2025, January 15:  Mars at Opposition

January 15, 2025:  Earth passes between the Red Planet and the sun.  Mars is at opposition.

Mars, November 28, 2020
2020, November 28: In the east-southeast after sunset, Mars is 1.6° to the lower right of Epsilon Piscium (ε Psc) and 2.0° to the upper right of 80 Piscium (80 Psc).

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by Jeffrey L. Hunt

Mars at Opposition

2007, December 1: Late winter in the northern hemisphere shows clouds above the northern polar cap and some above the southern cap.
Photo Caption – 2007, December 1: Late winter in the northern hemisphere shows clouds above the northern polar cap and some above the southern cap. (NASA Photo)

Mars is at opposition on January 15, 2025. This occurs when Earth overtakes the Red Planet and passes between it and the sun.  Mars is at its closest to Earth and appears brightly in the sky.

Mars revolves around the sun in 1.9 years, nearly twice Earth’s orbital period. Because it is near our world, we overtake Mars, passing between the planet and the sun every 771 days. 

Perihelic Oppositions

In this exaggerated diagram, the relative positions of perihelion, perigee, perigee, and apogee.
Chart Caption: In this exaggerated diagram, the relative positions of perihelion, perigee, perigee, and apogee.(NOAA diagram)

Like Earth, Mars’ orbit is best described as an ellipse. At opposition, the separation between the two planets varies.  If opposition occurs when Mars is near its closest point to the sun, known as perihelion, the planet is brighter than Jupiter.

Mars at Perihelion. Lowell and his canals
Photo Caption – Percival Lowell and his map of Mars (Photo Credit: Lowell Observatory)

During the 20th century, Mars’ polar ice caps were observed, and its moons were first observed. Percival Lowell thought he saw canals on the planet.  The closest separation at perihelic opposition occurred during 2003 when it was less than 35 million miles away.  Lengthy global dust storms sometimes veil the enter globe near perihelion.

The cycles of the Earth and Mars sync every 15-17 years for these close oppositions. The next one occurs in 2035, when Earth passes 35.4 million miles from Mars.

Mars
The Red Planet from the Mars Global Surveyor shows the effects of a global dust storm (NASA)

Nearing Aphelic Opposition

Currently the Earth-Mars separations at opposition are increasing.  When Earth passes by, Mars is near its farthest point from the sun, called aphelion.  The next aphelic opposition occurs February 19, 2027, when Mars is 63 million miles from Earth, not a favorable distance for telescopic discoveries.

Mars Against the Starfield

As Earth overtakes Mars, the planet appears to move eastward compared to the starfield.  As the separation decreases, the planet seems to stop moving eastward and it begins to backup or retrograde.  During the current cycle, this occurs December 6th.  As Mars retrogrades, Earth passes between Mars and the sun, opposition on January 15, 2025. Because the orbit is elliptical, the two planets are closest, 63 million miles three days earlier.

At opposition, the planet rises at sunset, appears in the southern sky near midnight, and sets before sunrise.  It is opposite the sun’s place and time in the sky. As Earth passes by, Mars seems to move eastward again.

Orbits of Mars and Earth

Mars at opposition
Chart Caption – September 19, 2024-May 17, 2025: The orbits of Earth and Mars are displayed as opposition occurs January 15, 2025. As Earth overtakes Mars, the Red Planet appears to pass bright stars in Gemini and retrograde.

The chart above shows the relative orbits of the two planets, with the sun at the center of the coordinate plane. Conjunction events with Castor, Pollux, and Wasat (δ Gem) are noted. The line of sight connects to two planets and extends into space.  The closest approach date and opposition are shown.

Mars, Gemini, Cancer

Mars at opposition
Chart Caption – September 19, 2024-May 17, 2025: Mars’ path against Gemini and Cancer is displayed. Notable events are labeled.

Mars is plotted against the starfield against the starfield showing a series of three conjunctions, known as a triple conjunction with the brightest stars.  Opposition occurs when Mars is nearly in a line with Castor and Pollux.

On both charts, triple conjunctions are color-coded, and their separations are noted.

Watch Mars appears to move against the background stars and brighten as it appears to perform a celestial dance.

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