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Last week, you probably heard that NASA
slammed a spacecraft into an asteroid, on purpose.
After hurtling through space at nearly 23,000 kilometers per hour,
NASA’s Double Asteroid Redirection Test,
otherwise known as DART, smashed into the tiny asteroid Dimorphos,
which is in orbit around a larger space rock called Didymos.
And humanity collectively held its breath while watching the live streamed event.
Observatories around the world and in space tuned in as well.
That included big fancy space telescopes like the Webb and Hubble,
but it’s those ground-based observatories
that are set to play a pivotal role in what comes next!
DART is a piece of NASA’s overall planetary defense strategy,
a way to protect Earth from dangerous collisions with large space rocks.
But to be clear, there is no immediate threat of an asteroid slamming into Earth.
NASA is just planning ahead.
DART’s mission was to show how much one little spacecraft could shift an asteroid’s path.
But its impact will also inform astronomers of Dimorphos’s composition.
And knowing an asteroid’s composition is crucial to preventing a collision with Earth.
Asteroids of the same size come in a range of masses
depending on what they’re made of,
from super dense iron and nickel to lighter stuff like stone and clay.
And the more massive an asteroid is, the harder it is to move out of the way.
But also, that material could be packed more or less tightly,
which affects how much debris gets thrown into space after an impact.
The fluffier an asteroid is, the more stuff gets ejected,
and the /easier/ it is for a spacecraft like DART to move that asteroid.
Both the Webb and Hubble space telescopes
revealed some pretty impressive debris plumes after DART collided with Dimorphos.
But this is where ground-based telescopes are key to the DART mission.
Astronomers will use them to track the light of those plumes.
And that light will reveal the asteroid’s composition and fluffiness.
Meanwhile, ground-based telescopes will also track how Dimorphos’s orbit
has shifted around Didymos.
As Dimorphos passes in front of and behind its larger sibling,
the light we see from Earth periodically dims and brightens.
How quickly that change happens tells us how long one orbit takes.
And astronomers have spent so much time observing this system
that they have the orbit of Dimorphos calculated down to the /minute/.
Now that DART has made its impact,
they’ll be able to measure how much that orbital period has changed.
And because the asteroid is so bright and so close to Earth…
a mere 11 million kilometers…
it’s not just the telescopes at massive research facilities that can track the impact.
Amateur astronomers, and even middle schools can get in on the observation action,
and contribute their data to the worldwide mission.
But even after all that info rolls out, we’re not done with Dimorphos.
In 2024, the European Space Agency plans
to launch a spacecraft named Hera to give the world a closer follow-up.
Hera will perform detailed surveys of both Dimorphos and Didymos,
focusing on the crater left by DART
and getting a precise determination of the asteroid’s mass.
DART is just the beginning of an international collaboration between multiple organizations,
all united with the goal of keeping Earth safe from another mass extinction event.
Speaking of asteroids and extinction events…
A paper published this week in AGU Advances presents how
the Chicxulub impact 66 million years ago…
the one associated with the death of all the non-avian dinosaurs…
triggered a /monstrous/ tsunami that scraped up the ocean floor around the entire globe.
The researchers used a computer to model the asteroid impact event
and the subsequent response of the ocean water it slammed into. ~
While the asteroid’s impact crater now resides partially beneath the Yucatan Peninsula,
the authors estimate that the asteroid smacked
into ocean water that was between 100 and 200 meters deep.
And the energy of the resulting tsunami was up to 30,000 times
greater than that of the 2004 Indian Ocean tsunami,
which is one of the largest in recorded history.
The waves from the Chicxulub impact would have towered over the land,
reaching heights of over 100 meters in what is now the Gulf of Mexico,
and over 10 meters as they spread to the Atlantic and Pacific coastlines.
But the team also needed to see if there was evidence
for their computer-modeled tsunami in the geologic record.
So they reviewed published records of marine sediments at over 100 sites worldwide,
collected during ocean-drilling projects.
They focused on sediments that were deposited just before
and after the asteroid’s impact by locating the K-Pg band,
which is a thin layer of sediment that contains more of the element Iridium. ~
This Iridium comes directly from the asteroid,
and the band marks the end of the Cretaceous period.
At these sites, the researchers found either a gap
in the sedimentary record or a bunch of older sediments mixed up with newer stuff.
Meaning something big had come along to remove
an entire layer from the geologic record, or at least churn it all up.
In particular, the team noted highly mixed-up sediments
on the eastern shores of New Zealand's north and south islands,
which are more than 12,000 kilometers from the asteroid’s impact site.
These jumbled sediments were originally thought to be the result of local tectonic activity.
But after evaluating the age of the deposits and their location,
which is right in the path of their modeled tsunami,
the researchers suspect they were transported there by this massive wave.
This study is a good example of models and verification data matching up nicely,
which doesn’t always happen in scientific research.
It also helps us better understand the impacts
that a massive asteroid slamming into our planet
could bring to Earth beyond killing off a bunch of life.
While it’s too bad that modern-day technology
wasn’t around to keep our planet safe from an impact 66 million years ago,
better understanding the effects of a large asteroid slamming into Earth
can help humans protect themselves from any future asteroid collisions.
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