The mysterious moons of Mars

The mysterious moons of Mars

Mars is a veritable wonderland that has sung for centuries with an alluring siren song to those who seek to solve its many mysteries. In fact, the two moons of Mars are named after them Phobos And Deimosoffer some great puzzles of their own. Where did the moons of Mars come from? For a long time, their strange irregular shapes suggested that they were both born asteroids that escaped from main asteroid belt between Mars and Jupiter – only to be hunted down by the Red Planet’s gravitational embrace when they wandered too close to what was to become their adopted parent planet. However, in April 2018, planetary scientists at Southwest Research Institute (SwRI) in San Antonio, Texas, an alternative scenario to explain the origin of these two small potato-shaped moons. The new theory suggests that Phobos And Deimos They were actually born as a result of an ancient influence when he was a young elf protoplanet It exploded in the primordial Mars. The paper describing this new paradigm is published in the April 16, 2018 issue of the journal Journal Science advances.

The primordial solar system has often been likened to a “cosmic shooting gallery” in which bodies, large and small, were constantly crashing into each other – wreaking havoc. The ancient giant collision between a young and ill-fated Mars protoplanet It would have been nearly identical to the one generally thought to have been responsible for the formation of Earth’s large moon. According to this model, Earth’s moon was born when Mars fell in size protoplanet name of the thing Thea It collided with our still-forming planet.

Astronomers have been debating the origin of the mysterious duo of Mars’ moons for decades. The conundrum, which has been difficult to solve, is whether the moons are actually captured asteroids or They were born instead from a disk of debris orbiting primordial Mars. The surrounding debris disk was created as a result of the proposed giant impact. This gigantic effect model demonstrates the origin Phobos And Deimos It is considered the most promising explanation. Unfortunately, previous models of this process have been hampered by low digital resolution, as well as an overly simplistic modeling technique.

In the case of a giant collision model between the primordial Earth and the tragedy that was TheaThe violent impact threw debris into the sky above our planet. Eventually, the debris coalesced to create Earth’s beautiful moon companion.

“Our model is the first self-consistent model to quantify the type of impact required to lead to the formation of two small moons of Mars,” said study lead author Dr. Robin Canup on April 16, 2018. SWRI press release. Dr. Canopus is an associate vice president at SwRI Department of Aerospace Science and Engineering, as well as one of the leading scientists using large-scale hydrodynamic simulations to model planet-scale collisions, including the favored giant-impact Earth-Moon formation model.

Quite a pair

Since its discovery in 1877 by the American astronomer Asaph Hall (1829-1907), Phobos And Deimos Astronomers were bewildered and bewildered in search of an elusive answer to the question of how Mars managed to have a binary of small, oddly shaped moons. Phobos It has an orbit that brings it closer to Mars than its sibling moon, with a semi-major axis of 5,827 miles, unlike Mars Deimos 14,580 miles.

When the moon is in orbit around its parent planet, everything is going well for both the planet and the moon –Only as long as the gravity holding the moon in one piece outweighs the powerful pull of its planet. Trouble begins if the afflicted moon wanders too close to the gravitational grip of its ruined parent planet. This is because the planet’s tidal forces begin to override the gravitational bond holding the unlucky moon together –this It means that the moon will crumble. Earth’s relatively large moon is very lucky because the limit – it’s called Roach Limit– A little less than 10,000 km, which is 385,000 km from our planet safely.

Unfortunately, other moons may not be so lucky. This happy state of Earth and its lunar companion is not the case for the moons of Mars. Phobos It is the largest moon of the duo, about 22 kilometers in diameter, and is currently slowly trolling towards Mars. Phobos He is a doomed young moon scientist, because he will approach Mars Roach Limit in about 20 million years. when you do that, Phobos It will be pulled apart, forming a mess of debris that will create an amazing ring around the Red Planet. in contrast, Deimos– The youngest of the duo – will be left without his companion, the Moon. Deimos It orbits the mother planet at a greater and safer distance. This last surviving Martian moon will become the only remaining object in the Martian sky.

