iPhone 4 hard case cover with portrait of Steve Jobs are on sale on October 9, 2011 in Shenzhen, Guangdong Province of China. Apple co-founder Jobs died on October 5, 2011 at the age of 56. (Photo by ChinaFotoPress/Getty Images)

A surfer heads out at Coldingham Bay an inlet in the North Sea on February 15, 2012 in Coldingham, Scotland. (Photo by Jeff J. Mitchell/Getty Images)

In this November 2, 2017 photo, Mathew Fulkerson and his wife Leigh Ann pose at their Subterra Airbnb located in a former underground missile silo base near Eskridge, Kan. It was designed to house a nuclear warhead six decades ago – but now, this Cold War silo is the perfect spot for a mini break at just $133 a night. (Photo by Thad Allton/The Topeka Capital-Journal via AP Photo)

Three-month old cheetah cubs make their public debut at the Smithsonian National Zoo on July 24, 2012 in Washington, DC. (Photo by T.J. Kirkpatrick)

An engineer begins the process of conducting a block-by-block inspection of the exterior of the Washington Monument while suspended by ropes September 27, 2011 in Washington, DC. The National Park Service has closed the landmark in the nation's capital indefinitely due to damage caused by a 5.8 magnitude earthquake in August. (Photo by Win McNamee/Getty Images)

Bao Bao, the Giant Panda cub is seen by the media for the first time January 6, 2014 inside his glass enclosure at the Smithsonian's National Zoo in Washington, DC, a few days before going on display to the general public. Bao Bao was born at the Smithsonian's National Zoo August 2, 2013. (Photo by Paul J. Richards/AFP Photo)

New York Police Department tactical police officers stand guard near the New York Stock Exchange on September 9, 2011 in New York City. Officials are stepping up security in New York and Washington D.C. a day after U.S. officials received a credible but unconfirmed terror threat to utilize car bombs on bridges or tunnels in New York or Washington. (Photo by Justin Sullivan/Getty Images)