The Light Italian CubeSat for Imaging of Asteroids (LICIACube) has returned a series of close-up images of the asteroid Dimorphos, following last week’s successful impact of the Double Asteroid Redirect Test (DART) probe. LICIACube was built and operated by the Italian Space Agency (ASI) and was designed to capture post-impact images for the DART team, to help assess the effects of the impact.
The initial set of images received after impact show a dramatic plume of dust and debris. They were captured about 2 minutes and 45 seconds after impact, during a flyby of Dimorphos. This same plume was clearly visible to ground-based telescopes. Future images should hopefully reveal details of the impact crater and could help researchers better understand the composition of the small asteroid. The shoebox-sized CubeSat will spend the next few weeks sending the remaining data back to Earth. If he has enough propellant left, he can hopefully return for a second flyby.
The DART mission was launched in November 2021, to test the feasibility of redirecting an asteroid by crashing into it. If a large body were to be discovered in our solar system that is on a collision course with Earth, we might be able to knock it off course. In theory, even a small space probe crashing into the object at a high enough speed should alter its trajectory enough to prevent it from crashing into Earth later, provided it is done early enough. But theory is not enough, which is why the DART mission was developed to test and confirm that it can be done and will work as intended.
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The DART target, Dimorphos, is a small asteroid with a length of about 160 meters. It orbits a larger companion named Didymos, with a diameter of about 780 meters. The two objects take 11 hours and 55 minutes to orbit each other, at a distance of 1.18 kilometers. If the theoretical models of the impact are correct, this orbital period should have been shortened by a few minutes. This estimate is only an approximation, however, based on the probable masses of the two objects.
The DART spacecraft, weighing 570 kg, crashed into Dimorphos on September 26, 2022, at around 22,500 km/h. The impact is the first test of the “Kinetic Impact” method of redirecting asteroids. If astronomers were ever to detect an asteroid on a collision course with Earth, and if it is massive enough to pose a threat to human life or property, the best action to take would be to alter its trajectory so that the collision never occurs. The kinetic impact method of redirection simply involves shooting a heavy object at it, giving it enough kinetic energy to push it into a slightly different orbit. Because asteroids are so massive, even a very powerful impact would probably only change its velocity by a very small amount, but even a small deflection would be enough to guarantee failure if it happens early enough.
Didymos and Dimorphos couple occupy an elliptical orbit around the Sun. Its perihelion, or lowest point in its orbit, is slightly farther from the Sun than Earth, and its highest point, or aphelion, is a little past Mars. This orbit is inclined to the ecliptic plane by about 3 degrees, so it never intersects the trajectories of Earth or Mars. This means that the binary asteroid system Didymos will never approach Earth and pose no risk of collision. The DART impact would have changed Dimorphos’ speed by only a fraction of a percent, far too little to create a risk of collision with Earth or any other planet.
LICIACube is the first Italian deep space mission. It was entirely built and is operated by ASI. The small spacecraft was transported by DART to its current location and is currently positioned near Didymos and Dimorphos, two objects orbiting each other to form a double asteroid orbiting the Sun.
Its mission was to capture images of both bodies through all phases of the DART mission and send that data back to the mission’s ground controllers. The images are intended to help measure how Dimorphos’ orbit has changed. They will also show us what effect the impact has on the asteroid itself and will likely provide useful data for scientists who would like to better understand the composition of the asteroid itself.
Other methods being explored to protect Earth from an asteroid impact include landing on the asteroid and installing a rocket engine; station a spacecraft near the object to gravitationally deflect it; or even paint one side of the asteroid so that it is heated unevenly by the Sun, causing it to emit more thermal radiation on one side than the other, creating a tiny amount of thrust! All of these ideas are sound in theory and may even be practical under varying circumstances, but the kinetic impact method has the advantage of simplicity and does not require the development of any new technology.
For more information on DART, visit the mission overview page at https://dart.jhuapl.edu/
And for more information about LICIACube: https://www.ssdc.asi.it/liciacube/