What is more, most of the 13 tonnes is made up by the propellants unsymmetrical dimethylhydrazine (UDMH) and dinitrogen tetroxide (DTO), both of which are toxic.

BBC: Stricken Mars probe stays silent

There will be a self-ignition of the UDMH and if it does not all burn up, it will be so dispersed there will not be a critical concentration.

BBC: Video tracks stricken Mars probe

The propellants, unsymmetrical dimethylhydrazine (UDMH) and dinitrogen tetroxide (DTO), are highly toxic but they will almost certainly be consumed in the fireball that engulfs Phobos-Grunt when it makes its death dive to Earth.

BBC: Video tracks stricken Mars probe