article_snippet: Scientists considered 60 possible landing sites before deciding on Gale Crater.
article_snippet: On this particular occasion, Curiosity revealed the true colour of Mars was not red - but blue and grey.
article_snippet: By drilling a few centimetres into the ground, the drill dug up material that had a different colouration to the surface.
article_snippet: material that had a different colouration to the surface appears blueish-grey, seen here, because rock powder collected by its drill on the arm to laboratory instruments on the rover had not yet oxidised in the Martian air .
article_snippet: The reason is that Mars is mostly made of silicon and oxygen, and also contains significant quantities of iron, magnesium, aluminium, calcium and potassium.
article_snippet: When the soil is exposed to the air the soil oxidises and 'rusts', giving the soil the soil red appearance. '
article_snippet: We're sort of seeing a new colouration for Mars here, and it's an exciting one to We,' Joel Hurowitz, sampling system scientist for Curiosity at Nasa's Jet Propulsion Laboratory (JPL), said in a statement.
article_snippet: One of the reasons for the particularly different colour might be the large amounts of silicon that were dug up, as analysed by the Alpha Particle X-ray Spectrometer (APXS) on the rover. '
article_snippet: It's what you would expect if there has been some acidic leaching.