Can an attachment be put on a hero that is from another sphere than the sphere of the attachment.

For example, Can the "Blood of Numenor" attachment which has a spirit resource icon be put on a tactics hero?

The text states: Condition. Attach to a Gondor ro Dunedain hero. Action: Spend 1 resource from the attached hero's resource pool to give attached hero +1 defewnse for each resource in its resource pool until the end of the phase. (Limit once per phase.)

This attachment does not specify that it has to be put on a Spirit hero, so as long as I can resource match to actually play the card from my hand can I put it on any Gondor or Dunedain hero?

Yes. Unless the card specifies otherwise, you can place attachments on characters of any sphere.

Great! Thanks for your reply soldat7