On September 26, 2022, NASA’s Double Asteroid Redirection Test (DART) intentionally slammed into Dimorphos, a moonlet of the asteroid Didymos. According to NASA, the impact altered Dimorphos’ orbit around its parent asteroid by 32 minutes.
This image from ASI’s LICIACube satellite shows the plumes of ejecta streaming from Dimorphos after DART made impact with it on September 26, 2022. Each rectangle represents a different level of contrast in order to better see fine structure in the plumes. By studying these streams of material, we will be able to learn more about the asteroid and the impact process. Image credit: ASI / NASA / Johns Hopkins Applied Physics Laboratory.
“All of us have a responsibility to protect our home planet. After all, it’s the only one we have,” said NASA Administrator Bill Nelson.
“This mission shows that NASA is trying to be ready for whatever the Universe throws at us.”
“ NASA has proven we are serious as a defender of the planet. This is a watershed moment for planetary defense and all of humanity, demonstrating commitment from NASA’s exceptional team and partners from around the world.”
Prior to DART’s impact, it took Dimorphos 11 hours and 55 minutes to orbit Didymos.
The impact altered Dimorphos’ orbit by 32 minutes, shortening it to 11 hours and 23 minutes. This measurement has a margin of uncertainty of approximately plus or minus 2 minutes.
“This result is one important step toward understanding the full effect of DART’s impact with its target asteroid,” said Dr. Lori Glaze, director of NASA’s Planetary Science Division at NASA Headquarters.
“As new data come in each day, astronomers will be able to better assess whether, and how, a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if we ever discover one headed our way.”
This chart offers insight into data the DART team used to determine the orbit of Dimorphos after impact — specifically, small reductions in brightness due to eclipses of Didymos and Dimorphos. The new observations show the Dimorphos eclipses occur at different times (green arrows) than if the period were unchanged (gray arrows). The top timeline shows observations the DART team used to determine Dimorphos’ new orbital period, with two sets of that data (from September 29, 2022, and October 4, 2022) shown in detail. The observed decreases in relative brightness for each night’s dataset correspond to Dimorphos eclipses from a new orbital period of 11 hours and 23 minutes — demonstrating that the eclipse timing differs from pre-impact period of 11 hours and 55 minutes. Image credit: NASA / Johns Hopkins Applied Physics Laboratory / Astronomical Institute of the Academy of Sciences of the Czech Republic/Lowell Observatory / JPL / Las Cumbres Observatory / Las Campanas Observatory / European Southern Observatory Danish telescope / University of Edinburgh / The Open University / Universidad Católica de la Santísima Concepción / Seoul National Observatory / Universidad de Antofagasta / Universität Hamburg / Northern Arizona University.
The DART team is still acquiring data with ground-based observatories around the world.
Focus now is on shifting toward measuring the efficiency of momentum transfer from DART’s roughly 22,530 km per hour (14,000 mph) collision with its target.
This includes further analysis of the ejecta — tons of asteroidal rock displaced and launched into space by the impact.
The recoil from this blast of debris substantially enhanced DART’s push against Dimorphos — a little like a jet of air streaming out of a balloon sends the balloon in the opposite direction.
To successfully understand the effect of the recoil from the ejecta, more information on of the asteroid’s physical properties, such as the characteristics of its surface, and how strong or weak it is, is needed. These issues are still being investigated.
“DART has given us some fascinating data about both asteroid properties and the effectiveness of a kinetic impactor as a planetary defense technology,” said DART coordination lead Dr. Nancy Chabot, a researcher at the Johns Hopkins Applied Physics Laboratory.
“The DART team is continuing to work on this rich dataset to fully understand this first planetary defense test of asteroid deflection.”
For this analysis, the astronomers will continue to study imagery of Dimorphos from DART’s terminal approach and from ASI’s Light Italian CubeSat for Imaging of Asteroids (LICIACube) to approximate the asteroid’s mass and shape.
Roughly four years from now, ESA’s Hera project is also planned to conduct detailed surveys of both Dimorphos and Didymos, with a particular focus on the crater left by DART’s collision and a precise measurement of Dimorphos’ mass.
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This article is based on text provided by the National Aeronautics and Space Administration.
