NASA to Crash a Spacecraft Into an Asteroid to Change its Orbit

In just over a month, we will learn whether we are able to defend against asteroids capable of destroying entire cities.

Asteroids capable of destroying entire cities or even causing extinction events are a certain possibility, and we will know in just over a month whether we can defend ourselves against the said possibility.

Sixty-five million years ago, a massive asteroid impacted a region just off the present-day coast of Yucatan. The space rock is said to have been responsible for a mass extinction event, sealing the fate of the dinosaurs.

Such events, while maybe uncommon, are a threat to Earth, and we must develop techniques to help us deflect or destroy such space rocks.

Luckily, NASA and its partners are already working on that.

On Monday, September 26, NASA’s Double Asteroid Redirection Test (DART), the world’s first mission to test technology to defend Earth from asteroid threats, will test its capabilities.

Dimorphos is the target of the mission, an asteroid orbited by a smaller one in the 65803 Didymos system. Didymos A (the primary) measures about 780 meters in diameter, while Dimorphos (the moon) measures 160 meters in diameter and orbits the primary at roughly one kilometer (0.62 miles).

In total, the Didymos system is estimated to weigh 528 billion kilograms, of which 4.8 billion kilograms come from Dimorphos. The smaller asteroid Dimorphos will be targeted by DART. Asteroid Didymos does not cross Earth’s orbit, so an impact hazard cannot be posed by the deflection experiment.

An infographic showing the sizes of DART and Didymos. A comparison is also made between the two asteroids in the Didymos system and some objects on Earth in this infographic. Image Credit: NASA / Johns Hopkins APL.
An infographic showing the sizes of DART and Didymos. A comparison is also made between the two asteroids in the Didymos system and some objects on Earth in this infographic. Image Credit: NASA / Johns Hopkins APL.

It is estimated that 500 kg (1,100 lb) DART will impact at 6.6 km/s (4.1 mi/s), causing a 0.4 mm/s velocity change, which results in a small change in the asteroid system’s trajectory over time, but a significant shift.

A hypothetical asteroid headed for Earth could be mitigated over time by the cumulative trajectory change caused by such a small change in velocity. It is estimated that Dimorphos’ orbital period will be reduced by roughly 10 minutes due to the impact, which targets the center of its figure.

It is imperative that the spacecraft hits Dimorphos in the opposite direction to the asteroid’s motion.

Since the topology of the surface determines the actual change in velocity and orbital shift, we cannot know the changes until after they have taken place.

Upon impact, Dimorphos’ orbital speed drops slightly, which in turn reduces the orbital radius around Didymos. Dimorphos has a much lower mass than Didymos, so its trajectory is modified in reduced proportions.

Due to recoil momentum caused by impact ejecta, there is an unpredictably pronounced “momentum enhancement” effect.

The purpose of this test is to show that a spacecraft can navigate autonomously to an asteroid and intentionally collide with it to change its motion so that astronomers can observe it from the ground.

It will provide critical data to prepare for the possibility of an asteroid impacting Earth if one is found.


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Written by Ivan Petricevic

I've been writing passionately about ancient civilizations, history, alien life, and various other subjects for more than eight years. You may have seen me appear on Discovery Channel's What On Earth series, History Channel's Ancient Aliens, and Gaia's Ancient Civilizations among others.

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