Oh, I read this: "I leave this in our usual location. Knowing these files have not been touched since that day, I doubt this will be of assistance. But just in case ... Please, Mara, reach out. Contact Petra, contact me. If you can." - Audio file, Royal data vault, timestamp four days after the battle at Saturn Says who four days after the battle, why would they be telling her to contact Petra?

Where did you read this at?

I saw it on the last part of the Petra quest, it's up on the destiny wiki too.