I’m holding Martian soil!…..well…not really. but sort-of..
When you say ‘the Red Planet,’ most people will know you’re talking about Mars. The surface of Mars is a lovely reddish brown, reminiscent of the beaches in Prince Edward Island, Canada (I highly recommend visiting there, it’s beautiful). The colour of the soil on both Mars and in PEI is due to the same thing: rust. The physical process that creates rust is called oxidation, which is when an atom/molecule/ion increases its oxidation state (this has to do with the charge, positive or negative, of the atom/molecule/ion). Rust forms when the iron abundant in the soil is oxidized by oxygen, to form Iron-Oxide (of which there are many kinds: FeO, Fe2O3, Fe3O4, etc.). The oxidation of iron by oxygen is typically found in wet environments, indicating Mars had a warmer and wetter history.
The difference between Mars and PEI is we can’t study Martian soil up close here on Earth. We can either study it by satellites in Mars orbit, or we use our rovers like Mars Science Laboratory (Curiosity).
In order to try and do research here on Earth, scientists will create a ‘regolith analog;’ a simulant of the soil of another world, based on our observations and samples of it. There has been much research and development to create both Lunar and Mars soil analogs. In the case of the moon, we benefit from having many lunar samples from the Apollo program. In order to create Martian simulant, we use only that which we’ve learned from satellites and rovers (and I suppose Martian meteorites).
Here, I’m holding a sample of JSC Mars-1 (developed by Allen et al. 1997), a Martian regolith simulant developed for education and scientific research. This dirt is both chemically and spectroscopically similar to Martian soil, as well as the same in grain size, volatile content, density, and magnetic properties. Sample provided by John Moores (@arcticsaxifrage).