How NASA plans to stop killer asteroids

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A massive asteroid impact ended the age of the dinosaurs, and it’s almost certain that an equally large asteroid or comet will head for Earth again at some point in the future – but unlike to dinosaurs, we may be able to stop a threat. space rock to get us out.

The birth of planetary defense

In 1993, scientists determined that Shoemaker-Levy 9 (SL9), a newly discovered comet orbiting Jupiter, was likely to collide with the gas giant the following year. This was huge news, as astronomers had never had the chance to witness such an impact event before.

For six days in July 1994, they trained their telescopes on Jupiter and watched pieces of SL9 crash into the planet, sending giant plumes of superheated material high into its atmosphere.

“Shoemaker-Levy 9 was kind of a punch in the gut.”

Heidi Hammel

The dark scars created by SL9 in Jupiter’s cloud tops dissipated a few months later, but the comet’s impact on the astronomical community lives on in “planetary defense” – efforts to detect and track asteroids, comets and other near-Earth objects (NEOs), predict possible impacts with Earth and prevent potentially devastating collisions.

“Shoemaker-Levy 9 was kind of a punch in the gut,” said Heidi Hammel, who led the team using NASA’s Hubble Space Telescope to observe the SL9 collision, in 2019. really invigorated our understanding of the importance of monitoring our local neighborhood, and understanding what the potential for impacts on Earth are in the future.

looking up

We can’t protect Earth from a threatening asteroid we don’t know exists. That’s why, in 1998, NASA established the Near-Earth Object Observations (NEO) program to fund efforts to identify, track, and categorize near-Earth objects.

In 2005, Congress ordered the program to identify at least 90% of the predicted number of NEOs over 460 feet wide – the size a space rock would need to be to wipe out a city – but as of June 2021, only 40 % of the estimated number of large NEOs had been identified.

This missing data could also have very real consequences. In 2019, an asteroid estimated to be 195 to 425 feet wide flew within 40,000 miles of Earth – about a fifth of the distance to the moon – and it was only spotted on the day of its flyby.

The number of identified asteroids has increased over the past few decades. Credit: NASA NEO Study Center / Our World in Data

One of the factors holding back the NEO program is its heavy reliance on ground-based optical telescopes – because these can only be used to hunt threatening asteroids at night, astronomers cannot see any approaching our planet during the day from the direction of the sun.

A wave of new asteroid discoveries could be on the horizon, however, thanks to the Near-Earth Object Surveyor (NEO Surveyor) space telescope, the world’s first spacecraft specifically designed to find dangerous near-Earth objects.

“NEO Surveyor operates at thermal infrared wavelengths and is therefore very sensitive to dark objects,” NEO Surveyor principal investigator Amy Mainzer told SpaceNews. “It searches the near-sun regions of the sky, allowing it to find objects with the most Earth-like (and therefore potentially dangerous) orbits.”

An illustration of NASA’s NEO Surveyor. Credit: NASA / JPL-Caltech

NASA has yet to set a launch date for NEO Surveyor – it could launch in 2026, but funding issues could push it back to 2028. Either way, the telescope is expected to identify around 66% of NEOs threatening the city within 5 years of launching and achieving the goal of 90% within 10 years.

“While a significant impact on Earth is of course a very rare event, we don’t know when the next might be, and NEO Surveyor is designed to find out,” defense officer Lindley Johnson told SpaceNews. NASA planetary.

“Software can now do things that you wouldn’t even dream of 20 or 30 years ago, that you wouldn’t even think of.”

Zeljko Ivezic

NEO Surveyor isn’t our only hope of detecting more asteroids, either.

In early 2022, the NASA-funded Asteroid Terrestrial-impact Last Alert System (ATLAS) system was updated to include two new telescopes, bringing the total to four and making it the first system capable of studying the whole sky. nocturnal to threaten NEOs every 24 hours. .

Researchers from the University of Washington and the Asteroid Institute then unveiled THOR, a computer algorithm capable of spotting threatening new asteroids in old telescope data, in May 2022 – it has already been used to identify more than 100 previously unknown near-Earth objects.

“[S]oftware can now do things that you wouldn’t even dream of 20, 30 years ago, that you wouldn’t even think of,” THOR researcher Zeljko Ivezic told The New York Times.


Being able to predict a species-threatening NEO impact is a major part of planetary defense, but it’s not worth much if we can’t actually defend our planet from space rock – we would be like the dinosaurs, but with the added benefit of knowing that an apocalyptic event was imminent.

After years of researching NEO, the “prevention” side of planetary defense recently took a huge leap forward thanks to NASA’s Double Asteroid Redirection Test (DART), the first demonstration of a technology that could eventually prevent an incoming asteroid from hitting our planet.

“It’s like throwing a tennis ball at a 747.”

Elena Adams

The goal of the DART mission was to hurl a refrigerator-sized spacecraft onto Dimorphos, a 530-foot asteroid orbiting the much larger asteroid Didymos, in hopes of shifting its orbit.

The asteroids are millions of miles from Earth – too far away to pose a collision threat, but perfectly situated to study the effect of a spacecraft crashing into a space rock.

“It’s like throwing a tennis ball at a 747,” Elena Adams, a DART mission systems engineer at Johns Hopkins Applied Physics Laboratory (APL), told CBS News. “If it goes fast enough, you will move it.”

“[DART is] a first test of, can we really do it? she continued.

DART’s goal is to shorten Dimorphos’ orbit around Didymos by 1%. Credit: NASA / Johns Hopkins APL

NASA passed this test on September 26, 2022, when DART successfully hit its target 10 months after launch.

Scientists are currently studying observations of the collision collected by space telescopes, DART’s own imaging instrument (before it was destroyed) and a small satellite launched by DART just 15 days before impact, called LICIACube, developed by the Italian Space Agency.

This data should help determine whether the impact pushed Dimorphos and shortened its orbit around the larger asteroid by about 1%, as NASA hoped.

While this change might not seem like much, even a slight push, if given early enough, could steer an asteroid off a collision course, which means DART’s ability to move Dimorphos would bring us considerably closer to the ability to protect the Earth from a threat. NEO.

“NASA works for the benefit of mankind, so for us, it’s the ultimate fulfillment of our mission to do something like this – a demonstration of technology that, who knows, one day might save our home,” said said Pam Melroy, NASA assistant administrator.

The DART collision photographed by NASA’s Hubble (left) and James Webb (right) space telescopes. Credit: NASA

DART may have been the first demonstration of planetary defense technology, but it likely won’t be the last – China’s National Space Administration plans to launch its own asteroid deflection test in 2026.

In the more distant future, we may see tests of other means of preventing an impact – planetary defense researchers are exploring the viability of systems designed to slice near-Earth objects into non-threatening pieces and (yes, really) use nuclear bombs just to blow them up. at the top.

The bottom line

Thanks to these and other planetary defense efforts, we are now better prepared than ever to prevent a potentially devastating impact.

That still don’t mean we would Actually be able to stop a collision, however – in 2021 NASA’s Planetary Defense Coordination Office failed to prevent an asteroid impact during a simulation exercise.

This hypothetical asteroid was expected to hit Earth just six months after its discovery, and NASA believes it would need 5-10 years’ notice to effectively deflect a menacing space rock – further underscoring the need to discover as many dangerous asteroids as possible. possible, as soon as possible. as possible.

“Our goal is to find any possible impact years to decades in advance so that it can be deflected with a capability using the technology we already have, like DART,” Johnson said. “DART, NEO Surveyor and ATLAS are all important parts of NASA’s work to prepare Earth in case we face an asteroid impact threat.”

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