The Light Italian CubeSat for Imaging of Asteroids (LICIACube) has returned a series of close-up images of the asteroid Dimorphos, after 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 imagery for the DART team, to help assess the effects of the impact.
The initial set of images received after the impact, show a dramatic plume of dust and debris. They were captured about 2 minutes and 45 seconds after the impact, during a fly-by 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 little asteroid. The shoebox-sized CubeSat will spend the next few weeks sending the remaining data to Earth. If it has enough propellant remaining, it will hopefully be able to 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 should be discovered in our Solar System that is on a collision course with Earth, we may be able to deflect it from its course. In theory, even a small space probe crashing into the object at a high enough speed should change its course enough to stop it from later crashing into Earth, provided this is done early enough. But theory is not enough, so the DART mission was developed to test and confirm that it can be done, and that it will work as expected.
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DART’s 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 one another, at a separation of 1.18 kilometers. If 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 likely masses of the two objects.
The DART spacecraft, weighing in at 570 kg, rammed into Dimorphos on 26 September, 2022, at roughly 22 500 km/h. The impact is the first test of the “Kinetic Impact” method of asteroid redirection. If astronomers should ever detect an asteroid on a collision course with Earth, and if it is massive enough to be a threat to human life or property, the best action to take would be to change its path so that the collision never happens. The kinetic impact method of redirection involves simply firing a heavy object at it, imparting enough kinetic energy to nudge it into a slightly different orbit. Because asteroids are so massive, even a very powerful impact would likely only change its velocity by a very tiny amount, but even a small deflection would be enough to ensure a miss if it happens early enough.
The Didymos and Dimorphos pair occupy an elliptical orbit around the Sun. Its perihelion, or the lowest point in its orbit, is slightly further out from the Sun than Earth, and its highest point, or aphelion, is a little past Mars. This orbit is tilted from the plane of the ecliptic by about 3 degrees, so it never crosses the paths of either Earth or Mars. This means that the Didymos binary asteroid system will never approach Earth, and is not a collision risk. The DART impact would have changed the speed of Dimorphos by only a fraction of a percent, far too little to create any risk of a collision with Earth or any other planet.
LICIACube is Italy’s first deep space mission. It was built in its entirety, and is operated, by ASI. The little spacecraft was carried piggy-back by DART to its current location, and is currently positioned near Didymos and Dimorphos, two objects orbiting each other to make a double asteroid orbiting the Sun.
Its mission was to capture images of both bodies through all phases of the DART mission, and sending those data back to the mission’s ground controllers. The images are meant to help measure how the orbit of Dimorphos has changed. They will also show us what effect the impact has on the asteroid itself, and likely provide useful data to 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 motor; stationing a spacecraft near the object to deflect it gravitationally; or even painting one side of the asteroid so that it gets unevenly heated by the Sun, making it emit more heat radiation from one side than the other, creating a tiny amount of thrust! All 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 doesn’t require the development of any new technology.
For more information about DART, visit the mission overview page at https://dart.jhuapl.edu/
And for information about LICIACube: https://www.ssdc.asi.it/liciacube/