NASA has found that near-Earth object 1998 SH2 is affected by a subtle force beyond gravity. The object, long listed as an asteroid, appears to release tiny amounts of gas that gently alter its orbit.
The finding matters because orbit forecasts depend on more than an object’s starting position and planetary gravity. Even a faint, persistent push can change where an object is expected to be over time.
A Clue from a Close Approach
In August 2025, 1998 SH2 passed about 3 million kilometers from Earth. Radar observations through NASA’s Deep Space Network showed that its position did not fully match a gravity-only orbit prediction.
Researchers investigated the discrepancy with high-precision optical astrometry. Their analysis pointed to a non-gravitational disturbance in the object’s trajectory.
Jet Propulsion Laboratory scientist Davide Farnocchia said the disturbance indicates very small gas jets. The gas may be released as sunlight heats ice mixed with rocky material on or near the object’s surface.
Why It Looked Like an Asteroid
Discovered in 1998, 1998 SH2 was initially classified as a near-Earth asteroid. That classification was reasonable because observers did not see a coma or tail, the visible features commonly associated with comets.
Its activity is too weak to produce readily visible dust and gas structures. This behavior connects the object to a class known as dark comets, which can show comet-like orbital effects while remaining visually inactive in conventional observations.
Mediaindonesia.com reported that some dark comets may still be active, but at levels below the detection threshold of ordinary telescopes. That possibility makes detailed physical characterization an important part of tracking near-Earth objects.
Implications for Planetary Defense
Determining whether an object behaves as an asteroid or an active comet can improve the accuracy of its motion model. This distinction is relevant to NASA’s planetary defense work, which relies on reliable projections of future paths.
Early detection and continued observation can reduce uncertainty for objects whose properties are not yet fully understood. More precise orbit mapping also supports assessments of their future proximity to Earth.
| Detection Target | Observation Challenge | NEO Surveyor Capability |
|---|---|---|
| Dark asteroids | They reflect little light | Detects emitted heat |
| Weakly active comets | Dust and gas are difficult to see | Helps identify faint objects |
| Objects toward the Sun | Ground telescopes can be affected by glare | Extends search capability |
Infrared Search for Faint Objects
NASA is preparing NEO Surveyor, a space-based infrared telescope intended to detect difficult-to-find asteroids and comets. Rather than relying on reflected visible light, it will search for heat emitted by celestial objects.
NEO Surveyor is scheduled to launch in September 2027. NASA expects the mission to expand the near-Earth object catalog, including objects like 1998 SH2 that conceal comet activity behind an asteroid-like appearance.