What is this based on? One of the chief contributors to the mass of a Mars voyage is shielding.
https://science.sciencemag.org/content/340/6136/1080.abstrac...
*Edit - but the comment higher up isn't right either, that most Mars-bound astronauts will have decreased lives. The paper linked above estimates 3% of astronauts to die from cancer caused by the trip (assuming no exposure on the surface of Mars, meaning they're in the ground).
This unfortunately resulted in people thinking Mars is a 'one way' mission. Elon Musk has repeated that to make live on Mars sustainable, you need roundtrips. You can't keep making new rockets, eventually you need them back. Otherwise it would become too expensive.
Info here: https://en.wikipedia.org/wiki/Mars_One
> for Mars Ascent and Earth return, SpaceX should develop a mini Starship, sized to be an upper stage of an F9. This would create a fully reusable medium lift booster, and reduce Mars propellant making requirements by a factor of 5. A Starsip could lift one of these to LEO fully fueled, after which it could fly to Mars, and return. any full sized Starships that land on Mars should stay on Mars. SpaceX will make plenty of Starships, it won't need any back that go to Mars. A Starship on Mars is much more valuable than one on Earth.
https://old.reddit.com/r/spacex/comments/hgy64k/ask_me_anyth...
It also gets debunked by replies. This will never happen.