NASA's Perseverance rover captures Earth vanishing behind Phobos from Mars
This digest was compiled by AI from multiple sources — links to the originals are below.
NASA’s Perseverance rover recorded Earth disappearing behind Phobos in the Martian evening sky on July 2, mission sol 1,907. The Mastcam-Z sequence marked the first time Earth has been observed vanishing behind another object from the surface of another planet. The composite shows Earth as a single-pixel point of light while Phobos, about 17 miles across, passes in front.
Key Facts
- Perseverance recorded the sequence with its Mastcam-Z instrument at about 7 p.m. local solar time on July 2, the 1,907th Martian day, or sol, of the mission.
- At the time, Earth was about 195 million miles (314 million kilometres) from Mars and appeared as a single-pixel-sized point of light.
- NASA describes the observation as the first made from the surface of another planet in which Earth was seen disappearing behind an object.
- The published composite was assembled from nine still images, not one continuous exposure or movie.
The July 2 Observation
NASA's Perseverance rover recorded the sequence with its Mastcam-Z instrument at about 7 p.m. local solar time on July 2, the 1,907th Martian day, or sol, of the mission. Earth moved diagonally from the upper left toward the lower right, while Phobos traveled in the opposite direction from the lower left toward the upper right. By the third image in the sequence, the two objects lined up and Earth briefly disappeared behind the shadowed edge of Phobos. Justin Maki, Mastcam-Z deputy principal investigator at NASA's Jet Propulsion Laboratory, called the composite 'a unique Earth self-portrait, taken from the surface of another planet, with a Phobos photobomb.' The published result is an annotated composite assembled from nine still images, not one exposure and not a continuous movie.
Earth, Phobos, and the Occultation
From Perseverance's location along the rim of Mars' Jezero Crater, Earth was about 195 million miles (314 million kilometres) away and appeared as a single-pixel-sized point of light. Phobos is a lumpy, potato-shaped moon about 17 miles (27 kilometres) across at its widest and orbits about 4,850 miles (7,800 kilometres) from Mars. Because of that orbit, Phobos appeared about one-third as wide as Earth's Moon appears from our planet when Perseverance took the images. Mark Lemmon, a Mastcam-Z co-investigator at the Space Science Institute, said Phobos crosses the Martian sky three times a day and Earth is visible for months at a stretch, but catching one directly behind the other 'takes planning and a little luck.'
Occultation, Transit, and Eclipse
Astronomers describe the event Perseverance witnessed as an occultation, which happens when an object that appears larger from the viewer's perspective completely blocks a more distant object behind it. An eclipse occurs when one object enters the shadow of another; a lunar eclipse occurs when the Moon moves through Earth's shadow, and a solar eclipse occurs when the Moon passes in front of the Sun and appears roughly the same size. A transit occurs when the situation is reversed and a smaller-appearing object moves across the face of a larger-appearing object.
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NASA's Perseverance rover captures Earth vanishing behind Phobos from Mars
