26.12.2024

Mars is on the cusp of becoming bigger and brighter than at any point since 2022 as it comes into alignment with Earth and the sun.

Have you noticed Mars has been getting brighter and redder in the past few months?

On Sunday, Jan. 12, 2025, Mars will make its closest approach to Earth since 2022 and enter its annual opposition shortly thereafter. In addition to providing the best opportunity to see Mars at its biggest and brightest, this will be the best time for sending spacecraft to the Red Planet.

Every 789 days, Mars, Earth and the sun come into alignment, which astronomers call opposition. Planetary oppositions for Jupiter, Saturn, Uranus, and Neptune occur almost annually, as Earth's faster orbit allows it to pass between each of these planets and the sun nearly once a year but Mars is a bit different.

That's because Mars and Earth are relatively close together. Earth's orbit of the sun, at roughly 365 days, is much shorter than Mars' 687-Earth-day orbit. Consequently, Earth passes between Mars and the sun every 789 days — just over two Earth years — at which point Mars and Earth are at their closest.

During its opposition, Mars also gets the sun's full glare, as seen from Earth. That makes the Red Planet's surface features more easily observed by amateur astronomers and astrophotographers using good backyard telescopes, as well as by professional astronomers using space-based telescopes.

Key features to observe on the rusty-red surface of Mars include the canyon systems of Valles Marineris; the largest volcano in the solar system, Olympus Mons; and the planet's southern polar ice cap. These prominent features are best seen using a refractor telescope with a long focal length (the distance from the objective lens to the focal point) that accommodates eyepieces offering 200x magnification.

In addition to being able to see 100% of Mars' disk lit up by the sun at night, opposition offers the chance to observe Mars rising in the east at sunset and setting in the west at sunrise, making these by far the most convenient times to observe the Red Planet, whether through telescopes or with the naked eye.

A visualization depicting Mars at opposition and its closest approach. (Image credit: NASA's Scientific Visualization Studio)

There is an official date for the opposition of Mars, but that's not the only night to observe it. The Red Planet will actually be brighter three days earlier, when it's closer to Earth (a consequence of both planets having elliptical orbits). There will also be a few close conjunctions near its opposition date that will arguably make for the most dramatic and brightest views of Mars.

Here are some key dates to note:

• Sunday, Jan. 12, 2025 (13:38 UTC): Mars will make its closest approach to Earth since 2022, at 59,703,891 miles (96,084,099 kilometers) while in the constellation Cancer.
• Monday and Tuesday, Jan. 13 and 14, 2025: Mars will be occulted by the full Wolf Moon overnight from North America, according to In-The-Sky.org, which gives timings for all locations.
• Thursday, Jan. 16, 2025: Mars will reach opposition while in the constellation Gemini.
• Sunday, Feb. 9, 2025: Mars will be in conjunction with the waxing gibbous moon

While important, these exact dates can detract from the overall advice: The prime window for viewing Mars is December 2024 through February 2025.

During its opposition, Mars will shine in the constellation Gemini. It will be a dramatic event because the Red Planet will appear as a bright, red point of light and dominate the night sky. However, relatively speaking, this Mars opposition won't be particularly impressive. That's because 2025 is not what astronomers call a "perihelic opposition," which is when Mars gets closest to Earth while near its closest point to the sun on its slightly elliptical orbit.

During a perihelic opposition, the disk of Mars can appear as large as 24 arcseconds, and the planet can shine at a magnitude of -2.6. In 2025, it will be a much smaller 14.6 arcseconds (2.6 arcseconds smaller than during the same period in 2022, according to the Association of Lunar and Planetary Observers), and shine at a dimmer magnitude of -1.4.

Perihelic oppositions occur only once every 15 to 17 years; the last one was in 2018, and the next one will be in 2033.

Any journey between Mars and Earth takes the least amount of time just before Mars reaches opposition. So, come December, a launch window opens for efficient, cost-effective missions taking a Hohmann transfer orbit, which has them launch from Earth just before the spacecraft catches up and overtakes Mars. Making the journey as short as possible is vital because about half the weight of most spacecraft is fuel.

NASA has been planning to launch its Escape and Plasma Acceleration and Dynamics Explorers (EscaPADE) mission, in which a spacecraft containing two orbiters will study the planet's real-time response to space weather. It was due to launch atop Blue Origin's New Glenn rocket in October 2024 to take advantage of Mars' proximity, but it was postponed to spring 2025 or later.

Although opposition occurs in early 2025, the Red Planet will be prominent for most of the year. However, it will become lost in the sun's glare in late November 2025. The following opposition of Mars will occur on Feb. 19, 2027.

Quelle: SC

Here's everything you need to know about seeing and understanding Mars at opposition in 2025.