The Moon Occults Mars for North America Monday Night, Just Before Opposition 2025

Now is the best time to observe Mars in 2025.

January has an amazing parade of evening planets, well worth braving the cold for. We have brilliant Venus, high to the west after sunset, reaching greatest elongation on January 10^th. Fainter Saturn sits just above Venus as the two meet on January 19^th. Meanwhile, Jupiter dominates the eastern sky, fresh off of opposition in December. But stay awake just a bit longer after dusk, and you can see Mars rising in the east.

As a special treat, observers in most of North America will also see the nearly Full Moon pass in front of Mars Monday night.

Mars Opposition 2025

This works because Mars reaches opposition in January 2025, rising ‘opposite’ to the setting Sun. Think of the Red Planet as a slower runner on the outside track of the solar system, with the faster Earth approaching on the inside lane.

This also marks the center season to observe Mars. As Earth approaches the Red Planet, the apparent disk swells in the view of a telescope from a tiny dot to a larger globe where features can be discerned.

Dates to watch for involving Mars in 2025 include:

-Sunday, January 12^th: Mars is closest to the Earth at 0.642 AU (96 million kilometers) distant;

-Wednesday, January 15^th: Mars is brightest, shining at magnitude -1.5

-Thursday, January 16^th: The planet Mars reaches opposition for 2025

-Monday, February 10^th: Mars reaches its northernmost point at declination 26 degrees, 14’ north

-Wednesday, April 16^th: Mars reaches aphelion at 1.6 AU from the Sun

-Monday, April 21^st: Reaches eastern quadrature, 90 degrees from the Sun.

This serves as a prelude to checking out all naked eye planets in the evening sky in 2025, once Mercury joins the evening scene in late March.

Mars Spends late January near Pollux, and then heads to Cancer and transits the open cluster Messier 44 on May 4^th. On June 16^th the planet passes just over a degree from Regulus, and the planet loiters in the evening for the remainder of 2025, until reaching solar conjunction on January 9^th, 2026.

An Aphelion Opposition

Not all oppositions are created equal. This is because the orbits of both the Earth and Mars are elliptical, but its mainly the fault of the Red Planet: the planet can vary from 207 million kilometers from the Sun at perihelion, to 249 million kilometers away at aphelion. Oppositions for Mars occur every 26 months on average, roughly once every other calendar year. Perihelic oppositions are favorable with Mars reaching an apparent size of 25” across, while an opposition near aphelion sees the planet only reaching a measly 14” across. Moreover, these trend in cycles. 2003 saw an historic near-perihelion apparition of Mars, which then diminished on every pass to a paltry aphelion appearance in 2012. In 2025, we’re still headed towards unfavorable aphelic passes. Earth just reached perihelion in early January—while Mars reaches aphelion in mid-April. 2027 sees the nadir of the 15 year cycle, while 2033 sees us reaching favorable oppositions once again.

At its maximum, Mars will appear 15” across in 2025. The planet reaches -1.5 magnitude at opposition this year, rivaling nearby Jupiter in brightness.

The ‘Great North American Occultation’

North American observers are in for a treat on the night of January 13^th when the near Full Moon actually occults (passes in front of) Mars. This is the best lunar-planetary occultation for the region for 2025. This occurs just five hours after Full, and two days prior to opposition. The Moon will take about 30 seconds to fully cover and then later reveal the Red Planet, in what promises to be a fine event.

Note that, contrary to the old internet meme, Mars will not appear ‘as large as a Full Moon’ on this—or any other—year. This does, however, give you the rare chance to see the planet in the daytime just before sunset or immediately after sunrise on January 13-14^th, using the nearby Full Moon as a guide.

The Moon occults Mars three more times in 2025: Once for northern Asia and Scandinavia on February 9^th, again for the eastern Pacific and the west coast of South America on June 30^th, and one last time for the remote Antarctic on July 28^th.

Check or the IOTA’s dedicated site for ingress/egress times for select locations.

Observing Mars Near Opposition

It’s fascinating to examine Mars near opposition… it’s the one planet that presents an actual surface to explore at the eyepiece. The white northern polar cap (currently tipped into view) is the most prominent feature. Settling in, darker swathes of terrain such as Syrtis Major may become apparent.

Fun fact: if you’re watching Mars at the same time every evening, you’re seeing nearly the same swatch of the planet turned Earthward, just rotated slightly in longitude from one night to the next. This happens because Mars rotates somewhat slower than the Earth, once every 24 hours and 38 minutes.

The ever-present possibility of a global dust storms can always make opposition season interesting. You can actually notice that something is afoot on Mars in terms of global dust storms, simply by noting the color of the planet, as a sickly yellow versus the healthy traditional red.

Finding Phobos and Deimos

Opposition is also a good time to try and cross the Martian moons of Phobos and Deimos off of your observing ‘life list.’ Discovered by astronomer Asaph Hall using the U.S. Naval Observatory’s then-new 26” refractor in 1877, the faint moons never stray far from dazzling Mars. +11.5^th magnitude Phobos orbits the planet once every 7.7 hours and reaches a max separation of 14”, while outer 12.4^th magnitude Deimos orbits once every 30.3 hours and reaches 45” away. Use an occulting bar eyepiece or nudge the planet just out of view to help you in your quest. Use a planetarium program such as Stellarium to see if a moon is currently visible.

Rovers on Mars actually catch sight of the Martian moons on occasion, including this fine transit of Phobos in front of the Sun from late 2024:

These transits actually help to refine the orbits of the two moons.

If skies are clear, be sure to check out Mars while you can, and don’t miss the best occultation of the year.