New Delhi: In 2018, the Hayabusa2 mission successfully collected samples from the asteroid Ryugu, through a touch-and-go mechanism and then delivered these to the Earth in 2020. The Japan Aerospace Exploration Agency (JAXA) decided to maximise the science returns, and extended the mission, planning a high-speed flyby of the asteroid 98943 Torifune in 2026, followed by a final encounter with the asteroid 1998 KY26 in 2031. The plan is to use the sampling mechanism to distress the surface of the asteroid and study the results. Ground based observations have now revealed that the target is three times smaller than previous estimates, and is spinning twice as rapidly.
1998 KY26 was discovered in 1998 when it came within twice the distance between the Earth and the Moon. The initial analysis indicated that the asteroid was about 30 metres across and rotated once every 10.7 minutes, which is how long a day lasts on the rock. This was the fastest-rotating asteroid known at that time. In 2024, 1998 KY26 returned to a close encounter with the Earth, and was observed by powerful ground-based telescopes, that allowed for more precise measurements of the characteristics of the asteroid, compared to the limited radar and photometry a quarter of a century prior. The observations revealed that the asteroid measures only 11 metres across, and is tumbling at 5 minutes 21 seconds. The target may prove to be challenging for Hayabusa2 to land on.
An understudied population
Such small asteroids are not well-known and are not well-studied, because they are at the detection limits of human technology, despite being abundant. Hayabusa2 will have a rare opportunity of studying a small asteroid. While scientists have not entirely ruled out that 1998 KY26 is a loosely-held together rubble pile, the observations suggest that it might be a fragment of a larger asteroid or even a planet that got battered to bits in the chaotic infancy of the Solar System. The scientists hope to gather valuable information on 1998 KY26, even if Hayabusa2 fails to land.