Mars Moons Were Created By A Massive Impact

Posted: Apr 19 2018, 3:35pm CDT | by , Updated: Apr 19 2018, 3:39pm CDT, in News | Latest Science News

Mars Moons were Created by a Massive Impact
This composite image compares how big the moons of Mars appear in relation to the size of Earth's Moon. Credit: NASA/JPL-Caltech/Malin Space Science Systems/Texas A&M University

Latest model hints at a violent birth of the tiny Martian moons Phobos and Deimos

New study suggests that Mars moons were formed by a collision between proto-Mars and a dwarf-planet-sized object, hinting at a violent origin of Martian natural satellites. Although the impact was similar to one resulted in the formation of Earth’s moon, it was less intense and happened on a relatively small scale.

Mars has two moons: Phobos and Deimos. The larger, Phobos, is 14 miles across, while the smaller, Deimos, is only 8 miles, making them some of the smallest moons in the solar system. The origin of Martian moons remained a mystery. Scientists have long debated whether they are asteroids captured by Mars gravity or whether they are formed from an equatorial disk of debris. The latter explanation seems logical because these moons orbit very close to Mars. In fact, Phobos orbits around its planet closer than any other moon in the solar system. However, it does not present the complete picture of how Martian moons formed. The latest model based on hydrodynamical simulations determines the size of the object that crashed into Mars and created Mars moons.

"Ours is the first self-consistent model to identify the type of impact needed to lead to the formation of Mars' two small moons. A key result of the new work is the size of the impactor; we find that a large impactor – similar in size to the largest asteroids Vesta and Ceres – is needed, rather than a giant impactor." said lead author Dr. Robin Canup from SwRI Space Science and Engineering Division.

“The model also predicts that the two moons are derived primarily from material originating in Mars, so their bulk compositions should be similar to that of Mars for most elements. However, heating of the ejecta and the low escape velocity from Mars suggests that water vapor would have been lost, implying that the moons will be dry if they formed by impact."

Researchers suggest that Deimos and Phobos were formed around 4.5 billion years ago, the same timeframe as Earth’s moon. But they involved a much smaller impactor than our planet’s moon.

"We used state-of-the-art models to show that a Vesta-to-Ceres-sized impactor can produce a disk consistent with the formation of Mars' small moons," said co-author, Dr. Julien Salmon, an SwRI research scientist. "The outer portions of the disk accumulate into Phobos and Deimos, while the inner portions of the disk accumulate into larger moons that eventually spiral inward and are assimilated into Mars. Larger impacts advocated in prior works produce massive disks and more massive inner moons that prevent the survival of tiny moons like Phobos and Deimos."

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<a href="/latest_stories/all/all/47" rel="author">Hira Bashir</a>
The latest discoveries in science are the passion of Hira Bashir (). With years of experience, she is able to spot the most interesting new achievements of scientists around the world and cover them in easy to understand reporting.




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