When did Mars become inhospitable?

[Spaced]

I seem to recall Ra mentioning that when the Maldek entities first came to Earth they incarnated within the earth rather than on the surface and that they incarnated in 2D form but with 3D minds (though still tangled by the knot of fear). I suppose they existed in this state for some time before being able to incarnate on the surface as humans, which is maybe what happened around that 46,000 years ago date.

relevant quotes:
6.13 Questioner: Is all of the Earth’s human population then originally from Maldek?
Ra: I am Ra. This is a new line of questioning, and deserves a place of its own. The ones who were harvested to your sphere from the sphere known before its dissolution as other names, but to your peoples as Maldek, incarnated, many within your Earth’s surface rather than upon it. The population of your planet contains many various groups harvested from other second-dimension and cycled third-dimension spheres. You are not all one race or background of beginning. The experience you share is unique to this time/space continuum.

9.17 Questioner: Is there any particular race of people on our planet now who were incarnated here from second density?
Ra: I am Ra. There are no second-density consciousness complexes here on your sphere at this time. However, there are two races which use the second-density form. One is the entities of the planetary sphere you call Maldek. These entities are working their understanding complexes through a series of what you would call karmic restitutions. They dwell within your deeper underground passageways and are known to you as “Bigfoot.”[...]