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Mars moons have a common ancestor



Mars moons have a common ancestor

The artist̵

7;s impression of the collision of a primitive satellite on Mars with an asteroid may have led to the formation of Phobos and Deimos. Image Credit: Mark Garlick/markgarlick.com

Since they were discovered in 1877, the two moons of Mars, Phobos and Demos, have puzzled researchers. They are very small: Deimos has a diameter of 22 kilometers, which is 160 times the diameter of our moon, while Deimos has a smaller diameter, only 12 kilometers in diameter. . Amirhossein Bagheri, a doctoral student at the Institute of Geophysics at ETH Zurich, said: “Our satellites are basically spherical, while the satellites of Mars are very irregular, like potatoes.” He added:. ”

This makes people suspect that they may actually be asteroids captured in the gravitational field of Mars. Bagley said: “But this is the beginning of the problem.” It is expected that the captured object will follow an eccentric orbit around the Earth, and the orbit will have a random inclination. Contrary to this assumption, the orbit of the Martian satellite is almost circular and moves in the equatorial plane of Mars. So, what is the explanation for the current orbit of Phobos and Demos? To solve this dynamic problem, researchers rely on computer simulations.

Calculate the past

Amir Khan, a senior scientist at the Institute of Physics of the University of Zurich and the Institute of Geophysics of the ETH Zurich, said: “The idea is to trace the orbit and its changes. It turns out that the orbits of Phobos and Deimos seem to be in the past. Intersect. Khan said: “This means that the satellites are likely to be at the same location and therefore have the same origin. The researchers concluded that there were larger celestial bodies orbiting on Mars at that time. The original moon may have been hit by another corpse and decomposed. The lead author of the study Bagheri said: “The Phoenix and Di Moss is the remainder of this lost moon. ” Natural astronomy.

Although these conclusions are easy to understand, they require extensive preliminary work. First, researchers must perfect existing theories describing the interaction between the moon and Mars. Khan explained: “All celestial bodies exert tidal forces on each other.” These forces cause a form of energy conversion, called dissipation, whose magnitude depends on the size of the object, its internal composition, and the distance between each other.

Insight into the interior of Mars and its moons

The National Aeronautics and Space Administration (NASA) InSight mission is currently exploring on Mars, and ETH Zurich has participated in the seismograph electronics of the project to record earthquakes and meteorite impacts. Khan said: “These records allow us to see the interior of the Red Planet, and these data are used to limit our calculations in the Mars model and the dissipation that occurs within the Red Planet.”

Images and measurements from other Mars probes show that Phobos and Phobos are made of very porous materials. Their density is less than 2 g/cm3, which is much lower than the earth’s average density of 5.5 g/cm3. Khan suspected, “There are many cavities inside Phobos, which may contain ice water. This is where the tide causes a lot of energy to dissipate.”

Using these discoveries and their refined theories about tidal effects, researchers performed hundreds of computer simulations to track the time the satellite’s orbit moved backwards until they reached the point of intersection (the moment when Phobos and Deimos were born). According to simulations, this time point was between 100 and 2.7 billion years in the past. Bagheri said: “The exact time depends on the physical properties of Phobos and Deimos, that is, their porosity.” A Japanese probe scheduled to launch in 2025 will explore Phobos and send samples back to Earth. Researchers expect that these samples will provide the necessary details about the interior of the Martian moon, so that its origin can be calculated more accurately.

The end of Phobos

Another thing they calculated was that Phobos and Demos’ common ancestor was farther from Mars than Phobos. The researchers explained that although the smaller Deimos remains where it appeared, tidal forces are bringing the larger Phobos closer to Mars, and the process is still ongoing. Their computer simulations also show the future development of satellite orbits. It seems that Deimos will leave Mars very slowly, just as our moon is slowly receding from the earth. However, Phobos will fall to Mars in less than 40 million years, or be destroyed by gravity when approaching Mars.


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More information:
Amirhossein Bagheri et al. Regarding the dynamic evidence of Phobos and Demon as the remnants of the destroyed common progenitor cells, Natural astronomy (2021). DOI: 10.1038 / s41550-021-01306-2

Citation: Mars moons have a common ancestor (February 23, 2021), retrieved from https://phys.org/news/2021-02-martian-moons-common-ancestor.html on February 23, 2021

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