June’s Night Sky Notes: Seasons of the Solar System

Two planets, Uranus, are shown side-by-side for comparison, highlighting their unique seasonal patterns. Uranus’ seasons last around 40 years due to its tilted axis and slow orbit.
Mars experiences a Martian Autumn every year, lasting about 687 Earth days, with temperatures ranging from -18°F to -12°F (-27°C to -24°C) in the week of May 20, 2025.
Saturn’s seasons last seven years due to its 29-year orbit, and scientists can observe a ring plane crossing on Earth instead. The most recent plane crossing took place in March 2025.
Neptune’s seasons are much slower and less dramatic than on Earth, with each season lasting over 40 years due to its tilted axis and slow orbit. Scientists have observed seasonal activity in Neptune’s atmosphere using Hubble Space Telescope images.
A Suntrack model can be used to demonstrate the path the Sun takes through the sky during the seasons, providing a fun way to explore the changing of the seasons on other planets.

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June’s Night Sky Notes: Seasons of the Solar System

Two views of the planet Uranus appear side-by-side for comparison. At the top, left corner of the left image is a two-line label. The top line reads Uranus November 9, 2014. The bottoms line reads HST WFC3/UVIS. At the top, left corner of the right image is the label November 9, 2022. At the left, bottom corner of each image is a small, horizontal, white line. In both panels, over this line is the value 25,400 miles. Below the line is the value 40,800 kilometers. At the top, right corner of the right image are three, colored labels representing the color filters used to make these pictures. Located on three separate lines, these are F467M in blue, F547M in green, and F485M in red. On the bottom, right corner of the right image are compass arrows showing north toward the top and east toward the left.

Credits:
NASA

by Kat Troche of the Astronomical Society of the Pacific

Here on Earth, we undergo a changing of seasons every three months. But what about the rest of the Solar System? What does a sunny day on Mars look like? How long would a winter on Neptune be? Let’s take a tour of some other planets and ask ourselves what seasons might look like there.

Martian Autumn

Although Mars and Earth have nearly identical axial tilts, a year on Mars lasts 687 Earth days (nearly 2 Earth years) due to its average distance of 142 million miles from the Sun, making it late autumn on the red planet. This distance and a thin atmosphere make it less than perfect sweater weather. A recent weather report from Gale Crater boasted a high of -18 degrees Fahrenheit for the week of May 20, 2025.

A diagram of Mars' orbit around the Sun, labeled with seasons for both hemispheres (Northern Spring/Southern Autumn, Northern Winter/Southern Summer, etc.). Key points like perihelion (closest to Sun) and aphelion (farthest from Sun) are marked, illustrating how seasons align with orbital position.

Credit: NASA/JPL-Caltech

Seven Years of Summer

Saturn has a 27-degree tilt, very similar to the 25-degree tilt of Mars and the 23-degree tilt of Earth. But that is where the similarities end. With a 29-year orbit, a single season on the ringed planet lasts seven years. While we can’t experience a Saturnian season, we can observe a ring plane crossing here on Earth instead. The most recent plane crossing took place in March 2025, allowing us to see Saturn’s rings ‘disappear’ from view.

A Lifetime of Spring

Springtime on Neptune: Increased Brightness Shows Seasonal Change

NASA Hubble Space Telescope observations in August 2002 show that Neptune’s brightness has increased significantly since 1996. The rise is due to an increase in the amount of clouds observed in the planet’s southern hemisphere. These increases may be due to seasonal changes caused by a variation in solar heating. Because Neptune’s rotation axis is inclined 29 degrees to its orbital plane, it is subject to seasonal solar heating during its 164.8-year orbit of the Sun. This seasonal variation is 900 times smaller than experienced by Earth because Neptune is much farther from the Sun. The rate of seasonal change also is much slower because Neptune takes 165 years to orbit the Sun. So, springtime in the southern hemisphere will last for several decades! Remarkably, this is evidence that Neptune is responding to the weak radiation from the Sun. These images were taken in visible and near-infrared light by Hubble’s Wide Field and Planetary Camera 2.

Credit: NASA, L. Sromovsky, and P. Fry (University of Wisconsin-Madison)

Even further away from the Sun, each season on Neptune lasts over 40 years. Although changes are slower and less dramatic than on Earth, scientists have observed seasonal activity in Neptune’s atmosphere. These images were taken between 1996 and 2002 with the Hubble Space Telescope, with brightness in the southern hemisphere indicating seasonal change.

As we welcome summer here on Earth, you can build a Suntrack model that helps demonstrate the path the Sun takes through the sky during the seasons. You can find even more fun activities and resources like this model on NASA’s Wavelength and Energy activity.

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Q. What is unique about Mars’ seasons compared to Earth’s?

A. A year on Mars lasts 687 Earth days due to its average distance from the Sun, making it late autumn on the red planet.

Q. How long does a single season last on Saturn?

A. A single season on Saturn lasts seven years, which is much longer than any season on Earth.

Q. What is causing Neptune’s increased brightness observed by NASA Hubble Space Telescope in 2002?

A. The increase in brightness is due to an increase in the amount of clouds observed in Neptune’s southern hemisphere, possibly caused by seasonal changes.

Q. How often does a ring plane cross Saturn’s rings, and what can be seen during this event?

A. A ring plane crosses Saturn’s rings every 14 Earth years, allowing us to see Saturn’s rings ‘disappear’ from view.

Q. What is the rate of seasonal change on Neptune compared to Earth?

A. The rate of seasonal change on Neptune is much slower than on Earth due to its farther distance from the Sun and longer orbital period.

Q. How long does a season last on Neptune, considering its 164.8-year orbit of the Sun?

A. Each season on Neptune lasts over 40 years.

Q. What is the significance of Neptune’s rotation axis being inclined at 29 degrees to its orbital plane?

A. This inclination causes seasonal solar heating during Neptune’s 164.8-year orbit of the Sun, leading to changes in cloud cover and brightness.

Q. How does the axial tilt of Saturn compare to that of Mars and Earth?

A. Saturn has a 27-degree tilt, which is very similar to the 25-degree tilt of Mars and the 23-degree tilt of Earth.

Q. What can be observed on Earth instead of experiencing a Saturnian season?

A. We can observe a ring plane crossing here on Earth, allowing us to see Saturn’s rings ‘disappear’ from view.

Q. Why is it difficult for humans to experience seasons on other planets like Mars and Neptune?

A. The distance of these planets from the Sun and their thin atmospheres make it less than perfect sweater weather, making seasonal changes challenging to observe or experience.