But for the second one, more information on artificial gravity through centripetal force makes a lot of sense.
Because of the ISS we know that stays of greater than 12 months in zero gravity have real but minor impacts on the human body. So 3-4 month trips to Mars in zero-g are feasible.
If we assume they aren't, those trips would be far more resource intensive.
The ISS is nothing more than Mir 2, built around the DOS-8 module, it's a Salyut with American funding because this time America wanted to keep the Russian space program solvent to make it harder for Iran/etc to recruit that Soviet talent. And because NASA likes long term projects that require around the clock staffing because that's great for budgets and careers. That's why the ISS exists.
Also we aren't going to Mars. Sorry. A lot of individuals are passionate about that but at an organization level there is no drive for it. NASA likes to use the talk of it for fundraising but never makes progress on it and Congress won't ever greenlight it, and SpaceX uses it to keep their employee moral up but all they are demonstrably working towards is being the king of launching satellites. The only money to be made in space is with stuff pointed at Earth. There is no economic case for Mars colonization. It's not happening. I wish it weren't so because I'm a sci-fi junky, but it is what it is.
I doubt that. ISS served in space longer than Mir and Salyut-7 combined, I would expect it to run more experiments and get more data - especially as the equipment is more modern and experiments are planned with the benefit of knowledge of the previous works.
The people on ISS were doing a multitude of scientific programs during that long time. That's important. Just like you wouldn't say that Hubble already seen everything and JWST isn't needed.
We still have no idea what long term stays in Martian or even Lunar gravity does to a human body. We don't know because we have spent the past half a century fucking around with useless zero-g space stations instead of building von Braun wheels which could easily be used to simulate those conditions. Because forget about Mars colonization, merely finding the political willpower to do something as conceptually simple as spinning in space is evidently impossible for us.
(I assume the astronauts in 2001 A Space Odyssey jogged in the direction that made themselves weigh more, to make their workout more intense.)
A big wheel may be too costly, but it can be replaced by either 2 identical bodies with a long link between them, or with a single body linked to a counterweight, in which case the cost would be only marginally greater than for the current spaceships.
It would be embarrassing if the mouse babies come out crippled, even if it doesn't immediately generalize to humans and the low-g environment of Mars.
> Twenty out of 30 eggs (nine out of ten 10-day-old eggs; 10 out of ten 7-day-old eggs; 1 out of ten 0-day-old eggs) were recovered alive after landing. The only living embryo of the 0-day-old egg died 24 days after launch, and was comparable to a 16-day-old embryo when it died. The high mortality of the 0-day-old eggs appeared to be related to the specific inner structure of the egg. The yolk (specific gravity, 1.029) would not have separated from the albumen (1.040) during space flight.
1: https://pubmed.ncbi.nlm.nih.gov/9600757/ ( https://archive.is/r66W3 )
https://finchwench.wordpress.com/2011/09/06/cosmoquails/
Still, trying it with mice (or other mammals) would have been worth it, because we can't rule out mammals being more robust during embryogenesis than birds. The ISS actually has still a few years left, so there would be some time left for such an experiment. Though I doubt it will happen.
We do know. The radiation kills us well before the lack of gravity does. The end.
We have to have shieldings thick and heavy as nuclear bunkers for a real space station to work, and such shielding is just way too heavy to be launched from Earth(unless e.g. we'd be okay with launching a toilet stall worth of habitable volume per Starship), so the station has to be mostly fabricated "in space", which is both technically and politically not yet feasible. There are theories that horizontal branches that may exist in natural crevices on the Lunar surface might work. Or for Mars some say we can just drill some mineshafts there and live inside. but all those options are equally sketchy in its own ways at this moment.
We're barely flying hatchbacks up to orbits and we want airport garages out there to park it. We're not hauling the whole building in the back of a Prius, not even on Earth, obviously.
What NASA, ESA, etc. had been doing is to drive up that Prius to the trailer home left in the middle of the desert, have them change lightbulbs, celebrate themselves and rotate crews. That's basically useless, but they keep repeating that useless "expeditions" because they'll have to start over from reinventing tubeless wheels if they stop paying for the gas even just for one year.