Jupiter and Mars moons line up in stunning image

Deimos walked past Ganymede, Europa, Io, and Callisto. It was all captured by ESA ‘s Mars Express probe .


ESA ‘s Mars Express orbiter has imaged the rare moment when Mars ‘s small moon Deimos passes in front of Jupiter and its four larger moons.

Celestial alignments like these allow a more precise determination of the orbits of the Martian moons.

The fortuitous alignment of Deimos as it passed in front of Jupiter on February 14, 2022 allowed Deimos’s position and orbit to be more precisely determined. That is, by measuring the duration of the occultation, when the light of one celestial body is blocked by another, the orbit can be calculated.

Such an alignment is extremely unusual because Deimos must be exactly in the orbital plane of Jupiter ‘s moons for the alignment to occur, the ESA reports .

a transit of moons

The animated sequence of 80 images from the High Resolution Stereo Camera (HRSC) shows the bumpy surface of the small, irregularly shaped moon 15 km wide as it passed in front of Jupiter. Jupiter ‘s moons appear as small white specks, due to their distance of almost 750 million km from Mars Express . This staggering separation is five times the distance between the Earth and the Sun.

The animation first shows Deimos passing in front of the icy moon Europa. The largest moon in the Solar System, Ganymede, is hidden from view . The gas giant Jupiter, appearing as a large white spot in the center, then disappears behind Deimos.

Deimos then covers the extremely active volcanic moon Io, which is about the same size as Earth’s moon. Finally, the cratered moon Callisto disappears behind Deimos.

Deimos appears to move up and down in the animation due to the small wobbling movements of Mars Express as it rotates to bring the HRSC camera into position. The movement of the solar wings, which extend 12 m from the spacecraft, as well as two long radar antennas, also contribute to the small vibrations.

After photographing the alignment with Jupiter , Mars Express turned its gaze to the moment Deimos was blocked by its older brother, Phobos, which measures about 27 km along its longest axis. The animation is made up of 19 HRSC images, taken on March 30, 2022 when Phobos was 12 km from the camera. From this perspective it is difficult to see the difference in size between the Martian moons, as Deimos is farthest from the camera at a distance of 28 km. ( EuropaPress )