Earth is About to Lose its Second Moon, Forever
Godspeed, SO 2020. Enjoy your journey around the sun.
By Brandon Specktor | Live Science Senior Writer

January 29, 2021 | Earth’s second moon will make a close approach to the planet next week before drifting off into space, never to be seen again.

Strange space object 2020 SO was discovered on September 17, 2020, on approach to Earth. On November 8, it slowly drifted into Earth’s sphere of gravitational dominance, to become a new mini-moon. It’ll escape back into a new orbit around the sun in March 2021. During that time, it’ll make 2 large loops around our planet. In this image, Earth is the blue dot. The moon’s orbit is the yellow circle. 2020 SO’s trajectory is the looping pink line. Image via Phoenix7777/ Wikimedia Commons.

“What second moon,” you ask? Astronomers call it 2020 SO — a small object that dropped into Earth’s orbit about halfway between our planet and the moon in September 2020. Temporary satellites like these are known as minimoons, though calling it a moon is a bit deceptive in this case; in December 2020, NASA researchers learned that the object isn’t a space rock at all, but rather the remains of a 1960s rocket booster involved in the American Surveyor moon missions.

This non-moon minimoon made its closest approach to Earth on Dec. 1 (the day before NASA identified it as the long-lost booster), but it’s coming back for one more victory lap, according to EarthSky.org. Minimoon 2020 SO will make a final close approach to Earth on Tuesday (Feb. 2) at roughly 140,000 miles (220,000 kilometers) from Earth, or 58% of the way between Earth and the moon.