Harvard astronomer argues that alien vessel paid us a visit

This 2002 Blue Marble featured land surfaces, clouds, topography, and city lights at a maximum resolution of 1 kilometer per pixel. rrNASA image by Robert Simmon and Reto Stˆcklirr NASA Goes to the Olympics ñ View all the cities that have hosted the modern Summer Olympics, starting with Athens in 1896 thru London in 2012. There have been 29 Summer Olympic Games held in 22 different cities. Repeating host cities include Athens, Paris, London and Los Angeles.nnCredit: NASA Earth ObservatorynnNASA image use policy.nnNASA Goddard Space Flight Center enables NASAís mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASAís accomplishments by contributing compelling scientific knowledge to advance the Agencyís mission.nnFollow us on TwitternnLike us on FacebooknnFind us on Instagramn