The possible surface of TRAPPIST-1f, one of seven newly discovered planets in the TRAPPIST-1 system that scientists using the Spitzer Space Telescope and ground based telescopes have discovered. (Photo by Reuters/NASA/JPL-Caltech)

Nyibol Lual, 13 years old, helps her family to prepare the land for cultivation on May 31, 2017, in Panthau, Northern Bahr al Ghazal, South Sudan. The family has a small land where they cultivate sorghum. An estimated 63 per cent of the population in Northern Bahr al Ghazal is experiencing severe food insecurity, according to the latest Integrated Food Security Phase Classification (IPC) report. The situation is particularly bad in Aweil West and Aweil South counties, where the exhaustion of household food stocks and growing dependence on financially inaccessible markets have left the population facing Emergency levels of food insecurity. (Photo by Albert Gonzalez Farran/AFP Photo)

A man sits next to a damaged idol of Hindu goddess Kali which was taken out after its immersion in the river Ganges in Haridwar, India, March 29, 2017. (Photo by Danish Siddiqui/Reuters)

A wide-angle view shows the ascent of the shuttle Challenger on January 28, 1986. In the seconds after ignition, the rocket engines' hot blast began the process of destruction. (Photo by NASA)

Female of pygmy hippopotamus called Malaya from Netherlands in zoo in Dvur Kralove nad Labem, Czech Republic, February 22, 2016. (Photo by David Tanecek/CTK via ZUMA Press)

A refugee sits in front of a Greek riot police cordon during a protest at the Greek-Macedonian border, near the Greek village of Idomeni, March 1, 2016. (Photo by Alexandros Avramidis/Reuters)

A fledgling solar system containing deep within it enough water vapor to fill all the oceans on Earth five times, located in our Milky Way galaxy about 1,000 light years from Earth in the constellation Perseus. (Photo by Reuters/NASA/JPL-Caltech)

View of the Villarrica volcano taken from Pucon, some 800 kilometres south of Santiago, showing signs of activity on December 06, 2017. (Photo by Christian Miranda/AFP Photo)