February 26, 2024

Mars Express Orbiter Unravels Mystery of Largest Martian Moon, Phobos, Using “Fake” Flybys

Utilizing a series of real and fake flybys, ESAs Mars Express has clarified a long-standing martian secret: if and how Mars largest moon, Phobos, shows the solar wind. Credit: ESA
By carrying out a series of real and fake flybys, ESAs Mars Express has revealed how Mars largest moon, Phobos, communicates with the solar wind of charged particles tossed out by the Sun– and spotted an evasive procedure that has actually only been seen at Phobos once in the past.
The solar wind streams out from our star, filling the Solar System with energetic particles. Earths Moon shows these particles continuously, and the very same backscattering is expected at Mars moon Phobos provided the similarities between the 2 (both are rocky, do not have a magnetic field and atmosphere, and orbit terrestrial planets in the inner Solar System). However, ESAs Mars Express has actually only seen this backscattering as soon as (in 2008), in spite of coming close to Phobos lots of times.
Researchers now report the second effective detection of reflected solar wind particles at Phobos, found throughout a flyby of the moon in January 2016.

” Phobos relationship with the solar wind has actually long been an enigma,” states Yoshifumi Futaana of the Swedish Institute of Space Physics (IRF), and lead author of the brand-new paper on the 2016 flyby. “We understand that Phobos must be connecting with these particles, but were not seeing them– why? Why is Phobos acting so in a different way to the Moon when the 2 seem rather comparable?
” For the first time in 8 years of flybys, were thrilled to again see signs of these reflected particles at Mars biggest moon.”
This infographic reveals 3 Mars Express flybys that took place in July 2008, January 2016 and May 2017– the previous 2 being genuine flybys finished in the vicinity of Phobos, and latter being a phony flyby performed to clarify whether a particular signal found by the spacecraft was a true detection of a procedure occurring on Phobos, or if it was due to reflection of particles from Mars Express itself. Credit: ESA
As this backscattering is so intermittent and hardly ever seen at Phobos, scientists questioned if the phenomenon could have been caused by Mars Express itself showing solar wind particles. During the 2008 flyby, the spacecraft moved its solar array and moved to point its instruments at Phobos– a maneuver that may have impacted the habits of surrounding particles.
” The very same criticism stayed for the 2016 flyby: how do we understand this detection is in fact reflection from Phobos, and not from Mars Express itself?” includes Yoshifumi.
Fake flybys
To explore this possibility, the researchers carried out 3 unprecedented unique operations, called phony flybys, with the spacecraft in 2017. Using the specific same operation series, control maneuvers, and solar selection adjustments, Mars Express flew in a patch of space filled with solar wind however without the presence of Phobos, essentially performing a flyby– only without its target.
Artists impression of Mars Express. The background is based upon an actual image of Mars taken by the spacecrafts high resolution stereo video camera. Credit: Spacecraft image: ESA/ATG medialab; Mars: ESA/DLR/FU Berlin, CC BY-SA 3.0 IGO
” In essence, we were completing a sort of laboratory experiment at Mars,” states co-author Mats Holmström, likewise of IRF and Principal Investigator for Mars Express ASPERA-3 instrument, which observed the shown particles. “The phony flybys let us explore how Mars Express influences the solar wind in a more controlled environment, so we might browse for indications of the spacecraft itself being the cause of the particle reflection.”
The phony flybys revealed no such signs that Mars Express produced or scattered any inbound particles, suggesting that Phobos did certainly reflect the identified particles back into space during the 2008 and 2016 flybys.
Sporadic scattering
Despite this, backscattered particles have actually only been spotted in two of over a dozen Phobos flybys, and even then, signals are periodic and erratic. This is entirely various to what we see at the Moon, another body that lacks both an atmosphere and electromagnetic field, and so would be anticipated to behave likewise. Why this distinction?
Yoshifumi and colleagues think about a variety of possibilities, from processes perhaps taking location on different spatial or temporal scales than those captured by Mars Express, to possible magnetism on Phobos, to differences in the surface area structures of Phobos and the Moon– and more.
” Overall, the intermittent particles are likely being reflected from the Phobos surface area, however we cant rule out another strange origin,” includes Yoshifumi. “However, the phony flybys helped us understand the circumstance significantly much better, clearly showing that Mars Express was not the source.
” To understand more, we need more Mars Express flybys of Phobos in different configurations. Even if no reflected particles are seen throughout those flybys, even an absence of signal will supply valuable statistics.”
The solar wind behaving differently at Phobos and the Moon indicates that the surface areas of each have developed in a different way, raising appealing concerns about how the Mars system differs from our own.
Exploring Phobos
As one of just three moons in the inner Solar System, Phobos is of fantastic interest for space expedition– previous, present, and future.
From the Soviet Phobos program of the 1980s through to future objectives such as the Japanese Space Agency (JAXA)s Martian Moons expedition (MMX) objective planned for launch in the mid-2020s, there have actually been lots of dedicated efforts to check out the origin, environment, behavior, and evolution of Mars biggest moon.
This image, taken by the High Resolution Stereo Camera (HRSC) on board ESAs Mars Express spacecraft, is among the highest-resolution pictures up until now of the Martian moon Phobos. The image shows the Mars-facing side of the moon, drawn from a distance of less than 200 kilometers with a resolution of about seven meters per pixel during orbit 756, on August 22, 2004. Credit: ESA/DLR/FU Berlin (G. Neukum), CC BY-SA 3.0 IGO
ESA is partnering with JAXA on the MMX objective, providing communications devices, support in spacecraft tracking and control, and chances for researchers to sign up with the objectives science group. MMX will define both martian moons, Phobos and Deimos, release a rover to Phobos surface, and return a sample of Phobos to Earth for analysis. An essential objective of MMX is to figure out if the moons are asteroids recorded by Mars gravity, or particles staying in orbit after a huge effect on Mars.
Beyond our knowledge of Phobos– and other rocky or icy bodies displaying comparable physics that ESA plans to check out, from Mercury to asteroids to the Galilean moons of Jupiter– understanding how charged particles behave in space is important to space exploration.
Astronauts on the Moon are exposed to the solar wind, a key factor to consider for ESAs forthcoming strategies for human expeditions to space. Surface area interactions on moons and worlds are also a core part of surface area chemistry, potentially consisting of how bodies keep and form water.
” This finding utilizes Mars Express in a really unique way to solve a continuous cosmic mystery– it shows wonderful ingenuity and highlights the versatility and varied abilities of the mission,” states ESAs Mars Express task scientist Dmitrij Titov.
” The research study likewise reveals the value of our operations colleagues and data archives in enabling new discovery and knowledge and making crucial work such as this possible. We need to comprehend the space environment to explore it with either satellite or astronaut, and so revealing the dynamics at play in the martian system is an essential advance.”
Yoshifumi and associates accessed information from the 2016 Phobos flyby supplied by the ESA Planetary Science Archive.

Earths Moon shows these particles constantly, and the very same backscattering is expected at Mars moon Phobos offered the resemblances in between the two (both are rocky, do not have a magnetic field and atmosphere, and orbit terrestrial planets in the inner Solar System). ESAs Mars Express has just seen this backscattering as soon as (in 2008), in spite of coming close to Phobos many times.
Artists impression of Mars Express. MMX will define both martian moons, Phobos and Deimos, release a rover to Phobos surface, and return a sample of Phobos to Earth for analysis. An essential objective of MMX is to identify if the moons are asteroids recorded by Mars gravity, or debris remaining in orbit after a giant effect on Mars.