When a 140-meter-wide asteroid glides silently through the dark, its invisible gravitational hand might just nudge a tiny gold-platinum cube floating inside one of LISA’s three spacecraft, drifting 50 million kilometers behind Earth. That almost imperceptible tug—smaller than a snail’s pace—could reveal the asteroid’s true mass, transforming a once-ignored signal into a breakthrough for planetary science. Slated for launch in July 2035, the Laser Interferometer Space Antenna (LISA) was built to catch ripples from colliding black holes across the universe, not to weigh space rocks. Yet, as a new study shows, it may do both.
Measuring an asteroid’s mass is crucial: it determines impact risk, resource potential, and structural integrity. But today, fewer than 35% of near-Earth asteroids have mass estimates accurate within 10%, most relying on spectral guesses rather than direct measurement. The gold standard—sending a spacecraft—remains too costly to scale across the 41,000 known near-Earth asteroids. That’s where LISA comes in, not by design, but by serendipity.
Physicists Sara Marques of the University of Bern and Oliver Jennrich of ESA discovered that LISA’s ultra-sensitive instruments—capable of detecting picometer-scale shifts in free-floating test masses—can capture the faint gravitational pull of passing asteroids. When an asteroid comes within its Minimum Orbital Intersection Distance (MOID) of one of LISA’s arms, the resulting velocity change in the test mass becomes measurable. Using Time-Delay Interferometry (TDI), a technique that filters out laser noise, the team proved these signals can be isolated from gravitational wave data, turning what was once considered noise into valuable science.
Over its planned 10-year mission, LISA could precisely weigh about three asteroids—each measurement reducing uncertainty to within 20%, far better than current estimates for most asteroids. And because we’ve only identified about 38% of near-Earth asteroids larger than 140 meters, there’s real potential for LISA to detect gravitational tugs from objects we don’t even know exist. Positioned far from Earth’s interference, LISA offers a pristine vantage point for such discoveries.
While its primary mission remains the hunt for spacetime ripples from cosmic collisions, LISA’s hidden talent could reshape how we assess asteroid threats and opportunities. As Marques and Jennrich’s work shows, sometimes the most powerful tools aren’t just built—they’re discovered in the data.