Thanks to Omaze for sponsoring today’s video. Almost one year ago, NASA’s DART was launched. The
goal of the mission was to test a new method of planetary defence by crashing the DART spacecraft
into a Near Earth Object, or NEO, named Dimorphos. If successful, the kinetic impact would slow
Dimorphos a tiny amount and permanently alter its orbit. Why is that a big deal? Well,
over time, even small changes to an object’s orbit can have big long-term effects. Dimorphos
itself poses no threat to us, but theoretically, if we were to identify a dangerous object many
years before it reached Earth, we could deflect it far enough in advance that it would miss us
entirely. In theory, such technology could save the Earth from a cataclysmic event like Chicxulub,
the asteroid that likely killed off the non-avian dinosaurs 65 million years ago. So far, we’ve
identified about 30,000 asteroids larger than 140 meters in our planetary neighbourhood, none
of which have a chance of hitting us anytime soon (and scientists think they’ve found all the ones
larger than 10 kilometres). But with an estimated 60% of NEOs greater than 140 meters still unknown,
scientists take the threat seriously, which is why the DART mission is so significant. Now the
wait is finally over. On September 26, 2022, 10 months after its launch, DART completed
its mission when it crashed into Dimorphos. In the days and weeks since, images and data have
come pouring in, and NASA has already released its early findings. So, was DART a success? And
how, for that matter, has NASA defined “success”? I’m Alex McColgan, and you are watching
Astrum. Join me today as we learn about the latest findings of the DART mission and look
at the stunning final images the spacecraft took before its fatal crash into Dimorphos. Let’s
start with a quick recap. DART stands for Double Asteroid Redirection Test. It’s a joint
project between NASA and Johns Hopkins Applied Physics Laboratory, with international partners
in Italy, Japan and the European Space Agency. The “Double Asteroid” in DART refers to the fact
that Dimorphos is part of a binary system. It’s actually a 160-meter moonlet which orbits
the much larger 780-meter asteroid Didymos. Dimorphos has an orbital period of 11.9 hours
and maintains a distance of about 1 kilometre from Didymos. The system orbits the Sun every
2.1 Earth-years and made its approach to Earth in October 2022, coming within 10.6 million
kilometres – the closest it’s been since 2003 – meaning this was the perfect time to
visit it. Compared to other spacecraft, DART doesn’t have a lot of frills. It’s about the size
of a refrigerator and weighs just 610 kilograms, which is minuscule compared to Dimorphos’s
estimated weight of 5 billion kilograms. DART has one payload, an aperture camera called
DRACO (short for Didymos Reconnaissance and Asteroid Camera for Optical Navigation), as well
as sensors and an autonomous navigation system. It also comes paired with a small secondary
spacecraft called LICIACube – making it a binary spacecraft visiting a binary system!
Built by the Italian Space Agency, ASI, LICIACube is a small CubeSat with its own
autonomous navigation system designed to separate from DART 15 days before impact. LICIACube is
tasked with recording the impact and its aftermath with two optical cameras named LUKE and LEIA.
(Yes, you heard that correctly, Star Wars fans.) After blasting off on November 23, 2021, on a
SpaceX Falcon 9 rocket, DART spent the next 10 months in transit. In the 4 hours leading up
to impact, at a distance of 90,000 kilometres, DART’s internal navigation system took over, and
90 minutes before impact, its SMART Nav System put the spacecraft on its final trajectory. When
DART was 24,000 kilometres away, Dimorphos became visible on camera, taking up 1.4 pixels. This is
one of DRACO’s last images where you can see both Dimorphos and its parent asteroid in the same
frame. As DART hurtled closer to its target at a speed of 22,000 km per hour, Dimorphos and its
potential impact site came into spectacular view. In this image, taken just 3 seconds before
impact, you can really see how Dimorphos is a loose pile of rubble, essentially
leftover from the Solar System’s birth. This remarkable photograph is DART’s final fully
transmitted image. It was taken at a distance of 12 kilometres, a mere 2 seconds before
impact. For reference, the scale is roughly 3 centimetres per pixel. And here, finally,
is DART’s last, partially transmitted image. The downlink was interrupted by DART’s
previously scheduled, shall we say, disassembly. As strange as it sounds, this is my favourite of
these images. Its incompleteness seems to capture the drama and intensity of the moment, as though
freezing for all time the breathtaking instant when DART completed its 17.5-million-kilometre
journey in the blink of an eye. To the very end, DART did what it was designed to do with
incredible precision, and it’s a testament to the ingenuity of those of NASA. Here is the entire
sequence, sped up and played as a timelapse. The video you see corresponds to the final 5.5
minutes of DART’s final trajectory. As you’ll notice, some of the images look a bit blurred.
That’s because DART’s ion thrusters came into play, causing vibrations to the spacecraft and its
camera. This sequence is incredible to me due to the speed involved. It hit such a tiny object!
