Former U.S. Vice presidential candidate and Alaska Governor Sarah Palin (R) greets some of the thousands of motorcycle enthusiasts and military veterans participating in 'Rolling Thunder' rally May 29, 2011 in Arlington, Virginia. Although not an official guest, former U.S. Vice presidential candidate and Alaska governor Sarah Palin is expected to participate in today's motorcycle parade from the Pentagon to the National Mall.

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)

A grizzly bear eats a frozen fruits during a hot summer day at Rio de Janeiro's zoo January 13, 2015. According to a local climate institute, temperatures in Rio de Janeiro on Tuesday rose up to 34 degrees Celsius (93.2 degrees Fahrenheit). (Photo by Sergio Moraes/Reuters)

Visitors play in front of hot air balloons during the 2016 International Hot Air Balloon Festival in Taitung, southeast of Taiwan, 01 July 2016. Thirty-one hot-air balloon teams from 14 countries join the six days of competition during the festival, which will run from 01 July to 07 August 2016. (Photo by Ritchie B. Tongo/EPA)

Maksym Demchuk of Ukraine takes part in the FAI World Hot Air Balloon Championship near Gross-Siegharts, Austria on August 20, 2018. (Photo by Heinz-Peter Bader/Reuters)

Dotty, a short-haired pointer belonging to Simon Kirby MP, devours a Parliament shaped cake watched by a jack russell Maximus (L) owned by Matthew Offord MP during the Westminster Dog of The Year competition in Victoria Tower Gardens on October 13, 2011 in London, England. The annual competition was won by Conservative MP for Tiiverton and Honiton Neil Parish with his Labrador Wilberforce, who was among the 15 Conservative MPs to enter versus only two Labour MP entrants. (Photo by Peter Macdiarmid/Getty Images)

Seven month old Christine Joy shares her pram with two 5 week old Gunsure Golden Cherry's cocker spaniel pups from Gunsure Kennels in Ashford, Middlesex. 22nd May 1953. (Photo by Fred Morley/Fox Photos)