On September 26, 2022, NASA Double asteroid redirection test (DART) collided with Dimorphos, the small moon orbiting the larger asteroid Didymos. In doing so, the mission successfully demonstrated a proposed strategy for deflecting Potentially Hazardous Asteroids (PHAs): the kinetic impact method. By October 2026, the ESA mission will Hera's Mission will rendezvous with the double asteroid system and conduct a detailed study of Dimorphos after the impact to ensure that this method of planetary defense can be repeated in the future.
However, while the kinetic method could successfully deflect asteroids from threatening Earth, it could also create debris that could hit Earth and other celestial bodies. recent studyAn international team of scientists explored how this impact test also presents an opportunity to observe how this debris could one day reach Earth and Mars in the form of meteorites. After running a series of dynamic simulations, they concluded that the asteroid's ejected debris could reach Mars and the Earth-Moon system within a decade.
The research team was led by Dr. Eloy Peña-Asensio, associate researcher at the Deep space astrodynamics research and technology (DART) group in the Milan Polytechnic InstituteHe was joined by colleagues from the Autonomous University of Barcelona, the Institute of Space Sciences (ICE-CSIS), part of the Higher Council for Scientific Researchhe Institute for Space Studies of Catalonia (IEEC) and the European Space Agency (ESA). The paper detailing their findings was recently published appeared online and has been accepted for publication by Journal of Planetary Science.
For their study, Peña-Asensio and his colleagues relied on data obtained by the Italian lightweight CubeSat for asteroid imaging (LICIACube), which accompanied the DART mission and witnessed the kinetic impact test. These data allowed the team to constrain the initial conditions of the ejection, including its trajectories and velocities, ranging from a few tens of meters per second to about 500 m/s (1,800 km/h; ~1,120 mph). The team then used NASA's supercomputers to Installation of auxiliary information and navigation (NAIF) to simulate what will happen to the ejected material.
These simulations tracked the 3 million particles created by the DART mission's impact with Dimorphos. As Peña-Asensio told Universe Today via email:
“LICIACube provided crucial data on the shape and direction of the ejecta cone immediately after the collision. In our simulation, the particles ranged in size from 10 centimeters to 30 micrometers; the lower range represented the smallest sizes capable of producing observable meteors on Earth with current technology. The upper range was limited by the fact that only ejecta of one centimeter in size were observed.”
The results indicated that some of these particles would reach Earth and Mars in a decade or more, depending on the speed at which they traveled after impact. For example, particles ejected at speeds below 500 m/s could reach Mars in about 13 years, while those ejected at speeds above 1.5 km/s (5,400 km/h; 3,355 mph) could reach Earth in as little as seven years. However, their simulations indicated that it would likely take up to 30 years before any of this ejecta would be observed on Earth.
“However, these faster particles are expected to be too small to produce visible meteors, based on initial observations,” says Peña-Asensio. “However, ongoing meteor observation campaigns will be critical to determining whether DART has created a new (man-made) meteor shower: the dimorphids. Meteor observation campaigns in the coming decades will have the final say. If these ejected dimorphid fragments reach Earth, they will pose no risk. Their small size and high speed will cause them to disintegrate in the atmosphere, creating a beautiful luminous trail in the sky.”
Peña-Asensio and his colleagues also note that future Mars observation missions will have the opportunity to witness Martian meteorites as fragments of Didymos burn up in its atmosphere. In the meantime, their study has provided the potential characteristics that these and any other meteors that burn up in our atmosphere in the future will have. This includes the direction, speed, and time of year they will arrive, which will allow any “dimorphs” to be clearly identified. This is part of what makes the DART mission and its companion missions unique.
In addition to validating a key strategy for planetary defense, DART has also provided an opportunity to model how impact ejecta might one day reach Earth and other bodies in the Solar System. As Michael Küppers, the project scientist for ESA’s Hera mission and co-author of the paper, told Universe Today via email:
“A unique aspect of the DART mission is that it is a controlled impact experiment, meaning an impact where the properties of the impactor (size, shape, mass, velocity) are precisely known. Thanks to the Hera mission, we will also have a good understanding of the properties of the target, including those of the DART impact site. Data on the ejecta come from LICIACube and from post-impact ground observations. There is probably no other planetary-scale impact with as much information about the impactor, the target, and the formation and early development of the ejecta. This allows us to test and improve our models and scaling laws of the impact process and ejecta evolution. These data provide the input data (source location, size, and velocity distribution) used by ejecta evolution models.”
Further reading: arXiv
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