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You can go to linode.com/scishow to learn more and get a $100 60-day credit  on a new Linode account. [ INTRO ] 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. Modern-day technology rocks! That’s why we’re proud to have Linode  supporting this SciShow News video.

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