From European Space Agency – United space in Europe via Manu García : “Queen guitarist Brian May studies the origin of asteroids.” 

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From European Space Agency – United space in Europe

From United Space in Europe

6.17.20

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Queen astrophysicist and guitarist Brian May has joined a team of asteroid researchers to study the striking similarities and an enigmatic difference between two objects explored by space probes. With the help of supercomputers, the scientists created a “fight club” with which they simulated large collisions to study the possible origin of the asteroids. Their work is published in the journal Nature Communications.

Brian May, astrophysicist and Rockstar. Hera is an ESA candidate mission that will be humanity’s first investigation to encounter a binary asteroid system, Didymos.

ESA’s proposed Hera spaceraft depiction

In the ESA Hera: Planetary Defense Mission video, from which this screenshot is taken, Queen guitarist Brian May tells the story behind this ambitious mission. Credit: ESA – Office of Science

Both the asteroid Bennu, 525 m in diameter and visited by NASA’s OSIRIS-REx probe , and the asteroid Ryugu, studied by the Japanese probe Hayabusa2 , have the same spinning top shape and densities of similar materials. However, they contain different amounts of water, as revealed by the spectral mapping of hydrated materials. Ryugu appears to have weak hydration compared to Bennu, despite being comparatively young in terms of asteroids, as it is estimated to only be 100 million years old.

“The shapes of asteroids and their level of hydration can serve to trace their origin and history,” says Brian May, co-author of the study.

A mystery in the form of a spinning top.

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Both the 525 m diameter Bennu asteroid visited by NASA’s OSIRIS-REx and the 1 km diameter Ryugu asteroid hit by Japan’s Hayabusa2 have the same distinct top shape and similar material densities. However, the pair contains different amounts of water, as revealed in the spectral mapping of hydrated materials. Ryugu seems weakly hydrated compared to Bennu, despite being a comparative youngster in terms of asteroids, estimated to be just 100 million years old. Credit: ESA

The study was led by Patrick Michel, research director of the French CNRS French Riviera Observatory and chief scientist at ESA’s Hera planetary defense mission . He notes that this research is also relevant to Hera, who will explore the Didymos binary asteroid system once NASA’s DART spacecraft deflects the smaller of the two objects.

NASA DART Double Impact Redirection Test vehicle depiction schematic

“This form of the spinning top of Benny and Ryugu, including its pronounced bulge at the equator, is also presented by many other asteroids, such as the main object of the Didymos system, 780m in diameter,” Patrick explains.

“One of the most widespread hypotheses suggests that its high speed of rotation caused the shape to change over time by the action of centrifugal force , which would have caused the material to move from the poles to the equator. This turning speed could have been accelerated due to the gradual heating caused by sunlight. Known as Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP), this effect owes its name to four asteroid researchers.

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NASA DART hitting an asteroid. NASA’s double-asteroid redirect test mission DART aims to collide with the smaller of the two bodies of the Didymos binary asteroid system in the fall of 2022. ESA’s Hera mission will make subsequent follow-up observations. to impact. Credit: ESA.

“In the case of Didymos, this could explain the origin of Didymos A’s smaller moon, formed from material torn apart from the equator during its rapid movement. In that of Bennu and Ryugu, however, there is a problem: close observation by their respective probes has revealed the existence of large craters on the equatorial ridges, indicating that these bulges formed in very early stages of their history”.

As Ron Ballouz of the Lunar and Planetary Laboratory at the University of Arizona and co-author of the study explains : “These properties: shape, density, higher or lower levels of hydration, are they a consequence of the evolution of these objects once they are formed or more? well the immediate result of your training? ”.

Travel to the past with supercomputer simulations.

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The “fight club” asteroid simulations were performed using the Bluecrab group of supercomputers operated by the Maryland Center for Advanced Research Computing, through Johns Hopkins University and the University of Maryland. Credit: University of Maryland.

In order to observe the past, the researchers ran numerical simulations of asteroid collisions in the 100 km category. These collisions released countless fragments that regrouped to form aggregates, a process by which it is believed that most asteroids larger than 200m would have formed.

