‘Icy moons, space volcanos and more’: 7 most incredible discoveries of NASA’s Voyager-1 during its cosmic journey

Launched in 1977, Voyager 1 set out to explore the outer planets but its path and speed ultimately propelled it far beyond its initial mission, making it the most distant human-made object in space. More than forty years later, it continues to send valuable data, serving as humanity’s first direct contact with interstellar space. Although its hardware is aging and power supplies are limited, engineers maintain the spacecraft by carefully cycling its instruments on and off and have recently reactivated backup thrusters to keep it on course. Voyager 1’s data still yield surprises, including the discovery of a thin, highly energetic layer near the heliopause, often referred to as a ‘wall’ of superheated plasma with temperatures estimated between 30,000 and 50,000 K. Here's a list of 8 most important discoveries made by Voyager 1:

In 2012, Voyager 1 crossed the heliopause, the boundary where the Sun’s solar wind meets the interstellar medium. Data showed an abrupt rise in plasma density and a shift in the mix of charged particles, proving there is a clear edge to the Sun’s influence rather than a gradual fade-out. This confirmed a long-debated frontier and gave scientists the first direct measurements from beyond it.

Once outside the heliosphere, Voyager 1 found that the space between stars is not empty or still. Its instruments detected turbulence, density waves and magnetic fluctuations in the surrounding plasma. These features reveal an active, shifting interstellar environment, shaped by events such as supernova shockwaves and the influence of magnetic fields stretching across light-years.

Voyager’s detectors measured cosmic rays both inside and outside the heliosphere, helping scientists see how the Sun’s protective bubble reduces the intensity of these high-energy particles. Understanding their behaviour is essential for planning crewed deep-space missions and for refining models of how cosmic rays travel through the galaxy.

In 1979, during its Jupiter encounter, Voyager 1 captured images of towering volcanic plumes erupting from Io. This was the first direct evidence of active volcanism beyond Earth and revealed the powerful effect of tidal heating caused by Jupiter’s gravity. The discovery showed that even small worlds can be geologically active, and it identified Io as a major source of plasma feeding Jupiter’s magnetosphere. Later missions expanded on this work, but the moment Voyager revealed Io’s volcanic activity remains one of the great milestones in planetary exploration.

Voyager’s flybys hinted that some icy moons, notably Europa and Enceladus, might hide liquid oceans beneath their frozen crusts. Smooth, bright surfaces and unusual chemistry suggested ongoing geological activity. While the probe could not confirm subsurface oceans, its clues guided later missions towards these worlds, now seen as prime locations in the search for extraterrestrial life.

Beyond its headline discoveries, Voyager 1 recorded an array of surprises: faint ring systems, unusual atmospheric patterns, and small satellites invisible to ground-based telescopes. Each observation enriched our understanding of how planetary systems form and evolve, and how moons and rings influence the space environment around their host planets.

Voyager 1’s visit to Saturn produced detailed maps of the planet’s rings, uncovering fine structures and several previously unknown moons. Its magnetometer and particle instruments charted Saturn’s magnetosphere and radiation belts, providing the first close-range measurements of their extent and behaviour. These results reshaped theories of planetary magnetic fields and demonstrated how moons, rings and charged particles interact to create complex space environments. The findings influenced how future missions would study not just Saturn, but other giant planets as well.

Now more than 24 billion kilometres from Earth, Voyager 1 continues to send data despite dwindling power. Engineers have reactivated backup thrusters and rotated instruments on and off to extend its lifespan. Among its latest findings is a thin, extremely hot but sparse plasma layer near the heliopause, a phenomenon that challenges models of the Sun’s boundary. These continuing surprises prove that even after decades in space, Voyager 1 remains a vital scientific tool.