Orbital debris cannot be recovered without permission.
Wireless power beaming burns the atmosphere. If it is n % efficient, then where is the other 100-n % of that energy?
What is the minimum latency to each of the LaGrange points?
We should send humanoid robots to establish human-sized habitats with airlocks for a number of years before risking humans.
-- 2026
Can Humans that breathe CO2 breathe on Earth?
Humans with tardigrade DNA for radiation resistance risk their offspring losing said advantage if they cross with a person who is not so hardened.
Without artificial gravity and fortification, humans' musculoskeletal structures will not develop sufficiently in lower gravity to survive on Earth. If a person is born on Mars, what do they need to do to physically return to Earth?