And I’m astonished some of these images are in focus at all, imagine how quickly the camera
had to adjust to the rapidly approaching object. Now, I’m sure you’re itching to know whether
the impact was successful. To relieve you of the suspense, the answer is: yes! In fact, the
early results have surpassed expectations. Before DART’s kinetic impact, NASA defined success as a
change in Dimorphos’s orbital period of at least 73 seconds. Yet based on what we know so far, the
data shows that DART shortened Dimorphos’s orbit by a full 32 minutes, from 11 hours and 55 minutes
to 11 hours and 23 minutes. Even with a margin of error of plus or minus 2 minutes, that is 25 times
NASA’s benchmark. A truly remarkable outcome. The impact released 19 gigajoules of energy, the
equivalent of nearly 5 tons of TNT, and blasted a crater up to 150 meters wide in the asteroid’s
surface, pretty big considering the moon was only 160 metres to begin with. But why did the impact
shorten Dimorphos’s orbit? Well, due to orbital mechanics, the crash pushed Dimorphos closer
to Didymos, which in turn, sped up its orbit. Scientists confirmed this finding through
observations from optical telescopes here on Earth, including the Southern Astrophysical
Research Telescope in Chile. (SOAR also happened to capture some of the very best images of the
encounter, including this breathtaking photograph of a 10,000-kilometer trail of debris two days
after impact making it look like a comet.) Because Didymos is a two-asteroid system,
its brightness fluctuates as Dimorphos passes through the shadow of its parent asteroid and
out again in front. By tracking the light curve, scientists can calculate the speed of
Dimorphos’s orbit. These results were further supported by radar data collected by
observatories in California and West Virginia. DART wasn’t the only camera watching the event
though. The closest images of the crash scene were captured by LICIACube, and they are phenomenal.
As you might recall, LICIACube separated from DART two weeks before impact to conduct its own
flyby using its autonomous navigation systems. 2 minutes and 45 seconds after DART’s impact,
LICIACube flew past Dimorphos to photograph the impact site with its evolving plumes and ejecta.
Here is an action-packed image of Dimorphos after the impact, with Didymos overexposed in the
foreground. Notice the huge plumes of material emanating from Dimorphos. Some of them seem to
be spiralling, almost like tendrils of a vine. This indicates that the material
changed directions as the plume grew. We think this phenomenon may be caused by the
composition of the asteroid, as impact tests on finer sediment mixed with coarser debris
sometimes yield similar ejection patterns. This is a more distant image, also captured by
LICIACube, with Dimorphos on the rightmost side. Notice how the asteroid itself is barely
visible due to the huge clouds of material splashed up by the impact. But LICIACube and
Earth-based telescopes weren’t the only tools observing the impact’s aftermath: Hubble and
the Webb Telescope also got in on the action. Here, you can see a spectacular series of images
from Hubble showing the progression of the plumes in size and number. Notice how some of the plumes
look like rays emanating from the asteroid. Strangely, some of these “rays” appear
curved. Why? As of now, NASA isn’t sure. While Hubble has observed the impact
from the visible spectrum of light, the Webb telescope captured its own images from
the infrared spectrum. This is pretty impressive, since Dimorphos was travelling three times faster
than Webb was meant to be able to track. The timelapse you are looking at starts right before
impact and continues until 5 hours afterwards. Notice the sudden flare of light, coinciding with
the material released from impact. I also love how the Webb images give you a great sense of the
spiralling plumes emanating from the asteroid. Over the coming weeks and months, scientists will
continue to study the data from DART’s impact. But the real investigative work will be carried
out in the future by Hera. Hera is a mission currently being developed by the European
Space Agency that will launch in October 2024. Carrying a sophisticated payload of instruments
including cameras, a spectrometer and an altimeter, HERA will intricately document the
size, shape and composition of the crater left behind by DART’s impact. It will also carry
two nanosatellites named Milani and Juventas. Most exciting of all, Hera will conduct
observations of Dimorphos’s internal and subsurface structures. This modelling will
not only advance our understanding of the binary Didymos system itself but provide a
more nuanced understanding of how a NEO’s physical characteristics influence the transfer of
momentum, as well as how kinetic energy transfers to a NEO and its ejected materials. All of this
will allow for a greater understanding of DART’s kinetic impact and provide a useful guideline for
improving deflection technologies in the future. So, there we have it: everything you
could want to know about the DART mission. Right now, we’ve barely scratched the surface
of deflection technologies, but if you look at what this mission has accomplished, it
appears the future of planetary defence has taken a bold and promising first step. So do
you think this mission was worthwhile? Do you think we’ll have to use this technology within
our lifetimes? Let me know in the comments! When DART reached Dimorphos, it was going 6.6km/s.
While we can’t quite reach those kind of numbers here on Earth, acceleration in a fast car
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27th at 11:59pm PST, you don’t want to miss this! Did you know, DART isn’t the first time we crashed
a probe into an object to see what would happen. Check out the Deep Impact video for more info! A big thanks to my patrons and members for
supporting the channel. If you want your name added to this list too, check the links in the
description. All the best, and see you next time.
