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NASA’s Juno mission has provided the first measurements of the temperature below the surface of Jupiter’s moon Io, revealing significant heating within the shallow subsurface of the most volcanically active world in the solar system. Collected during two close flybys, the data also shows that most of Io’s surface is remarkably smooth and composed of material of very low density.
Published Wednesday in the Journal of Geophysical Research: Planets, these findings break new observational ground for both fiery and icy worlds beyond our planet.
Io’s extreme volcanism is powered by tidal heating. The moon is constantly stretched and squeezed by Jupiter’s immense gravity as it travels its slightly elliptical orbit, generating internal heat output many times greater than Earth’s. Until now, virtually everything known about that heat came from infrared observations, which sense only the temperature of the top surface. The latest findings are derived from data collected by the spacecraft’s Microwave Radiometer (MWR) instrument.
“The Juno Microwave Radiometer directly observed Io’s heat output by looking below the surface,” said Scott Bolton, study coauthor and Juno’s principal investigator at Southwest Research Institute in San Antonio. “The surprising discovery that we could see below a rocky moon’s surface has important implications for studying Earth’s volcanoes. Juno has taught us that if we look with an MWR-type instrument near a volcano on Earth, we might see a similar signature in the subsurface temperature gradient, providing new information on how terrestrial volcanoes work.”
Juno’s Microwave Radiometer was designed by Bolton to peer beneath Jupiter’s cloud tops to investigate the dynamics and composition of the gas giant’s deep atmosphere. The MWR’s six microwave antennas serve as a single instrument, simultaneously detecting microwaves at a wide range of wavelengths, from about half an inch to 20 inches (1.3 to 51 centimeters). During the mission’s extended phase, the MWR instrument has provided the opportunity to observe three of the planet’s Galilean moons: Ganymede, Europa, and Io.
“The technique is novel in that each wavelength explores different depths, providing a new way to characterize the deep atmosphere of giant planets and the subsurface crusts of icy and rocky moons,” said Bolton. “At Ganymede and Europa, we explored tens of miles below the surface, assuming their ice shells were mostly pure water, but the ability to probe into the volcanic rock at Io was an unexpected discovery.”
During flybys on Dec. 30, 2023, and Feb. 3, 2024, the solar-powered Juno spacecraft came within about 930 miles (1,500 kilometers) of the moon’s surface.
“The instrument measured Io’s thermal emission at depths ranging from a few inches down to tens of feet. Everywhere we looked, we found the temperature rising by more than 40 degrees Fahrenheit just several feet into the surface — a gradient far steeper than solar heating alone can explain,” said Shannon Brown, the paper’s lead author at NASA’s Jet Propulsion Laboratory in Southern California.
The data suggests two possible explanations. First, heat could be rising steadily through a conductive crust. While this background heat flow — measured at 1 to 3 watts per square meter — is relatively gentle on a local scale (roughly equivalent to a small nightlight glowing under every square yard), across the entire moon it represents a release of energy up to 30 times Earth’s average. Alternatively, the signal could be coming from cooling lava flows, capped by roughly 30 to 35 feet (9 to 11 meters) of solidified crust, that cover about 10% of the moon’s surface at any given time.
“Io provides a unique window into learning how tidal heating works throughout the cosmos, a fundamental process that provides energy and heat to worlds that are far from their parent star,” said Bolton. “This process can not only create the most volcanic body in the solar system, in the case of Io, but also fuels the subsurface oceans on the moons of giant planets, such as Europa and Ganymede. Up until this point we could only observe the heat escaping at the surface or through eruptions. Now we can characterize how the heat is moving from the interior toward the surface.”
Another big insight gained from the two flybys is just how smooth Io is. Prior to the recent findings, the moon was known for its tall mountains, but the MWR indicates that apart from this visible topography, the surface features expansive smooth patches that stretch for 60 miles (100 kilometers) or more. Because Juno flew by overlapping regions of Io at different angles, the team was able to map how the surface reflects microwaves, much like an airline passenger might see the ocean flash with sunlight only at specific angles.
“Away from its mountains, the surface is more like the Great Plains of North America, and even though Io is a rocky body, the surface material has a very low density — more like pumice or a fluffy volcanic ash than solid rock,” said Brown.
