24 November/December 2020
PHOTO^ ILLUSTRATIONCREATED^ BY^ ALYSE^ MARKEL^ USING^ GETTYIMAGESSpace
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// BY JENNIFER LEM A N //Could a Cosmic
Lasso Divert
Extinction-Level
Asteroids?
I
N 2013, A METEOR EXPLODED 14 MILES
above Chelyabinsk, Russia, knocking out
windows across 200 square miles and injur-
ing more than 1,600 people. It was a wake-up
call for astronomers to help defend Earth from
more potentially hazardous asteroids.
Of the almost 1 million known comets and
asteroids in our solar system, more than 2,000 have
the potential to be hazardous to Earth. These aster-
oids are typically 450 feet wide or larger, on an orbit
that swings them within 14 million miles of Earth’s
orbit. “Although asteroid def lection might sound
like science fiction, it is a serious topic,” says Flavi-
ane Venditti, Ph.D., an observatory scientist at the
Arecibo Observatory in Puerto Rico. “Out of all nat-
ural disasters, an asteroid impact is the only one we
have the power to avoid.”
Proposed defensive measures against oncom-
ing asteroids look blunt so far. In 2021, NASA
will attempt their Double Asteroid Redirection
Test (DART). This mission will involve slamming
an oven-sized spacecraft into an asteroid called
Dimorphos—scheduled to make a close (but safe)
approach to Earth in 2022—as scientists measure
how the impact changes Dimorphos’s trajectory.
It’s risky to Hulk-smash an Earth-bound, extinc-
tion-level asteroid, though. “In general, when we
move an asteroid, we want to keep it in one piece,”
says planetary astronomer and DART co-lead
Andrew Rivkin, Ph.D., of Johns Hopkins Applied
Physics Laboratory. The rock could break apart
and create a wave of several smaller “city-killing”
asteroids instead. (This risk also applies to an
Armageddon-style nuclear solution, we’re told—
there are no plans to test a space nuke at this time.)
But Venditti’s team of researchers has suggested
a way to sidestep the fragmentation conundrum
with something we might call the cosmic lasso
method. As the team explained in a paper for The
European Physical Journal, this method involves
towing a smaller space rock to an oncoming aster-
oid and tethering the two. Attaching additional
mass would displace the first asteroid’s center of
mass and shift it to a new, safer orbit. “Thus, no
unwanted consequences related to fragmentation
would happen after the def lection,” Venditti and
her researchers wrote.
To test the lasso method, the team ran a series
of computer simulations targeting the potentially
hazardous asteroid Bennu. Venditti and her col-