People help a wounded person after Yishai Schlissel, an ultra-Orthodox Jew, attacked people with a knife during a gay pride parade in Jerusalem on Thursday, July 30, 2015. Schlissel lunged into a group of revelers leading Jerusalem's annual gay pride parade and stabbed several of them Thursday evening as they marched in the holy city, Israeli police and witnesses said. (Photo by Sebastian Scheiner/AP Photo)

Children, some in tears, are escorted down a road in Barcelona, Spain, Thursday, August 17, 2017. Police in Barcelona say a white van has mounted a sidewalk, struck several people in the city's Las Ramblas district. (Photo by Manu Fernandez/AP Photo)

Medics carry a wounded person at the scene after an attack at a popular nightclub in Istanbul, early Sunday, January 1, 2017. Istanbul Governor Vasip Sahin said that an armed assailant has opened fire at a nightclub in Istanbul during New Year's celebrations. Turkish authorities have banned distribution of images relating to the Istanbul attack within Turkey. (Photo by IHA via 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)

A victim under a blanket lays dead outside the Bataclan theater in Paris, Friday November 13, 2015. (Photo by Jerome Delay/AP Photo)

Indian policemen carry the body of one of their colleagues killed in a rebel attack in the town of Dinanagar, in the northern state of Punjab, India, Monday, July 27, 2015. Indian forces fought an extended gunbattle Monday with militants who attacked a moving bus and stormed into a police station in a northern town bordering Pakistan. (Photo by Channi Anand/AP Photo)

Afghan firefighters spray water on a U.S. armoured vehicle after a suicide attack on the outskirts of Jalalabad, January 5, 2015. A suicide attacker targeted a U.S. convoy on the outskirts of Jalalabad on Monday but so far no causalities have been reported yet, provincial spokesman Ahmadzia Abdulzai said. (Photo by Reuters/Parwiz)

Somalis remove the body of a man killed in a blast in the capital Mogadishu, Somalia Saturday, October 14, 2017. A huge explosion from a truck bomb has killed at least 20 people in Somalia's capital, police said Saturday, as shaken residents called it the most powerful blast they'd heard in years. (Photo by Farah Abdi Warsameh/AP Photo)