You're not getting it. The Mars probe didn't crash because of bad unit conversion. It crashed because there were no units in the data!!! Go read about it you

You're not getting it. The Mars probe didn't crash because of bad unit conversion. It crashed because there were no units in the data!!! Go read about it yourself. NASA got some data from a contractor. The data had no units at all. The contractor assumed the data to be in some kind of US-standard units. NASA got these raw numbers and assumed they were in some kind of SI units. Having enforced units in your language isn't going to help in this situation at all. They weren't exchanging code, they were exchanging raw data, or more specifically, a table with a bunch of numbers on it. The people at NASA simply assumed some units (instead of calling the contractor and asking), and they would have done this in your scenario too.