The Spacecraft Tarot: Juno

Tippy Ki Yay
6 min readJan 31, 2021
The original watercolor illustration is by me, Tippy Ki Yay. The background image is Hubble imagery and the credit belongs to NASA, ESA, and J. Olmsted (STScI).

The Empress protects you with her motherly spirit.

Our mothers are our first introduction to this world. They are our first environments, our first source of nutrition, our first understanding of home. However, motherhood can extend to other forms as well: whether the Empress is a friend, a mentor, or simply a maternal presence, she thrives on being a good provider for others. She is always there for us — whether we need comfort, encouragement, or protection. Our success is her success. Our happiness is her happiness.

The Empress has a strong influence on our beginnings. The Juno spacecraft captures the power of a mother’s spirit, and as it improves our understanding of our early solar system through its scrutiny of the planet Jupiter.

Jupiter is a unique planet in our solar system. In addition to being the largest, containing twice as much mass as all the other planets combined, it was also probably one of the first to be created. The composition of the planet is very similar to that of the Sun, containing mostly hydrogen and helium, and is believed to be mostly unchanged since its inception — providing us with a way to trace our solar system’s history.

Voyager 1 captured this photo of Jupiter on February 13, 1979. Image Credit: NASA

Jupiter has been of great interest to the space community ever since Galileo used a telescope to make the first detailed observations of the planet in 1610. He discovered that Jupiter is in fact, not just a planet, but an entire system of moons. Galileo’s observation called into question pre-existing notions that nothing could possibly orbit anything other than Earth, because Earth was understood to be at the center of the universe. Jupiter defied this logic.

NASA’s Pioneer-series spacecraft were the first to explore Jupiter. The first of the Pioneer spacecraft were launched in 1958 to attempt a lunar flyby, but none were successful until Pioneer 4, which became NASA’s first spacecraft to escape the Earth’s gravitational field in 1959.

Pioneer 4 was the first U.S. spacecraft to leave the Earth’s gravitational field. The spacecraft came within 37,300 miles of the Moon’s surface. Image Credit: NASA

On May 2, 1972, Pioneer 10 launched from NASA’s Kennedy Space Center, Florida, to take measurements of the solar wind as it soared toward its destination through the asteroid belt.

When Pioneer 10 arrived to Jupiter on December 3, 1973, the spacecraft proved that the asteroid belt could be survived in order to traverse parts of the solar system, paving the way for future spacecraft.

As Pioneer 10 flew as close as 81,000 miles above the tops of Jupiter’s clouds, it captured hundreds of images and other types of data. Pioneer discovered that Jupiter has a strong and extremely large magnetosphere, a magnetic field similar to Earth’s that rotates with the planet and sweeps up swarms of electric particles. As a result, Jupiter is surrounded by an intense radiation environment. Pioneer measurements of this radiation environment prepared scientists to build future Jupiter-exploring spacecraft, such as Voyager and Galileo.

Over the course of forty years, these spacecraft and others brought Jupiter into sharper and sharper focus, discovering new moons, new rings, and new atmospheric observations.

NASA’s Voyager 1 spacecraft captured this close-up of swirling clouds around Jupiter’s Great Red Spot in early 1979. Image Credit: NASA’s Goddard Space Flight Center and NASA/JPL

When NASA’s Juno spacecraft launched from Cape Canaveral Air Force Station on August 5, 2011, one of the spacecraft’s main objectives was to paint a clearer picture of Jupiter’s turbulent atmosphere. As a gas giant, the planet’s surface consists of a layer of swirling gas, encircling a solid core and an ocean of liquid metal. The stripes of vivid colors that adorn the planet are bands of gases being pushed along by strong jet streams, caused by Jupiter’s rapid rotation rate. One of Jupiter’s most distinguishing features, the Great Red Spot, is in fact a giant hurricane. However, scientists are still learning about how deep Jupiter’s atmosphere is, and whether these storms are shallow or extend into the planet’s interior. Juno is the first mission to map what is beneath Jupiter’s thick cloud cover to investigate.

Ballooning fifteen times wider than the Sun, Jupiter’s magnetosphere is the largest object in our solar system. Juno is also the first spacecraft to directly sample the charged particles and magnetic field to near Jupiter’s poles in order to understand similar magnetic objects, such as young stars.

An image of Jupiter’s magnetosphere, constructed from data from NASA’s Cassini spacecraft. Image Credit: NASA/JPL/Johns Hopkins University Applied Physics Laboratory

Most importantly, Juno’s examination of Jupiter will reveal to us more about the origins of our solar system. Details about Jupiter’s interior can explain more about how the planet formed, which could illuminate how other giant planets form around other stars in the universe.

Since arriving to Jupiter on July 4, 2016, Juno has shed light on all of these features and more. The spacecraft travels in a highly elliptical orbit, making a swooping pass 2,600 miles over the gas giant’s cloud tops once every 53 days in order to avoid constant exposure to Jupiter’s damaging radiation. Juno’s instruments have peeked under Jupiter’s cloud cover to reveal a Great Blue Spot — similar to the planet’s Great Red Spot, only, this spot is a magnetic storm as opposed to an atmospheric storm. The Great Blue Spot is powerful enough to cause fluctuations in Jupiter’s entire magnetic field.

According to Juno, we have also been able to take more precise measurements of the Great Red Spot, which currently appears to be shrinking (which doesn’t mean it’s still not very large — the storm is over three times the diameter of Earth.) Dark material unwinds from the center in tendrils, suggesting that the storm may be unraveling. Juno also discovered the Great Red Spot is 200 miles deep, 50 to 100 times deeper than Earth’s oceans. The colorful belts that travel near Jupiter’s equator penetrate deep into the planet’s atmosphere as well, but this changes closer to the poles.

Never-before-seen images of Jupiter’s polar regions reveal clusters of new Earth-sized storms. All of Juno’s discoveries have pointed to Jupiter being an environment in constant flux, filled with powerful energies and dynamic features.

A composite image of Jupiter from three filters, compiled from the James Webb Space Telescope. Image Credit: NASA, ESA, CSA, Jupiter ERS Team; image processing by Judy Schmidt.

However, Juno’s mission is far from over. Originally the mission was supposed to end in July 2021, but it has been extended through September 2025 to include 42 additional orbits that will fly by some of Jupiter’s moons and explore the faint rings that encircle the planet — providing a more complete picture of the Jovian system.

In Greek and Roman mythology, the god Jupiter was often unfaithful to his wife, Juno. He disguised himself as swans, bulls, and even rays of light to trick the objects of his affection and evade detection from Juno. Many of Jupiter’s well-known moons are named after the men and women Jupiter seduced, such as Io, Callisto, Europa, and Ganymede.

Juno was often clever enough to see through Jupiter’s disguises and see him for who he really was. The Juno spacecraft is clever as well, with a diverse suite of instruments in order to see what is hidden beneath the planet’s thick and colorful cloud cover.

Juno is powered by the Sun and moves around with a spinning motion that makes the spacecraft stable and easy to control. The same can be said of the Empress — she is busy, occupied by her motherly duties, but thrives in her work with an impressive steadiness. Both the Empress and the Juno spacecraft are effective at what they do: for the Empress, she is cultivating the next generation of children. For Juno, it is cultivating data that shed light on the origins of our solar system.

A view of Jupiter from the Juno spacecraft. Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill

Read the complete Spacecraft Tarot series.