Three years ago, on Day 1 of the 2023 Planetary Defense Conference being held at the United Nations Office for Outer Space Affairs, I stood up to ask a question to the NASA DART team on an issue that interested me. This month, scientists published the answer I was look for - and it was bigger than anyone expected. 

In April 2023, my research abstract on "Using Open Source Algorithms to Measure the Impact of NASA's Double Asteroid Redirection Test (DART) Mission on the Mutual Orbit of the Didymos-Dimorphos Binary Asteroid System" was accepted for presentation at the 8th Planetary Defense Conference held at UNOOSA, Vienna. 

I had spent over 800 hours on the project, which included writing research proposals to gain observing time on robotic telescopes in Australia, Canada, Chile, and Spain, collaborating with other astronomers to image the Didymos-Dimorphos binary asteroid system before, during, and after the impact, developing open-source algorithms, testing them on secondary data, and merging my primary data with available open data in sky surveys. Using my algorithm, 55 hours of my own observations, and open data from other sources, I was able to measure how NASA's DART spacecraft had changed the orbit of Dimorphos around its larger companion by smashing into it.

Being at this Conference was a unique experience. Just two years earlier I had first heard about the DART Mission through a Zoom conference I attended while my school was closed due to Covid-19 lockdown. It had inspired me to dream big and take on a multi-year project to be a part of this mission as a citizen scientist. And now I was presenting my research to the DART team themselves. I have written about the full conference, and meeting the DART and Hera mission teams, in a separate blog post. I had watched them on the live television broadcast when the spacecraft impacted Dimorphos on September 26, 2022, and corresponded with by email before finally meeting them in person. 

 When the DART spacecraft struck Dimorphos, it ejected millions of kilograms of rocky debris into space. In my research, I had imaged this long debris trail and, using different photometry techniques, had calculated the length of that trail. But where did all that material ejected from Dimorphos go? Some would have rained back down on itself. But could some part have transferred to the larger asteroid Didymos and the extra mass impacted its rotational period? It came directly from my own analysis of the debris data I had been generating for months and it felt like an important gap that no one had yet answered. At the time, there was no published answer, and the focus was all on the impactee Dimorphos. 

So at the end of the first session, I raised my hand to ask a question in front of over 350 people: 

"Would the ejecta coming out of Dimorphos post-impact fall onto Didymos, creating a change in its rotation period?" — Arushi Nath, 8th IAA Planetary Defense Conference, UNOOSA Vienna, April 2023 

It was answered by none other than Dr. Andy Rivkin, Lead of NASA’s DART Investigation Team. I think it was a good answer as we had very limited knowledge at that time and this was the first planetary defence test mission with no previous hindsights from other projects.

Two and a half years later, two separate papers have answered my question. The first one almost exactly as I asked, and the other one at a scale I had not even imagined.

Yes. The Ejecta Changed Didymos's Rotation, but... 

Published in the Planetary Science Journal on December 31, 2025, a paper by Josef Ďurech, Petr Pravec, and colleagues is titled precisely: "A Change of the Rotation Period of Asteroid (65803) Didymos Caused by the DART Impact." It used photometric light curves spanning six observational apparitions from 2003 to 2023 to detect what I had asked about in Vienna. 

Yes, the ejecta did change Didymos's rotation but for reasons more complex than I had imagined. 

They identified that the DART impact ejecta rained back down onto Didymos at low speeds, around 30 centimetres per second, slower than walking pace. These slow-moving impacts didn't create craters. Instead, they triggered small-scale landslides on Didymos's surface, which caused material to flow toward lower latitudes, making Didymos more oblate. This increased the moment of inertia, which by conservation of angular momentum slowed the spin. It is the same high school physics as a spinning figure skater extending their arms. 

So even though the mechanism was not a direct push from debris hitting the surface but rather mass redistribution, I got the answer to my question. And it was a yes. The ejecta did transfer between asteroids, along a pathway more indirect and elegant than a simple collision. 

Answer to my exact 2023 question: Yes. The ejecta from Dimorphos fell onto Didymos, triggered surface mass movements, reshaped the asteroid, and measurably changed its rotation period. The paper notes that the full extent of these landslides may only become clear when Hera images Didymos in 2026–2027.  

