Mars atmosphere shedding charged particles onto Phobos? |

Oval-shaped, pinkish rocky moon with many mostly small craters.

Mars’ largest moon Phobos, as seen by NASA’s Mars Reconnaissance Orbiter spacecraft on March 23, 2008. Picture through NASA/ JPL-Caltech/ College of Arizona.

A brand new examine means that Mars’ bigger moon Phobos orbits by means of a stream of charged particles flowing off the planet’s ambiance. The findings, published February 1, 2021, within the peer-reviewed journal Nature Geoscience, counsel that the ions of oxygen, carbon, nitrogen, and argon charged particles smashing into Phobos have been accumulating on the moon’s floor for billions of years. The researchers say evaluation of Phobos’ soil might present necessary new particulars concerning the historical past of each worlds.

Blurry, irregular orange ball lighted from the left on a blurry blue background.

Phobos as noticed by the MAVEN orbiter’s Imaging Ultraviolet Spectrograph. Orange reveals mid-ultraviolet daylight mirrored from the floor of Phobos, exposing the moon’s irregular form and plenty of craters. Blue reveals far ultraviolet gentle, which is scattered off of hydrogen gasoline within the prolonged higher ambiance of Mars. Picture through CU/ LASP/ NASA.

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For a number of a long time, scientists have been learning Mars by analyzing the planet with orbiters, landers and rovers. In reality, there are presently 3 missions slated to arrive at Mars this month (February 2021), together with NASA’s Perseverance, the United Arab Emirates’ first-ever interplanetary mission, referred to as Hope, and China’s first Mars exploration mission, referred to as Tianwen-1. The authors of the brand new examine, researchers at College of California’s Space Sciences Laboratory, say there may be an extra strategy to study concerning the pink planet: by learning the floor of Phobos, considered one of Mars’ two moons (the opposite is known as Deimos). The scientists say that evaluation of the soil on the floor of this small potato-shaped moon might reveal necessary clues about Mars’ ambiance and historical past.

Since Phobos, just like the smaller moon Deimos, is a small rocky physique utterly separate from Mars itself, how can it inform us something about Mars’ ambiance? The reply is solely that many charged atoms and molecules – comparable to oxygen, carbon, nitrogen and argon – escape from and stream off the skinny Martian ambiance into area. A few of these charged particles – referred to as ions – in the end collide with Phobos. Scientists say that they could possibly be preserved on Phobos’ floor. Lead writer Quentin Nénon stated in a statement:

We knew that Mars misplaced its ambiance to area, and now we all know that a few of it ended up on Phobos.

If a few of these particles could possibly be collected and studied in labs, they might present necessary particulars about Mars’ ambiance and the way it has developed and is step by step being misplaced to area.


Since Phobos is tidally locked to Mars, that means that the identical facet of the moon at all times faces the planet, the close to facet of Phobos, dealing with Mars, has been bombarded by Martian ions for billions of years, about 20 to 100 instances extra so than its far facet. Nénon stated:

With a pattern from the close to facet, we might see an archive of the previous ambiance of Mars within the shallow layers of grain, whereas deeper within the grain we might see the primitive composition of Phobos.

Nénon and his crew made this evaluation after analyzing information from NASA’s Mars Ambiance and Unstable EvolutioN (MAVEN) orbiter. MAVEN has been learning the Martian ambiance for over six years and, throughout its main mission, crossed the orbit of Phobos 5 time every day. The researchers  determined to make use of these measurements to study extra about Phobos itself.

MAVEN’s Suprathermal and Thermal Ion Composition instrument (STATIC) was used to check the Martian ions in Phobos’ orbit, by measuring the kinetic energy and velocity of incoming particles. That, in flip, allowed scientists to measure their mass. Decrease-mass ions got here from the solar, however heavier-mass ones originated from Mars. The researchers estimated that these ions might penetrate a number of hundred nanometers (nm) into the soil on Phobos, about 250 instances lower than the final width of a human hair. One nanometer is one-billionth of a meter. In response to co-author Andrew Poppe:

What Quentin has achieved is take investigations we’ve achieved on the moon and at different moons of the photo voltaic system and utilized the identical strategies to Phobos for the primary time.

Serious young man with NASA logo behind him.

Quentin Nénon on the College of California, Berkeley, lead writer of the brand new examine. Picture through SSERVI.

Learning particles from Mars on its moons can be supreme for the easy cause that there isn’t any wind or water to change or destroy them. They’re nonetheless in an untouched, pristine state of preservation. It’s the identical for particles from Earth which have landed on our personal moon. Poppe stated:

What we’ve seen in Apollo samples is that the moon has been patiently recording particular person atoms coming from the solar and from Earth. It’s a very cool historic file.

In a lot the identical manner as with Mars, scientists suppose that getting extra samples from our moon’s floor will assist them higher perceive not solely the historical past and geology of our personal pure satellite tv for pc, but in addition Earth’s historic ambiance and early magnetic subject.

The thought for searching for charged Martian particles on Phobos happened over espresso sooner or later on the lab when there was no web service, Poppe recounted:

I used to be compelled to speak to my colleagues over espresso as a result of we had nothing higher to do.

The query got here up as as to whether Phobos could possibly be subjected to Martian ions like Earth’s moon is subjected to them from Earth. Poppe requested:

Do you guys see any proof of this?

Satellite with two large solar panels above a reddish planet with craters on its surface.

Artist’s idea of MAVEN in orbit round Mars. The brand new findings are based mostly on evaluation of knowledge despatched by MAVEN again to Earth. Picture through NASA/ Goddard House Flight Heart.

It turned out that this was one thing no one had checked out a lot, if in any respect. When Nénon joined the House Science Laboratory, he made a degree of going by means of the info from MAVEN, and located that there was certainly proof for related charged particles being transferred from Mars to Phobos. As he surmised:

So hopefully this discovering will have an effect on the scientific actions of the MMX mission.

The Japan Aerospace Exploration Agency is now making ready to ship the Martian Moons Exploration (MMX) probe in 2024 to go to Phobos. For the primary time, samples will likely be taken straight from the floor of the small moon and introduced again to Earth for additional examine. As Nénon famous, it may be helpful, given the MAVEN findings, to land on the close to facet of Phobos. Amassing a few of these particles could possibly be invaluable for understanding the historical past of each Phobos and Mars.

Backside line: Particles escaping from Mars’ ambiance have been accumulating on the floor of the planet’s largest moon Phobos for billions of years. They may present necessary new particulars concerning the historical past of each worlds.

Source: Implantation of Martian atmospheric ions within the regolith of Phobos


Paul Scott Anderson


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