What European Space Agency (ESA) mission is expected to arrive at the double asteroid Didymos in November 2026 to study the impact left by NASA's DART mission?

The European Space Agency's (ESA) Hera mission is the spacecraft expected to arrive at the double asteroid Didymos in November 2026. Its primary objective is to thoroughly investigate the impact left by NASA's Double Asteroid Redirection Test (DART) mission. Hera will conduct a detailed post-impact survey, providing crucial data that will transform asteroid deflection by kinetic impact from an experimental concept into a reliable method for safeguarding Earth.

The DART mission, launched by NASA in November 2021, was the world's first full-scale planetary defense technology demonstration. In September 2022, DART intentionally crashed into Dimorphos, the smaller moonlet of the binary asteroid system Didymos. This impact successfully altered Dimorphos' orbit around the larger Didymos by 32 minutes, demonstrating that a kinetic impactor can indeed change the trajectory of a celestial object. Neither Didymos nor Dimorphos posed a threat to Earth, making them an ideal target for this planetary defense test.

Hera, which launched in October 2024, will provide an up-close examination of the impact site, measuring the size and morphology of the crater created by DART and assessing the momentum transferred. It will also study the physical properties and internal structure of both Didymos and Dimorphos, including their surface characteristics and porosity. This detailed information is vital for refining future planetary defense strategies and increasing our understanding of asteroids, which are remnants from the early solar system. Hera will also deploy two CubeSats, Milani and Juventas, to conduct additional scientific measurements, including radar sounding of an asteroid's interior for the first time.