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 is still very exciting. That being the case,
would you ever want to climb into the driver’s seat of the fastest production sedan ever made
and effortlessly zoom from 0-100kmph in 1.99 seconds? With Omaze, maybe you can. Omaze is
offering a chance to win a Custom Tesla Model S-APEX. This car is top of the line, with
prestigious interior finishing and a carbon-fibre wide bodykit. It looks so good, and you won’t find
another car like it, because this custom $250k car is actually a one-of-kind. The thing I like
about Omaze is that it’s win-win, by entering you are also supporting a charity, and for this
sweepstake it’s the Petersen Automotive Museum, a non-profit that explores and presents the history
of the automobile and its impact on global life and culture. So head to Omaze.com/astrum
and enter NOW! The experience closes on January 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.