If an observer on Mars stood near the equator, full Phobos It will be about a third the size of Earth’s full moon. but, Phobos It would appear much smaller if an observer stood farther from the Martian equator – and it would be completely invisible if an observer were looking at the Martian sky while standing on one of its polar ice caps. Deimos It looks very much like a star or a planet that is especially bright when seen by an observer on Earth. There is no total solar eclipse on Mars. This is because the moons are much too small to completely block the sun. In dramatic contrast, a total lunar eclipse Phobos They happen almost every night.

The motions of Mars’ moons will look very different from those of Earth’s moon. Speed ​​demon Phobos It rises in the west, settles in the east, and then rises again only 11 hours later. On the other side, Deimos– being out of a synchronous orbit – rising as expected in the east. However, Deimos performs this feat very slowly. Despite its 30-hour orbit around its parent planet, it takes 2.7 days Deimos To fall in the west as it slowly recedes behind the rotation of Mars.

Both moons of Mars are gradually closed, always showing the same face towards Mars. Numerous string craters have been observed on Mars, and they are tilted further from the equator as they get older. This indicates that there may have been many minor moons that perished in the currently expected way of dying Phobos–and that the crust of Mars as a whole shifted between these events. in contrast, Deimos Far enough from its parent planet to slowly boost its orbit instead – as is the case for Earth’s moon. When Earth’s moon was born it was much closer to our planet. The primordial moon was a much larger object in the ancient Earth’s sky than it is now. As time passed, Earth’s moon traveled farther and farther; It looks smaller and smaller in the sky as a result.

The birthplace of the moons of Mars is a hotly debated topic. Both minor moons have a lot in common C-type carbonaceous asteroids, of albedo, density, and spectra very similar to those of c- or D-type asteroids. Because of this similarity, one theory suggests that both moons could be captured Main belt asteroids. However, both Phobos And Deimos It has circular orbits located roughly in the equatorial plane of Mars. For this reason, capture origin requires a mechanism to rotate the initially highly eccentric orbits, modifying their inclinations in the equatorial plane. This was likely caused by a combination of atmospheric drag and tidal forces – although it is not clear that sufficient time would have been available for this to occur in the case of Deimos. Circular orbits are an indication that a rotating object was born in place, while eccentric orbits indicate the opposite. Another problem with capture theory is that capture itself requires energy dissipation. Mars’ atmosphere today is too thin to take a picture Phobos-Body size by air braking. However, capture might have occurred if the original body was indeed a binary asteroid that broke up as a result of tidal forces.

An explosion in the Martian past

The new model suggests a much smaller effect protoplanet than those considered in previous studies. The cataclysmic impact that is believed to have created Earth’s moon occurred about 4.5 billion years ago – a time when our 4.6 billion year old solar system was very young. Earth is about 9,000 miles in diameter, while Mars is just over 4,200 miles in diameter. Earth’s moon is just over 2,100 miles in diameter, a quarter the size of Earth.

Phobos And Deimos formed in the same time frame. Both minor moons hug their parent planet in close orbits. proposed Phobos Deimos The collider formation would be roughly the same size as the asteroid Vista– the second largest population main asteroid belt after the dwarf planet Ceres. Vista It has a diameter of 326 miles, while Ceres It is about 587 miles wide.

We used the most recent models to show that A Vista to CeresA collider of size could produce a disk that matches the composition of Mars’ small moons. The outer parts of the disc accumulate in Phobos And Deimos, while the disk’s interiors accrete into larger moons that eventually roll inward and are absorbed into Mars. The larger impacts advocated in previous work produce massive disks and more massive inner moons that prevent the survival of small moons such as Phobos And Deimos,” Dr. Julien Salmon explained on April 16, 2018 SWRI press release. Dr. Salmon is a Research Scientist at SwRI.

These new findings are important for Japan Aerospace Exploration Agency (JAXA) Mars Moon Exploration Mission (MMX)which is scheduled to be launched in 2024. MMX It will include a tool provided by NASA. the MMX The spacecraft will visit two small moons of the Red Planet, as well as land on a surface Phobos In order to obtain a surface sample that will be returned to Earth for study in 2029.

The primary objective of MMX task Determining the origin of the Martian moons, and having a model that predicts…the compositions of the moons will provide…a major constraint to achieving this goal,” Dr. Canopus explained on April 16, 2018. SWRI press release.


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