Mark was already remarried in less than 4 years, and he wouldn't give her dog back.
A more dependant man would have killed himself, a slightly less dependant man would have wallowed in grief for 20 years then died of a broken heart, a yet still more slightly less dependant man would have divorced or murdered his new wife upon finding out that Kathryn was still alive... And so on.
4 years is quick.
If he wasn't hitting on women at Kathryn's funeral, pulling prime tottie using lines about needing consolation that worked so well, he then crashed every funeral for all 150 crewmen to keep his wick wet for the next 2 years.
4 years is far too quick.
Mark must have been already having an affair with at least one woman when Kathryn was lost in space.