DART mission to try out a strategy for shielding Earth from killer asteroids - NASA is about to launch a multimillion-dollar spacecraft - and ...
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NEWS 19 November 2021
NASA spacecraft will slam into asteroid
in first planetary-defence test
DART mission to try out a strategy for shielding Earth from killer asteroids.
Alexandra Witze
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NASA is about
Manage to launch
Settings a multimillion-dollar
Accept All Cookies spacecraft — and slam it into an asteroid.
Rather than being a catastrophic error, however, it will be the first test of a way to
protect Earth from killer asteroids.
The asteroid that NASA is smashing into, called Dimorphos, is not a threat to Earth. But
researchers want to see whether they can change its trajectory, long before they might
need to use such a strategy to deflect a truly dangerous asteroid.
“The odds of something large enough to be a problem, that we would have to deflect,
are pretty slim in our lifetimes,” says Andy Rivkin, a planetary scientist at the Johns
Hopkins University Applied Physics Laboratory ( JHU-APL) in Laurel, Maryland, which
built the spacecraft for NASA. “But sometimes your number comes up when you don’t
expect it, and it’s good to have an insurance policy.”
Slated to launch from California on 23 November, the spacecraft is called the Double
Asteroid Redirection Test (DART)1. Its target is a pair of asteroids that travel together
through space, one orbiting the other as they circle the Sun (see ‘A not-so-gentle
nudge’). Dimorphos, the smaller of the two at 160 metres wide, orbits Didymos, which
is nearly 5 times larger and is named after the Greek word for ‘twin’.
A NOT-SO-GENTLE NUDGE. Graphic detailing the Double Asteroid Redirection Test
(DART) mission taking place in 2022..
Credit: Adapted from NASA/Johns Hopkins University APL
If DART launches successfully, in late September or early October of next year it will
slam headlong into Dimorphos at 6.6 kilometres per second. The impact should shrink
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Dimorphos’s orbit so that it circles Didymos at least 73 seconds faster than before.
(Dimorphos
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change the asteroid’s orbit.) Astronomers using telescopes on Earth will watch
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brightness changes over time, as Dimorphos passes in front of and behind it.
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This complicated
Manage Settings choreography is meant to test the idea that smashing into an asteroid
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can give it enough of a nudge to keep it from hitting Earth, says Nancy Chabot, aplanetary scientist at JHU-APL who works on the mission. Using the non-threatening
pair Dimorphos and Didymos is “a really smart and a safe way to do this first test”, she
says. The impact will occur when the asteroids are 11 million kilometres from Earth.
Battling asteroids
Small asteroids and asteroid fragments hit Earth all the time, but most of them
disintegrate in the atmosphere or fall harmlessly to the ground as meteorites. NASA has
identified more than 27,000 asteroids with trajectories that bring them close to Earth.
The worry is that some new asteroid could appear, headed directly towards the planet
— and that it would be large enough to cause serious consequences when it hits, just as
with the asteroid that helped to kill off the dinosaurs and other life on Earth 66 million
years ago.
Space scientists have floated all sorts of ideas to battle incoming asteroids, the most
dramatic of which involves blasting them with nuclear weapons2. Other, less
cinematically worthy strategies involve altering the asteroid’s trajectory by flying a
spacecraft alongside to tug on it using gravitational forces, or smashing into it as the
US$330-million DART mission will.
Members of the DART team at APL inspect the spacecraft in a clean room.
Researchers at the Johns Hopkins University Applied Physics Laboratory inspect the DART spacecraft
during testing in July. Credit: Ed Whitman/NASA/Johns Hopkins University APL
Depending on the angle at which DART hits the asteroid, it could kick up a small cloud
Your
of dustprivacy
and rubble. The impact will probably leave a crater that could be around 10
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metres across. At the same time, bits of the spacecraft’s wreckage might scatter across
content and advertising, provide social media features and analyse how people use our site. By accepting some or
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from a pure crime-scene sense, a lot of us are curious about that,” Rivkin says.
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Researchers will have a chance to get answers, because minutes later, a tiny probe
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funded by the Italian Space Agency will fly by to photograph the aftermath3. NamedLICIACube, it will travel aboard DART and is the agency’s first autonomously guided
deep-space mission. LICIACube will be released from DART 10 days before impact, and
come within 55 kilometres of Dimorphos. As it whizzes past, its cameras should spot
the dust cloud, if the impact kicks one up, and possibly the resulting crater. “We might
be surprised by the images we collect,” says Elisabetta Dotto, an astronomer at the
National Institute for Astrophysics in Rome, which is leading the collaboration of Italian
universities and institutions involved in LICIACube.
In 2026, a follow-up spacecraft, the European Space Agency’s Hera mission, will visit
Dimorphos to take more detailed pictures of the impact site.
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Data collected by the DART mission should help scientists
to understand how impacts affect asteroids, says Megan
Bruck Syal, a physicist at the Lawrence Livermore National
Laboratory in California, who will model what happens to
Dimorphos. But DART is just one test involving one kind
of space rock. There could be scenarios in which planetary
Record number of asteroids defenders want to hit an asteroid with more speed than
seen whizzing past Earth in
2020 DART will reach when it hits Dimorphos, or in which they
need to pummel an asteroid with several impactors to
change its course. “We need to do more experiments like this,” Bruck Syal says.
Although many other spacecraft have been deliberately smashed into celestial objects
at the ends of their lives, DART promises to be the first to hit a planetary body in the
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name of saving Earth.
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doi: https://doi.org/10.1038/d41586-021-03471-w
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References
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1.Manage
Rivkin, A. S. et al.Accept
Settings Planet. Sci. J. 2, 173 (2021).
All Cookies2. King, P. K. et al. Acta Astronaut. 188, 367–386 (2021).
3. Dotto, E. et al. Planet. Space Sci. 199, 105185 (2021).
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