Since it arrived at Jupiter in 2016, NASA’s Juno spacecraft has been probing beneath the dense, forbidding clouds encircling the giant planet – the first orbiter to peer so closely. It seeks answers to questions about the origin and evolution of Jupiter, our solar system, and giant planets across the cosmos.




Aug. 5, 2011




Explore the Jovian system

Watch Live: Juno's Io Encounter

On Saturday, Feb. 3, NASA's Juno spacecraft will buzz Jupiter's volcanic moon, Io – passing less than 1,000 miles above its turbulent surface.

About 12:48 p.m. EST (9:48 a.m. PST), Juno will reach its closest point above Io – roughly 935 miles from its unstable surface, or the distance from New York City to Orlando, Florida. It's the spacecraft's second such encounter in five weeks, and mission scientists hope the visits will expose the source of Io’s massive volcanic activity, whether a magma ocean exists underneath its crust, and the effects of tidal forces from behemoth Jupiter pushing and pulling this moon, only a bit larger than Earth's moon. Meanwhile, the gravitational pull of Io on Juno during the Feb. 3 flyby is expected to reduce the spacecraft’s orbit around Jupiter to 33 days. It originally had been circling Jupiter and its environs in 53-day orbits, after it arrived at the giant planet on July 4, 2016.

Follow Along with NASA's 3D Interactive, Eyes on the Solar System
This JunoCam image of Jupiter's moon Io captures a plume of material ejected from the (unseen) volcano Prometheus. The image was taken by NASA's Juno spacecraft on June 15, 2023.
This image of Jupiter's moon Io was taken by the JunoCam visible-light imager as NASA's Juno spacecraft flew past the Jovian moon on October 15, 2023. A plume over the location of the volcano Prometheus can be seen just standing out from the darkness on the left side of the image, just below the terminator (the line dividing day and night).

Io, Ready for Its Close-Up

On Saturday, Feb. 3, the Juno spacecraft will sail past Jupiter's "tortured moon," following up a close flyby on Dec. 30, when it captured unprecedented images and data.

Juno's encounter with Io was the closest since a visit by the Galileo spacecraft in October 2001. And Juno is scheduled to make another pass Feb. 3, studying the most volcanically active world in the solar system, only a bit larger than Earth's Moon. Io is caught in a tug-of-war between Jupiter's powerful gravity and the smaller pull from two neighboring moons, churning its insides and creating eruptions and lakes of lava that cover its surface. See where Juno is now, or sail along with the spacecraft during its Feb. 3 flyby, using NASA's 3D interactive, Eyes on the Solar System.

Relive the Dec. 30 Flyby on NASA's Eyes
A rust-colored sphere is shown against a black background. The left half is concealed in shadow, with only a very dim outline visible. The right half is fairly well-lighted, with the surface smooth in some areas and in others covered with splotches and peaks of light tan, or spots and dimples of dark orange or dark grayish brown.
Jupiter's turbulent moon, Io, captured during a close approach by NASA's Juno spacecraft on Dec. 30, 2023. Juno's flyby was the closest of any spacecraft since the Galileo orbiter's visit two decades earlier, and brought Juno within about 930 miles (1,500 kilometers) of Io, the most volcanic world in our solar system. This image was compiled from JunoCam's red, blue, and green filters, from an altitude of 1,764 miles (about 2,840 km), during Juno's 57th orbit around Jupiter.

Juno makes closest visit to volcanic moon since 2001

The Dec. 30 flyby of Jupiter's moon Io – the most volcanic world in our solar system – offers the nearest view since the Galileo orbiter visited two decades ago.

Juno has monitored Io from afar since the spacecraft arrived at Jupiter in 2016. Then, as part of its 57th orbit around Jupiter, Juno came within roughly 930 miles (1,500 kilometers) of Io's surface – less than the distance between Los Angeles and Seattle. It will make another close pass Feb. 3, enabling scientists to compare data and images from these visits with previous observations that Juno and other craft made of this volatile world, slightly larger than Earth's Moon.

