“I think Mars would smell chalky (like when you do DIY and the whole place smells of dust) but with an iron-rich blood undertone. I think due to the sulphur compounds present it would also have a hint of egg.” Dr Louisa Preston, Dept of Space & Climate Physics at University College London, and Planetary Groups' Habitability Lab at the Mullard Space Science Laboratory.

“...dry desert, dusty, rusty sandy smell.” Professor Hilary Downes, Professor of Geochemistry, Department of Earth and Planetary Sciences, Birkbeck, University of London.

In order to imagine what it would be like if we could breathe while standing on the surface of Mars, we had to consider the chemistry and mineralogy of the Martian atmosphere and surface. Once we thought about that, we realised that the smell of Mars would be rather peculiar, but not necessarily that ‘revolting’.

Mars has a very thin atmosphere with a composition of: 95.32% carbon dioxide, 2.7% nitrogen, 1.6% argon, 0.13% oxygen, 0.08% carbon monoxide, and in minor quantities of parts per million water, nitrogen oxide, neon, hydrogen-deuterium-oxygen, krypton and xenon.

Unlike with the Moon, we do not have any rock samples from Mars, so what we know about its chemistry and mineralogy is derived from remote sensing data obtained from orbit, in situ measurements taken by robotic landers, and studies of Martian meteorites.

The famous red dust... The Martian surface is covered by a thin layer of very fine red dust; the rusty colour is due to the presence of ferric iron oxides. This dust also contains some form of strongly magnetic mineral, sulphates and chlorides.

Beneath the dust... are coarser soils and volcanic rocks, which are of basaltic composition in the ancient highlands of the southern hemisphere, but richer in silica in the younger plains of the northern hemisphere. There are also hydrated minerals such as haematite and clays, opaline and sedimentary deposits, and this is one of the reasons why we know that there was water on early Mars.

At the poles... Mars has two polar caps, but unlike the Earth’s polar caps, which are made solely of water ice, Mars’s polar caps are made of a combination of water ice and carbon dioxide ice (better known as dry-ice). When temperatures rise (imagine the chilliest summer of your life), the carbon dioxide changes directly from ice to gas – this is known as sublimation – and it floats in the atmosphere until it gets colder and it freezes again. As the polar cap shrinks during the warmer months, it develops dark spots, rifts and ragged edges, and surface details that were obscured can be seen.

With all this in mind, we imagine that the smell of Mars would be an acrid and suffocating combination of dusty smells, acid, sulfuric and chlorine notes, and dry rusty metal. Imagine sucking on a rusty metal coin while cooking a huge pot of cabbage and eggs. Of course, we have tried to make it a little bit less off-putting so that it can be smelled for at least a few seconds!

MORE ABOUT MARS

Currently inhabited by aliens...from Earth.

Average distance from the Sun: 227,940,000 km

Length of year: 687 Earth Days

Length of day (a Martian day is called a ‘sol’): 24 hours 37 minutes

Equatorial radius: 3396.2 km

Mass: 6.42 x 10^23 kg

Surface gravity: 3.71 m/s2

Mean density: 3933 kg/cm3

Escape velocity: 5.03 km/s

Surface temperature range: -140 to 30°C

Number of moons: 2, Phobos and Deimos