DART



Today, Bruce Willis, Billy Bob Thornton, Liv Tyler, Ben Affleck, Robert Duval, Tea Leoni, Elijah Wood, and Morgan Freeman are proud astronauts and scientists.

Twenty-four years after the summer that gifted the world with the films Armageddon and Deep Impact, astronomers have finally started the process of catching up with late-20th-century film science. Both movies deal with impending doom to Earth, thanks to a massive celestial body. Deep Impact features a comet, while Armageddon stars an asteroid. The job of the brave and smart characters is to keep the collisions from claiming life on the planet.

On 24 November 2021, NASA launched a mission called the Double Asteroid Redirection Test (DART). The goal was to ram a spacecraft into an asteroid with the hopes of changing its course. This test could open an avenue for future astral bodies that might pose a risk to Earth.

Contrary to what you might gather from the mission’s name, DART did not aim to smash into two asteroids. Instead, they targeted a binary asteroid system, named Didymos, the Greek word for “twin.” The larger of the two bodies is known as 65803 Didymos; the smaller is called Dimorphos, which arises from the Greek word for “having two forms.”  Dimorphous orbits Didymos and it was this minor-planet moon that DART targeted for a crash landing.

The Didymos system is currently about 7 million miles away and does not cross the orbit of Earth, so neither rock poses a risk to the planet. These two asteroids were chosen as great candidates for the test, partially because we can mess with their trajectories and not endanger the planet. Another reason lies in their duality. Since Dimorphos orbits Didymos, we can use Earth-based telescopes to watch for the bigger rock to dim slightly as its moon transits. Using this method, we can attempt to quantify the effect of slamming a spaceship into Dimorphos by watching for changes in its orbit.

A diagram of the double system and the potential change in orbit - NASA
Graphic by NASA

Unlike some space missions and despite the late 2021 launch, we do not have to wait for a payoff on DART.

The long-term effects of the explosion might not present in the near future, but we already know the mission is on the way to triumph. In the past several hours, DART successfully collided with Dimorphos. 

But the best part is the spacecraft was taking pictures every second of the way. The video linked below begins with about two minutes until DART smashes into Dimorphos. From this point, the distant asteroid begins as a small, fuzzy object, before slowly growing bigger and bigger. The features of the rock start to appear. Soon, the target fills the entire view.

Then nothing.

After sending the craft 7 million miles, NASA missed their target landing spot by an estimated 18 feet!

The main portion of DART is now destroyed, but the mission does not end with its destruction. As you can see in the image above, a small satellite, called LICIA Cube, separated from the main craft on 11 September. The satellite, crafted by the Italian Space Agency, will orbit the system at a distance of 50 kilometers (31 miles), beaming information back to us about the impact and preliminary data on any changes to the orbit of Dimorphos.

Further, the European Space Agency plans a 2024 launch of a mission that will study the Didymos system. Hera will arrive there in 2027 and will provide us with a much better picture of the impact of the impact on the asteroid.

Dimorphos on the way in - NASA
The last complete image sent from DART - NASA

While the step is small, we’ve just made the first foray into planetary defense. Perhaps by 2098, the 1998 fiction of Deep Impact and Armageddon might be a possible reality.

We’ll excitedly keep tabs on this mission since we don’t wanna miss a thing.

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