A team of student engineers has developed a novel concept for the first controlled landing on Io, Jupiter’s perpetually erupting moon. The proposed lander, named UNAGI, would navigate the treacherous journey to the Ionian surface without using traditional rocket propellant for its descent. Instead, it would rely on an innovative braking system that harnesses the immense power of Jupiter’s own magnetic field to slow its approach and achieve a soft touchdown on the most volcanically active body in the solar system.
Developed by Spartan Space Systems, an engineering group at San Jose State University, the UNAGI mission concept aims to solve the immense challenge of landing in a high-gravity, high-radiation environment where fuel economy is critical. By replacing heavy fuel tanks with a long, conductive tether, the lander could dedicate more of its mass to a suite of scientific instruments designed to probe Io’s internal structure, analyze its unique geology, and observe its violent volcanic processes up close. The mission, presented at the AIAA 2025 Regional Student Conference, leverages proven technologies from other Jupiter-bound spacecraft while introducing a revolutionary approach to deep-space exploration.
A Bold Concept from Student Engineers
The UNAGI lander concept emerged from Spartan Space Systems at San Jose State University, a group with a growing reputation for ambitious aerospace projects. The university is recognized for its contributions to the development of CubeSats, and its student-led teams have previously tackled complex challenges, including the design of 3D-printed liquid-fueled rocket engines under “Project Spartan Spear” and advanced transportation concepts with “Spartan Hyperloop”. The UNAGI proposal continues this tradition of forward-thinking engineering by addressing a high-value scientific target that has long been considered unreachable for a surface mission. By presenting their detailed framework, the students hope to provide a viable pathway for academia and industry to explore extreme worlds.
The Hostile Ionian Environment
Landing on Io presents a series of monumental challenges that have prevented previous mission concepts from moving forward. The moon is a world of extremes, defined by intense radiation, blistering and freezing temperatures, and a constantly changing, violent surface. Any lander must be designed to withstand one of the harshest environments in the solar system.
Intense Radiation Fields
Io orbits deep within Jupiter’s powerful magnetic field, which traps a doughnut-shaped torus of intense ionizing radiation. The moon itself is largely responsible for supplying this radiation belt with particles, as its volcanoes spew sulfur, oxygen, and other elements into space. The resulting radiation levels at Io’s surface are lethal, capable of destroying unprotected spacecraft electronics in a short amount of time, making robust shielding and resilient systems a fundamental requirement for survival.
Temperature Extremes and Tenuous Atmosphere
The surface of Io is a place of stark thermal contrasts. While its active silicate lava flows can reach temperatures of 1,630°C (3,000°F), the average surface temperature is a cryogenic -163°C (-262°F). Furthermore, Io possesses an incredibly thin atmosphere, primarily composed of sulfur dioxide, which is millions of times less dense than that of Mars. This near-vacuum renders parachutes and other aerobraking techniques ineffective for slowing a spacecraft’s descent, forcing any landing system to rely entirely on powered or alternative braking methods.
A Geologically Active Surface
With over 400 active volcanoes, Io is the most geologically dynamic object known. Its entire surface is constantly being reshaped by volcanic activity, with vast plains of silicate and sulfurous materials burying any impact craters. Plumes of sulfur and sulfur dioxide are ejected as high as 500 kilometers (300 miles) into space. This relentless geological turmoil means the surface is unpredictable, requiring a lander to have a robust system capable of handling potentially uneven and unstable terrain upon touchdown.
A Novel Propellantless Landing System
At the heart of the UNAGI mission is its solution to the challenge of descent: a propellantless system using an electrodynamic tether (EDT). This technology exchanges momentum with Jupiter’s magnetic field, eliminating the need for heavy chemical propellants and freeing up mass for scientific instruments.
Harnessing Jupiter’s Magnetism
The system works by deploying a 50-kilometer-long (31-mile) conductive wire, or tether, as it orbits Jupiter. As this long conductor sweeps through the planet’s powerful magnetic field, an electric current is naturally induced along its length, a fundamental principle of electromagnetism. The Jovian system is an ideal environment for this technology, as its combination of a strong magnetic field and high orbital velocities generates a significant electrical potential across the tether.
The Lorentz Force as a Brake
The electric current flowing through the tether creates a phenomenon known as the Lorentz force. This force acts as a persistent drag on the spacecraft, opposing its direction of motion and converting its orbital kinetic energy into electrical energy. Mission controllers can precisely modulate this braking force by managing the current, allowing for a controlled, gradual reduction in altitude. This process lets the spacecraft de-orbit and align for landing on Io without firing a single rocket engine for deceleration.
Final Approach and Touchdown
Once the EDT has sufficiently slowed the lander’s velocity and guided it to its target, the final touchdown would be cushioned by airbags. This landing method was successfully used by early Mars rovers like Sojourner and Spirit, demonstrating its effectiveness for setting a craft down on an unprepared, rocky surface. This final step completes the challenging process of arriving safely on Io’s volatile surface.
Scientific Goals on a Volcanic World
The primary purpose of the UNAGI lander is to conduct the first-ever surface investigation of Io. Its scientific payload is designed to answer fundamental questions about the moon’s interior, its extreme volcanism, and its relationship with the wider Jovian system.
Probing the Interior
Unlike the icy moons of the outer solar system, Io is composed primarily of silicate rock surrounding a molten iron or iron sulfide core. A key objective for UNAGI is to probe for a suspected subsurface magma ocean or body that likely feeds its widespread volcanism. On-the-ground measurements would provide unprecedented insight into the tidal heating mechanism—caused by the gravitational tug-of-war between Jupiter and its other moons—that generates the immense energy within Io.
Surveying a Dynamic Surface
UNAGI will be equipped to analyze the unique composition of Io’s colorful surface, which is coated in various forms of sulfur, sulfur dioxide, and silicate materials from its constant eruptions. The lander will map surface modifications resulting from volcanic and hydrothermal processes, characterize active melt generation, and study outgassing and plume activity. By studying these processes, scientists can better understand the evolution of this geologically young world and compare its exotic volcanism to processes that occurred on early Earth.
Advanced Instrumentation
To achieve its scientific objectives, the lander will carry a sophisticated suite of instruments. The payload includes infrared spectrometers to analyze the chemical composition of surface materials, magnetometers to study Io’s interaction with Jupiter’s magnetic field, seismometers to detect “Io-quakes” and probe the crust, and chromatographs to investigate the makeup of volcanic gases. This combination of tools will provide a comprehensive picture of Io’s geophysics.
Mission Heritage and Future Outlook
While the UNAGI concept is innovative, its design stands on the shoulders of giants. The student team incorporated technologies and learnings from major space missions, including NASA’s Juno orbiter, the Europa Clipper, and the European Space Agency’s JUICE (Jupiter Icy Moons Explorer) spacecraft, to ensure its proposals are grounded in proven systems. Currently in a preliminary design phase, the UNAGI lander represents a creative yet feasible framework for future exploration. The concept is adaptable and could be integrated as a rideshare component on a future NASA or ESA mission to the Jovian system, potentially making the first landing on this volcanic moon an achievable goal.