The Asteroid That Vanished From Radar Came Back a Comet

Astronomers had asteroid 1998 SH2 clocked. They'd watched it for nearly three decades, logging steady images and pinning down its orbit with confidence, until August 2025, when the 380-meter rock made a close pass by Earth at about 0.02 AU and a team pointed the 70-meter DSS-14 radar antenna at Goldstone Observatory toward it. There was no trace of the asteroid in the radar data.

Gone. A rock the size of a stadium. Just gone.

It wasn't until August 31 that the missing asteroid was spotted again, roughly 190 kilometers from where three decades of orbital math said it should be. A new paper led by Davide Farnocchia of NASA's Jet Propulsion Laboratory, published in Nature Astronomy, confirmed what everyone assumed was a normal asteroid was actually a "dark comet."

The line between asteroids and comets has always been blurry. Textbooks typically draw it at the coma, a halo of gas and dust surrounding a comet, but in some cases that coma is so faint it's nearly impossible to detect. Dark comets look inert but are quietly outgassing, enough to nudge their trajectory in ways gravity alone can't explain. That kind of subtle push was apparently enough to throw off decades of confident calculations.

The handful of known dark comets evaded detection long enough that researchers suspect they're the tip of the iceberg. The authors stress the importance of closely tracking the orbital paths of any potentially hazardous space rock, regardless of classification, because some of those rocks, it turns out, have been keeping secrets.

The universe contains multitudes. Some of them are 380 meters wide and currently reclassifying themselves.

Read the full story at Universe Today, July 22, 2026

Hot Take: Twenty-seven years of confident tracking, and the whole time this rock was a comet quietly nudging itself off course while everyone assumed it was inert. The scary part isn't that we missed it: missing them is the entire point of being a dark comet, and we're being asked to feel reassured by a sample size of one.