After NASA deliberately toss a car-sized spacecraft into an asteroid next week, it’s up to the European Space Agency’s Hera mission to investigate the “crime scene” and uncover the secrets of these potentially devastating space rocks.
NASA’s Double Asteroid Redirection Test (DART) aims to collide with the asteroid moon Dimorphos Monday night, hoping to slightly alter its orbit — the first time such an operation has been attempted.
While Dimorphos is 11 million kilometers (6.8 million miles) away and poses no threat to Earth, the mission is a test flight in case the world needs to divert an asteroid from our side one day.
Astronomers around the world will be watching the impact of DART and its effect will be closely monitored to see if the mission passed the test.
After that, the European Space Agency’s Hera mission, named after the ancient Greek queen of the gods, will follow in his footsteps.
The Hera spacecraft is scheduled to launch in October 2024, with the goal of arriving at Dimorphos in 2026 to measure the exact impact of DART on the asteroid.
But scientists are excited not only to see DART’s crater, but to explore an object very much out of this world.
‘A new world’
Dimorphos, which orbits a larger asteroid Didymos as they race through space together, not only provides a “perfect test opportunity for a planetary defense experiment, but it’s also a completely new environment,” said Ian Carnelli, mission manager for ESA’s Hera.
Hera will be loaded with cameras, spectrometers, radars and even toaster-sized nanosatellites to measure the asteroid’s shape, mass, chemical composition and more.
NASA’s Bhavya Lal said understanding the size and composition of such asteroids was critical.
“If an asteroid is composed of, for example, loose gravel, the approaches to disrupting it may be different than if it were metal or some other type of rock,” she told the International Astronautical Congress in Paris this week.
So little is known about Dimorphos that scientists will discover “a new world” along with the public on Monday, said Patrick Michel, principal investigator of the Hera mission.
“Asteroids aren’t boring space rocks — they’re super exciting because they have great diversity” in size, shape and composition, Michel said.
And because they have a low gravity compared to Earth, matter can behave very differently there than expected.
“Unless you touch the surface, you cannot know the mechanical reaction,” he said
‘Behaved almost liquid’
For example, when a Japanese probe dropped a small explosive near the surface of the Ryugu asteroid in 2019, it was expected to create a two or three-meter crater. Instead, it shot a 50-meter-long hole.
“There was no resistance,” Michel said.
“The surface behaved almost like a liquid,” rather than solid rock, he added. “How weird is that?”
One way the Hera mission will test Dimorphos is to land a nanosatellite on the surface, in part to see how much it bounces.
Binary systems such as Dimorphos and Didymos represent about 15 percent of known asteroids, but have not yet been explored.
At just 160 meters in diameter — about the size of the Great Pyramid of Giza — Dimorphos will also be the smallest asteroid ever studied.
Learning about the impact of DART is important not only for planetary defense, Michel said, but also for understanding the history of our solar system, where most cosmic bodies were formed by collisions and are now littered with craters.
That’s where DART and Hera were able to shine a light not only on the future, but also the past.