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Dumbbell-shaped comets may have new implications for NASA's Planetary Defense testing mission

via:cnBeta.COM     time:2019/2/19 12:01:28     readed:78

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Comet 67P/Culiumov-Grassimecco has a dumbbell-like shape and two distinct bulges connected by the central part, making 67P/CG the target of the European Space Agency Rosetta mission. In November 2014, the Philadelphia lander landed on an asteroid. Although the final mission failed, it sent back valuable details about the chemical composition.

Now, using data from Rosetta OSIRIS cameras - optical, spectral and infrared remote imaging systems to track visible, near-infrared and near-ultraviolet wavelengths - ESA has assembled confusing faults and fissures of comets. Using stress modeling and 3D analysis, we can understand how various forces shape rocks and ice.

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"These geological features are generated by shear stress, which is a mechanical force that often occurs in earthquakes and glaciers on Earth and other planets, when two objects or blocks push and move each other in different directions," said Christophe Matonti of the University of Ix-Marseilles in France, the lead author of the study. "It's very exciting: it reveals the shape and internal structure of a comet, and how it changes and evolves over time."

Researchers say that the two parts of comet 67P/Chuliumov-Grassimynko attempt to move in different directions, creating strong shear stress in the "neck" between them. "It's like every hemisphere's material is pulling and splitting, twisting the middle part - the neck - and thinning it through mechanical erosion," explains co-author Olivier Groussin.

The key is that nothing found in the study can be explained by thermal processes. On the contrary, it may indicate that the interior of 67P/CG is much more vulnerable than initially thought. A similar shape was recently observed during NASA's New Horizon flight over Ultima Thule.

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According to scientists, insights into the shape of comets over time are crucial to understanding how the wider universe evolves. "We only used detectors to detect a few comets, 67P is the most detailed comet we have ever seen," said Matt Taylor, a scientist at ESA's Rosetta project. "Rosetta shows a lot about these mysterious and cold visitors, and according to the latest results, we can study the outer edges and early stages of the solar system in ways we have never done before."

However, these findings may have a greater impact. NASA has been working on a project called the Double Asteroid Redirection Test (DART) for many years. The goal of the project is to find a way to move asteroids along potentially dangerous routes toward Earth, or even to be completely destroyed.

To do this, DART will use so-called "kinetic energy impactor technology": basically crushing one object into another. The project plans to launch a probe in 2022 that will reach Didymos B, an asteroid about 530 feet in diameter, which is expected to be relatively close to Earth by the end of 2022 and then again in 2024. When close enough, the DART probe will lock in the asteroid and then accelerate its impact on the asteroid.

NASA should travel at 3.7 miles per second when it hits. Even so, it's only a fraction of Didymos B's overall speed. The theory behind DART is that a small change can be applied early enough to potentially dangerous asteroids to move their routes significantly as they approach Earth. Through the application of 67P technology to better understand the internal geometry and composition of asteroids, it can well shape the future use of the dual asteroid redirection test project.

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