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Ringing in the Martian new year on Earth

David Dickinson, Correspondent
Jun 18, 2015, 20:52 UTC

Sen—The planetary seasons are turning. While the summer solstice occurs this weekend for northern hemisphere residents on planet Earth on June 21, this week also marks the start of spring for the northern hemisphere of the planet Mars.

The northward equinox on the Red Planet occurs on Thursday, June 18, 2015 and marks the start of the Martian new year. And this week, NASA plans on bringing the festivities to Earthlings, with a three-day celebration kicking off this Friday in the town of Mars, Pennsylvania.

The extravaganza will feature exhibits, outreach activities and a keynote speech from NASA’s director of Planetary Science Jim Green. Green recently served as a technical consultant on the upcoming film adaptation of The Martian, now set to hit theatres on October 2 of this year.

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A spaceship landmark in downtown Mars, Pennsylvania. Image credit: Jon Dawson/Creative Commons

Martian years are reckoned from the start of the northward equinox, with Year One beginning on April 11, 1955. 2015 sees the start of Martian Year 33. In some aspects, seasons on Mars are similar to Earth: the planet rotates only 40 minutes faster than Earth, and its axis is tilted 25.2° relative to the plane of its orbit, versus Earth’s 23.4°.

The similarities, however, end there. A Martian year is 690 Earth days long—about a month shy of two Earth years—and its orbit has a high eccentricity of nine per cent. Mars also does not enjoy the stabilizing effect of a large Moon such as Earth’s, meaning the tilt of its poles is subject to much wider variations than Earth’s over geologic time scales.

In the current epoch, Mars reaches aphelion near its northern hemisphere summer solstice. This is another coincidence it currently shares with the Earth, as aphelion for 2015 on our planet occurs on July 6, 15 days after the June solstice. This also assures that the northern hemisphere climate is much more temperate than the southern.

The cycle of the Martian year also dictates when we can launch spacecraft to Mars. This window occurs every 26 months, with the next mission slated to make the journey being NASA’s InSight lander. We’re also entering a cycle of favorable oppositions to observe Mars, with the July 27, 2018 opposition being nearly as close and favorable as the historic 2003 opposition.

Happy Martian New Year!