When meteoroids intersect with the Earth's atmosphere at night, they are likely to become visible as meteors. If meteoroids survive the entry through the atmosphere and reach the Earth's surface, they are called meteorites. Meteorites are transformed in structure and chemistry by the heat of entry and force of impact. A noted 4-meter asteroid, 2008 TC3, was observed in space on a collision course with the Earth on 6 October 2008 and entered the Earth's atmosphere the next day, striking a remote area of northern Sudan. It was the first time that a meteoroid had been observed in space and tracked prior to impacting the Earth. NASA has produced a map showing the most notable asteroid collisions with the Earth and it’s atmosphere from 1994 to 2013 from data gathered by U.S. government sensors (see below).