Level 1 — Absolute Beginner

NASA has a robot car on Mars called Perseverance. It has cameras. It takes pictures of Mars and space.

On July 2, Perseverance took seven pictures in a row. The pictures showed something amazing. They showed Earth going behind Phobos, a small moon of Mars.

In the pictures, Earth looked like a tiny dot of light. Earth was very far away, about 195 million miles from Mars. Then Earth disappeared behind Phobos for a moment.

This is the first time anyone has seen this happen from the ground of another planet. Scientists are excited about this new picture from space.

rover

a robot vehicle that explores the surface of a planet or moon

camera

a device used to take pictures

moon

a natural object that orbits around a planet

planet

a large round object in space that orbits a star

dot

a very small round mark or point

disappear

to go out of sight

space

the area outside Earth's atmosphere where planets and stars are

amazing

causing great surprise or wonder

Level 2 — Elementary

NASA's Perseverance rover has captured a striking series of images on Mars, showing Earth briefly disappear behind Phobos, one of the Red Planet's two small moons. The rover used its Mastcam-Z camera to record seven images in a row on July 2.

In the sequence, Earth moves slowly across the sky while Phobos moves in the opposite direction. By the third image, the two objects line up, and Earth briefly vanishes behind the shadowed edge of the moon before reappearing.

Because Earth was about 195 million miles away from Mars at the time, it appeared as nothing more than a single point of light, too small and far away to show any detail. Phobos, by contrast, is a lumpy, potato-shaped moon about 17 miles wide at its widest point, so it was easily large enough in the images to block Earth from view.

NASA scientists say this is the first time humanity has observed, from the surface of another planet, an object passing in front of and completely hiding Earth. The achievement adds to a growing collection of unusual space photography captured by the long-running Perseverance mission, which has been exploring Mars's Jezero Crater since landing there in February 2021.

sequence

a series of related things or events that follow a particular order

shadowed

partly dark because light is blocked

reappear

to become visible again after disappearing

detail

a small individual feature that can be seen clearly

lumpy

having an uneven, bumpy shape

achievement

something accomplished successfully, often after effort

mission

a planned and organized task, especially one in space exploration

crater

a large bowl-shaped hollow formed by an impact or explosion

Level 3 — Intermediate

NASA's Perseverance rover has recorded a rare astronomical event on Mars: a sequence of seven images, captured by its Mastcam-Z instrument on July 2, the 1,907th Martian day, or sol, of the mission, showing Earth pass behind and briefly vanish behind Phobos, the larger of Mars's two small moons.

In the composite sequence, Earth traces a diagonal path from the upper left toward the lower right of the frame, while Phobos moves in the opposite direction, from the lower left toward the upper right. By the third frame, the paths intersect and Earth briefly disappears behind the moon's shadowed limb before emerging on the other side. Image processing removed extraneous background light to enhance the contrast between the two celestial bodies.

The scale involved underscores just how distant the vantage point was: at roughly 195 million miles from Mars, Earth registered as a single pixel-sized point of light, while Phobos, a lumpy, irregularly shaped moon roughly 17 miles across at its widest, was easily large enough from Perseverance's perspective to occult the much more distant Earth entirely.

NASA scientists describe the observation as the first time humanity has recorded, from the surface of a planet other than its own, an object passing in front of and completely obscuring Earth. The image adds to a long tradition of Perseverance capturing striking astronomical phenomena, including previous images of Martian sunsets, dust devils, and eclipses of the Sun by Phobos and Deimos, and reflects the rover's dual role as both a geological explorer of Jezero Crater and an inadvertent observatory for events unfolding in the Martian sky.

astronomical

relating to astronomy, the scientific study of stars, planets, and space

composite

made up of several parts combined into a single whole

limb

the edge or border of the visible disc of a celestial body such as a moon or planet

extraneous

irrelevant or unwanted; not part of what is essential

vantage point

a position that gives a clear view or perspective of something

occult

to hide a celestial body by passing in front of it, blocking it from view

phenomena

observable events or occurrences, especially ones that are notable or unusual

inadvertent

happening by chance or accident rather than by design

Level 4 — Advanced

NASA's Perseverance rover has furnished planetary science with a striking new visual record: a seven-frame sequence captured by its Mastcam-Z instrument on July 2, the mission's 1,907th sol, documenting Earth's transit behind Phobos, the larger and closer of Mars's two diminutive moons, in what mission scientists describe as the first observation of its kind ever recorded from the surface of a planet other than our own.

The composite sequence traces Earth moving diagonally across the frame as Phobos advances along an intersecting path in the opposite direction, the two bodies converging by the third exposure as Earth slips briefly behind the moon's shadowed limb before re-emerging. Post-processing stripped extraneous background luminance to heighten contrast between the celestial bodies, a technical necessity given the extreme disparity in both distance and apparent size between the two objects being imaged.

That disparity is instructive in its own right: at a separation of roughly 195 million miles, Earth registered as an unresolved, pixel-scale point source, its size and any surface detail entirely subsumed by the vastness of the intervening distance, while Phobos, an irregular, elongated body roughly 17 miles across at its greatest extent, orbiting Mars from a mere 3,700 miles above the surface, proved more than sufficient to fully occult its far more distant, far larger counterpart.

Beyond its aesthetic and public-engagement value, the observation underscores Perseverance's incidental function as an astronomical platform, a role the rover has fulfilled intermittently throughout a mission ostensibly dedicated to characterizing the geology and astrobiological potential of Jezero Crater, having previously documented Martian dust devils, Phobos and Deimos transiting the Sun, and the diffuse blue-tinted sunsets produced by fine atmospheric dust. Each such image, while scientifically secondary to the rover's primary sample-caching objectives, nonetheless offers a rare and evocative reminder of Earth's own comparative insignificance when viewed from beyond its own gravitational neighborhood, a perspective historically associated with far more distant spacecraft than one still operating on a neighboring planet's surface.

transit

the passage of one celestial body across or in front of another as observed from a given point

diminutive

extremely small in size

luminance

the intensity or brightness of light in an image or scene

disparity

a great difference between two things being compared

unresolved

in imaging, describing an object too small or distant to show any visible detail or shape

subsumed

absorbed or included within something larger, losing its own distinct identity

astrobiological

relating to the study of life's origins and potential existence elsewhere in the universe