The shape of Dimorphos may have changed dramatically as a result of the DART collision sorae universe portal website

「Dimorphos“It is a NASA (National Aeronautics and Space Administration) asteroid orbit change mission.”Arrow(Double Asteroid Redirection Test).” A large amount of rocks were seen flying from Dimorphos, which the spacecraft collided with at high speed, both in space and on Earth. A post-impact case of dimorphos was observed by the European Space Agency's (ESA) asteroid probe “Hera(Hera)” is to be observed in detail.

A research team led by SD Raducan of the University of Bern has modeled Dimorphos and predicted how its shape would change after a DART impact. As a result, the crater caused by the DART collision was found to have a very flat shape, so it may not be visible to the naked eye. also,The appearance of Dimorphos itself has changed significantly.There is a possibility.

■ “DART” experiment to change the orbit of the asteroid

About 66 million years ago, an asteroid collided with Earth, causing the extinction of many species, including dinosaurs. Although such a large collision is not expected to occur in the near future, it may happen in the distant future. In this case, changing the asteroid's orbit to avoid collisions is a promising option.

A satellite orbiting asteroid No. 65803 DidymosDimorphos' is the object chosen to test the effectiveness of this method. NASA's DART mission to change the orbit of the asteroid, with the probe itself, which has a mass of about 500 kilograms, will collide with the demorphos, which is estimated to weigh about 4 million tons (almost like the Pyramid of Cheops), and change the path of the demorphos. It revolves around Didymus with the aim of change. The collision experiment was conducted in 2022, and the event was monitored in space and on Earth.

Related article: Multiple meter-wide rocks spotted ejected from 'Dimorphos' target of DART impact experiment (August 8, 2023)

The DART collision shortened Dimorphos' orbital period by about 33 minutes, which was more than previously expected. The changing appearance of the surface can be seen by the European Space Agency's spacecraft, which is scheduled to arrive in 2026.Hera“It will be photographed by

■Simulation of fine rock aggregate

The Raducan research team attempted to use model calculations to predict the state of Dimorphos after the DART collision. A dimorphos is a celestial body composed of loosely interconnected rocks of different sizes, and the way the force is transmitted during a collision is very complex and difficult to predict. For example, the asteroid Ryugu visited by JAXA Hayabusa 2 is a celestial body composed of loosely bound rock, just like dimorphos. In the artificial crater formation experiment conducted by Hayabusa 2 in 2019, a crater with a diameter of 14.5 meters was created, significantly exceeding the previously expected diameter of 2 metres.

Raducan and his colleagues modeled Dimorphus based on what it actually looks like based on observational data from DART. Accordingly, we performed approximately 250 simulations in which parameters were varied for unknown factors, such as the bulk density of the dimorphos (density including voids) and the DART impact angle, and calculated the movement of the rocks in the two hours following the simulation. impact. . Then, by comparing the size, quantity, angle, etc. of the rocks imaged in space and on Earth after the impact, we verified the most appropriate simulation. This is a huge task, considering that it takes about a week and a half to run one simulation.

The simulation results showed that the bulk density of Demorphos is approximately the same as that of the main body of Didymos, and the results of simulations performed using parameters that assumed bonds between rocks were substantially weak more closely matched the observed results. This is it,The bonding force between the rocks that make up dimorphos is very small, and they are held together only by weak gravity.It shows that.

The DART impact ejected or dislodged a large amount of rock from the dimorphos, which had an escape velocity of only 10 centimeters per second. As a result, about 1% of the total mass flew into space, and about 8% was significantly displaced. Furthermore, it was found that the impact site was affected by the rotation of the Dimorphos' body, causing the rocks to be ejected at an angle of about 160 degrees. This is a fairly flat number considering that rocks ejected from natural craters have an angle of about 90 degrees.

Taking these things into account, we can predict the shape of Didymos that Hera will depict in 2026. Because DART has flattened part of Didymos itself, it does not have the shape of a crater as you would normally imagine, so you may not be able to recognize it as a crater. In fact, given that Didymos was shaped like a marbled chocolate before the impact, the Didymos depicted by Hera appears to have been partially chewed or crushed.The DART collision radically changed the appearance of Didymos himself.There is a possibility.

■ Results that will be utilized in “actual production”

The most important discovery of this research is that the bonds between the rocks that make up Didymos themselves are much more flexible than previously expected. It is very likely that the looseness of this connection is related to the fact that the degree of change in DART's orbit due to the collision was greater than expected.

Related article: Verification of NASA's Asteroid Orbit Change Mission “DART” once again confirms better-than-expected results (March 15, 2023)

If all goes as planned, we will be able to verify whether the model's calculations are correct by imaging Hera in 2026. If this is correct, it will also lead to improvements in future “real” simulations.

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Written by Riri Aya