New propulsion systems for rocket engines would use mercury as a fuel, which could run the risk of spreading toxic chemicals through Earth’s atmosphere.
Title from the contents list in the SlideShare transcript of the publisher upload; order and section from contents page numbers. Quote added 2026-10-02 from the full slide transcript of the publisher upload (SlideShare, Wayback capture of the newer page format); source_url points at the section that holds the page.