From the western rim of Jezero Crater, Earth was not a blue world on 2 July 2026. It was a single vivid pixel, 314 million kilometres away, shifting throughout the night sky of Mars. A skinny crescent of Phobos approached from the opposite course. Then, for a number of moments in a picture sequence made by NASA’s Perseverance rover, the pixel was gone.
NASA describes this as the primary remark constructed from the floor of one other planet through which Earth was seen disappearing behind an object. The historic declare is actual, however it’s narrower than saying that no off-world digicam had ever watched Earth develop into hidden. The Moon and orbiting spacecraft have provided different types of Earthset and occultation imagery. What occurred at Mars was the primary from a digicam standing on one other planet.
There’s one other necessary qualification. The printed result’s an annotated composite assembled from nonetheless pictures, not one publicity and never a steady film. That doesn’t make the occasion much less outstanding. It tells us precisely what Perseverance’s digicam recorded and the way NASA made a particularly small alignment seen to human eyes.
9 frames from the Martian night
Perseverance made the remark close to 7 p.m. native photo voltaic time on mission sol 1,907. Its Mastcam-Z instrument took 9 pictures whereas Earth moved from higher left to decrease proper and Phobos travelled from decrease left to higher proper. Within the third body, the brilliant level of Earth winked out behind the moon’s shadowed edge earlier than showing once more.
The official NASA Photojournal record reveals each the broad panorama and enlarged variations of the occasion. Within the panorama, the alignment occupies a tiny outlined sq. above the Martian horizon. The inset combines a number of exposures from that patch of sky and raises the distinction so {that a} reader can comply with two objects that may in any other case be nearly not possible to differentiate.
NASA and the Mastcam-Z group have been subsequently not presenting an unbroken movie. They have been reconstructing an actual passage from a timed sequence. The whole annotated sequence spans roughly 40 seconds, and its order is unambiguous: Earth approaches Phobos, disappears behind it and returns on the opposite facet.
This was an occultation
The technical time period for the occasion is an occultation. An apparently bigger foreground physique utterly hides a extra distant background physique. Nothing bodily occurred to Earth, and Phobos didn’t forged a shadow throughout our planet. From Perseverance’s specific location, the moon merely occupied the identical line of sight and lined Earth’s one-pixel picture.
That differs from a transit, through which a foreground object seems smaller and crosses the seen face of a background object with out masking it utterly. It additionally differs from an eclipse brought on by one physique coming into one other’s shadow. In extraordinary reporting these phrases usually blur collectively, however the geometry right here is very clear as a result of Earth vanished fully from the rover’s view.
Mars rovers have used Phobos for different alignments. In 2022, Perseverance recorded Phobos moving across the Sun. The irregular moon lined solely a part of the photo voltaic disc, so its lumpy define remained seen. The July 2026 sequence reversed the dimensions relationship: tiny, distant Earth was absolutely hid by the a lot nearer moon.
A frequent moon and an unusual alignment
Phobos is small, measuring roughly 27 kilometres throughout at its widest, but it surely travels solely about 6,000 kilometres above the Martian floor. Its nearness makes it seem about one-third as large as Earth’s Moon seems in our sky. Earth, in the meantime, was greater than 300 million kilometres from the rover and registered as a single pixel.
Based on NASA’s account released on 5 August, Phobos crosses the Martian sky 3 times every day, whereas Earth can stay seen for months at a time. These info make the assembly sound inevitable. It was not. The rover, the moon and Earth needed to align inside an exceptionally slender angle, the remark needed to happen whereas the objects have been seen, and the cameras needed to be pointed on the proper patch of sky.
Mark Lemmon, a Mastcam-Z scientist on the Area Science Institute, mentioned the remark required each planning and luck. Orbital calculations provided the expected geometry, however the small obvious dimension of Earth and the moon’s irregular define left little margin. The consequence was attainable as a result of a digicam designed for geological work also can make fastidiously timed astronomical observations.
What “the primary time” means right here
The wording issues. Cameras past Earth have photographed our planet for many years. Lunar missions have seen Earth strategy or go behind the Moon’s horizon. Spacecraft have recorded Earth and the Moon collectively from deep house. Mars rovers have additionally photographed Earth as some extent of sunshine, and Curiosity imaged Earth setting in 2024 whereas Phobos rose close by.
None of these is similar class as an instrument resting on one other planet and recording Earth being utterly lined by a separate object in that planet’s sky. NASA’s declare is particularly that that is the primary time humanity has captured such an remark “from the floor of one other planet”. The phrase excludes cameras in orbit and cameras on the Moon, which is Earth’s satellite tv for pc slightly than a planet.
That boundary prevents an interesting picture from turning into an inflated declare. Perseverance didn’t take the primary distant portrait of Earth, nor the primary picture of Earth disappearing from any location past our world. It added a brand new viewing place to that historical past: the floor of Mars, with a Martian moon passing in entrance.
Why Phobos crosses the sky backwards
Phobos completes an orbit in about seven hours and 39 minutes, a lot quicker than Mars rotates. It consequently strikes throughout the sky from west to east, rising and setting in the other way to the acquainted every day movement of the Solar and distant stars. NASA’s overview of the Martian moons notes that its orbit is regularly shrinking as tidal forces draw it in the direction of the planet.
Its fast circuit creates repeated alternatives for rover groups to watch it, though one location doesn’t see each orbit. As a current SpaceDaily examination of Phobos’s motion defined, finishing greater than three orbits per sol interprets to roughly two seen passages per Martian day for a stationary observer. The distinction comes from the altering relationship between the moon’s orbit, the rotating floor and the native horizon.
Repeated measurements of Phobos can refine fashions of that movement. Photo voltaic transits, specifically, give rover groups sharply outlined timing and place knowledge. The Earth occultation is extra notable as a tough piece of geometry and a primary viewing perspective than as a significant new measurement of the moon, but it surely belongs to the identical lengthy file of Martian sky watching.
The smallest attainable self-portrait
Perseverance was despatched to Mars primarily to review Jezero Crater’s geology, seek for indicators of historic liveable environments and cache samples for attainable return to Earth. The Mars 2020 mission carries cameras for navigation, engineering and scientific context. Mastcam-Z, mounted excessive on the rover’s mast, can zoom, make color and three-dimensional pictures, and look effectively past the rocks instantly in entrance of it.
On this event, its topic was the planet from which the rover, its builders and each human observer got here. The picture incorporates no continents, oceans or environment {that a} reader can determine. Earth is just one illuminated detector ingredient. But its disappearance is exactly what confirms that the pixel is a world located behind one other world’s moon.
Justin Maki, Perseverance’s imaging scientist at NASA’s Jet Propulsion Laboratory, referred to as it a singular self-portrait, with Phobos coming into the body. The lightness of that description doesn’t obscure the dimensions contained within the sequence. A machine on Mars watched the entire of Earth cross a slender strip of alien sky, vanish behind a moon scarcely wider than a metropolis, and return.
