Updated

Updated · spacedaily.com · Aug 17

Perseverance Captures Earth Vanishing Behind Phobos in 9 Frames From Mars Surface

Updated

Updated · spacedaily.com · Aug 17

Perseverance Captures Earth Vanishing Behind Phobos in 9 Frames From Mars Surface

Q: What complex calculations allowed Perseverance to catch this seemingly impossible 40-second cosmic photobomb from Mars?

Perseverance caught the event because NASA solved a very tight line-of-sight geometry problem: where Earth, Phobos and the rover would all be, to the second, from one fixed spot on Mars. That required high-precision ephemeris calculations for Mars and Earth, plus Phobos’ fast orbit around Mars. Phobos circles Mars in about 7 hours 39 minutes and crosses the Martian sky three times a day, so mission planners had to predict exactly when its irregular, 27-kilometre-wide silhouette would pass over the single-pixel position of Earth, which was about 314 million kilometres away. Even a tiny error in angle, timing or rover pointing would have missed the occultation. The calculations also had to include Perseverance’s exact location on the western rim of Jezero Crater, the local Martian time and twilight conditions, and the apparent motions of both objects in the rover’s sky. From the rover’s view, Earth was moving one way across the frame while Phobos moved the other, so the camera team had to model their crossing path and trigger a short imaging sequence at the right moment. NASA says the observation depended on orbital mechanics, camera targeting and a bit of luck. Mark Lemmon, the Mastcam-Z scientist who planned it, said the challenge was that Earth was visible only as a bright dot and Phobos has an uneven outline, leaving almost no margin for error. The result was a timed nine-frame sequence over about 40 seconds, later assembled into the published composite.

3 articles · Updated · spacedaily.com · Aug 17

Nine Mastcam-Z images taken on 2 July from Jezero Crater show Earth—314 million km away—disappearing behind Phobos for the first time ever recorded from another planet’s surface.
The annotated composite spans about 40 seconds on mission sol 1,907, with Earth winking out in the third frame as the Martian moon crossed the rover’s line of sight.
NASA said the event was an occultation, not a transit or eclipse: Phobos fully covered Earth’s one-pixel image from Perseverance’s viewpoint.
Phobos crosses the Martian sky frequently, but this observation still required a very narrow alignment of rover, moon and Earth, plus precise camera timing and some luck.
The claim is narrower than a first off-world Earth disappearance image, excluding lunar and orbital cameras; its novelty is that a camera standing on Mars saw it happen.