Hitting Rocks for Science Mission

There are specific minerals locations that you have to go to (they are marked as quest objectives on the map)
When you get there, there will be a specific one you have to scan. It stands out a bit because you can't harvest the mineral from that particular node.

There are some on each planet you visit.

I have found areas but the radiation is so high I just die. Is this a mission I can leave and come back for? Do the radiation levels finally go down on the planet? 

I'm having the issue that I cannot scan the mineral. My cursor turns green and chimes noting that I have something scan-able but when I left click to do so it doesn't register. I am almost complete with this mission and would love to finish it.

EOS - After you restart the vault, complete the First Murder quest, and create an outpost, just go back to Nexus and continue on til you finish a few other planets.

Eventually Bradley will send you an email asking you come back to help Hainly (the scientist) with something.  

By then, all the radiation should be gone and you can explore the rest of Eos easily and do all the rock and memory trigger missions along with gathering caches.