Question: What was the first thing that you about Red planet?

Natasha Stephen answered on 18 Jun 2014:

The first thing I learnt about the Red Planet I guess was that it isn’t really red! It looks red, or maybe orange, from Space because of a fine layer of dust on the surface a bit like soil. This dust is ‘rusty’, which gives it the characteristic colour! What has happened is that over time on Mars, the rocks on the surface of the planet have been broken down by natural processes similar to the ones with have on Earth, weathering and erosion.

As these rocks break down, some of the minerals within them start to separate and if those minerals are rich in Iron (Fe), which a lot of the rocks on Mars are, this iron can start to oxidise in the atmosphere, i.e. it reacts with oxygen. This causes the minerals to rust!

It’s the same process that can happen to metal on Earth, like an old car that might go rusty if you leave it outside without covering it for years. The minerals are just rusting and changing colour on the surface to the orange/red colour that we see from space! If we brush away the loose material though, this rusty dust, the colour of the rocks beneath is a grey-green colour so a little different to what we are used to thinking of when someone says “the Red Planet”!