Under pressure: the strange neck of Rosetta Comet sculpted by shear stress

The strange "neck" between the lobes of comet 67P / Churyumov-Gerasimenko, spotted by the Rosetta spacecraft formed in part because the comet had a fragile interior, reveals a new study.

67P photos taken by Rosetta Between 2014 and 2016, associated with new modeling and three-dimensional analyzes, revealed networked faults and fractures in the comet extending up to 500 meters underground and hundreds of meters wide. The tension reached its peak in the thinnest part of the comet's neck, which connected the two lobes of the 67P.

The discovery not only helps scientists understand the 67P, but also to understand how comets have formed around the solar system said in a statement about the new search. These tiny worlds of ice and dust surround the sun; as they get closer to the heat and pressure of the star's particles, ice dissipates directly into space in a process called sublimation. This process often creates a tail of water vapor protruding from the comet. But sublimation alone can not explain the presence of newly discovered cracks in the 67P, the researchers said.[[[[In pictures: The latest pictures of comet Rosetta Spacecraft during a crash]

"These geological features were created by shear stress, a mechanical force often observed during earthquakes or glaciers on Earth and other terrestrial planets, when two bodies or blocks grow and move in different directions. different directions, "Christophe Matonti, lead author of the new report and an astrophysicist from the Aix-Marseille University in France, said in the statement. "It's extremely exciting: it says a lot about the shape of the comet, its internal structure and its evolution over time."

Mechanical shear stress has helped shape the Comet 67P over time.

(Image: © ESA / Rosetta / MPS for the OSIRIS MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA team, C. Matonti et al (2019))

"It's as if the material present in each hemisphere was separating and separating, bypassing the middle part – the neck – and slimming it through the resulting mechanical erosion," added the co – author Olivier Groussin, astronomer at the University of Aix-Marseille. same statement. "We think that this effect was originally created because of the rotation of the comet and its initial asymmetric shape.A couple formed at the place where the neck and the" head "meet, these protruding elements revolve around the center of gravity of the comet. "

The evolution of Comet 67P over 4.5 billion years, combining the effects of mechanical erosion and sublimation erosion (ice boiling directly in space, without going through a liquid step).

(Image: © C. Matonti et al (2019))

While sublimation sunsets at 67P, beyond Jupiter's orbit, at nearly 6 Earth-Sun distances (astronomical units), stress will continue to act for billions of years. years since the formation of the comet, the researchers said.

Although stress is low, the effects will accumulate over time. Sublimation would affect the comet much faster over millions of years, researchers said. Sublimation is maximum when the 67P approaches the orbit of Mars to get closer to the sun, every 6.5 years. (A billion years equals a billion years ago, the solar system dates back about 4.5 billion years, to give you an idea.

The shape of comet 67P is similar to that of the 2014 object MU69, nicknamed Ultima Thule.

(Image: © NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute, right: ESA / Rosetta / NAVCAM / CC BY-SA IGO 3.0)

After passing Pluto in 2015, NASA has New Horizons The spacecraft approached another double-lobe object when it flew in 2014, MU69 (which NASA has nicknamed Ultima Thule) January 1st. The object is embedded in a region called the Kuiper Belt, a huge reservoir of comets and small objects beyond Neptune. Although the analysis is ongoing, until now, researchers have detected no signs of shear stress in MU69, said Mantoni.

A study based on research has been published on February 18 in the journal Nature Geoscience.

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