Apple CEO Steve Jobs announced on Monday that he was taking a medical leave of absence to concentrate on his health.  The U.S. stock markets were closed on Monday, for Martin Luther King day, but markets in Europe saw Apple shares drop by as much as 8 percent.

This is the third medical leave of absence for Jobs in the last 10 years.  His first was for treatment of a rare form of pancreatic cancer, and his second was for a liver transplant.  Both times these details were not available until after he returned. 

That is the case this time as well.  While there are no details as to why or how long he will be gone, Jobs will remain as CEO of the company, while Cheif Operating Officer Tim Cook will be responsible to day-to-day operations, as he was during Jobs last leave of absence.