Two small asteroids, recently discovered by astronomers at the NASA-funded Catalina Sky Survey (CSS) near Tucson, Arizona, are safely passing by Earth within one lunar distance this week.

The first of this week’s close-approaching asteroids – discovered by CSS on Feb. 4 – is designated asteroid 2018 CC. Its close approach to Earth came Tuesday at 12:10 p.m. at a distance of about 114,000 miles. The asteroid is estimated to be between 50 and 100 feet in size.

 Of potentially greater interest is asteroid 2018 CB, which will also pass closely by Earth on Friday, Feb. 9 at around 2:30 p.m. at a distance of about 39,000 miles, which is less than one-fifth the distance of Earth to the Moon. The asteroid, which is estimated to be between 50 and 130 feet in size, was also discovered by CSS on Feb. 4.

“Although 2018 CB is quite small, it might well be larger than the asteroid that entered the atmosphere over Chelyabinsk, Russia, almost exactly five years ago, in 2013,” said Paul Chodas, manager of the Center for Near-Earth Object Studies at NASA’s Jet Propulsion Laboratory. “Asteroids of this size do not often approach this close to our planet — maybe only once or twice a year.”

JPL hosts the Center for Near-Earth Object Studies for NASA’s Near-Earth Object Observations Program, an element of the Planetary Defense Coordination Office within the agency’s Science Mission Directorate.