Yes. A hole. That is what an HZE particle makes in your brain and other structural tissues. And other structures. Including helmets and a roof. In a metal, for example, this is a hole the size of the nucleus of the ion. Not a macroscopic hole. Not the kind of hole that things pass through, but the kind of hole that gradually alters the crystalline structure, resulting in increased brittleness or other gradual property changes.

In your brain and other living tissues, however, the hole is much bigger because its effects are multiplied by the damage to DNA and the inflammatory results of that damage, plus the effect of the secondary radiation. Human tissue is very sensitive, for example, to neutron radiation. HZE particles kick neutrons out of some of the nuclei that they strike.

If anyone is not worried about this happening, then anyone doesn't understand the first thing about particle radiation and needs to read first and type later.

Furthermore, the Curiosity results have been widely debunked. They were announced prematurely and without adequate analysis. The detector is inadequate to the task of estimating human structural tissue dose over a long period.

Have a look at this image. See those HZE events? See how frequent they are? Those are in a detector with a cross-sectional area much smaller than your brain. Well say goodbye to at least one neuron (and more probably dozens, or even hundreds, of neurons) each time one of those events occurs. That's time in hours and minutes across the bottom. The detector is covered in thin foil, like a roof or a helmet, except thinner. Remember that, for secondary radiation from HZE events, thicker is worse.

Nobody who has any idea about the subject is worried about cancer. People who know nothing about radiation beyond LEO equate radiation dosage with cancer risk. The most significant risk has nothing to do with cancer; it is the risk of damage to non-regenerative structural tissues, like the central nervous system.

Medicine is rapidly improving...

Yes, but the physics of the interaction of HZE particles with structural tissues isn't. High kinetic energy in a non-regenerative tissue makes a big mess. Improved medicine isn't going to do much for the splat you make when you hit the ground at Mach 1, either. Kinetic energy, like gravity, is a harsh mistress.

Plant life can potentially be genetically modified... blah, blah, blah

Now you're into science fiction, which is the whole point. It's not that we can't potentially live on Mars, it's just that we haven't done the necessary science.

And why are you talking about UV? Did I say anything about UV? No, I did not. Nobody is talking about UV. Filtering UV is no issue. Are you aware that different types of radiation are qualitatively different in their effect upon human tissue? It doesn't sound like it.