NASA’s Perseverance Rover Captures Earth Disappearing Behind Phobos

NASA’s Perseverance Mars rover has captured a stunning celestial event: Earth briefly vanishing behind Phobos, one of Mars’ two moons. This unprecedented observation marks the first time humanity has recorded Earth disappearing behind another object from the surface of a different planet.

Details of the Observation

The remarkable sequence was recorded on July 2 at approximately 7 p.m. local solar time, during the 1,907th Martian day (sol) of the mission. Using its Mastcam-Z instrument, Perseverance captured Earth as a tiny point of light while Phobos traversed the Martian sky, blocking Earth from view. The composite images illustrate Earth moving diagonally from the upper left to the lower right, while Phobos moves oppositely from the lower left to the upper right. By the third image, Earth lined up perfectly behind the shadowed edge of Phobos.

“The composite image makes for a unique Earth self-portrait, taken from the surface of another planet, with a Phobos photobomb,” remarked Justin Maki, deputy principal investigator for Mastcam-Z at NASA’s Jet Propulsion Laboratory in Southern California.

Distance and Scale

From its location along the rim of Jezero Crater, Perseverance observed a significant contrast in size and distance between Earth and Phobos. Phobos, which measures about 17 miles (27 kilometers) across at its widest point, orbits Mars at a distance of just 4,850 miles (7,800 kilometers). This proximity made it appear about one-third the size of Earth’s Moon as viewed from our planet.

In contrast, Earth was approximately 195 million miles (314 million kilometers) away, appearing as a single pixel-sized point of light in the images. “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,” said Mark Lemmon, a co-investigator for Mastcam-Z from the Space Science Institute in Boulder, Colorado.

Astronomical Context

The event captured by Perseverance is categorized as an occultation, where a larger object obscures a more distant object from view. In contrast, an eclipse occurs when one object enters the shadow of another. Notably, the distinction is important; lunar eclipses occur when the Moon passes through Earth’s shadow, while solar eclipses involve the Moon blocking the Sun from view. Conversely, a transit occurs when a smaller object moves across a larger one, a phenomenon that Perseverance has also documented, including instances when Phobos or Deimos passes across the Sun as seen from Mars.

About Perseverance

NASA’s Jet Propulsion Laboratory in Southern California, managed by Caltech, built Perseverance and oversees its operations as part of NASA’s Mars Exploration Program. Arizona State University leads the operations of the rover’s Mastcam-Z instrument, collaborating with Malin Space Science Systems in San Diego for its design, fabrication, and testing.