What’s so particular about recognizing Phobos crossing in entrance of the Solar?
Positive. It’s simply one other picture of Phobos, crossing the disk of the Solar, as seen from the floor of Mars. Like a lot of the trendy area period, these photographs, as soon as superb, are actually nearly routine. However there’s some actual science behind tasking the Mars rovers to conduct a bit of ‘Martian astronomy.’
Alternative was the primary rover to immediately spy a Mars moon transiting the Solar, method again in 2004. Viking 1 additionally caught the shadow of Phobos skimming its Chryse Planitia touchdown website in 1977. Each Curiosity and Perseverance have since made the trouble to ‘lookup’ and monitor the celestial scene from time to time. The newest picture was captured courtesy of Percy’s principal Mastcam-Z digital camera, and was taken on Mars Sol 1948 for the mission earlier this month on August twelfth, 2026.
An actual-time view, of this month’s Phobos photo voltaic transit. Credit score: NASA/JPL-Caltech/ASU/MSS/SSI
Do you say eclipse, occultation or transit? Actually, Phobos’s irregular potato-shape silhouette lends itself to extra of a misshapen annular eclipse of the Solar. Orbiting Mars at just below 6,000 kilometers above the planet’s floor, speedy Phobos takes simply 7 hours and 39 minutes to orbit the Pink Planet, quicker than the planet rotates. It covers only a quarter of the obvious disk of the Solar at its most, and you’d see it transferring in actual time, taking below a minute to cross the Solar’s disk.
I do know what you’re pondering… is it protected for Percy to stare on the Solar? “Mastcam-Z used photo voltaic filters, very similar to eclipse glasses, to take the photographs,” Mark Lemmon (Area Science Institute) instructed Universe As we speak. “The filter change was executed earlier than aiming on the Solar; the opposite order wouldn’t have resulted in harm, however that may be a easy precaution. Not one of the devices on the distant sensing mast might be broken by the Solar when they’re aimed that method and never in use.”
The rovers witness different unusual sights, together with dusty blue sunsets, and transits of the lesser of the 2 Martian moons, Deimos. The rovers have even been tasked to try to spot interstellar comet 3I/ATLAS on its shut 29 million kilometer cross close to Mars on October third, 2025, and the shut 140,000 kilometer cross of Comet C/2013 A1 Siding Spring previous Mars on October nineteenth, 2014.
Percy follows Comet 3I/ATLAS on October 4th, 2025. Credit score: NASA/JPL-Caltech/ASU/MSSS.
And only in the near past, Perseverance caught a bizarre occultation of the Earth by Phobos. Mars is the one place within the photo voltaic system that you may stand on stable floor, and witness an asteroid-shaped physique crossing in entrance of the Solar.
The beginning of a Deimos photo voltaic transit in 2024. Credit score: NASA/JPL-Caltech/ASU/MSSS.
You’ll be aware that Percy additionally caught a number of sunspots on the photo voltaic disk. These kinds of observations come in useful when Mars is close to photo voltaic conjunction on the farside of the Solar versus the Earth. Percy famous a massive sunspot region in early Could 2024, which later rotated into view for Earthbound observers and sparked an historic photo voltaic storm and auroral present a few week later.
Sunspots on the photo voltaic farside seen by Perseverance in 2024. Credit score: NASA/JPL-Caltech/ASU/MSSS.
The Science Behind the Picture
Catching sight of Phobos crossing the Solar additionally permits researchers the possibility to assist and refine the positional orbits of the 2 Martian moons.
“We picture the transits as a result of they offer exact measurements, higher than 100-meter accuracy, of the placement of Phobos at a particular immediate,” says Lemmon. “This constrains the Phobos orbit significantly better than might be executed with the largest telescope on Earth, for the reason that rover is a lot nearer. The Solar makes for a fantastic goal as a reference for Phobos’ place. Higher data of the orbit is good for planning: the primary time transit imaging was executed from Mars, Deimos was 40-kilometers off target utilizing Viking-era ephemerides, however this drawback is on the kilometer degree now. Nevertheless, the most important function is to make use of the orbital evolution as a probe of the Martian (and Phobos’) inside. Tides raised by Phobos on Mars trigger the orbit to alter; the modifications probe the flexibleness of the Martian mantle. That is why we hold doing it, we would like a very long time baseline of those high-quality measurements. From the Spirit and Alternative measurements, to Curiosity and now Perseverance, we’re within the third decade of this experiment. As well as, orbiter groups have been engaged on this with photographs of Phobos’ shadow and occasional photographs of Phobos with stars from orbit.”
This can show helpful after we need to method, land on and discover the 2 moons. And that’s coming proper up, because the joint JAXA/NASA Mars Moons Explorer (MMX) is launching on a H3-24L rocket from the Tanegashima Area Heart in Japan this yr on October nineteenth. The mission will method Phobos in 2027, and return samples to Earth beginning someday in 2031.
Lastly, look ahead to extra Mars-based astronomy, at the moment underway. “We’re in the course of a nighttime Phobos imaging marketing campaign that will likely be 5-6 nights in the long run,” says Lemmon. “Three are executed, with picture information on the bottom for 2. These have been designed to enhance the photo voltaic photographs by observing Phobos close to background stars in several components of its orbit. These are meant so as to add to the above measurements, since an entire description of an orbit at a second in time requires 6 parameters, and the transit solely measures two at excessive precision (after all, it measure the one that’s by far most necessary in comparison with how well-known it’s, which is how far alongside the orbital path Phobos is). For this, we use quick exposures to see the place Phobos is and lengthy exposures to measure the star trails for a place reference.”
Phobos, imaged at evening by Perseverance on August twenty eighth, 2026. Credit score: NASA/JPL-Caltech/ASU.
Phobos was found by American astronomer Asaph Corridor utilizing the U.S. Naval Observatory’s new 26” refractor (the most important on this planet on the time) throughout a positive Mars opposition in 1877. Trendy astrophotographers have managed to tease out the elusive moons from the glare of Mars close to opposition season. At present excessive within the pre-dawn sky within the astronomical constellation Gemini, Mars is as soon as once more approaching opposition on February nineteenth, 2027.
An astrophotographer picture of Mars (over-exposed) Phobos and Deimos (annotated). Credit score: Shahrin Ahmad.
Actually, it’s helpful to have observers stationed on Mars providing a novel and separate vantage level within the inside photo voltaic system versus our Earthbound perspective. Maybe sooner or later, we’ll have a devoted observatory based mostly on Mars, to bear witness to the wonders of the Martian sky.
