LISA May Be Able to Weigh Near-Earth Asteroids Without Visiting Them

A Gravitational-Wave Mission With a Planetary Science Bonus

The Laser Interferometer Space Antenna, or LISA, is being built to detect gravitational waves from some of the universe’s most violent events. But a new paper suggests the mission could also double as an asteroid scale, using its extraordinary sensitivity to measure the mass of nearby near-Earth asteroids without any hardware changes.

The idea is simple in concept but technically unusual. LISA will consist of three spacecraft flying in triangular formation, with instruments capable of detecting extremely small changes in the positions of free-falling test masses inside each spacecraft. Those measurements are meant to capture ripples in spacetime from distant astrophysical events. The same sensitivity, however, could also register tiny gravitational pulls from passing asteroids.

Why Asteroid Mass Is Hard to Measure

Mass is one of the most important characteristics of an asteroid, but one of the hardest to determine well. It influences impact risk, resource potential, and orbital behavior. Yet for most near-Earth asteroids, scientists do not directly measure mass. Instead, they often estimate it by combining optical observations with an assumed density based on spectral properties.

The source says that for fewer than 35% of near-Earth asteroids, mass can be estimated with uncertainties as low as 10%. The most reliable measurements often come from binary asteroids, where orbital dynamics provide extra information, or from rare cases where an asteroid interacts gravitationally with another body in a measurable way. Sending a spacecraft to each object would be more accurate, but that is not practical for the more than 41,000 known near-Earth asteroids mentioned in the article.

How LISA Could Help

If an asteroid passes close enough to one of LISA’s spacecraft, specifically within what is called the Minimum Orbital Intersection Distance, its gravity would slightly tug on the spacecraft’s free-falling test masses. LISA’s instruments are precise enough to detect picometer-level changes, and the new paper argues those perturbations could be separated from the mission’s other signals.

What mission designers originally saw as noise might therefore become data. Instead of treating ordinary Newtonian tugs as an annoyance in the hunt for gravitational waves, researchers suggest they could be modeled and exploited for planetary science.

The paper highlighted in the source comes from Sara Marques of the University of Bern and Oliver Jennrich of ESA. Their work modeled what the asteroid-induced signal would look like and argues that the effect could be identifiable rather than lost in background measurement complexity.

A Low-Cost Scientific Add-On

One reason the proposal stands out is that it does not depend on adding new instruments. LISA is already planned for launch in July 2035 as a flagship gravitational-wave observatory. If asteroid mass estimates can be extracted from the same measurements, the benefit would come from analysis rather than extra spacecraft hardware.

That is appealing because asteroid characterization remains data-poor relative to how important these objects are for planetary defense and future resource discussions. Even a modest increase in the number of objects with better-constrained masses could improve risk modeling and scientific understanding.

• LISA is designed to detect gravitational waves, not asteroids.
• Its instruments may also detect tiny gravitational tugs from nearby near-Earth asteroids.
• The approach could improve asteroid mass estimates without changing mission hardware.

The concept remains prospective, and the mission is still years from launch. But it reflects a broader pattern in space science: extremely sensitive instruments built for one frontier question can sometimes unlock answers in a neighboring field. In this case, a mission aimed at black holes and other cosmic events may also help solve a more local problem in planetary science.

If the method works as proposed, LISA would not just listen to the deep universe. It would also help weigh some of the small bodies moving through our own celestial neighborhood.

This article is based on reporting by Universe Today. Read the original article.