The asteroid NASA smashed into may still be slowing down

The discovery was made by a school teacher and his students.
Loukia Papadopoulos
An artist's impression of the DART mission.jpg
An artist's impression of the DART mission.


In October of last year, NASA declared the Double Asteroid Redirection Test (DART) mission, which successfully redirected an asteroid’s trajectory by deliberately crashing in it with a spacecraft, a success.

"As far as we can tell, our first planetary defense test was a success," said at the time Elena Adams, DART's mission systems engineer at the Johns Hopkins University Applied Physics Laboratory (JHUAPL). "I think Earthlings should sleep better. Definitely, I will."

Changing paths

The DART spacecraft collided with the target asteroid Dimorphos on September 26, 2020 but researchers, who had been meticulously analyzing and monitoring the celestial body's course, only announced the mission's success on October 11, 2022 when they were able to report that the spacecraft had considerably changed the asteroid's path in space.

DART is a NASA mission designed to test asteroid deflection technology. Its main objective is to show that we can use a kinetic impactor technique to alter the trajectory of an asteroid. 

The primary goal of DART was to hit the Didymos binary asteroid system and its moonlet, known as Dimorphos. The main target, Dimorphos, has a diameter of about 525 feet (160 metres), whereas Didymos, which is larger, has a diameter of around 2,560 feet (780 metres). Scientists stipulated that they could evaluate the success of the kinetic impactor technique by aiming for the smaller moonlet.

And so they did.

DART's spacecraft deliberately crashed into the smaller moonlet at high speed, approximately 14,764 miles per hour (6.6 kilometers per second), changing its orbit around the larger asteroid. 

According to NASA, Dimorphos would complete one orbit around Didymos in 11 hours and 55 minutes prior to the impact event. Ground measurements taken post impact revealed that the orbital period had been shortened by 32 minutes, or 11 hours and 23 minutes. This is equivalent to Dimorphos moving "tens of metres" closer to Didymos.

A larger number

Now, according to New Scientist, a teacher and his students appear to have discovered that Dimorphos' orbit has continued slowing down since the now famous crash. "The number we got was slightly larger [than NASA’s], a change of 34 minutes," Jonathan Swift, a math and science teacher at the Thacher School in California, told the science news outlet. "That was inconsistent at an uncomfortable level."

Two scenarios could be happening here. One of the calculations may be wrong or the celestial object may still be slowing down. If the case is the second, it means that NASA has achieved its goal.

Swift claims that there are no errors in his formula telling New Scientist: "We tried our best to find the crack in what we had done, but we couldn’t find anything." Swift’s finding will now be published in a paper in the American Astronomical Society journal.

Meanwhile, NASA will be releasing a report on the results of the DART mission. The mission serves as a proof-of-concept for planetary defence techniques even if Didymos and Dimorphos are not considered to be dangerous to earth. The project offers important insights on how we might defend our planet in the future against potentially harmful asteroids.