(MENAFN- Gulf Times)
The success of NASA’s recent Dart (Double Asteroid Redirection Test) mission, which saw a spacecraft deliberately crash into an asteroid to push it into a faster orbit, marked the world’s first test of a system planetary defense designed to prevent a possible apocalyptic collision of a meteorite with Earth. The relevance of the proof-of-concept mission, which spanned seven years of development, points directly to the fact that the Cretaceous mass extinction event that occurred approximately 66 million years ago, killing 78 % of all species, including the remaining non-avian dinosaurs, was most likely caused by an asteroid (later named Chicxulub) striking Earth in what is now Mexico, potentially exacerbated by flood volcanism in course in what is now India.
The Dart mission was also a first for humanity to alter the motion of a celestial body, as announced by the US space agency. The results of telescope observations released at a NASA press briefing in Washington confirmed that the suicide test flight of the Dart spacecraft on September 26 had achieved its main objective: to change the direction of an asteroid by pure kinetic force. Astronomical measurements over two weeks after impact showed the target asteroid had moved slightly closer to the larger parent asteroid it orbits and its orbital period had been shortened by 32 minutes. “This is a watershed moment for planetary defense and a watershed moment for humanity,” NASA chief Bill Nelson told reporters as he announced the results. “It looked like a movie plot, but it wasn’t Hollywood.”
Last month’s impact, 10.9 million kilometers from Earth, targeted an egg-shaped asteroid named Dimorphos, roughly the size of a football stadium and orbiting a parent asteroid. about five times bigger called Didymos once every 11 hours and 55 minutes. The test flight ended with the Dart impact vehicle, no bigger than a refrigerator, directly impacting Dimorphos at around 22,531 km/h. Comparing the measurements before and after the impact of the Dimorphos-Didymos pair as one eclipses the other shows that the orbital period was shortened to 11 hours and 23 minutes as the smaller object collided with tens of meters from its parent.
The result “demonstrated that we are capable of deflecting a potentially dangerous asteroid of this size” if discovered sufficiently in advance, said Lori Glaze, director of NASA’s planetary science division. “The key is early detection.” Neither the two asteroids involved, nor Dart itself, posed any real threat to Earth. But a Dimorphos-sized asteroid, while incapable of posing a planet-wide threat, could level a major city with a direct hit. Scientists had predicted that the Dart impact would shorten Dimorphos’ orbital path by at least 10 minutes, but would have considered a change as small as 73 seconds a success. Thus, the actual change of more than half an hour, with a margin of uncertainty of plus or minus two minutes, exceeded expectations.
Launched by a SpaceX rocket in November 2021, Dart flew most of its journey under the direction of flight directors on the ground, with control handed over to the craft’s autonomous onboard navigation system in the final hours of the trip. Both Dimorphos and Didymos are tiny compared to the cataclysmic Chicxulub. Smaller asteroids are far more common and of greater near-term theoretical concern, making the Didymos pair suitable test subjects for their size, according to NASA scientists and planetary defense experts. Additionally, the two asteroids’ relative proximity to Earth and their dual configuration made them ideal for the Dart mission.
The moon Dimorphos is one of the smallest astronomical objects to be given a permanent name and is one of 27,500 known near-Earth asteroids of all sizes tracked by Nasa. Although none are known to pose a foreseeable danger to humanity, NASA believes that many other asteroids remain undetected in Earth’s near vicinity.
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