JAXA did a 1/6 g (like the Moon) experiment with rats in a centrifuge on the ISS this summer and when that gets published we'll have our first data point on how

JAXA did a 1/6 g (like the Moon) experiment with rats in a centrifuge on the ISS this summer and when that gets published we'll have our first data point on how low gravity effects mammal physiology. But really, we currently have no idea if Mars gravity is just as good as Earth gravity or just as bad as freefall.