Against The Wind: Sun’s Particles Do Weird Things At Martian Moon

A Martian asteroid-like moon appears to be making waves in the stream of particles the sun sends across the universe.

From space, a European Space Agency spacecraft did an experiment to confirm a weird effect first observed at the moon, which is called Phobos, in 2008. The Mars Express spacecraft noticed Phobos "backscattering" or reflecting solar particles during one flyby, but has been unable to spot this again despite zooming by the moon several more times over the years.

Scientists thought they saw more backscattering during a 2016 flyby, but the position of Mars Express at that time led to another hypothesis: maybe the spacecraft itself had caused the effect. So this led to another weird trick: why not do some “fake” flybys of the moon to see if the spacecraft can induce backscattering on another world?

That led to a fun sequence in 2017, the European Space Agency stated, when Mars Express replicated the exact same solar array adjustments and control maneuvers in space with no nearby target except for the solar wind.

The sun's power unleashes all across the solar system, in the form of a stream of particles called ... [+]

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“The 'fake' flybys let us explore how Mars Express influences the solar wind in a more controlled environment, so we could search for signs of the spacecraft itself being the cause of the particle reflection,” stated Mats Holmström, principal investigator for the Mars Express Analyzer of Space Plasmas and Energetic Atoms instrument, which spotted the reflected particles in 2008 and 2016.

The experiment confirmed Mars Express didn’t induce the backscattering at Phobos, but the larger question is why the effect is so sporadic. At Earth’s moon, the effect is easier to predict, and there are all sorts of questions as to why that’s the case — but no firm answers yet. Possible research investigations could include the magnetic field on Phobos, or even differences in the dust on each of these moon’s surfaces.

But we’re likely going to need a landing mission to learn more; happily, the European-Japanese Martian Moons eXploration (MMX) mission is targeted to launch in 2024 for a landing in 2025. In the meantime, the Mars Express team will try to learn as much as they can.

“Overall, the intermittent particles are likely being reflected from the Phobos’ surface, but we can’t rule out another mysterious origin,” Yoshifumi said. “However, the 'fake' flybys helped us understand the situation significantly better, explicitly showing that Mars Express was not the source.”

Source: https://www.forbes.com/sites/elizabethhowell1/2021/12/06/against-the-wind-suns-particles-do-weird-things-at-martian-moon/?sh=21197143c4e5