What ESA mission is expected to arrive at the Didymos asteroid system in 2026 to study a double asteroid?

The European Space Agency's Hera mission is a crucial component in humanity's efforts to understand and potentially defend against asteroid impacts. This innovative spacecraft, launched in October 2024, is on its way to the Didymos asteroid system and is expected to arrive in late 2026. Its primary objective is to conduct a detailed post-impact study of Dimorphos, the smaller moonlet of the binary asteroid Didymos, which was deliberately struck by NASA's DART (Double Asteroid Redirection Test) mission in September 2022.

The Didymos system consists of a larger asteroid, Didymos, approximately 780 meters in diameter, and its smaller orbiting moonlet, Dimorphos, which is about 160 meters across. The DART mission was the world's first full-scale demonstration of asteroid deflection technology, aiming to alter Dimorphos's orbit around Didymos through a kinetic impact. Hera's arrival will allow scientists to thoroughly examine the aftermath of this collision. It will precisely measure the impact crater left by DART, determine the mass of Dimorphos, and study the moonlet's internal structure and surface properties.

By gathering this unprecedented data, Hera will provide invaluable insights into how an asteroid responds to such an impact, helping to validate and refine planetary defense models. Understanding the momentum transfer, the ejected material, and the resulting changes in the asteroid's orbit is essential for developing effective strategies to protect Earth from potential future asteroid threats. The mission also carries two small CubeSats, Milani and Juventas, which will conduct additional scientific investigations, including detailed imaging and geophysical characterization of the asteroids. This comprehensive study of the Didymos system will significantly advance our knowledge of binary asteroids and their formation, contributing broadly to asteroid science and planetary safety.