Encounter circumstances of asteroid 99942 Apophis with the catalogue of known asteroids (2403.00541v1)

Abstract: Asteroid 99942 Apophis will pass near the Earth in April 2029. Expected to miss our planet by a safe margin, that could change if Apophis' path was perturbed by a collision with another asteroid in the interim. Though the statistical chance of such a collision is minuscule, the high risk associated with Apophis motivates us to examine even this very unlikely scenario. In this work, we identify encounters between known asteroids and Apophis up to April 2029. Here we show that Apophis will encounter the 1300 meter diameter asteroid 4544 Xanthus in December 2026. Their Minimum Orbit Intersection Distance (MOID) is less than 10,000 km, with Xanthus passing that closest point just four hours after Apophis. Though a direct collision is ruled out, the encounter is close enough that material accompanying Xanthus (if any) could strike Apophis. We also identify other asteroid encounters that deserve monitoring.

• The paper evaluates pre-Earth flyby collision risks by quantifying metrics like the Minimum Orbit Intersection Distance and time offsets between Apophis and other asteroids.
• The authors compare predictions from JPL and NeoDys databases, revealing discrepancies caused by observational uncertainties and differing orbit determination methodologies.
• The study recommends continued telescopic monitoring and integration of high-precision astrometric data to refine orbital predictions and enhance planetary defense strategies.

Encounter Circumstances of Asteroid 99942 Apophis with the Catalogue of Known Asteroids

The paper by Wiegert and Hyatt provides a comprehensive analysis of potential encounters between asteroid 99942 Apophis and other known asteroids, leading up to Apophis’ significant Earth flyby in 2029. The authors meticulously assess the prospects of an impact event due to perturbations induced by possible collisions with other minor bodies.

The primary focus of this research is to quantify the probability of Apophis colliding with another asteroid before its close approach to Earth. Given Apophis’ notoriety as a potentially hazardous asteroid, even minuscule perturbations to its trajectory could have significant implications. This paper evaluates these scenarios by identifying the Minimum Orbit Intersection Distance (MOID) and the time offset between Apophis and other asteroids. Such metrics provide crucial insight into whether two celestial bodies might occupy the same spatial region at similar times.

A key finding is the December 2026 near-encounter between Apophis and the 1300-meter diameter asteroid 4544 Xanthus. Despite a non-collisional outcome—the MOID being less than 10,000 km, with Xanthus passing four hours post-Apophis—this proximity suggests monitoring for material detected along Xanthus’ trajectory, which could impact Apophis.

Several other objects were found to possess moderate probabilities of a close approach. Notably, asteroids 2009 JG2, 2016 FB12, and 2022 KN3 exhibited encounter probabilities ranging from nominal to moderate based on their observational uncertainties. Furthermore, the paper emphasizes differences between data derived from the JPL and NeoDys databases, illustrating the variances in predicted outcomes due to different observational inputs and methodologies. Such discrepancies highlight areas for potential improvement in observational data acquisition and orbit determination methods.

Moreover, the paper identifies asteroids with significant uncertainties in their orbital elements, such as 2016 CL18, which showed conflicting approach scenarios between the datasets. The authors suggest additional telescopic observations and archival data analysis to refine these orbits and further mitigate any unreported uncertainties.

While the probabilistic chance of Apophis colliding with another known asteroid or associated debris is low, the paper underscores the high stakes implicated by even minor orbital perturbations. The authors advocate for continued monitoring of both Apophis and potentially pertinent minor bodies to maintain an accurate risk assessment landscape. They suggest targeted observational campaigns during critical encounter windows where perturbative interactions are plausible, both from material potentially accompanying asteroids and from unmodelled gravitational influences.

Future developments could benefit from the integration of high-precision astrometric data, further reducing the uncertainties in asteroid orbits and improving the robustness of collision likelihood forecasting. Moreover, advancements in techniques such as radar imaging could play a critical role in enhancing orbit determination for poorly constrained objects.

In summary, the investigation by Wiegert and Hyatt provides a detailed methodological approach to assessing collision probabilities between Apophis and cataloged solar system bodies. The paper contributes valuable insights within the framework of planetary defense and encourages refining and extending current prediction methodologies to encompass even the most improbable scenarios while preserving scientific scrutiny and accuracy.