Saturn is now in the “September” of its long year, and an iconic space telescope is watching the change of season of the small planet.
Spring and autumn only officially began here a few days ago here on the northern and southern hemisphere of the earth with the arrival of the spring equinox. The arrival and departure of seasons is possible if a planet has a tilted axis – and Earth and Saturn have a lean in their turn.
But there is a big difference in the length of the seasons. The earth takes one year to orbit the sun, during which our planet experiences the cold and gloomy, the sunny and delightful and every seasonal middle ground in between. But Saturn, the sixth planet from the sun, takes 29 Earth years to orbit our star once. The earth moves through all its seasons repeatedly, while Saturn remains in just one season; it takes about seven Earth years before Saturn begins and ends one of its seasons.
Related: Saturn has no summer blues on this amazing Hubble photo
Fortunately, long space missions such as NASA’s Cassini mission and the Hubble Space Telescope have had enough time to observe seasonal changes on Saturn.
On March 18, Hubble crew members based on NASA’s Goddard Space Flight Center in Greenbelt, Maryland, released new images showing subtle shadow differences in the appearance of Saturn’s clouds over the past few years. In these images Hubble took during 2018, 2019 and 2020, the northern hemisphere of Saturn experiences summer and comes after autumn. Meanwhile, it was on the southern hemisphere of Saturn, as on earth, winter (spring goes on).
“What we found was a slight change from year to year in color, possibly cloud height and wind – not surprisingly the changes are not large, as we are only looking at a small fraction of a Saturn year,” according to Amy Simon, planetary scientist at Goddard, who commented in the NASA press release describing the new images. “We expect big changes on a seasonal time scale, so it shows the progress towards the next season.”
The Hubble data show that the equator brightened by about 5% to 10% from 2018 to 2020, and that some cloud bands that were visible during certain years did not appear at other times.
According to NASA, the wind speed has also changed. When Cassini observed Saturn during the years 2004 to 2009, the wind near the equator was about 800 miles per hour (about 1,300 kilometers per hour), according to the release.
Hubble’s 2018 observations show that equatorial wind speeds have become much faster, about 1000 km / h (about 1600 km / h). By 2019 and 2020, however, Hubble detected that wind speeds had dropped back to the Cassini speeds of more than a decade ago.
The Hubble Space Telescope has been in operation since 1990. The 30-year-old spacecraft is briefly in safe mode this month, but has returned to its scientific work from March 11.
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