An asteroid the size of a semi-truck and two other space rocks are flying by Earth today

Three asteroids are making close approaches to our planet today (March 23), but don't worry; the small rocks pose no threat as they drift by Earth, passing closer than the average distance between our planet and the moon.

The largest of the three space rocks, a house-size asteroid called 2021 FH, passed by Earth today at approximately 12:52 p.m. EDT (1652 GMT) at a distance of roughly 145,940 miles (234,870 kilometers), or 0.61 times the average Earth-moon distance. NASA estimates the asteroid's diameter is between 39 feet and 89 feet (12 meters to 27 meters), or about the length of a semi-truck.

Details about its orbit have been published online by NASA Jet Propulsion Laboratory's Small-Body Database Browser, a database of all known small worlds in our solar system. The International Astronomical Union's Minor Planet Center also sent a circular to the community with observations from various astronomers around the world, including updated orbital elements.

Video: 3 asteroids zoom closer than moon in less than 24 hours

These three orbit diagrams show the paths of the near-Earth asteroid 2021 FO1, 2021 FH and 2021 FP2, which are making close approaches to Earth on March 23, 2021. (Image credit: NASA JPL/Space.com)

Small asteroids and comets pass by Earth on the regular, and in fact, this isn't the only small world that went by our planet this week. The newly discovered 2021 FO1, now cataloged by JPL, zoomed by Earth quite safely on Monday, March 22 at 11:05 p.m. EDT (Tuesday, March 23 at 0305 GMT).

The newfound world was quite a bit smaller – roughly 11 feet to 25 feet (3.4 to 7.6 meters) in width. At its closest approach, 2021 FO1 was about 199,850 miles (321,640 kilometers), or 0.84 times the average Earth-moon distance. (For comparison, the moon's distance from our planet averages roughly 239,000 miles, or 384,000 km.)

And tonight at 6:35 p.m. EDT (2235 GMT), another asteroid called 2021 FP2 is expected to make a close flyby of Earth, passing within 200,780 miles (323,120 km) of our planet — just a little bit farther than 2021 FO1. NASA's Minor Planet Center lists about a dozen more near-Earth asteroids that will fly by our planet this week, but none will be closer than the moon.

NASA's Planetary Defense Coordination Office and a suite of partners around the world keep track of small asteroids through telescopic observations, and over several decades of observations by scientists, no imminent problems have been found yet. Earlier this month, the infamous Apophis asteroid made a flyby of our planet; scientists have ruled out any threat to our world from Apophis in 2029.

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Elizabeth Howell (she/her), Ph.D., was a staff writer in the spaceflight channel between 2022 and 2024 specializing in Canadian space news. She was contributing writer for Space.com for 10 years from 2012 to 2024. Elizabeth's reporting includes multiple exclusives with the White House, leading world coverage about a lost-and-found space tomato on the International Space Station, witnessing five human spaceflight launches on two continents, flying parabolic, working inside a spacesuit, and participating in a simulated Mars mission. Her latest book, "Why Am I Taller?" (ECW Press, 2022) is co-written with astronaut Dave Williams.