Considering that Rarity and Twilight carried 2 tons boulder on they back in Discord episode and Sweetie Bell was hauling tons of stuff for Rarity in one of season 3 episodes, I am more then sure that Dinky can hold Dr. Who and Derpy from falling into that thing.
If it was not for they big strength, those 2 would now end up as space food ( Dr. Who would recover, sure, but what fun it would be to travel without his faithful assistant.
Well.... this is just odd. *Thinks* They are on one of Jupiter's moons, where they are escaping from aliens. Probably alien robots. And trying to escape, one of them tried to pull out Derpy and fell into the monster pit thing, and now the doctor is trying to pull her back in while Dinky tries to help.