Mars Year 39 begins at the planet’s northern spring equinox

Mars began Year 39 at its northern spring equinox on 30 September 2026, according to the European Space Agency. ESA placed the start at 08:16 UTC on Earth; a calendar maintained by NASA’s Planetary Data System lists 08:16:26 UTC. The date marks the start of another Martian seasonal cycle, which lasts nearly twice as long as an Earth year.

The year number comes from a convention for tracking Mars’s position around the Sun. It gives scientists and readers a shared way to identify a seasonal cycle, rather than marking a change in the planet’s conditions at a single moment. ESA describes this year’s boundary as the beginning of northern spring and southern autumn on Mars.

When did Mars Year 39 begin?

ESA’s announcement gives 10:16 CEST, equivalent to 08:16 UTC, on 30 September. The Planetary Data System table records the boundary to the second, at 08:16:26 UTC. The figures agree at the minute level; the extra seconds come from the precision of the calendar table.

The same Planetary Data System table places the start of Mars Year 38 on 12 November 2024 and Year 40 on 17 August 2028. Those dates show why the Martian new year does not fall on the same Earth calendar date from one cycle to the next. ESA also lists 17 August 2028 as the date of Year 40.

How is a Martian year measured?

NASA Goddard Institute for Space Studies identifies zero degrees of areocentric solar longitude, written Ls, with the northern vernal equinox. Its technical notes mark the subsequent points in the cycle at 90, 180 and 270 degrees. These markers let researchers place observations within a Martian season, even when the corresponding Earth date changes.

The numbering starts with Mars Year 1 on 11 April 1955, according to the Planetary Data System. That starting point is a calendar convention. ESA says the sequence began in 1955 and associates its first year with a major dust storm known as the great dust storm of 1956. Year 39 therefore names a point in a modern counting system, rather than Mars’s 39th journey around the Sun.

How long are a Martian year and day?

ESA gives a Martian year as about 687 Earth days, close to 1.88 Earth years. It also describes a year as 668 sols, using a rounded count. A sol is a Martian solar day: the interval used to count days on Mars, which is slightly longer than a day on Earth.

NASA Goddard’s technical notes give a more precise mean tropical year of 686.9725 Earth days, or 668.5921 sols. The tropical year measures the return of the seasonal cycle and is the relevant figure for a calendar that starts at the equinox. NASA also distinguishes a sidereal year, measured against fixed stars, of 668.5991 sols. Those two definitions produce slightly different lengths; neither makes 668 an exact count of sols in every Martian year.

The mean sol lasts 24 hours, 39 minutes and 35.244 seconds in Earth time, according to NASA Goddard. Its extra 39 minutes help explain why an Earth day and a sol cannot be treated as interchangeable when comparing calendars. Expressing the year in Earth days or sols changes the number used to describe the same seasonal interval.

What begins at the northern spring equinox?

The equinox opens spring in Mars’s northern hemisphere and autumn in its southern hemisphere, ESA says. Mars has four seasons, but ESA notes that they are unequal in length because the planet follows a more elliptical orbit than Earth. A Martian year is therefore a full seasonal cycle, not four equal blocks of time.

ESA says the second half of a Martian year is often marked by strong dust storms, sometimes large enough to spread across the planet. It describes how, as Mars moves closer to the Sun, atmospheric heating can help winds lift fine soil particles. That account describes a recurring seasonal tendency; the start of Year 39 does not itself establish that a particular storm has begun.

For anyone reading Mars observations, the year number and solar longitude supply a seasonal reference alongside an Earth date. The Planetary Data System offers both a Mars-year filter and a solar-longitude filter for searching data products. Its table of UTC start times anchors those labels to Earth time, including the 30 September boundary for Year 39.