"Mars cannot be terraformed so that we can live there because there is not enough carbon dioxide, scientists reveal"

Sorry Elon.

From The Independent:

We will 'need technologies well beyond our current grasp' if we plan to move to the red planet, a new study has found

We won't be able to comfortably live on Mars, experts have revealed.

Scientists – as well as science fiction fans – have long hoped that we might be able to change Mars so it has an Earth-like atmosphere, allowing us to comfortably live there. Plans to do so have included dropping thermonuclear weapons at the planet's poles – an idea supported by Elon Musk.

But there simply isn't enough carbon dioxide on the planet to allow the atmosphere to ever become habitable for humans, according to new research. At best we could achieve only a fiftieth of what is needed, and would only be able to raise the surface temperature by less than 10 degrees Celsius, the study published in Nature Astronomy reveals.

Proponents of terraforming often suggest that we could use the greenhouse gases that are stored in Mars' rocks and polar ice caps. If those were released back into the atmosphere, it would make it thicker, heat up the planet, and allow liquid water to remain on the surface.

That, in turn, would allow future Mars settlers to roam around the planet without dying, they suggest....MORE

Not dying, major selling point.

Here'sthe paper at Nature:
Inventory of CO₂ available for terraforming Mars