I quit using ZFS when FreeBSD managed to somehow lose the entire zpool it was installed on. That was a long time ago, so I'd hope it's better now, but I've had no reason or inclination to waste my time with it since.
I've lost a 3T collection of HDTV movies back in the day (student) because of WD green drive that decided to return something else that was written to it in a USB box. Took me a while to realize what's going on, but seeing cksum errors when this particular drive was a member of zraid1, I didn't lose any more data (blocks with correct data and checksum were returned from pool) and was able to replace it on my schedule and money. Since then, I just don't feel like gambling on bitrot. Neither on movies, nor on family photos.
If you don't ask question two, there's no point in asking question one.
Unless they find the place teeming with life, which nobody expects, it's more likely that anything they find hitched a ride from Earth instead of originated on the planet. So if they're not willing to rule that possibility out, they'll just end up causing decades of speculation and conspiracy theories.
