Mars Express Watched Deimos Pass in Front of Jupiter and its Moons

By Nancy Atkinson October 13, 2022
Mars Express Watched Deimos Pass in Front of Jupiter and its Moons

That’s no moon … wait … yes, it is, and more!

ESA’s Mars Express has captured an unusual and rare occultation, all from its vantage point in orbit of Mars.  The spacecraft’s orbit brought it to the right place where it could witness the moment Mars’ small moon Deimos passed in front of Jupiter and its four largest moons. Scientists say that celestial alignments like these enable a more precise determination of the Martian moons’ orbits.

https://youtu.be/Mtz07_IV4XQ

If you’ve seen Jupiter and its moons through binoculars or a small telescope, you might be envious of Mars Express’ view, especially when Deimos passes through the field of view.

ESA said this sequence is made up of a series of 80 images taken by the High Resolution Stereo Camera onboard Mars Express on February 14, 2022. In the foreground, the images show the irregular shaped Deimos, with its rocky and cratered surface, and in the background Jupiter and the four Galilean satellites are visible. Jupiter is the large bright white spot and the moons appear as small white specks of light.

The distance between Mars Express and Jupiter is about 745 million km (463 million miles). In order for distant Jupiter and the moons to show up in this video, the images have contrast enhanced. Otherwise, because of the difference in brightness compared to the nearby Deimos, the distant objects would not have been visible.

Phobos and Deimos, as seen by Mars Express. Credit: ESA.

The workhorse Mars Express has been in orbit of the Red Planet since 2003 and Mars’ two moons, Deimos and Phobos, have been studied frequently by the spacecraft. Mars Express data has helped scientists understand more about the moons’ composition, especially Phobos’ mysterious grooved terrain, and learn more about the moons’ puzzling origin. This includes tracking their orbits.

Scientists say the moons experience strong tidal forces from Mars, causing their orbits to fluctuate constantly. Phobos orbits extremely close to Mars at just 6,000 km (3,700 miles), and is moving towards the planet, while Deimos moves away from it. It is difficult to measure their orbits from Earth due to the brightness of Mars in comparison to these small bodies.

https://youtu.be/7ZgO5yjS0zI

About a month and half after imaging the alignment with Jupiter, Mars Express captured another occultation, when Deimos was blocked by its larger sibling, Phobos. The images were taken on March 30, 2022 when Phobos was 12 km away from the camera. From this perspective it is difficult to see the size difference between the martian moons, as Deimos is further from the camera at a distance of 28 km.

Deimos has a diameter of 12 km (7.5 miles) and Phobos has a diameter 22 km (14 miles).

Nancy Atkinson

Nancy Atkinson

Nancy Atkinson is a space journalist and author with a passion for telling the stories of people involved in space exploration and astronomy. She is currently retired from daily writing, but worked at Universe Today for 20 years as a writer and editor. She also contributed articles to The Planetary Society, Ad Astra (National Space Society), New Scientist and many other online outlets.

Her 2019 book, "Eight Years to the Moon: The History of the Apollo Missions,” shares the untold stories of engineers and scientists who worked behind the scenes to make the Apollo program so successful, despite the daunting odds against it. Her first book “Incredible Stories From Space: A Behind-the-Scenes Look at the Missions Changing Our View of the Cosmos” (2016) tells the stories of 37 scientists and engineers that work on several current NASA robotic missions to explore the solar system and beyond.

Nancy is also a NASA/JPL Solar System Ambassador, and through this program, she has the opportunity to share her passion of space and astronomy with children and adults through presentations and programs. Nancy's personal website is nancyatkinson.com