Read More About the Flyby
The volcano-laced surface of Jupiter's moon Io was captured in infrared by the Juno spacecraft's Jovian Infrared Auroral Mapper (JIRAM) imager on July 5, 2022.
NASA's Juno mission captured this infrared view of Jupiter's volcanic moon Io on July 5, 2022, when the spacecraft was about 50,000 miles (80,000 kilometers) away. This infrared image was derived from data collected by the Jovian Infrared Auroral Mapper (JIRAM) instrument aboard Juno. In this image, the brighter the color the higher the temperature recorded by JIRAM.

Jupiter's Volatile Moon, Io

The turbulent world is dotted with hundreds of volcanoes, some erupting so powerfully they're visible with large telescopes on Earth

The moon – one of four that astronomer Galileo Galilei discovered to be orbiting Jupiter in 1610 – is caught in a gravitational tug-of-war between its sibling moons, Europa and Ganymede, and the massive Jupiter. This creates tremendous tidal forces, like ocean tides on Earth, but which cause Io's solid surface to bulge up and down (or in and out) by as much as 330 feet (100 meters).

Read More About Io
Just hours before NASA's Juno mission completed its 53rd close flyby of Jupiter on July 31, 2023, the spacecraft sped past the planet's volcanic moon Io and captured this dramatic view of both bodies in the same frame.
Just hours before NASA's Juno mission completed its 53rd close flyby of Jupiter on July 31, 2023, the spacecraft sped past the planet's volcanic moon Io and captured this dramatic view of both bodies in the same frame. The surface of Io is marked by hundreds of volcanoes that regularly erupt with molten lava and sulfurous gases. Juno will gather additional images and data from its suite of scientific instruments during even closer passes in late 2023 and early 2024. To create this image, citizen scientist Alain Mirón Velázquez processed a raw image from the JunoCam instrument, enhancing the contrast, color, and sharpness. At the time the raw image was taken on July 30, 2023, Juno was about 32,170 miles (about 51,770 kilometers) from Io, and about 245,000 miles (about 395,000 kilometers) above Jupiter's cloud tops.
Image data: NASA/JPL-Caltech/SwRI/MSSS
Image processing by Alain Mirón Velázquez © CC BY

juno firsts

juno arrives

First solar-powered spacecraft operating at Jupiter.

Five engineers in cleanroom suits inspect the Juno spacecraft's massive solar panels before launch.

Farthest solar-powered spacecraft from Earth.

Detailed view of Jupiter and its immense swirling cloud patterns.

First mission to orbit an outer planet from pole to pole.

Illustration of the tri-winged spacecraft over the planet Jupiter, which is tan and white striped, with a streak of blue above the Great Red Spot, a swirling orange storm on Jupiter, at lower left

Closest orbiter to Jupiter, grazing deadly radiation belts.

great red spot swirling in Jupiter's clouds

Highest-resolution images ever captured at Jupiter.

After enduring a five-year, 1.7 billion-mile journey from Earth, and navigating the dangerous radiation in Jupiter's extensive magnetic field, Juno has provided breathtaking images and breakthrough discoveries from Jupiter and its moons. And in their quest to engage and inspire the public, the Juno mission team shares the data and pictures with the world, fueling citizen science and creative artistry.

Embarking on 53-day orbits reaching from Jupiter’s cloud tops to the frontiers of its magnetic field, Juno has upended our views of the gas giant and its surroundings. The spacecraft recently found evidence of organic compounds and salts on the large moon Ganymede – remnants of a deep underground ocean that once reached its surface – and answered a decades-old question about winds on Jupiter extending hundreds of miles toward the planet’s interior. Juno is scheduled to continue investigating the solar system’s largest planet, its moons, faint rings, and surrounding environment through September 2025.

Art and Science: A Sampler of Jupiter Images from JunoCam