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Although no known asteroid poses a threat to Earth for at least the next century, the catalogue of near-Earth asteroids is incomplete for objects whose impacts would produce regional devastation 1 , 2 . Several approaches have been proposed to potentially prevent an asteroid impact with Earth by deflecting or disrupting an asteroid 1 – 3 . A test of kinetic impact technology was identified as the highest-priority space mission related to asteroid mitigation 1 . NASA’s Double Asteroid Redirection Test (DART) mission is a full-scale test of kinetic impact technology. The mission’s target asteroid was Dimorphos, the secondary member of the S-type binary near-Earth asteroid (65803) Didymos. This binary asteroid system was chosen to enable ground-based telescopes to quantify the asteroid deflection caused by the impact of the DART spacecraft 4 . Although past missions have utilized impactors to investigate the properties of small bodies 5 , 6 , those earlier missions were not intended to deflect their targets and did not achieve measurable deflections. Here we report the DART spacecraft’s autonomous kinetic impact into Dimorphos and reconstruct the impact event, including the timeline leading to impact, the location and nature of the DART impact site, and the size and shape of Dimorphos. The successful impact of the DART spacecraft with Dimorphos and the resulting change in the orbit of Dimorphos 7 demonstrates that kinetic impactor technology is a viable technique to potentially defend Earth if necessary. The impact of the DART spacecraft on the asteroid Dimorphos is reported and reconstructed, demonstrating that kinetic impactor technology is a viable technique to potentially defend Earth from asteroids.

The NASA Double Asteroid Redirection Test (DART) mission performed a kinetic impact on asteroid Dimorphos, the satellite of the binary asteroid (65803) Didymos, at 23:14 UTC on 26 September 2022 as a planetary defence test 1 . DART was the first hypervelocity impact experiment on an asteroid at size and velocity scales relevant to planetary defence, intended to validate kinetic impact as a means of asteroid deflection. Here we report a determination of the momentum transferred to an asteroid by kinetic impact. On the basis of the change in the binary orbit period 2 , we find an instantaneous reduction in Dimorphos’s along-track orbital velocity component of 2.70 ± 0.10 mm s −1 , indicating enhanced momentum transfer due to recoil from ejecta streams produced by the impact 3 , 4 . For a Dimorphos bulk density range of 1,500 to 3,300 kg m −3 , we find that the expected value of the momentum enhancement factor, β , ranges between 2.2 and 4.9, depending on the mass of Dimorphos. If Dimorphos and Didymos are assumed to have equal densities of 2,400 kg m −3 , β = 3.61 − 0.25 + 0.19 ( 1 σ ) . These β values indicate that substantially more momentum was transferred to Dimorphos from the escaping impact ejecta than was incident with DART. Therefore, the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos. The authors report on a determination of the momentum transferred to an asteroid by kinetic impact, showing that the DART kinetic impact was highly effective in deflecting the asteroid Dimorphos.

The Double Asteroid Redirection Test (DART) spacecraft successfully performed the first test of a kinetic impactor for asteroid deflection by impacting Dimorphos, the secondary of near-Earth binary asteroid (65803) Didymos, and changing the orbital period of Dimorphos. A change in orbital period of approximately 7 min was expected if the incident momentum from the DART spacecraft was directly transferred to the asteroid target in a perfectly inelastic collision 1 , but studies of the probable impact conditions and asteroid properties indicated that a considerable momentum enhancement ( β ) was possible 2 , 3 . In the years before impact, we used lightcurve observations to accurately determine the pre-impact orbit parameters of Dimorphos with respect to Didymos 4 – 6 . Here we report the change in the orbital period of Dimorphos as a result of the DART kinetic impact to be −33.0 ± 1.0 (3 σ ) min. Using new Earth-based lightcurve and radar observations, two independent approaches determined identical values for the change in the orbital period. This large orbit period change suggests that ejecta contributed a substantial amount of momentum to the asteroid beyond what the DART spacecraft carried. The 33 minute change in the orbital period of Dimorphos after the DART kinetic impact suggests that ejecta contributed a substantial amount of momentum to the asteroid compared with the DART spacecraft alone.

Some active asteroids have been proposed to be formed as a result of impact events 1 . Because active asteroids are generally discovered by chance only after their tails have fully formed, the process of how impact ejecta evolve into a tail has, to our knowledge, not been directly observed. The Double Asteroid Redirection Test (DART) mission of NASA 2 , in addition to having successfully changed the orbital period of Dimorphos 3 , demonstrated the activation process of an asteroid resulting from an impact under precisely known conditions. Here we report the observations of the DART impact ejecta with the Hubble Space Telescope from impact time T  + 15 min to T  + 18.5 days at spatial resolutions of around 2.1 km per pixel. Our observations reveal the complex evolution of the ejecta, which are first dominated by the gravitational interaction between the Didymos binary system and the ejected dust and subsequently by solar radiation pressure. The lowest-speed ejecta dispersed through a sustained tail that had a consistent morphology with previously observed asteroid tails thought to be produced by an impact 4 , 5 . The evolution of the ejecta after the controlled impact experiment of DART thus provides a framework for understanding the fundamental mechanisms that act on asteroids disrupted by a natural impact 1 , 6 . Observations with the Hubble Space Telescope reveal a complex evolution of the ejecta produced by the Double Asteroid Redirection Test (DART) spacecraft impacting Dimorphos.

