For four years, the Messenger space probe sent images of Mercury, the solar system's smallest planet, closest to the Sun. It has revealed that Mercury has a dangerous secret that may one day threaten life on Earth. <br /><br />Thanks for watching. Follow for more videos. <br />#cosmosspacescience <br />#howtheuniverseworks <br />#season6 <br />#episode6 <br />#cosmology <br />#astronomy <br />#mercury <br />#historyofmercury <br />#space <br />#nasa <br />#spacetime <br />#formationofmercury <br />#spacescience <br /><br />
