NASA has created an ultra-miniature probe called GIRO that “listens” to the gravity of exoplanets. NASA engineers have unveiled the Gravity Imaging Radio Observer (GIRO) concept — a tiny, battery-powered radio probe capable of mapping the internal structure of distant planets, moons, and asteroids. Instead of cameras or radars, GIRO measures the “hillyness” of the gravitational field: the slightest deviations in the trajectory of the probe and its accompanying mother station, piecing together information about the density and layering of deep rocks or the presence of a metallic core.
The system works simply: the mother vehicle sends a radio signal that is reflected by GIRO; the Doppler shift of the signal reveals millimeter deviations in the orbits of both vehicles caused by the uneven mass beneath the surface of the target body. According to calculations, the accuracy of this method exceeds ground-based tracking networks by 10–100 times, and the probe weighs only a few kilograms and can operate for up to ten days even near distant icy planets.
The authors propose launching entire “swarms” of GIROs, which will be added to already planned flights to Uranus or potentially dangerous asteroids. This approach reduces the cost of gravitational experiments and allows data to be obtained even where long-term orbital missions are impossible due to radiation or the risk of collision with rings. The first prototypes are ready for testing; under an optimistic scenario, the technology could be integrated into the 2028–2030 launch window.
High-resolution gravity tomography reveals clues to the formation of planetary cores, the evolution of magnetic fields, and the heat flows that fuel volcanism. This, in turn, refines our models of atmospheric formation and the potential habitability of exoplanets. Thanks to GIRO’s compact size, such data can be collected “along the way” with the main missions, accelerating the selection of candidates for future telescopes and even the search for landing sites for robotic landings.
Technologies such as GIRO demonstrate how quickly we are learning to “scan” distant worlds without even touching their surface. But in order to witness such landscapes with their own eyes, humanity will still have to traverse vast distances within its own stellar “neighborhood.” Find out how long it would take to travel to Mars, Uranus, or Pluto with current rocket technology in our article “How long does it take to fly to other planets in the Solar System?”
