Tourists look at other festival-goers playing in the mud during the Boryeong Mud Festival at Daecheon beach in Boryeong, about 190 km (118 miles) southwest of Seoul, July 19, 2013. About 2 to 3 million domestic and international tourists visit the beach during the annual mud festival, according to the festival organisers. (Photo by Lee Jae-Won/Reuters)

An Indonesian woman watches an eruption from the Mount Sinabung volcano from Tiga Pancur village, in Karo in North Sumatra on November 3, 2017. Sinabung roared back to life in 2010 for the first time in 400 years. After another period of inactivity it erupted once more in 2013, and has remained highly active since. (Photo by Ivan Damanik/AFP Photo)

Indian onlookers stand near the collapsed portion of the flyover in Kolkata on March 3, 2013. A huge portion of a flyover on the eastern side of the Indian metropolis collapsed leaving three persons injured, the flyover connects the airport with Eastern Metropolitan Bypass and the eastern and southern suburbs. As the debris fell into a canal running below the flyover, it took down a truck the driver and two others were rescued from the canal by fire-brigade personnel and locals. (Photo by Dibyangshu Sarkar/AFP Photo)

A 2-year-old Florida panther is released into the wild by the Florida Fish and Wildlife Conservation Commission (FWC) on April 3, 2013 in West Palm Beach, Florida. The panther and its sister had been raised at the White Oak Conservation Center since they were 5 months old. The FWC rescued the two panthers as kittens in September 2011 in northern Collier County after their mother was found dead. The panther is healthy and has grown to a size that should prepare him for life in the wild. (Photo by Joe Raedle)

Tourists play at a beach covered by a thick layer of green algae in Qingdao, China, on July 3, 2013. A large quantity of non-poisonous green seaweed, enteromorpha prolifera, hit China's Qingdao coast last month. More than 20,000 tons of such seaweed has been removed from the city's beaches. This has now become an annual summer event. (Photo by Whitehotpix/ZumaPress.com)

An Indian bride, sits during a mass marriage of 162 Muslim couples in Ahmadabad, India, Sunday, March 3, 2013. Mass marriages in India are organized by social organizations primarily to help the economically backward families who cannot afford the high ceremony costs as well as the customary dowry and expensive gifts that are still prevalent in many communities. (Photo by Ajit Solanki/AP Photo/LaPresse)

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)

The main church in the town of San Damian Texoloc, Mexico stands in front of the Popocatepetl volcano as is spews ash and vapor early Tuesday, July 9, 2013. Last Saturday, Mexico's National Center for Disaster Prevention raised the volcano alert from Stage 2 Yellow to Stage 3 Yellow, the final step before a Red alert, when possible evacuations could be ordered after the Popocatepetl volcano spit out a cloud of ash and vapor 2 miles (3 kilometers) high over several days of eruptions. (Photo by J. Guadalupe Perez/AP Photo)