Shulou(Shulou.com)11/24 Report--

CTOnews.com, March 5 (Xinhua)-- NASA's DART (double Asteroid Redirection Test) spacecraft successfully hit an asteroid called Dimorphos at the end of September 2022 in an attempt to change the asteroid's orbit by kinetic energy impact, the first test in the world to protect the Earth from the threat of asteroid impact.

NASA officially released an article on March 2 announcing a series of research results from the experiment and said it confirmed that kinetic energy impacts could be used as a method of planetary defense.

NASA said that since DART successfully hit its target on September 26, nearly five months ago-changing the orbit of asteroid Dimorphos for 33 minutes-the DART team has been trying to analyze the post-impact data.

According to reports, the DART mission uses an asteroid deflection technology called the Kinetic Energy Collider, which, in the simplest terms, crashes one object into another. According to the data, the DART investigation team, led by the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, found that kinetic energy impactor missions like DART can effectively change the trajectory of asteroids, a big step towards preventing future asteroids from hitting Earth.

The findings have been published in four papers in Nature, and CTOnews.com summarizes them as follows:

The first paper describes in detail DART's successful demonstration of kinetic energy impactor technology: reconstructing the impact itself, reporting the timeline before the impact, specifying the location and nature of the impact site, and recording the size and shape of the Dimorphos.

The findings suggest that intercepting asteroids about half a mile in diameter, such as Dimorphos, can be achieved without a pre-reconnaissance mission, requiring sufficient warning time-at least a few years, but preferably decades.

The second paper uses two independent methods based on earth light curve and radar observation. The team, led by Cristina Thomas of the University of Northern Arizona, measured the periodic changes in dynamic impacts twice: 33 minutes, plus or minus one minute. This change suggests that the recoil of material ejected into space by impact (called jets) produces a significant momentum change on the asteroid, exceeding the momentum change of the DART spacecraft itself.

In the third paper, the investigation team led by Andrew Cheng of APL calculated the momentum change of the asteroid caused by the dynamic impact of Dimorphos by studying the change of orbital period of DART. They found that the impact caused Dimorphos to instantly slow down along its orbit at a speed of about 2.7mm per second, suggesting once again that the recoil of the jet played an important role in magnifying the momentum changes directly imposed on the asteroid by the spacecraft. This momentum change is magnified by 2.2 to 4.9 times (depending on the mass of the Dimorphos), indicating that the momentum change transferred by the jet greatly exceeds the momentum change of the DART spacecraft itself.

The fourth paper is aimed at new research. Jian-Yang Li of the Arizona Institute of Planetary Science found that the impact of DART made Dimorphos an "active asteroid", a space rock that moves like an asteroid but has a material tail like a comet. The DART mission activated Dimorphos under precisely known and carefully observed impact conditions, thus the formation of active asteroids was studied in detail for the first time.

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