http://www.sciencemag.org/news/2019/10/nasa-must-rework-planetary-protection-plans-panel-advises

In the 1970s, the Mars Viking landers were sterilized in purpose-built ovens.

NASA rules that govern the potential spread of earthly microbes to other planets—and the potential return of alien life back to Earth—are often anachronistic and require broad rethinking, according to a report released today by an independent agency advisory panel.