The simulations were run using the Bluecrab supercomputer cluster, operated by the Maryland Advanced Research Computing Center (MARCC) through Johns Hopkins University and the University of Maryland.

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Re-accumulated asteroid fragments. Fragment simulation snapshots at time steps 1 minute, 0.75 hours, 2 hours and 5 hours after the asteroid collision. The first panel shows the immediate distribution of the particles that accumulate to form the final rotary final aggregate demonstrated in the last panel. Credit: Brian May and Claudia Manzoni.

“The simulations were very intense for the supercomputers and lasted for several months,” adds Patrick Michel. The most difficult thing was to simulate the accumulation process, with detailed coding of the contact between particles, including their rolling, sliding and shear friction. We also considered the level of warming of the fragments after impact to determine their level of hydration. ”

“What we discovered was that, although the accumulation process gives rise to different shapes, there is a certain tendency towards spinning top, because the added material can be captured in a central disk to form a spinning top or, at least, a spheroid accumulated. Then this spheroid can rotate under the YORP effect to form an equatorial bulge in a short time in terms of asteroids, less than a million years old, which would explain what we see in Benny and Ryugu. ”

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Didymos and Didymoon. With its proposed Hera mission, ESA hopes to visit the double asteroid Didymos. About 15% of asteroids are believed to be double (or triple) asteroid systems. Some of these have been discovered through their light curves or radar studies, but parallel ground discoveries have also been made, with ‘doublet’ impact craters caused by binary impacts, such as adjacent Nördlinger Ries and Steinheim in Bavaria, Germany, along with others seen on Mars and Venus. The formation of asteroid moons has been shown to be a natural result of large asteroid disruptions, during which some fragments are ejected and remain attached. Many of these bodies have a “rubble pile” composition. This has inspired a theory that gradual increases in its rotation due to the heating of sunlight could actually lead to matter being thrown into space by centrifugal force, leaving part of it attached to the central body and forming a “moon ” Due to the relatively small masses and gravities of the bodies involved, the smallest asteroids orbit their parents at a relatively low speed, less than a meter per second. This opened up the possibility that it would be feasible to change the orbit of one of these asteroid moons in a measurable way, something that would not be so precisely possible with a lone asteroid in a much faster moving solar orbit. Hera will take advantage of this option to try to find out if asteroids can deviate if they pose a risk to Earth. This artist’s impression is taken from the video Hera: ESA Planetary Defense Mission. Credit: ESA – Office of Science.

The team also discovered that final hydration levels can vary significantly between aggregates formed by initial object disruption. Brian May worked with Claudia Manzoni of the London Stereoscopic Company to produce 3D stereo images of the immediate moment after impacts, revealing that the individual fragments show great variability in warming levels and, consequently, also in levels hydration.

“Thus, during a collision, an aggregate such as Bennu, which experienced little impact heating, and other material with a higher level of heating, such as Ryugu, may form,” explains Brian May.

The family tree of asteroids.

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Japan’s Hayabusa2 mission to asteroid Ryugu. Credit: JAXA.

atrick Michael adds: “The bottom line is that Bennu and Ryugu could be part of the same asteroid family and originate from a single object, even though their hydration levels are currently very different. We know that they come from the same region of the asteroid belt, which would increase the probability of a common ancestor, although we will only doubt when we can analyze the samples of the asteroids after the return of Hayabusa2 and OSIRIS-REx ”.

Brian May’s participation is the result of his asteroid research activities, including his work in the scientific teams of Hayabusa2 and OSIRIS-REx, as he is a member of the advisory committee of the NEO-MAPP project (Near-Earth Object Modeling and Payload for Protection), funded by the European Commission’s Horizon 2020 program.

This month, ESA celebrates UN-recognized Asteroid Day to raise awareness of asteroids and their role in shaping our solar system, how we can use its resources, how asteroids can pave the way for exploration. future and how we can protect our planet from its impact. For more information and to see the entire schedule for the month, visit http://www.asteroidday.org

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