This asteroid, 2014 DX110, is estimated to be about 100 feet (30 meters) across. Its closest approach to Earth will be at about 217,000 miles (about 350,000 kilometers) from Earth at about 4 p.m. EST on March 5. The average distance between Earth and its Moon is about 239,000 miles (385,000 kilometers).
NASA detects, tracks, and characterizes asteroids and comets using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called “Spaceguard,” discovers these objects, characterizes a subset of them, and identifies their close approaches to determine if any could be potentially hazardous to our planet.