> works well enough for rotating in space but doesn't help on a planet surface. I'm not sure how you think that would work under low gravity on a planet.

like literally every small amusement park has one around.

in a planet you make a horizontal ring and rotate it, it would generate a centrifugal (pseudo) force. you put the floor you would walk on perpendicular to the resultant of Mars gravity and centrifugal force. if you have 0.4 g then if you don't rotate you have 0.4g as minimum, in which case the floor is horizontal. the quicker you spin it the more total gs you have and the more slanted you make the floor ( with a limit of but never reaching 90 degrees for extreme accelerations.

as for the low gs, sure we don't have specific data, but we already know poodle survive over a year in 0g with only minor issues, and some of the issues are actuality issues that affect your return ( you are ok in 0g with muscle and bone loss) .

and dime of the issues are related to not having a " down" those inmediately disappear on Mars, since it has a clear " down"

moderately low gs are clearly and inbetween case so they will be likely not much of an issues for adults, since they can already survive in 0g.

we have little to no data on pregnancy and davenport in zero gravity and none in Mars g, so those could be an issues or not, we don't know. in pregnancies it is probably either pregnancies can't get to term due to the lack of a down vector, or no effect at all. the fetus is already floating in liquid so the lack of gravity is unlikely an issue until after birth.

a child growth would presumably be affected somehow by lower weight, kids might grow thinner, or taller, or weaker. sobre will have to see. again it seems these are issues that are more likely to hinder the martian born from traveling to earth more than their life there. but in the worst case you could solve if not with weights and exercises with the rotating habitat creating 1g.