Kosmosest Newsletter #9: How To Redirect an Asteroid?
A quick overview of the space mission (DART) that changed the orbit of a space rock, and a look into such techniques. Plus in other news, Kosmosest was featured on Estonian TV!
Welcome to the 9th issue issue of Kosmosest! Today’s newsletter gives an overview of the space mission that changed the orbit of an asteroid.
Before I move on, apologies for a pause in March—PhD deadlines have been keeping me busy. On the outreach front, my path in space science and communication was featured on my native country’s TV. See the bottom of the newsletter for more.
DART 🎯
Asteroids are rocky, metallic or icy cosmic bodies with no atmosphere. Asteroids originate from the process by which planets formed from smaller clumps of material—that’s why they are often referred to as the relics of the Solar System’s origin. Sometimes, an asteroid’s orbit brings it into proximity with Earth.
In September 2022, a space mission intentionally crashed a spacecraft into asteroid Dimorphos. This was the Double Asteroid Redirection Test (DART) of NASA and partners. That asteroid did not pose threat to Earth—instead, it was used for finding out whether we'd be up for the task of changing an asteroid’s path if ever needed. The results of the impact are in, reporting success.
The technique: kinetic impactor
The target of DART is a system of two asteroids: aforementioned Dimorphos measures 160 m (525 feet) across, being the smaller component of the system. The bigger asteroid provided a frame of reference: the goal was to determine how much would the orbital speed of Dimorphos change after the impact, and it was done by measuring the change in its orbit around the larger asteroid (Didymos); see the illustration below. The diameter of Didymos is 780 meters or 0.48 miles.
DART was joined by LICIACube (Light Italian Cubesat for Imaging Asteroids), a miniature satellite contributed by the Italian Space Agency, which captured the aftermath of the impact.
The impact was also observed by numerous telescopes on Earth. Based on the observations, five studies in the journal Nature describe the final moments of the crash and its effect. The mission caused the asteroid’s orbit around the other one to shrink—Dimorphos now completes an orbit 33 minutes faster than before the impact*. While the orbit was predicted to shrink as in the illustration above, it did so about 20 minutes more than estimated.
The collision with Dimorphos ejected rock from it, which formed a tail that stretched for tens of thousands of kilometres behind the asteroid.
*Thomas, C. A. et al. Nature (2023).
What’s next?
In a longer timeframe, the European Space Agency's (ESA) Hera mission will follow up the mission with a more advanced set of instruments. They will analyze the outcome of the crash in detail, studying the crater, the structure of the two asteroids, and their chemical composition.
DART is part of a larger strategy for detecting and mitigating impact threats—which are fortunately very rare. However, the approach is that if we have space agencies, we might as well develop our capabilities to do something, should a danger be posed. An international collaboration known as AIDA (Asteroid Impact and Deflection Assessment) comprises ESA, the German Aerospace Center, Observatoire de la Côte d’Azur, NASA, and the John Hopkins University Applied Physics Laboratory. AIDA focuses on finding, tracking and characterizing the near-Earth asteroids.
Other redirection methods
Another version of the kinetic impactor: at China National Space Administration, researchers proposed deflecting asteroids with rockets (Long March 5 rocket). Their proposal was to keep the upper stage of the rocket and combine it with the spacecraft to make one large impacting body. Including the rocket’s upper stage increases the mass of the impacting body, which then allows it to move the asteroid more.
An article at space.comCrashing into the space rock wouldn’t be the optimal approach for all asteroid types. Another idea involves painting an asteroid white—this would change the way the asteroid is heated and cooled by the Sun, slowly affecting its orbit.
That idea was the winning entry in a contest back in 2012, submitted by Sung Wook Paek, an MIT graduate student at the time. The idea is linked to the Yarkovsky effect:
Credit: University of Arizona
Thanks for reading!
In other news, Kosmosest was featured on Estonian TV! In the video below, you can listen to Estonian (subtitles added) and learn about my path in space science.
Other highlights:
If you enjoy the newsletter, you can support by:
MLA