“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)

In this August 17, 2016, photo, from left to right, Chhering Chodom, 60, Tashi Yangzom, 50, Lobsang Chhering, 27, and Dorje Tandup, 58, drink milk tea on the side of the road. For centuries, the sleepy valley nestled in the Indian Himalayas remained a hidden Buddhist enclave forbidden to outsiders. Enduring the harsh year-round conditions of the high mountain desert, the people of Spiti Valley lived by a simple communal code – share the Earth's bounty, be hospitable to neighbors, and eschew greed and temptation at all turns. That's all starting to change, for better or worse. (Photo by Thomas Cytrynowicz/AP Photo)

The Rio de Janeiro Olympics kick off on August 5 for some two weeks of competitive games drawing athletes as well as audiences from around the world. As they prepare to cover the event, Reuters photographers look back on their favourite pictures from past Olympics where they captured the action on the ground as well as the participants' tears and joy that followed. (Photo by Lucy Nicholson/Reuters)

“Lofoten Glow”. I was desperately searching a good sunrise spot this particular morning. Normally Storvatnet Lake is completely covered in snow, so you can only imagine my surprise when I saw these crazy ice formations almost being shot out of the frozen lake. I put my crampons on and took a big risk walking out. I could hear the ice cracking underneath my feet, and when you’re all alone in a fjord/canyon like this – the cracks are echoed and sound really frightening. Was it worth it? I sure think so! Photo location: Storvatnet, Lofoten Islands in Northern Norway. (Photo and caption by Stian Klo/National Geographic Photo Contest)

A Christian pilgrim prays during her visit to the baptismal site known as Qasr el-Yahud on the banks of the Jordan River near the West Bank city of Jericho April 9, 2015. A day ahead of Orthodox Good Friday, the Easter period draws many Christian tourists to visit well-known religious sites, including Qasr el-Yahud, where it is believed John the Baptist baptised Jesus. (Photo by Amir Cohen/Reuters)

A Slovakian company has designed an egg-shaped and cozy micro-home that should work ideally for anybody who wants to “go off the grid” and “live off the land” – the Ecocapsule.

In this picture taken on Saturday, January 31, 2015, Zohreh Etezadossaltaneh, center, talks on her mobile phone, held with her foot, during a meeting at her friend's home in Tehran, Iran. Now 52 years old, the retired Iranian teacher who was born without arms has dedicated herself to helping others with similar disabilities live full and satisfying lives. (Photo by Ebrahim Noroozi/AP Photo)

15-year old American girl Donica Streling meets with members of SHINee (샤이니) at SM Entertainment head office on June 20, 2012 in Seoul, South Korea. Donica, diagnosed with Charcot-Marie-Tooth disease, visited Seoul, South Korea to meet her favorite K-pop groups SHINee and Super Junior after finding hope in listening to Korean pop. (Photo by Chung Sung-Jun)