Gather Vex Parts
Seek out Vex Transformers across Io, Nessus, and Mercury, and destroy them to collect the resulting scrap. It's the only way to repair the Sundial.
"The Vex use their Transformers to generate barriers, manipulate matter, and power their chronometric tech. The Sundial leverages the latter technology. Hunt Transformers across the system and gather the scrap." —Osiris