A division of Caltech in Pasadena, California, JPL manages the Juno mission for the principal investigator, Scott Bolton, of the Southwest Research Institute. Juno is part of NASA’s New Frontiers Program, which is managed at the agency’s Marshall Space Flight Center in Huntsville, Alabama, for the NASA’s Science Mission Directorate in Washington. Lockheed Martin Space in Denver built and operates the spacecraft. More information about Juno is at:
https://science.nasa.gov/mission/juno
News Media Contacts
DC Agle
Jet Propulsion Laboratory
818-393-9011
agle@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Deb Schmid
Southwest Research Institute, San Antonio
210-522-2254
dschmid@swri.org
2026-050
The milestone reflects aggregate swap volume routed across connected Solana liquidity pools. Jupiter is not just a single exchange pool. It is an aggregator, meaning it searches across venues to find better pricing and execution for users.
That role makes it central to Solana trading.
When users swap tokens on Solana, Jupiter is often part of the route. Passing $1 trillion in cumulative volume shows how much trading activity has flowed through the platform and how important aggregation has become for low-cost, high-speed DeFi.
Decentralized exchanges can become fragmented.
Liquidity is spread across pools, AMMs, order books, and protocols. If users have to manually search for the best route, trading becomes inefficient. Aggregators solve that problem by routing trades through the best available path.
Jupiter has become Solana’s most recognizable example of that model.
It helps users access deeper liquidity without needing to understand every underlying venue. That is especially useful on Solana, where low fees make smaller and faster trades more practical.
The $1 trillion milestone shows that users are not just experimenting with Jupiter. They are relying on it as part of Solana’s core market structure.
That matters because DeFi ecosystems are often judged by their liquidity layer.
If swaps are cheap, fast, and well-routed, the entire ecosystem becomes easier to use.
Solana’s early DeFi story was often overshadowed by meme coins and retail trading.
That attention brought volume, but it also made some investors question how much activity was durable. Jupiter’s cumulative volume milestone gives Solana a stronger infrastructure story.
A trillion dollars in routed volume does not happen without repeated use.
It suggests a large amount of trading activity has moved through Solana’s DeFi rails over time. That strengthens the argument that Solana is not only a speculative chain but also a serious venue for decentralized trading.
The launch of Jupiter’s Offerbook lending market adds another layer.
If Jupiter can expand from routing swaps into lending and broader market infrastructure, it may become even more central to Solana’s DeFi stack.
The number is impressive, but it should be understood properly.
Cumulative volume is not the same as current daily volume. It reflects all historical routing activity across connected pools. It does not mean $1 trillion is locked in the protocol, and it does not mean that every trade produced equal revenue or user value.
Still, cumulative volume is a useful adoption marker.
It shows that Jupiter has processed meaningful activity over a long period. For users, that can reinforce trust. For developers, it shows where liquidity is flowing. For Solana, it supports the network’s claim to be one of crypto’s leading trading environments.
The next question is how Jupiter maintains that position.
Competition in DeFi is constant. Aggregators need to keep routes efficient, interfaces clean, integrations broad, and execution reliable. If they fall behind, users can move quickly.
The broader story is Jupiter’s evolution.
The platform started as a critical swap aggregator, but it has increasingly expanded into other Solana-native financial products. Offerbook is part of that shift, pointing toward a wider DeFi role beyond simple token swaps.
That matters for Solana.
A strong ecosystem needs anchor applications. Ethereum has Uniswap, Aave, Lido, and Curve. Solana needs its own set of core venues that users return to repeatedly. Jupiter is clearly one of them.
Passing $1 trillion in cumulative routing volume reinforces that position.
For traders, it shows where Solana liquidity is moving. For SOL supporters, it gives a concrete metric supporting the network’s DeFi maturity. For Jupiter, it raises expectations.
The platform now has to prove that it can keep growing beyond aggregation while maintaining the execution quality that made it important in the first place.
For now, the milestone is a strong signal: Solana DeFi has real volume, and Jupiter remains one of its main arteries.
This article is based on Jupiter’s public statement and platform data.
This article was written by the News Desk and edited by Samuel Rae.
This report is based on information released in official primary source disclosures at primary source documentation.
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