Just like a science-fiction film, NASA has successfully carried out its first test run for planetary defence in which it has managed to redirect an asteroid. The question behind the mission was to imagine what would happen if Earth were threatened by an asteroid’s trajectory. Now we know, thanks to the Dart mission, which was watched closely by people around the world in real time. We tell you all about this incredible operation.
What is the DART mission?
The DART mission was conceived as the first test run for planetary defence against an asteroid. While no asteroids large enough to threaten life on Earth are expected in at least the coming 100 years, it is possible for a smaller body to come close enough to our planet with the potential to destroy cities. Obviously, in the long run (hundreds, thousands or millions of years in the future) it is very likely that the Earth will face the threat of an asteroid.
That is why NASA and the Johns Hopkins Applied Physics Laboratory (APL) designed and set up the DART (Double Asteroid Redirection Test) mission, which is based on the idea of having a spacecraft crash into a rock in order to divert it from its trajectory by enough of a margin to avoid a possible impact with the Earth.
In the words of NASA, “DART’s target was a binary asteroid system consisting of Didymos (Greek for “twin”), about a half-mile across, and its smaller companion called Dimorphos (Greek for “two forms”), about 530 feet across. DART used an autonomous targeting system to aim itself at Dimorphos. The spacecraft, roughly the size of a small car, struck the smaller body at about 4 miles per second on September 26, 2022.
This change in the trajectory was achieved without the use of any type of explosive, because one of the mission goals was to demonstrate the effectiveness of the technique called “kinetic impact”, which consists of hitting an asteroid with an object to nudge it slightly, enough to alter its trajectory.
The mission data show just how difficult it was: DART was around 62 feet long and weighed 580 kilograms, and it managed to hit an asteroid with a diameter of only 524 feet at a distance of 6,835,083 miles (11 million kilometres) from our planet. It has been described as hitting a hole in one on the Moon when shooting from Earth.
The Didymos Reconnaissance and Asteroid Camera for Optical navigation (DRACO) and a sophisticated set of algorithms called SMART Nav which served to guide, steer and control it, were the only instruments that DART had for this mission, allowing it to distinguish between Didymos and Dimorphos and aim at the smaller of the pair.
Besides this historic achievement, the DART mission also sought to test the effectiveness of earth telescopes for observing and measuring the changes in the behaviour of Dimorphos before and after the impact. Data analysis is fundamental for adapting the technique used in this mission for future endeavours, because the size and even the composition of the asteroid will determine whether a larger or smaller craft is needed to hit it and change its trajectory.
One simple idea for a highly complex mission has achieved a new milestone in aerospace technology, which has proved to be a viable plan for defence in the event that an asteroid should threaten to hit our planet with potentially catastrophic consequences.
A new milestone in space
This is the first time that humanity has altered the direction of a heavenly body, NASA explained, in the press conference held after the successful impact of DART. «This is a watershed moment for planetary defense and a watershed moment for humanity,» said NASA Administrator Bill Nelson.
The spectacular operation was broadcast live by NASA, as an event like a scene from a movie was watched by millions of people on Earth.
This was the moment when NASA showed the whole world the impact of DART against Dimorphos, and how the team running the operation experienced it.
Nancy Chabot, the DART coordination lead from the Johns Hopkins Applied Physics Laboratory (APL) in Laurel (Maryland), told the media that “DART has given us some fascinating data about both asteroid properties and the effectiveness of a kinetic impactor as a planetary defense technology”. “The DART team is continuing to work on this rich dataset to fully understand this first planetary defense test of asteroid deflection”, she added.
What comes after the DART mission?
The next step in planetary defence is planned for 2024, when the European Space Agency (ESA) launches Hera, a deep space probe that will travel to Didymos and the remains of Dimorphos to carry out a study of what has happened to this binary asteroid system after the impact and to make a detailed, three-dimensional reconstruction of the crater made by DART after the impact.
When all the information is collected and analysed, the next step will consist of creating a model that can decide what kind of spacecraft is needed to change the course of an asteroid that threatens the Earth, based on its mass, size and the time it will take to hit the planet.
For its part, the United States plans to launch the Near-Earth Object Surveyor (NEO) space telescope in 2026, with the aim of detecting and analysing asteroids and comets measuring more than 460 feet (140 metres). This telescope will enable infra-red vision that current conventional telescopes do not have, so that it can detect objects approaching from the direction of the Sun.