This artist's scoreboard displays a fictional game between Mars and Earth, with Mars in the lead. It refers to the success rate of sending missions to Mars, both as orbiters and landers. Of the previous 39 missions targeted for Mars from around the world, 15 have been successes and 24 failures. For baseball fans, that's a batting average of .385. The United States has had 13 successes out of 18 attempts, or a “batting average” of .722. NASA's Curiosity rover, set to land on the Red Planet the evening of Aug. 5, 2012 PDT (morning of Aug. 6 EDT), will mark the United States' 19th attempt to tackle the challenge of Mars, and the world's 40th attempt. (Image by NASA/JPL-Caltech)

Robert Price of TREWGrip LLC demonstrates a TREWGrip handheld rear-type keyboard and air mouse for Apple and Android tablets at the “CES: Unveiled”, media preview for International CES, at the Mandalay Bay Convention Center in Las Vegas on January 5, 2014. (Photo by Robyn Beck/AFP Photo)

Farmer Zhang Xianping rides his pig "Big Precious" during an interview with the media, in Zhangjiakou, Hebei province, China, November 2, 2015. Zhang, a pig breeder, instead of killing it, decided to keep the two-year-old "Big Precious" as pet when its weight reached 600 kg, according to local media. (Photo by Reuters/China Daily)

Couples take part in the “Love and Challenge Marathon” in Hanoi, Vietnam, 16 August 2015. Fifty couples, who are going to get married, participated in the event which is held the fifth time. This year, the winners of the marathon received a honeymoon trip to Malaysia. (Photo by Luong Thai Linh/EPA)

German car manufacturer BMW presents the “Vision Next 100” concept car during the 100th anniversary celebrations in Munich, Germany, Monday, March 7, 2016. (Photo by Matthias Schrader/AP Photo)

Hotel staff practice self-defence skills after a training session given by team member of Special Weapons and Tactics (SWAT) team, in Hangzhou, Zhejiang province, April 7, 2016. (Photo by Reuters/Stringer)

In a photo taken on June 5, 2017 a traffic security officer stands on duty at an intersection in Pyongyang. Officially known as traffic security officers but universally referred to as traffic ladies, they are chosen for their looks in a society that remains traditionalist in many respects. They must leave the role if they marry, and have a finite shelf-life, with compulsory retirement looming at just 26. (Photo by Ed Jones/AFP Photo)

Hospitality staff members laugh as they stand on Tiananmen Square before the closing ceremony of China's 19th Party Congress at the Great Hall of the People in Beijing, Tuesday, October 24, 2017. The ruling Communist Party on Tuesday formally lifted Xi Jinping's status to China's most powerful ruler in decades, setting the stage for the authoritarian leader to tighten his grip over the country while pursuing an increasingly muscular foreign policy and military expansion. (Photo by Mark Schiefelbein/AP Photo)