Terraforming Mars may have to wait yet a while longer.
The Martian surface is covered in UV-activated chemicals that inhibit the development of any lifeforms, as recent tests of the topsoil have shown.
ESA’s Exomars rover will now begin digging under Mars’ toxic surface, searching for any proof of current or past life on the planet.
Recent tests conducted on Martial soil have confirmed that oxidant compounds known as perchlorates permeate the the Red Planet’s surface.
Perchlorates are highly oxidized forms of chlorine, a chemical commonly used in household cleaning products and also as a disinfectant in swimming pools. The downside of it is that at high concentrations, chlorine is extremely toxic. It was weaponised and used as a chemical warfare agent during the First World War, for example.
Perchlorates were first thought to be present on the Martian soil as far back as 1976, when the Viking probes landed there. The compounds were detected again by the Curiosity rover, which is still marauding around Mars today.
The bad news is that when perchlorates are hit by UV radiation, which occurs on Mars pretty much all the time, the compounds become activated and turn into a particularly effective bactericide, killing off most microbial life.
This effect is a double edge sword. While the chemicals present on the Martial soil will destroy any microbe brought from Earth, thus preventing the contamination of Mars with exogenous bacteria, it also means that life on the surface is all but impossible at this point in time.
Scientists will now have to dig deep into the Martian subsoil to try and find any trace of life, past or present.