Hi there,

I'm afraid I can't offer much in terms of an answer, but I like the question a lot...gravity is a difficult one. Controlling experiments properly would be different. NASA, ESA or any similar agency may have more infos on that. Barometric pressure probably is easier to experiment with. One thing I can envisage is that for enveloped viruses, the fluidity of the envelope membrane may change. That may potentially inhibit infectivity. If O2 partial pressure is low, that may also lead to a less oxidative state of biomolecules (but that's only guesses). I guess more will be known about the influence on cells of the physical factors you mentioned. That may be a starting point. I'd be very curious to what you find out...