Khaled Nasraoui/picture alliance via Getty Images
- Videos appear to show mystery lights in the sky before Morocco's devastating earthquake.
- Scientists say so-called "earthquake lights" have long been reported when tremors hit.
- Experts still aren't sure what causes them because they are difficult to study.
Mysterious lights appear to have been spotted in Morocco before a devastating earthquake hit last week — and scientists still can't figure out what caused them.