how to make purple circle appear on atlas?

ive got 3 memory fragments from maps with a purple circle around it on the atlas. i know thats the only way to get one is to complete the maps with the blue circle... but how does the purple circle appear? randomly? or do i need to do something

wiki - "Players acquire Shaper's Orbs by collecting Memory Fragments and giving them to Zana. Memory Fragments are found by killing the bosses of Elder-influenced maps circled in purple on the Atlas. To acquire multiple Shaper's Orbs of tier 8-10, the map must be red tier and occupied by an Elder Guardian or the Elder himself."

nowhere on the page does it say how to make the purple circle appear

Run Shaper influence maps (cosmic effect) and kill their bosses, until you see Elder is starting to take them (tentacles effect).

Continue doing it with adjacent Shaper maps to spread Elder's influence and you will get maps with Memory Fragments inside the Elder zone.

Spread some more and you will get to fight Elder and his Guardians.

It's kind of random but you will slowly progress with this from White Tier to Yellow Tier to Red Tier maps, collecting fragments and getting Shaper Orbs in return.

Zana's quest line is to collect all fragments, which triggers

Each fragment corresponds to a map tier - the blue circle will pop up on any map of correct tier that you still lack the fragment from. Just spread Elder influence (tentacle stuff) toward higher tier maps.