Employees of the Park Royal resort wait for a shuttle to take them to work early in the morning on April 2, 2015 in Acapulco, Mexico. Despite problems with cartel violence Semana Santa is one of the biggest tourist weeks of the year in Acapulco, a city whose entire economy depends on tourism, and officials expect around 350,000 mostly Mexican visitors this week. (Photo by Jonathan Levinson/The Washington Post)

A contestant prepares backstage before the final show of the Miss International Queen 2018 transgender beauty pageant in Pattaya, Thailand March 9, 2018. Twenty-seven international contestants are participating in the annual beauty contest for transgender women which aims to promote the tourism industry in the resort city of Pattaya and create a positive image of transgender people. (Photo by Soe Zeya Tun/Reuters)

Aegean airlines air hostesses take selfies after a news conference in Athens, Wednesday, March 28, 2018. In a deal worth up to $5 billion, Greek airline Aegean says it will buy 30 new Airbus aircraft, with the option of an additional 12, to upgrade its fleet as the country expects to break tourism records. The signing of the final purchase agreement is expected in June. (Photo by Petros Giannakouris/AP Photo)

In this October 15, 2014 file photo, Katsu Nakamura, sky division manager for Yamaha USA, moves the RMax unmanned helicopter into position before a demonstration of its aerial application capabilities at the University of California, Davis' Oakville Station test vineyard in Oakville, Calif. Researchers at UC Davis have been studying the effectiveness of the drone's ability for spraying pest control and nutritional materials on the test vineyard in California's Napa Valley. (Photo by Rich Pedroncelli/AP Photo)

NASA says it could be another 20 years before humans touch down on Mars, but in a sense, the Mars Society has been exploring the red planet for more than a decade – in Utah. Photo: Csilla Orgel, a geologist of Crew 125 EuroMoonMars B mission, makes her way back to the Mars Desert Research Station (MDRS) in the Utah desert March 3, 2013. The MDRS aims to investigate the feasibility of a human exploration of Mars and uses the Utah desert's Mars-like terrain to simulate working conditions on the red planet. Scientists, students and enthusiasts work together developing field tactics and studying the terrain. All outdoor exploration is done wearing simulated spacesuits and carrying air supply packs and crews live together in a small communication base with limited amounts of electricity, food, oxygen and water. Everything needed to survive must be produced, fixed and replaced on site. (Photo by Jim Urquhart/Reuters)

“NASA's Pathfinder, Pathfinder Plus, Centurion and Helios Prototype were an evolutionary series of solar- and fuel-cell-system-powered unmanned aerial vehicles. AeroVironment, Inc. developed the vehicles under NASA's Environmental Research Aircraft and Sensor Technology (ERAST) program. They were built to develop the technologies that would allow long-term, high-altitude aircraft to serve as “atmospheric satellites”, to perform atmospheric research tasks as well as serve as communications platforms”. – Wikipedia

Photo: The solar-electric Helios Prototype flying wing is flies over the Hawaiian islands of Niihau and Lehua during the first solar-powered test flight July 14, 2001 from the U.S. Navy's Pacific Missile Range Facility on Kauai, HI. The 18-hour flight was a functional checkout of the aircraft's systems and performance in preparation for an attempt to reach sustained flight at 100,000 feet altitude later in the summer. (Photo Courtesy of NASA/Getty Images)

Human canvases modelling world famous artworks including Van Gogh's Sunflowers and Edvard Munch's The Scream take to the streets of London in a bid to mend Britain's disconnect with art on September 25, 2017. Award winning body paint artist Sarah Attwell was commissioned by online art platform Rise Art to show that great art is for everybody, following research that revealed 1 in 6 Brits have never set foot in an art gallery. (Photo by Imagewise Ltd/Rex Features/Shutterstock)

“Secrets of the Whales”. Skerry’s photographs celebrate the lives and culture of whales, illuminating recent research and their diverse behaviours. His latest work focuses on four key species: sperm whales, humpbacks, orca and beluga whales. Humpback whales bubble-net feeding off the coast of Alaska. They work cooperatively to feed on herring by blowing a perfect ring of bubbles underwater to form a net encircling the fish. The whales then swim up through the centre of the bubble net with their mouths open. (Photo by Brian Skerry/National Geographic Photo/Visa pour l'Image)