Can ethics be a hard science?

In hard sciences, scientists in the discipline seem compare to control groups and experimental groups, making quantitative measurements of each. That does not seem possible with ethics. Moreover, ethical values are measured by ordinal ranking and not in cardinal numbers. So I can measure one value against another by saying that I value my mother more than I value my hat, but I cannot say, with confidence, that my mother is worth exactly 100 utils to me, as opposed to 130 utils. Is that an obstacle to ethics being a hard science? What is the status of ethics as a science?