On 26 September 2022, the Double Asteroid Redirection Test (DART) spacecraft struck Dimorphos, a satellite of the asteroid 65803 Didymos 1 . Because it is a binary system, it is possible to determine how much the orbit of the satellite changed, as part of a test of what is necessary to deflect an asteroid that might threaten Earth with an impact. In nominal cases, pre-impact predictions of the orbital period reduction ranged from roughly 8.8 to 17 min (refs. 2 , 3 ). Here we report optical observations of Dimorphos before, during and after the impact, from a network of citizen scientists’ telescopes across the world. We find a maximum brightening of 2.29 ± 0.14 mag on impact. Didymos fades back to its pre-impact brightness over the course of 23.7 ± 0.7 days. We estimate lower limits on the mass contained in the ejecta, which was 0.3–0.5% Dimorphos’s mass depending on the dust size. We also observe a reddening of the ejecta on impact. Optical observations of Dimorphos, a satellite of the asteroid 65803 Didymos, before, during and after the impact of the DART spacecraft, from a network of citizen science telescopes across the world are reported.

The Double Asteroid Redirection Test (DART) had an impact with Dimorphos (a satellite of the asteroid Didymos) on 26 September 20221. Ground-based observations showed that the Didymos system brightened by a factor of 8.3 after the impact because of ejecta, returning to the pre-impact brightness 23.7 days afterwards2. Hubble Space Telescope observations made from 15 minutes after impact to 18.5 days after, with a spatial resolution of 2.1 kilometres per pixel, showed a complex evolution of the ejecta3, consistent with other asteroid impact events. The momentum enhancement factor, determined using the measured binary period change4, ranges between 2.2 and 4.9, depending on the assumptions about the mass and density of Dimorphos5. Here we report observations from the LUKE and LEIA instruments on the LICIACube cube satellite, which was deployed 15 days in advance of the impact of DART. Data were taken from 71 seconds before the impact until 320 seconds afterwards. The ejecta plume was a cone with an aperture angle of 140 ± 4 degrees. The inner region of the plume was blue, becoming redder with increasing distance from Dimorphos. The ejecta plume exhibited a complex and inhomogeneous structure, characterized by filaments, dust grains and single or clustered boulders. The ejecta velocities ranged from a few tens of metres per second to about 500 metres per second.

On September 26 th 2022, LICIACube monitored Double Asteroid Redirection Test (DART) mission impact on asteroid Dimorphos, which is the smaller component of a binary asteroid system. These close observations revealed the impact ejecta features of the first planetary defence test with a kinetic impactor.

The Chicxulub asteroid impact triggered mass extinction, mega-tsunamis and a spell of global warming that lasted for around 100,000 years. Although the recent Double Asteroid Redirection Test mission by NASA demonstrated that near-Earth objects can be successfully targeted, deflecting the most dangerous asteroids will require energy concentrations akin to nuclear explosions. However, targets suitable for practice missions are scarce. Here we demonstrate the simulation of asteroid deflection with an X-ray pulse from a dense argon plasma generated at the Z machine, a pulsed power device at Sandia National Laboratories. We use so-called X-ray scissors to place surrogate asteroidal material into free space, simultaneously severing supports and vapourizing the target surface. The ensuing explosion accelerates the mock asteroidal material in a scaled asteroid intercept mission. Deflection velocities of around 70 m s –1 for silica targets agree with radiation-hydrodynamic model predictions. We scale these results to proposed interceptor energies and predict that asteroids up to a diameter of (4 ± 1) km can be deflected with this mechanism, showing a viable way to prepare for future planetary defence missions. Deflection is one of the options discussed for preventing catastrophic collisions of asteroids with Earth. Now, a megajoule-class X-ray pulse is used to simulate such scenarios, demonstrating that it is a viable strategy at higher interceptor energies.

Spacecraft observations revealed that rocks on carbonaceous asteroids, which constitute the most numerous class by composition, can develop millimeter-to-meter-scale fractures due to thermal stresses. However, signatures of this process on the second-most populous group of asteroids, the S-complex, have been poorly constrained. Here, we report observations of boulders’ fractures on Dimorphos, which is the moonlet of the S-complex asteroid (65803) Didymos, the target of NASA’s Double Asteroid Redirection Test (DART) planetary defense mission. We show that the size-frequency distribution and orientation of the mapped fractures are consistent with formation through thermal fatigue. The fractures’ preferential orientation supports that these have originated in situ on Dimorphos boulders and not on Didymos boulders later transferred to Dimorphos. Based on our model of the fracture propagation, we propose that thermal fatigue on rocks exposed on the surface of S-type asteroids can form shallow, horizontally propagating fractures in much shorter timescales (100 kyr) than in the direction normal to the boulder surface (order of Myrs). The presence of boulder fields affected by thermal fracturing on near-Earth asteroid surfaces may contribute to an enhancement in the ejected mass and momentum from kinetic impactors when deflecting asteroids. Here, authors study boulders’ fractures on S-type asteroid, Dimorphos, and show that their size-frequency distribution and orientation are consistent with formation through thermal fatigue. Such fractures seem to propagate horizontally much faster (~kyr) than normal to the boulder’s surface (~Myr).

NASA’s Double Asteroid Redirection Test (DART) mission intentionally impacted the asteroid Dimorphos on September 26, 2022, and this kinetic impact changed Dimorphos’ orbit around its binary companion Didymos. This first planetary defense test explored technological readiness for this method of asteroid deflection.