Think cold, salty and dry to the extent of dessicated, and such a low atmospheric pressure that water ice evaporates straight to vapour. At the highest temperatures encountered, water will boil, or it might exist as thin films within the soil particles. Either way, it has a freezing point to Boiling point range of about 2 Celsius Degrees at the most.

The soil (regolith) itself acts as a dessicant. The nearest environment on Earth would be a laboratory vacuum dessicator, with dessicants so oxidising that they chemically destroy anything vaguely organic that land in it.

You could almost use it as a steriliser.

But then - drill down into the depths of Mars, and you just never know what you might find.

My own opinion is that we'll find rock and ice/CO2 clathrate - maybe some supercritical CO2 - but no life. Some people that work for NASA are more optimistic than me - or at least they have to seem optimistic to get the funds.

Mars is the only planet in this solar system where you have the possibility of supercritical CO2 and hydrothermal systems in close proximity.

Supercritical CO2 dissolves organic molecules (like oil), so when you evaporate off the CO2, we have a possibility of blobs of organic material surrounded by water and nutrients in hydrothermal vents. Add clay minerals and we have the first cell like structures.

It sounds like an interesting environment for life to have evolved - but that's pure speculation.

It should be possible to find life bearing planets some day. Just look for the oxygen signature in the absorption spectrum.  Oxygen means photosynthesis. Oxygen and Earth like temperatures are totally un-natural for planets without life.