NASA’s DART Mission Launches for Head-on Collision with an Asteroid

Last evening, a spacecraft constructed through the hardships of the COVID pandemic efficiently departed Earth on a one-way journey to an asteroid. The Double Asteroid Redirection Test, or DART, launched at 06:21:02 UTC November 23 and can crash into 65803 Dimorphos, the moon of asteroid Didymos, in September or October 2022. This isn’t an asteroid science mission — it’s the primary ever planetary protection mission.

“Planetary defense” refers to discovering, after which mitigating, threats to our planet from potential comet and asteroid impacts. In any given year, the chance of an asteroid influence in a populated space is extraordinarily low in comparison with the chance of different kinds of pure disasters. There’s no asteroid at present recognized to be on a collision course with Earth at any time within the foreseeable future. But what we don’t know may damage us: if a large enough asteroid is within the flawed place within the flawed time, it may destroy a metropolis, threaten human civilization, and even trigger a mass extinction.

Fortunately, impacts will be predicted, if we uncover doubtlessly hazardous asteroids early sufficient, after which the hazard will be mitigated, not less than in concept.

The strongest way to take away the specter of a doubtlessly hazardous impactor is to trace the asteroid. A 1-in-1000 likelihood of an influence virtually all the time turns into zero chance of influence as soon as astronomers have decided the asteroid’s path with larger precision. But if monitoring an asteroid reveals that it’s much more prone to crash into us, there are different choices.

We can transfer folks out of the way of the hazard or — higher but — redirect the asteroid itself, shifting it away from its harmful path. However, no person has ever redirected a space rock earlier than. Engineers have proposed a variety of doable strategies to change the trail of an asteroid sufficient to forestall an influence, however none has been examined in observe. Such testing needs to be accomplished rigorously, while you’re speaking about near-Earth asteroids: what in case your check goes in a way you don’t anticipate and truly will increase the danger of a future influence?

Dimorphos and its moon Dydimos
Near-Earth asteroid 65803 Didymos (proper) has a diameter of round 780 meters (2,600 toes) and rotates each 2.26 hours. Its moon Didymos (left) is 160 meters throughout; it completes an orbit across the bigger asteroid in about 12 hours.

DART will check a low-tech methodology for altering an asteroid’s path in a way that may’t probably enhance the menace to Earth. The mission that launched at this time will fly to the near-Earth asteroid Didymos. Altering Didymos’s orbit would have a tiny however actual danger of accelerating the danger to Earth. So we’re going to depart Didymos alone. But Didymos has a small moon, Dimorphos.

DART will crash head-on into Dimorphos. If DART and Dimorphos have been billiard balls of infinite power and elasticity, the end result of the influence can be simple to foretell: the spacecraft would bounce off virtually as quick because it hit, and the moon would gradual by a tiny quantity. But Didymos and Dimorphos are virtually definitely rubble piles, which aren’t bouncy like billiard balls. They’re loosely agglomerated piles of gravel with lots of empty space. What occurs then?

On one hand, the dearth of cohesion among the many particles may enable the swift-flying spacecraft to penetrate deeply into the floor, compressing it as an alternative of bouncing off. That would scale back the effectiveness of the collision.

On the opposite hand, the power DART imparts will mobilize Dimorphos particles, launching them off of the tremendous low-gravity asteroid moon. Each fragment will carry a few of Dimorphos’ momentum with it. The slowing impact of flying ejecta is predicted to rival the slowing impact of the head-on influence.

DART mission diagram
Diagram exhibiting the important thing elements of the DART mission.

Shortly earlier than DART arrives, an Italian-built cubesat named LICIACube will separate from the provider craft. Then DART will autonomously steer to a high-speed crash into Dimorphos, ending its existence. LICIACube will watch the influence, observing the spray of ejecta.

The loss of life of the DART spacecraft is when the science begins. The influence will occur when Didymos is comparatively near Earth, making it an simple goal for each optical and radio telescopes. Back on Earth, astronomers will watch Didymos, rigorously measuring the modifications in brightness, or mild curve, of the pair to measure Dimorphos’s orbital interval round Didymos. If scientists’ fashions are right, the influence ought to change Dimorphos’s interval by a number of minutes.

Whether the fashions are right or not, we’ll have carried out the first-ever experiment in altering an asteroid’s velocity, and we’ll have discovered helpful classes towards that inevitable time sooner or later when we have to transfer an asteroid deliberately away from a inhabitants heart.

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