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08 November 2018

A Falcon Asteroid Hunter

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The peregrine falcon can dive at speeds of 300 kilometres per hour when it identifies a prey that is worthwhile. It is not only the fastest animal on the planet, but also possibly the most accurate hunter. Inspired by this bird, the Japanese space agency (JAXA) designed its most ambitious program of space probes, Hayabusa—Japanese for “peregrine falcon”—designed to hunt asteroids and bring samples of their surface material back to Earth.

The first Hayabusa, launched in 2003, overcame a long journey full of accidents and challenges to successfully hunt the asteroid Itokawa and return tiny samples of it to Earth in 2010, a space exploration success.

Illustration of Hayabusa 2 descending to aspirate samples from the surface of the Ryugu asteroid. Credit: JAXA

A second improved version, Hayabusa2, was launched in 2014 with the aim of intercepting another asteroid, but the route to reach the object was not easy. It took four years to achieve the necessary velocity using an ion engine, but since June of this year the spacecraft has been orbiting the asteroid Ryugu. This object is not very far from Earth; in fact, it’s an example of a space object classified as near and also dangerous, since in the future it could collide with our planet.

Diverting dangerous asteroids

One of the main objectives of Hayabusa2 is to test technologies for intercepting dangerous asteroids. The question is not whether a large asteroid like the one that killed the dinosaurs will ever strike Earth again—the question is when it will happen. Having the capacity to neutralise this threat is what will allow us to change the object’s trajectory it and save our civilization in the future. Not only is it about intercepting asteroids, but we also need to understand what these objects are composed of and how they behave, since this information will be vital for the day when one of them has to be redirected.

Recreation of the two Minerva-II1 rovers. Credit: JAXA

Hayabusa2 carries cameras that are sending back large amounts of data that reveal all these unknowns, but this mission goes much farther than mere remote measurements. At the end of September, the probe launched the Minerva-II1 onto the surface of the asteroid, two tiny solar-powered rovers the size of cans that have captured spectacular images. In the photos can be seen the morphology of the asteroid, a conglomerate of rocks of different sizes and dust, united by the weak gravity generated by its small mass. Asteroids of this size, around one kilometre in diameter, have a consistency similar to that of the polystyrene that is used in packaging, a mass of balls weakly held together by a small force.

The future of space mining

The Minerva-II1 rovers are not the only devices on the surface of the asteroid. In early October, a metal box the size of a microwave oven touched down on the object, and then bounced around while taking measurements and photographs. This was the MASCOT lander from DRL, the German Aerospace Centre, which is collaborating in the mission. Once the device stopped moving, it used several detectors to analyse the surface of the asteroid. At the end of the scan it activated a system similar to the vibrator of a mobile phone, which with the low gravity of Ryugu caused it to hop off the surface and land several metres away, giving it a new spot to analyse, a sequence that it repeated. Designed to function for only 16 hours (its battery actually lasted 17 hours), it has left behind images for the history of space exploration.

Their analysis will help determine the presence of valuable elements such as platinum, palladium, rhodium or osmium, very abundant in asteroids, while on Earth they may become more expensive than gold because of their scarcity. These are useful resources in many industrial processes; more than half of consumer products contain or have needed these elements at some point in their production. For that reason, the asteroid Ryugu is valued by space mining companies at about 95 billion dollars, with a potential profit of 35 billion.

The origin of the Solar System and the planets

In the event that reaching an asteroid and depositing robots onto its surface is not exciting enough, the high point of the mission will occur when Hayabusa2 launches an explosive charge against its target. While the probe takes refuge on the opposite side of Ryugu, it will eject a projectile at two kilometres per second—twice the speed of a cannon—to form an impact crater that will expose the internal layers of the asteroid.

Then it will be time for Hayabusa2’s bird-like dive. While emulating a falcon, the probe will descend to the surface and employ a large funnel to absorb samples of the soil and the lower layers of the crater, which are not contaminated by micrometeorites or the solar wind.

Image from the surface of Ryugu taken by Minerva-II1. Credit: JAXA

These samples are remnants from the formation of the Solar System, unchanged for billions of years and chronicling its history, helping us to understand the creation of planetary systems and the molecules essential to nourish the primordial soup that gave rise to life on Earth.

Souvenir from an asteroid

After having completed its mission, Hayabusa2 will set a course back to Earth. In December 2019, it will depart from the asteroid and should arrive home at the end of 2020, depositing the container of precious samples in the Earth’s atmosphere in free fall over a monitored area in Australia, where it will be collected after landing.

While delivering its souvenir from the asteroid to us, Hayabusa2 will burn up completely during its re-entry into the atmosphere. From the surface, we will be able to see it as a shooting star, the perfect simile for this ambitious mission with which we are exploring the technologies to intercept and redirect an asteroid, evaluating the viability of space mining and searching for the remains of the birth of the Solar System that will help us to understand how planets are formed. Stay tuned to your screens because many surprises still await us.

Borja Tosar


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