NASA expects package tomorrow with piece of asteroid Bennu: Why this space rock? And what is the purpose? 5 questions answered | Science & Planet

In 2016, NASA launched the OSIRIS-REx space mission. Their target? The asteroid Bennu, a space rock with a diameter of 500 meters that was discovered in 1999. It is not without reason that the space agency chose this specimen.

Asteroids such as Bennu are time capsules that allow us to look back into the past. They are remnants from the time when the planets formed in our solar system. By collecting and then studying the material inside the asteroid, you can learn something about the formation of such asteroids, but also that of our planet. The advantage is that you know the origin of the piece of Bennu that you are taking along and that it is ‘untouched’. This is not the case with meteorites that fall here on Earth. For example, they are affected by their journey through our atmosphere and often long stay on Earth. That is why the sample from the OSIRIS-REx mission is much more interesting from a scientific point of view.

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In addition, Bennu was also chosen because it is a so-called carbon-rich space rock. Scientists suspect that it may contain complex carbon compounds, which are building materials necessary for the development of life on a planet. How such organic substances ended up here with us is still an unanswered question. Did they originate here? Or perhaps they hitched a ride on an asteroid that hit here when our planet was still young?

Finally, there was another purpose why NASA headed towards Bennu. There is a very small chance that the asteroid will end up on our planet in the distant future. That chance is greatest between 2135 and 2300, although even then it remains very small. For example, in September 2182 it is 0.04%. If Bennu were to crash on Earth, its 500 meters would be enough to wipe the Benelux off the map. By studying Bennu we can better protect ourselves in the future against new threats from space.

It is a first for the Americans, but certainly not for the world. The Japanese already did it before them in 2010 with the first Hayabusa mission. It returned less than a milligram of the asteroid 25143 Itokawa to Earth. The second mission followed in 2020 with 5.4 grams of material from asteroid Ryugu. The 250 grams taken by OSIRIS-REx is therefore not the first material ever, but it is the most.

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The OSIRIS-REx space probe left for Bennu in September 2016. The device with its solar panels has a length of 6.2 m and a width and height of 2.4 by 3.2 meters. It took 2 years for the spacecraft to come close to the asteroid and another 2 years to find a suitable landing site.

The time had come on October 20, 2020. During a so-called “touch and go” maneuver, OSIRIS-REx collected some material from the asteroid with a 3-meter-long cosmic vacuum cleaner. A technological feat since the space probe was about 320 million kilometers from Earth at the time. Making a quick adjustment was therefore not an option for the mission management. Even though a number of things did not go quite as expected, the space probe still managed to return home with 250 grams of material. Well over the target of 60 grams.

Now, after 7 years and 7 billion kilometers, the space probe is arriving back at its starting point.

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At 100,000 kilometers from Earth, about a third of the distance to the month, the space probe launches a capsule containing the sample towards our planet. Four hours later it flies into the atmosphere at 44,500 kilometers per hour, with the temperature rising to 2700 °C. Fortunately, there is a heat shield for protection. To slow down even further, the capsule uses parachutes before landing at 18 kilometers per hour in a secured piece of desert in the American state of Utah.

A recovery team of 4 helicopters then tries to find the capsule as quickly as possible to prevent contamination with terrestrial material. Part of Bennu then goes to labs all over the world. The rest disappears into a vault for future generations.

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After delivering its package, the space probe continues its flight and is given a new name OSIRIS-APEX. His new target is the 370 meter large asteroid Apophis. It will approach Earth in 2029 to within about 32,000 kilometers. Although we don’t have to fear an impact. Calculations by scientists indicate that the chance of this happening is virtually non-existent.

But that close passage is the ideal moment for OSIRIS-APEX to enter orbit around Apophis. What will follow will be 18 months of research during which the space probe will map the composition of Apophis.

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