The European Space Agency’s Hera spacecraft has captured its first image showing the asteroid pair Didymos and Dimorphos as two separate objects. The observation marks a major milestone as Hera approaches the system targeted in NASA’s historic planetary-defense experiment, in which the DART spacecraft intentionally altered Dimorphos’s orbit.
Hera resolves the two asteroids
The Didymos system is currently about 197 million kilometers from Earth. Hera used its black-and-white asteroid-framing camera to take the image on the night of October 18, when the spacecraft was approximately 1,280 kilometers from its target. The image captured by Hera’s onboard camera shows Didymos and Dimorphos as distinct objects rather than a single point of light.
“This image allows us to see the smaller Dimorphos asteroid for the first time,” explains Michael Küppers. “Prior to this acquisition, the spacecraft was still resolving the Didymos system as a single point. But now, although Dimorphos consists of only about one pixel in this initial image, it is clearly well separated from its parent object.”
The milestone follows a series of maneuvers intended to slow Hera as it approaches the asteroid system. In early October, the spacecraft fired its thrusters twice, with one maneuver taking place a week after the other. The adjustments reduced Hera’s velocity relative to the asteroid to just 20 meters per second, allowing mission controllers to manage the remainder of the approach carefully.
Although the asteroids appear small in the first image, both are substantial. Dimorphos has a diameter of approximately 151 meters, roughly the size of the Great Pyramid of Giza. Didymos is about 780 meters in diameter, making it slightly shorter than Dubai’s Burj Khalifa, the world’s tallest building.
Dimorphos orbits Didymos at an average distance of just 1.15 kilometers and travels at about 18 centimeters per second.
“For the first time, we are seeing the very double asteroid system for which this mission was designed and built, through Hera’s own eyes,” said mission manager Ian Carnelli.
“As Hera approaches, our view will become clearer. We will publish the first detailed images of Dimorphos, the solar system’s first object whose orbit has been visibly altered by human action, on November 25.”
Investigating NASA’s asteroid impact
Hera’s arrival will allow scientists to examine the consequences of a groundbreaking planetary-defense experiment conducted four years ago.
On September 26, 2022, NASA’s Double Asteroid Redirection Test (DART) spacecraft intentionally collided with Dimorphos at approximately 6.1 kilometers per second. The impact sent debris as far as 10,000 kilometers into space and shortened Dimorphos’s orbit around Didymos by about 33 minutes.
The experiment demonstrated that a spacecraft can intentionally alter an asteroid’s motion, an achievement with potentially major implications for protecting Earth from future asteroid threats.
However, the collision also produced results scientists are still working to explain. The change in Dimorphos’s orbit was much greater than computer simulations had predicted, raising questions about the physics of the impact and the asteroid’s response.
Researchers do not yet know whether DART created a crater on Dimorphos or significantly changed its overall shape. Explaining why the impact was so effective will require more precise measurements of the asteroid’s composition, internal structure and mass.
Answering these questions is essential to establishing the “dynamic impact” approach as a credible planetary-defense strategy.
Hera’s detailed investigation
Over the coming months, Hera will carry out a detailed “crash site investigation” to determine what NASA’s impact did to Dimorphos.
The spacecraft will use an array of scientific instruments to study the asteroid and its surroundings. It also plans to deploy two small satellites, known as CubeSats, which are about the size of shoeboxes and will collect additional observations from closer range. The investigation is eventually expected to include a landing operation.
These measurements should help scientists understand how asteroids respond to high-speed impacts and improve predictions of how future deflection attempts might work.
Following Hera’s journey
People interested in the mission can follow Hera’s journey through the Hera Space Companion. The interactive communication platform is more mission-focused than traditional AI chatbots and is designed to make the European Space Agency’s first planetary-defense mission accessible to the public.
Source: www.sciencedaily.com