På dette billede lavet fra en NASA-livestream styrter rumfartøjet Double Asteroid Redirection Test ind i en asteroide mandag den 26. september 2022. Kredit:ASI/NASA via AP
Et NASA-rumfartøj vædrede en asteroide med stormhastighed mandag i en hidtil uset generalprøve for den dag, hvor en dræbersten truer Jorden.
Det galaktiske slam fandt sted ved en harmløs asteroide 7 millioner miles (11,3 millioner kilometer) væk, hvor rumfartøjet ved navn DART pløjede ind i rumklippen med 14.000 mph (22.500 km/t). Forskere forventede, at nedslaget ville skære et krater ud, kaste strømme af sten og snavs ud i rummet og, vigtigst af alt, ændre asteroidens kredsløb.
"Vi har indflydelse!" Mission Controls Elena Adams annoncerede, hoppede op og ned og skød armene mod himlen.
Teleskoper rundt om i verden og i rummet sigtede mod det samme punkt på himlen for at fange skuespillet. Selvom virkningen umiddelbart var tydelig - DARTs radiosignal ophørte brat - vil det tage så lang tid som et par måneder at bestemme, hvor meget asteroidens vej blev ændret.
Missionen på $325 millioner var det første forsøg på at ændre positionen af en asteroide eller et hvilket som helst andet naturligt objekt i rummet.
"Så vidt vi kan se, var vores første planetariske forsvarstest en succes," fortalte Adams senere på en pressekonference, hvor rummet fyldtes med klapsalver. "Jeg synes, at jordboerne burde sove bedre. Det vil jeg bestemt."
På dette billede lavet fra en NASA-livestream og taget fra rumfartøjet Double Asteroid Redirection Test, ses asteroiden Dimorphos, mens rumfartøjet flyver mod det, mandag den 26. september 2022. Kredit:ASI/NASA via AP
NASA-administrator Bill Nelson mindede folk tidligere på dagen via Twitter om, at "Nej, dette er ikke et filmplot." He added in a prerecorded video:"We've all seen it on movies like "Armageddon," but the real-life stakes are high."
Monday's target:a 525-foot (160-meter) asteroid named Dimorphos. It's a moonlet of Didymos, Greek for twin, a fast-spinning asteroid five times bigger that flung off the material that formed the junior partner.
The pair have been orbiting the sun for eons without threatening Earth, making them ideal save-the-world test candidates.
Launched last November, the vending machine-size DART—short for Double Asteroid Redirection Test—navigated to its target using new technology developed by Johns Hopkins University's Applied Physics Laboratory, the spacecraft builder and mission manager.
In this image made from a NASA livestream, the Double Asteroid Redirection Test spacecraft approaches asteroid Dimorphos, center, as larger asteroid Didymos fades away from view on Monday, Sept. 26, 2022. Credit:ASI/NASA via AP
DART's on-board camera, a key part of this smart navigation system, caught sight of Dimorphos barely an hour before impact. "Woo hoo!" exclaimed Adams, a mission systems engineer at Johns Hopkins.
With an image beaming back to Earth every second, Adams and other ground controllers in Laurel, Maryland, watched with growing excitement as Dimorphos loomed larger and larger in the field of view alongside its bigger companion. Within minutes, Dimorphos was alone in the pictures; it looked like a giant gray lemon, but with boulders and rubble on the surface. The last image froze on the screen as the radio transmission ended.
Flight controllers cheered, hugged one another and exchanged high fives. Their mission complete, the DART team went straight into celebration mode. There was little sorrow over the spacecraft's demise.
"Normally, losing signal from a spacecraft is a very bad thing. But in this case, it was the ideal outcome," said NASA program scientist Tom Statler.
This illustration made available by Johns Hopkins APL and NASA depicts NASA's DART probe, foreground right, and Italian Space Agency's (ASI) LICIACube, bottom right, at the Didymos system before impact with the asteroid Dimorphos, left. DART is expected to zero in on the asteroid Monday, Sept. 26, 2022, intent on slamming it head-on at 14,000 mph. The impact should be just enough to nudge the asteroid into a slightly tighter orbit around its companion space rock. Credit:Steve Gribben/Johns Hopkins APL/NASA via AP
Johns Hopkins scientist Carolyn Ernst said the spacecraft was definitely "kaput," with remnants possibly in the fresh crater or cascading into space with the asteroid's ejected material.
Scientists insisted DART would not shatter Dimorphos. The spacecraft packed a scant 1,260 pounds (570 kilograms), compared with the asteroid's 11 billion pounds (5 billion kilograms). But that should be plenty to shrink its 11-hour, 55-minute orbit around Didymos.
The impact should pare 10 minutes off that. The anticipated orbital shift of 1% might not sound like much, scientists noted. But they stressed it would amount to a significant change over years.
"Now is when the science starts," said NASA's Lori Glaze, planetary science division director. "Now we're going to see for real how effective we were."
Planetary defense experts prefer nudging a threatening asteroid or comet out of the way, given enough lead time, rather than blowing it up and creating multiple pieces that could rain down on Earth. Multiple impactors might be needed for big space rocks or a combination of impactors and so-called gravity tractors, not-yet-invented devices that would use their own gravity to pull an asteroid into a safer orbit.
This illustration made available by Johns Hopkins APL and NASA depicts NASA's DART probe, upper right, on course to impact the asteroid Dimorphos, left, which orbits Didymos. DART is expected to zero in on the asteroid Monday, Sept. 26, 2022, intent on slamming it head-on at 14,000 mph. The impact should be just enough to nudge the asteroid into a slightly tighter orbit around its companion space rock. Credit:Steve Gribben/Johns Hopkins APL/NASA via AP
"The dinosaurs didn't have a space program to help them know what was coming, but we do," NASA's senior climate adviser Katherine Calvin said, referring to the mass extinction 66 million years ago believed to have been caused by a major asteroid impact, volcanic eruptions or both.
The non-profit B612 Foundation, dedicated to protecting Earth from asteroid strikes, has been pushing for impact tests like DART since its founding by astronauts and physicists 20 years ago. Monday's feat aside, the world must do a better job of identifying the countless space rocks lurking out there, warned the foundation's executive director, Ed Lu, a former astronaut.
Significantly less than half of the estimated 25,000 near-Earth objects in the deadly 460-foot (140-meter) range have been discovered, according to NASA. And fewer than 1% of the millions of smaller asteroids, capable of widespread injuries, are known.
This illustration made available by Johns Hopkins APL and NASA depicts NASA's DART probe, center, and Italian Space Agency's (ASI) LICIACube, bottom right, at the Didymos system before impact with the asteroid Dimorphos, left. DART is expected to zero in on the asteroid Monday, Sept. 26, 2022, intent on slamming it head-on at 14,000 mph. The impact should be just enough to nudge the asteroid into a slightly tighter orbit around its companion space rock. Credit:Steve Gribben/Johns Hopkins APL/NASA via AP
The Vera Rubin Observatory, nearing completion in Chile by the National Science Foundation and U.S. Energy Department, promises to revolutionize the field of asteroid discovery, Lu noted.
Finding and tracking asteroids, "That's still the name of the game here. That's the thing that has to happen in order to protect the Earth," he said. + Udforsk yderligere
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