The Hemoglobin Nebula
djm
How can a galaxy have an iron defency?
All that helium. Gives it gas. 
djm
It’s not lack of iron but B-12.
It turns out there are multiple varieties of anemia. Sideropenic anemia is caused by iron deficiency; Pernicious Anemia by a lack of B-12. There are other types of anemia though. I figured Sideropenic would be a more likely one though since B-12 would be a very definate sign of at least microbial life and would be all over the headlines by now.
Then again, anemia is broadly defined as a deficiency in the hemoglobin, so that should also be a pretty sure sign of life.