HERA

Space Safety

Once NASA's DART mission impacted Dimorphos, a new space mission called Hera will return to Didymos binary system in December 2026 to study carefully the effects of DART's impact, and measure the physico-chemical properties of both asteroids. The mission will also test a myriad of new technologies: from testing autonomous navigation around an asteroid up to operating instruments under low gravity proximity operations. Hera will be the first probe to rendezvous with a binary asteroid system to test and develop Planetary Defence goals.

Examining the first test of asteroid deflection

Hera is a European Space Agency (ESA) mission that will visit the binary asteroid Didymos to map Didymos and Dimorphos at high resolution at the same time it makes several technological demonstrations under low-gravity conditions. As an example, it is planned to use CubeSat technologies to collect complementary information on this binary asteroid. The main goal of Hera is obtaining clues on the nature and structure of both asteroids in order to use that knowledge to mitigate future encounters with hazardous asteroids.

The relevance of Hera also lies in the fact that the effects of DART’s impact on the binary system require to be quantified carefully. After the impact, Dimorphos orbital period was shortened in 33 minutes, but the physical reasons behind such an historic result need a more comprehensive compilation of the physico-chemical and surface properties of Dimorphos. We know that the target asteroid was a rubble pile, but many aspects on the nature and inner structure of this potentially hazardous asteroid remain to be quantified. This is why ESA is building Hera: to study the impact crater and its consequences on Dimorphos, and the Didymos system as a whole. Likewise, Hera will be able to assess its shape and structure with precision, at the same time that it will bring state-of-the-art instrumentation to characterise its composition, structure and nature.

Dimorphos (seen right), the small moon of the binary asteroid Didymos (seen left), while ESA’s Hera spacecraft takes a close-up survey of the crater. Credits: ESA-Science Office

ICE-CSIC's participation

As part of the Investigation Team we are performing spectroscopic laboratory studies of chondritic meteorites and other physical and mineralogical experiments to infer the physico-chemical properties of the two rubble pile asteroids forming the Didymos system. Our laboratory experiments have demonstrated that ordinary chondrites are excellent laboratory proxies of the rock-forming materials of both asteroids forming the Didymos system.

Hera mission will characterise the inner structure and surface of both asteroids, allowing significant scientific results on the collisional processing of these asteroids, an aspect with relevant know-how in our institute. Being exposed to interplanetary space during aeons, asteroid materials are affected by thermal changes, extreme irradiation fluxes and continuous impacts with meteoroids. The flux of metre-sized projectiles also excavates large craters, contributing to the so-called collisional gardening that alters the primordial surface mineralogy. Over time the surfaces are eroded by these projectiles and become formed by brecciated materials that contain implanted foreign clasts. Over time all these space weathering processes change the physico-chemical properties of hazardous asteroids, including their reflectance behaviours, as Chelyabinsk meteorite exemplified. Then, our laboratory studies of the reflectance spectra of a diversity of chondritic meteorites is useful in the interpretation of DART observations. The multidisciplinary nature of the research group on Meteorites, Minor Bodies and Planetary Sciences lead by Dr. Trigo-Rodríguez will contribute to get a better understanding of the challenging properties that Potentially Hazardous Asteroids have, and we hope it gives clues to improve and develop new mitigation strategies.