‘It’s normal to make mistakes in science’: NASA didn’t expect asteroid Dimorphos to be so distracting

'It's normal to make mistakes in science': NASA didn't expect asteroid Dimorphos to be so distracting

DART collided with the asteroid to change its orbit. NASA predicts that the time it takes for the object to orbit its parent body will change by just 1 minute. The test result is different: why?

For the first time in history, humanity succeeded in deliberately deflecting the path of an asteroid in space. On October 11, 2022, we found out DART task It successfully accomplished its main objective: disrupting orbit The asteroid, Dimorphos, crashed into the probe in late September. All this is an exercise: TheAsteroid Does not represent any known hazard.

Dimorphos is a large asteroid orbiting Didymos. After Impact of DART, scientists used powerful telescopes to scan the sky. Their conclusion: Dimorphos’ orbit around Didymos was shortened by 32 minutes. In other words, the smaller of the two asteroids takes less time to orbit the larger one. However, this is more than NASA expected: the space agency predicts that Dimorphos’s orbit will change by only 1 minute and 13 seconds. Why such deviation from predictions?

Scientists studying these asteroids made 2 mistakes

There are two reasons for this, explains Numerama Stéphanie Lizy-Destrez, editor-researcher at ISAE-SUPAERO: ” Uncertainty about the mass of the main body, Didymos, and error about the composition of Dimorphos – The second reason is the biggest “mistake” of the two.

To better understand these asteroids, scientists work with models. Here it is a binary system, with one asteroid orbiting the other. The models used are comparable to those used for the study of mobility the moon, which revolves around the Earth. ” Physical properties allow us to access distance, duration (number of laps done in a given time). Specifically, the mass of each object “, continues Stéphanie Lizy-Destrez.

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Representation of Didymos and Dimorphos. //Source: YouTube screenshot ESA

However, unless a mission is launched towards an asteroid to get a closer look, determining its mass is problematic. ” We receive information from light. We can estimate the mass [d’un astéroïde] Depending on the light received, it gives an impression of its composition. As these calculations are estimates, error is possible. This is what happened to the pair’s large asteroid. ” Didymos’ trick was not perfect. However, it plays into the mass of demorphoses. If we change the mass of the earth, the moon will have another movement. This was our first uncertainty. »

“It’s normal to make mistakes in science”

What happened to the composition of the other parameter, dimorphose? ” It was supposed to be very sturdy, but the footage revealed that it was made up of a lot of dustSummarizes the scientist with numerama. This means it had a large volume, but a small mass.. When the DART crashed in Dimorphos, a large amount of mass was ejected from it. ” what’s left [de Dimorphos] So it was small. Also, since this nucleus was smaller than we estimated, the deviation was larger than we expected.. »

These errors in the predictions do not question the success of the DART mission. ” Making mistakes in science is normal, that’s how we learnStephanie Lizi-Destres says. This is almost reassuring: the whole principle of deflecting an asteroid by a probe that hits it works. We’ve seen it work. Then, we can only improve on the accuracy of the result obtained. But it is extraordinary that we can touch an object so far away from Earth. »


Dimorphos after DART impact.  // Source: OBS E. Guido, M. Rocchetto, G. Savini, S. Fossey (cropped image)

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