Rebel fighters fire towards positions of regime forces in Ramussa on the southwestern edges of Syria's northern city of Aleppo on August 6, 2016. Syrian rebels said they have broken a three-week government siege of second city Aleppo, turning the tables on Russian-backed regime forces who are now on the defensive. (Photo by Fadi Al-Halabi/AFP Photo)

This image made available by the Johns Hopkins University Applied Physics Laboratory on Wednesday, May 31, 2017 depicts NASA's Solar Probe Plus spacecraft approaching the sun. On Wednesday, NASA announced it will launch the probe in summer 2018 to explore the solar atmosphere. It will be subjected to brutal heat and radiation like no other man-made structure before. (Photo by Johns Hopkins University Applied Physics Laboratory via AP Photo)

Mercury and Maia, fueled and overhauled, are waiting in the Tay at Dundee, for favorable weather to start the flight to the Cape, a distance of 6,370 miles. The composite machine moored in the Tay River, at Dundee, on September 23, 1938. (Photo by AP Photo)

Visitors to the annual Vivid Sydney light festival wear matching illuminated suits alongside the Sydney Harbour Bridge on the second night of the light and sound show in Sydney, Australia, May 28, 2016. (Photo by Jason Reed/Reuters)

Praia du Forte, Bahia. “This was the lead picture for a National Geographic story on Bahia, because it was both mysterious as well as a “geography” picture showing where the slaves arrived from Nigeria. Beach pictures seem like they should be easy to take, but for me they are actually quite difficult. Too easy to fall into cliche. When I saw the kid coming on the horse, I quickly ran to see if I could make something with a woman in a bikini that was not a bikini shot”. (Photo by David Alan Harvey/The Guardian)

Padaung ethnic women arrive to listen to the speech of Myanmar opposition leader Aung San Suu Kyi (not in picture), Chairwoman of the National League for Democracy (NLD) party, during Suu Kyi's first official election campaign at Demoso township of Kayah State, eastern Myanmar, 10 September 2015. Suu Kyi is on a three-day visit to Kayah State near the Thai-Myanmar border, as part of her first official election campaign. Myanmar political parties and candidates started their campaigns on 08 September ahead of the upcoming general election, which will be held on 08 November 2015. (Photo by Lynn Bo Bo/EPA)

Residents with faces covered in ash ride on a motorcycle as Mount Sinabung volcano erupts, in Sukandebi village in Karo Regency, Indonesia's North Sumatra province, Indonesia June 13, 2015, in this photo taken by Antara Foto. (Photo by Rony Muharrman/Reuters/Antara Foto)

Russian President Vladimir Putin, right, and North Korea's leader Kim Jong Un pose for photographers during their meeting in Vladivostok, Russia, Thursday, April 25, 2019. Putin and Kim are set to have one-on-one meeting at the Far Eastern State University on the Russky Island across a bridge from Vladivostok. The meeting will be followed by broader talks involving officials from both sides. (Photo by Alexander Zemlianichenko/AP Photo/Pool)