Take to the laundry mat and wash with vinegar to get the mold out. Either that or bleach, which might make the sheet all funky colored but will get the stains out! maybe.

Then just throw it in the dryer and tumble dry. To save your finances only dry till its mostly damp (IME blankets take a few rounds to get really dry) and then take it home and hang it up or drape over a fence. I think the last few times I've done it I just took them home wet, but its been a while.

"The surest sign that intelligent life exists elsewhere in the universe is that they haven't tried to contact us yet."