NASA will on Monday attempt a feat humanity has never before accomplished:
deliberately smacking a spacecraft into an asteroid to slightly deflect its
orbit, in a key test of our ability to stop cosmic objects from devastating
life on Earth.
The Double Asteroid Redirection Test (DART) spaceship launched from
California last November and is fast approaching its target, which it will
strike at roughly 14,000 miles (22,500 kilometers) per hour.
"It's the final cosmic collision countdown," tweeted mission control at
Johns Hopkins Applied Physics Laboratory in Maryland.
To be sure, neither the asteroid moonlet Dimorphos, nor the big brother it
orbits, called Didymos, pose any threat as the pair loop the Sun, passing
about seven million miles from Earth at nearest approach.
But NASA has deemed the experiment important to carry out before an actual
need is discovered.
If all goes to plan, impact between the car-sized spacecraft, and the
530-foot (160 meters, or two Statues of Liberty) asteroid should take place
at 7:14 pm Eastern Time (2314 GMT), viewable on a NASA livestream.
By striking Dimorphos head on, NASA hopes to push it into a smaller orbit,
shaving ten minutes off the time it takes to encircle Didymos, which is
currently 11 hours and 55 minutes—a change that will be detected by ground
telescopes in the days or weeks to come.
The proof-of-concept experiment will make a reality of what has before only
been attempted in science fiction—notably in films such as "Armageddon" and
"Don't Look Up."
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| Graphic on NASA's DART mission to crash a small spacecraft into a mini-asteroid to change its trajectory as a test for any potentially dangerous asteroids in the future. |
Technically challenging
As the craft propels itself through space, flying autonomously for the
mission's final phase, its camera system will start to beam down the very
first pictures of Dimorphos.
Minutes later, a toaster-sized satellite called LICIACube, which already
separated from DART a few weeks ago, will make a close pass of the site to
capture images of the collision and the ejecta—the pulverized rock thrown
off by impact.
LICIACube's pictures will be sent back in the next weeks and months.
Also watching the event: an array of telescopes, both on Earth and in
space—including the recently operational James Webb—which might be able to
see a brightening cloud of dust.
Finally, a full picture of what the system looks like will be revealed when
a European Space Agency mission four years down the line called Hera arrives
to survey Dimorphos' surface and measure its mass, which scientists can
currently only guess at.
Being prepared
Very few of the billions of asteroids and comets in our solar system are
considered potentially hazardous to our planet, and none are expected in the
next hundred years or so.
If DART succeeds, then it's a first step towards a world capable of
defending itself from a future existential threat, said planetary scientist
Nancy Chabot.
But "I guarantee to you that if you wait long enough, there will be an
object," said NASA's Thomas Zurbuchen.
We know that from the geological record—for example, the six-mile wide
Chicxulub asteroid struck Earth 66 million years ago, plunging the world
into a long winter that led to the mass extinction of the dinosaurs along
with 75 percent of all species.
An asteroid the size of Dimorphos, by contrast, would only cause a regional
impact, such as devastating a city, albeit with greater force than any
nuclear bomb in history.
How much momentum DART imparts on Dimorphos will depend on whether the
asteroid is solid rock, or more like a "rubbish pile" of boulders bound by
mutual gravity—a situation that's not yet known.
The shape of the asteroid is also not known, but NASA engineers are
confident DART's SmartNav guidance system will hit its target.
If it misses, NASA will have another shot in two years' time, with the
spaceship containing just enough fuel for another pass.
But if it succeeds, the mission will mark the first step towards a world
capable of defending itself from a future existential threat.
Source: AFP
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Space & Astrophysics