Two comets will brush past Earth on March 21 and 22. How close will these celestial visitors come to our home planet? Pictured here is the Discovery Channel Telescope, used to observe the bodies.
A pair of comets is due to make a close pass by the Earth on March 21 and 22. One of these passages will be the second-closest approach any comet has ever made to our planet since astronomers began records of the events.