Udomsak Ratanotayo, left, and Suttinan Boonsomkiat wear storm trooper costumes while donating blood at the Thai Red Cross in Bangkok, Thailand on Monday, April 28, 2014. Thai Star Wars fans will donate blood and give toys at an orphanage as part of a promotional campaign. (Photo by Sakchai Lalit/AP Photo)

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)

A cadet lies on the grass after collapsing during a promotion ceremony at a police school in Bogota December 7, 2012. (Photo by John Vizcaino/Reuters)

Technicians check a CRH high-speed train at Shanghai Hongqiao High-speed train base on December 28, 2011 in Shanghai, China. China's railway stations have started today to sell tickets for the 2012 Spring Festival travel season scheduled to run between January 8th and February 16th, centred around the Chinese New Year which this year falls on January 23rd. (Photo by ChinaFotoPress/Getty Images)

A damaged traffic signal is pictured along a street at a residential area flooded by the Kinugawa river, caused by typhoon Etau in Joso, Ibaraki prefecture, Japan, September 11, 2015. Unprecedented rain in Japan unleashed heavy floods on Friday that tore houses from their foundations, uprooted trees and forced more than 100,000 people from their homes. (Photo by Issei Kato/Reuters)

Magbola Alhadi, 20, and her three children pose for a portrait in Jamam refugee camp in Maban County, South Sudan on August 11th, 2012. Magboola and her family weathered aerial bombing raids for several months, but decided it was time to leave their village of Bofe the night that soldiers arrived and opened fire. With her three children, she travelled for 12 days from Bofe to the town of El Fudj, on the South Sudanese border. The most important thing that Magboola was able to bring with her is the saucepan she holds in this photograph. It wasn't the largest pot that she had in Bofe, but it was small enough she could travel with it, yet big enough to cook sorghum for herself and her three daughters (from left: Aduna Omar, 6, Halima Omar, 4, and Arfa Omar, 2) during their journey. (Photo by Brian Sokol/Panos Pictures)

Bridegrooms pose for a photograph as they attend a mass wedding ceremony at Arena Corinthians soccer stadium in Sao Paulo, Brazil, September 26, 2015. According to the event's organizers, at least 400 couples tied the knot during a mass wedding which was organized by the Department of Justice and Citizenship of the state of Sao Paulo. (Photo by Paulo Whitaker/Reuters)

People gather at the site of a bomb explosion in Sanaa December 23, 2014. Five bombs exploded on Tuesday in Sanaa's old quarter, where many supporters of the Shi'ite Muslim Houthi group live, killing at least one person and wounding another, a Yemeni security official said. No one has claimed responsibility for the attacks, but the Houthis have been fighting the Sunni Islamist militant al Qaeda group and allied tribesmen since its gunmen captured Sanaa in September and forced the resignation of a government they had long seen as corrupt. (Photo by Khaled Abdullah/Reuters)