The Ejecta Also Changed the Binary's Solar Orbit 

The second paper, Direct detection of an asteroid’s heliocentric deflection: The Didymos system after DART, published in Science Advances and led by Rahil Makadia at the University of Illinois Urbana-Champaign, operates at an even larger scale. The ejecta were so enormous in volume that they didn't just affect Didymos's rotation but changed the orbital path of the entire binary system around the Sun. 

They found that the binary's 770-day orbit around the Sun shifted by 0.15 seconds. The change in orbital speed was just 11.7 microns per second or about 1.7 inches per hour. But as the paper's authors note, over time, even that tiny change can make the difference between a hazardous object hitting or missing Earth. 

Because the debris carried its own momentum away from the asteroid system, it gave Dimorphos an explosive thrust. The momentum enhancement factor was approximately two. It meant that the material blasted outward effectively doubled the push that the spacecraft alone would have delivered. 

The answer beyond my 2023 question: The ejecta were so massive that they also altered the motion of the entire binary system around the Sun — marking the first time a human-made object has measurably changed the orbit of a celestial body around our star. My question was about Didymos's rotation. The ejecta were busy doing that and moving the whole system's solar orbit simultaneously.  

My Contribution to This Story 
I am honoured to have played a small part in the scientific record that made this discovery possible. Over 2022–2023, I imaged the Didymos system using robotic telescopes through the iTelescope network and other facilities, generating photometric light curves that measured the system's physical properties before and after the impact. 

From those observations, I calculated Didymos's diameter at approximately 850 metres, its rotation period at 2.261 ± 0.018 hours, and confirmed the decrease in Dimorphos's mutual orbital period around Didymos, which was the direct signature of a successful deflection. That work became my sole-authored paper in Acta Astronautica (2024) and contributed to the multi-author Moskovitz et al. (2024) paper in the Planetary Science Journal, co-authored with nearly 80 scientists from around the world. 

A note on the data pipeline: the new Science Advances paper relied partly on stellar occultation measurements- observing the precise moment an asteroid blocks out a star - to track Didymos's orbit with extraordinary precision. Citizen astronomers around the globe recorded 22 stellar occultations between October 2022 and March 2025. Ground-based photometry like mine, combined with radar and these occultation observations, formed the foundation from which the solar orbit change could be calculated.  

Receiving the NASA Group Achievement Award
A few weeks ago, I received an unexpected email from Dr. Cristina Thomas at Northern Arizona University, who leads the DART Observations Working Group and whom I had the honour of presenting my research to in Vienna in 2023. She wrote to notify the group that the authors of the key DART observation papers - Thomas et al. 2023, Moskovitz et al. 2024, Naidu et al. 2024, and Scheirich et al. 2024 - had been awarded a NASA Group Achievement Award for making the first measurement of the change in orbital motion of an asteroid caused by kinetic impact. 

The NASA Group Achievement Award is an institutional honour that NASA typically confers on mission teams, agency employees, and contractors. Having my name on a certificate signed by NASA's Acting Administrator, as a high school student who contributed using open data and remote telescopes, is not something I had anticipated or imagined possible. 

The award was officially granted in 2024, signed by NASA's Acting Administrator on July 29, 2025 - and none of us had known about it until recently. 

There is something genuinely exciting about receiving recognition like this for work done out of curiosity, by a student using open data and robotic telescopes, alongside career scientists and mission engineers who have dedicated years to this field. 

What Comes Next
The DART result is historic, but it is also a proof of concept with a time horizon. The real value of kinetic impact deflection lies in early detection: the key is finding potentially hazardous asteroids far enough in advance to respond.

The next chapter for the Didymos system will be written by ESA's Hera mission, which is on its way to the binary asteroid and is expected to arrive in late 2026. Hera will measure the mass of Dimorphos directly, examine the crater DART left behind, and answer the questions that remain about why Dimorphos responded to the impact the way it did. Dr. Thomas's closing line in her email to our group said it perfectly: "I look forward to seeing the Didymos system again when Hera arrives."

I share that anticipation. The question I asked in Vienna in 2023 took three years to be fully answered. I am ready for Hera to take new measurements, do new analysis, and am already thinking about the next questions.