Countdown to Earth’s first planetary defense test

But does humanity have the knowledge and technology to divert a celestial body from its natural path? The DART mission, the first test of planetary defense of the Earth, intends to answer this question on September 27.

Photo: Unsplash

By M. Isabel Herreros, Doctor in Physical Sciences, Researcher at the Center for Astrobiology specialized in Numerical Models applied to Planetary Sciences, Center for Astrobiology (INTA-CSIC), and Jens Ormö, Doctor in Geological Sciences. Scientific Researcher of Public Research Organizations, Astrobiology Center (INTA-CSIC)

Who has not ever wondered how the dinosaurs disappeared? Before there was scientific evidence, it was already suspected that their extinction must have been the consequence of a cataclysm of global magnitude, possibly a cosmic impact. And it is at this moment, upon becoming aware of their fragility in the face of an event of these characteristics, that human beings begin to fantasize about the possibility of being able to defend themselves against this great threat.

Asteroids are celestial bodies that, although they are small in size, travel through space at enormous speeds, so the collision of a medium-sized one with the Earth would release the energy equivalent to several thousand atomic bombs.

The experiment will serve in the face of a real impact threat

More than a decade ago, several scientists dreamed of carrying out the first experiment in history on a planetary scale that would allow them to test whether it is possible to modify the trajectory of an asteroid. That was the conceptual origin of NASA’s DART (“dart” in English) mission. The ultimate goal of this mission is to fine-tune a methodology that will allow, in the future, and in record time, to divert a potentially dangerous celestial body to Earth.

In November 2021, NASA launched a spacecraft, the size of a small car and barely 500 kg, which has since traveled through space reaching gigantic speeds. On September 27, it will hit the small moon Dimorphos, the satellite of a binary asteroid system called Didymos 65803.

DART’s challenge: moving a rock in space Trying to move a 160 m diameter rock by colliding a small 500 kg spacecraft does not seem like an easy task. If we add to this that the rock is 11 million kilometers away and is moving at 23 km/s, things become more complicated. To give a simple example, it would be like trying to shoot a fly in mid-flight located in Algeciras from Madrid, and also move it in the right direction.

The 160 m diameter asteroid Dimorphos compared to the Colosseum in Rome. ESA-Scientific OfficeThe mission is not only intended to move Dimorphos, but to divert it in a controlled manner. To achieve this, it is necessary to precisely decide the point of impact that allows a more efficient deflection. However, as of today, neither the composition nor the shape of the asteroid is known, so this decision will have to be made when the DART spacecraft is close enough to Dimorphos, just a few days before impact.

Numerical models allow us to reproduce any natural process governed by one or more mathematical equations. They have become an efficient way to perform “virtual experiments”, thus saving laboratory costs.

With numerical models it is possible to study processes under conditions that are often irreproducible experimentally, as is the case of the DART impact, which will occur in vacuum and microgravity conditions.

To fine-tune a model, and for the results to be truly reliable, it must be validated by comparing the numerical results with real experiments. For this reason, the CAB Impacts Laboratory (CSIC-INTA) is a fundamental part of the mission, since we have carried out the validation tests of one of the numerical models with which the mission has been designed and based on which Critical decisions will be made days before impact.

Experiments with a compressed gas cannon

The CAB Impact Laboratory is designed for low-velocity impact experiments. It consists of a compressed gas cannon that can fire projectiles at speeds of up to 420 m/s on materials of different characteristics with various angles of impact.

The experiments are recorded with high-speed cameras and the resulting craters can be scanned in 3D.
A special feature of the laboratory is that the tests can be carried out in a configuration that allows the formation of the crater to be studied in detail in section.

The experiments that we have carried out in the CAB take into account the effect of the heterogeneity, porosity, cohesion and friction of the material object of the impact, similar to Dimorphos. The results obtained have been recently published in Earth and Planetary Science Letters, successfully validating one of the most used codes in the mission to simulate the impact.
Now we can only wait for the day of the collision and cross our fingers: “Go DART!”

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