Familiarity with the articles recently published in Nature and arXiv, which discuss the results of the DART mission, reveals the following. Firstly, the key data interpretations and the validity of the conclusions are not convincing without taking into account the results of direct ground-based observations of the collision process and the subsequent ejection of the comparatively large asteroid fragments. Among the published results of such direct observations, the most informative data is contained in a video animation compiled from a large series of photographs obtained using the telescope of the University of Hawaii in South Africa. Particularly, see the second part of the video, around the 50th second:
View: https://www.youtube.com/watch?v=bfqVqOl9S9w
An analysis of this 500-fold time-compressed video animation provides evidence that the decrease in the asteroid's orbital period declared by the authors of the above articles, which follows from photometric observations of mutual occultations-eclipses and radar data, may have an alternative explanation. Specifically, it could be a consequence of geometric-photometric distortions caused by the essential asymmetric increase of the observed Dimorphos's size, which remained unchanged, while the small-sized component of the wide fan-shaped ejecta continued to move away. Since the brightness and scale of the background star images did not change, the metamorphosis of the asteroid's image cannot be attributed to inaccuracies or errors. This phenomenon is the appearance of an asymmetric and optically dense "cloud" of mini-satellites in orbits around Dimorphos, into which relatively larger fragments ejected at lower velocities turned.
Observations of only two successive occultations-eclipses during Dimorphos's orbital semi-period (Thomas et al., 2023) are able to create the illusion of a shortening of its orbital period due to the displacement of the photometric center of the distorted asteroid image relative to its center of mass. Estimates of the orbital period of the "cloud" of mini-satellites located at heights of several tens of meters above the surface of Dimorphos (according to the video animation) lead to its values being several times larger than the orbital period of the asteroid itself. Therefore, during these events, occurring about 6 hours apart, the "cloud" of mini-satellites will be located on opposite sides of the asteroid most of the time, which is moving in opposite visible directions. Finally, according to estimates, this should manifest as an opposite temporal shift in the positions of the brightness minima. The summarized shift will be close to the declared decrease in the orbital period of Dimorphos. Conversely, when using observational data of the same type occultations-eclipses, occurring only once during its orbital period, such a relative shift is unlikely, despite the presence of a distorting asymmetry in the visible image of the asteroid.
Additionally, the assertion that the ejection was much more efficient in transferring the pushing impulse compared to the actual impact also raises doubts. According to Li et al. (2023) and the above video animation, the mean initial speed of the wide fan-shaped ejection was around several meters per second. Therefore, with an estimated total ejecta mass of up to 1 million kg, its momentum was comparable to the impactor's. Moreover, it is clear that only a small area near the impact direction (i.e., close to the axis of the ejection cone) can effectively act on an asteroid. At the same time, the rest of the ejecta regions significantly compensated for each other's impulse transfer abilities, which is problematic in itself for a totally inelastic collision with a loose rubble pile asteroid.
In summary, at this point, the success of this generally complex and beautiful space experiment can be considered questionable in terms of its main stated goals. The interpretation of the photometric and radar observations in the published articles lacks the consideration of the direct ground-based observations of the collision process and the subsequent ejection of asteroid fragments, which are crucial for understanding the observed effects. The evidence provided by the video animation suggests an alternative explanation for the decrease in the asteroid's orbital period. The assertion that the ejection was much more efficient in transferring the pushing impulse than the actual impact also raises doubts. These issues highlight the need for further investigation and the integration of all available data for a comprehensive understanding of the DART mission's results.
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