New Delhi, March 24 -- In late 2024, astronomers spotted asteroid 2024 YR4 on a trajectory that could potentially threaten Earth. This observation triggered a fervid series of observations of the object - possibly as big as a football field - to determine that it will not hit. However, an impact on the moon cannot be ruled out.

Then in January of this year, the near approach of an asteroid perhaps a million times more massive went almost unnoticed.

Asteroid 2024 YR4 has a diameter between 40 to 90 metres and was referred to as a "city-killer" capable of causing regional damage and affecting the climate; the larger asteroid, 887 Alinda, is over four kilometres in diameter and could cause a global extinction event.

Alinda remains just ou...