massive energy kick' delivered quickly and he calculates that the explosion was the strength of 40 billion atomic bombs the size of those dropped on Hiroshima.