Plate Nº 39 · recorded September 30, 2026
Space & AstronomyReported finding
Mars Turns 39: The Red Planet Rings in a New Year on September 30
Mars begins Year 39 of its scientific calendar on September 30, 2026. The system, invented in 2000, helps researchers compare decades of climate data from the red planet.
By Elena Vasquez3 min read678 words
In brief
- Mars Year 39 begins on September 30, 2026; a Mars year lasts 687 Earth days.
- The Mars year-counting system was created by Todd Clancy of the Space Science Institute in a paper published in 2000.
- Mars Year 1 began April 11, 1955; a Mars Year 0 starting May 24, 1953 was added later to allow negative year numbers.
- A Martian day (a sol) lasts 24 hours and 39 minutes, and Mars seasons are unequal because of its elliptical orbit.
- Mars has an average yearly temperature of minus 60 degrees Celsius and often sees planet-wide dust storms in the second half of its year.
Mars gets a new year this month. On September 30, 2026, the red planet begins Year 39 of its own calendar, roughly 687 Earth days after its previous new year began on November 12, 2024.
Why 39, and why start counting at all? The answer lies with a scientist who wanted to compare climate data across decades of Martian observations.
Who invented the Mars calendar?
Earth and Mars formed together about 4.5 billion years ago from the same primordial nebula of gas and dust that created our sun. But while Earth's dominant calendar, the Gregorian calendar, has counted centuries and places us in the year 2026, the Mars calendar is far younger.
Todd Clancy of the Space Science Institute devised the system of labeling Mars years in a scientific paper published in 2000, which described temperature variations on the red planet. His goal was practical: numbering Mars years in orbit made it easier for researchers to compare data from different missions and eras. After his paper appeared, other scientists — especially those studying Martian climate — adopted the system.
The count begins with Mars Year 1 at the northern spring equinox on April 11, 1955. Clancy and his co-authors openly described that starting date as "arbitrary." But the choice has a convenient anchor: a major dust storm, sometimes called the Great Dust Storm of 1956, swept the planet during the second half of Year 1, giving scientists a memorable marker for the calendar's first year.
Later refinements added a Mars Year 0, defined as beginning May 24, 1953, which allows for negative year numbers — similar to how the Gregorian calendar uses A.D. and B.C., or more recently CE and BCE.
Days and years on Mars
A year, on any planet, means one full orbit around the sun. Mars takes 687 Earth days to complete that journey — almost twice as long as Earth's year.
As the European Space Agency (ESA) points out, this has a playful consequence: if you want to feel younger, divide your age by 1.88 and tell your friends that is your real age on Mars.
A Martian day is called a sol — the time the planet takes to rotate once on its axis. A sol lasts 24 hours and 39 minutes, only slightly longer than an Earth day.
Four seasons, but not equal ones
Mars has winter, spring, summer and autumn, driven by the planet's axial tilt just as Earth's seasons are. The Martian new year begins at the northern equinox, when northern spring and southern autumn start. During northern summer, the northern hemisphere receives more sunlight; during northern winter, the southern hemisphere does.
But there is a key difference from Earth: Martian seasons are not equal in length. Mars follows a more elliptical orbit than Earth's, so the planet moves faster when closer to the sun and slower when farther away.
Northern spring — southern autumn — is the longest season at 194 sols. Northern autumn — southern spring — is the shortest, at 142 sols.
That elliptical orbit also shapes Martian weather. During southern spring and summer, Mars swings closer to the sun and travels faster. The extra sunlight heats the atmosphere, creating turbulence that lifts very fine particles from the Martian soil. For this reason, the second half of a Martian year often brings fierce dust storms, which can sometimes grow to envelop the entire planet.
Cold, with a recurring giant cloud
Like Earth, Mars has cold winters and warm summers — but everything is chillier overall. The planet's average yearly temperature is minus 60 degrees Celsius (minus 76 degrees Fahrenheit).
Mars also hosts its own recurring weather phenomena. Every year around southern spring and summer, the Arsia Mons Elongated Cloud appears: a cloud of ice crystals stretching up to 1,100 miles (1,800 km) in length. It repeats for at least 80 sols before vanishing for the rest of the year.
So when September 30 arrives, the tally ticks over again. Year 39 begins on the fourth planet from the sun. Happy new year, Mars.
via britannica.com (Original)
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