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The New Year's Eve ball that will be lit and sent up a 130-foot pole atop One Times Square to mark the start of the 2019 new year in Times Square, New York. Julie Walker/AP hide caption

President Trump and Defense Secretary James Mattis at the White House in October. Mattis will be replaced by Deputy Defense Secretary Patrick Shanahan on Tuesday. Chip Somodevilla/Getty Images hide caption

Davi de Oliveira Moreira, known as "Sereio" (merman in Portuguese), poses in costume at Arpoador Rock on Ipanema Beach in Rio de Janeiro last May. Yasuyoshi Chiba/AFP/Getty Images hide caption

Serena Williams and Roger Federer, shown here at the Wimbledon Championships 2012 Winners Ball, are set to play each other at a mixed doubles match on New Year's Day at the Hopman Cup in Perth, Australia. Clive Brunskill/Getty Images hide caption

Russia's Federal Security Service announced Monday that it detained a U.S. citizen in Moscow last week. Alexander Zemlianichenko/AP hide caption

Arunachalam Muruganantham, inventor of a menstruation pad machine, tests the quality of the pads as local women, who are eager to learn how the machine works, look on. Anand Brian hide caption

Voters wait to cast their ballot outside a polling station in Democratic Republic of Congo on Sunday. FREDRIK LERNERYD/AFP/Getty Images hide caption

Protective equipment for Ebola care is left on the ground next to ransacked tents by demonstrators at the Ebola transit centre in Beni, following a demonstration last week against the postponement of elections in the territory of the Beni and the city of Butembo. Alexis Huguet/AFP/Getty Images hide caption

Indonesian Navy personnel watch as Anak Krakatau spews volcanic materials into the waters of Indonesia's Sunda Strait this week. Fauzy Chaniago/AP hide caption