NASA is set to revolutionize our understanding of gravitational forces with the development of the first quantum gravity sensor designed for space. The instrument, named Quantum Gravity Gradiometer Pathfinder (QGGPf), is a suitcase-sized device that could measure everything from underground water reserves to hidden petroleum deposits by observing the behavior of clouds of atoms under gravitational influence.
Researchers at NASA’s Jet Propulsion Laboratory (JPL), in collaboration with several partners, are behind this innovative project. QGGPf functions as a gravity gradiometer, which measures the acceleration differences between nearby objects. These differences correlate with the gravitational strength each object experiences, meaning that when gravity is stronger, objects—or in this case, test masses—fall faster.
The variability of Earth’s gravity is noteworthy; it is not a constant force but changes subtly due to mass movements across the planet. Geological activities such as tectonic shifts, calving glaciers, and draining aquifers can induce slight variations in gravitational pull. Although these changes are imperceptible on a human scale, advanced scientific instruments like those being developed can detect these nuances.
These minute variations in gravity are not mere curiosities of nature; they have substantial applications in navigation, natural resource mapping, and even national security. With advanced sensors, scientists can utilize gravitational data to reveal what lies beneath the Earth’s surface. The more precise the gravity map, the better our understanding of subsurface conditions.
According to Jason Hyon, chief technologist for Earth Science at JPL, “We could determine the mass of the Himalayas using atoms.” QGGPf will employ rubidium atoms cooled to just above absolute zero, allowing them to behave more like waves than particles in their measurements from space.
The quantum aspect of QGGPf is where the technology truly shines. The device utilizes two clouds of ultra-cold atoms as test masses, comparing their fall rates relative to each other. If one cloud falls faster than the other, it indicates stronger gravitational forces at that location. The differential acceleration between these clouds provides valuable information about gravitational anomalies.
In contrast to traditional gravity gradiometers, QGGPf leverages quantum physics to enhance both repeatability and precision. Physicist Sheng-wey Chiow remarked, “With atoms, I can guarantee that every measurement will be the same. We’re less sensitive to environmental noise.”
Weighing in at just 275 pounds (125 kilograms) and taking up around 0.3 cubic yards (0.25 cubic meters), QGGPf is compact by spaceflight standards. Quantum gravity gradiometers are projected to be ten times more sensitive than classical gravity sensors, providing sharper data, reducing blind spots, and allowing for greater insight into subterranean activity.
The launch of QGGPf is planned for the end of the decade, and its primary mission will be to validate the technology, as highlighted by its “Pathfinder” designation. “No one has flown one of these before,” stated JPL postdoc Ben Stray. “We have to test it in space to know what it’s really capable of.”
Should QGGPf successfully demonstrate its capacity in space, it could facilitate unprecedented mappings of our planet while paving the way for exploring the geological complexities of distant worlds.
image source from：https://gizmodo.com/nasa-wants-to-track-earths-gravity-with-a-cloud-of-floating-atoms-in-space-2000590151
