Another thing to remember is
the faint early
Sun paradox: the Sun was substantially fainter
early it its life.
That means that its luminosity and temperature were
lower, which means that the temperature at
Earth would have been substantially lower (except
for the fact of the CO2 atmosphere).
In other words, the habitable zone moves as a function
of time in the Solar System.
The last term to learn is the continuous habitable
zone, the region of the Solar System where liquid
water has always been possible throughout the entire
age of the Solar System.
This stuff will be on Homework 5 (I think) for you to calculate
and understand the details of.