Dimorphos is a small moonlet that orbits the bigger asteroid Didymos. In 2022, NASA rammed a spacecraft into Dimorphos to see if it could change its path. It worked and marked a watershed moment in planetary defense. The European Space Agency just launched the Hera follow-up mission to see what’s shaking with the binary asteroid system. Hera has a long journey ahead, but it took a moment to look back and capture a trio of lovely images of Earth.
Hera launched on Oct. 7 with an assist from a SpaceX Falcon 9 rocket. ESA turned on some of Hera’s instruments for the first time a few days after launch. Three different instruments captured images of Earth and the moon from over 870,000 miles away. It’s a fitting farewell for a spacecraft that won’t reach its destination until 2026. When it arrives at the binary asteroid, Hera will be about 121 million miles away from its home planet.
The clearest of the three images ESA released on Oct. 14 comes from Hera’s Asteroid Framing Camera, which is used for navigation and gathering data. The moon is a fuzzy speck in the upper center of the image.
The Thermal Infrared Imager also got in on the action. TIRI will essentially take the temperature of the asteroid’s surface. “By charting the ‘thermal inertia’ of surface regions—or how rapidly their temperature changes—physical properties such as roughness, particle size distribution and porosity can be deduced,” ESA said.
The third view comes from HyperScout H. HyperScout H sees a broader range of colors than the human eye. It will study the asteroid’s mineral composition. The moon is a faint blotch in the upper right of the image.
Hera is in a commissioning phase. The instruments are healthy and working as expected. Overall, the spacecraft carries 12 instruments. That includes instruments that will image the asteroid pair and measure gravity on the surface of Dimorphos. Two CubeSats—small satellites—are along for the ride. One is designed to land on the moonlet to study the surface closely.
NASA’s original Double Asteroid Redirection Test mission launched in 2021. It had a science fiction concept: to crash into an asteroid to see if it could alter the path of a space rock. NASA pulled off the feat in 2022. The impact shortened Dimorphos’ orbital period around Didymos. “This marks humanity’s first time purposely changing the motion of a celestial object and the first full-scale demonstration of asteroid deflection technology,” NASA said after the successful test.
There are no known asteroid threats to the planet in the near future, but NASA and ESA are planning ahead with the DART and Hera missions. Scientists have discovered nearly 36,000 near-Earth asteroids, but only a fraction of those are considered potentially hazardous. Researchers track known asteroids and continue to watch for and identify new space objects.
Dimorphos and Didymos are not a threat to Earth. Hera’s role is to gather more data on the impact of the DART mission “to help turn this ‘kinetic impact’ method planetary defense into a well-understood and potentially repeatable technique.” That’s how we turn science fiction into reality.
