NASA’s Double Asteroid Redirection Test (DART) spacecraft, which collided with asteroid Dimorphos in September, 2022, has successfully changed the asteroid’s motion in space, the United States space agency confirmed Wednesday. The DART mission marks humanity’s first successful attempt at changing the motion of a celestial object on purpose. It is also the first full-scale demonstration of asteroid deflection technology.
Before DART’s impact with Dimorphos, the orbital period of the asteroid around its larger parent asteroid, Didymos, was 11 hours and 55 minutes. Following DART’s intentional collision with Dimorphos on September 26, astronomers started using ground telescopes to measure how much the orbital period of Dimorphos has changed.
By how many minutes did DART change Dimorphos’ orbital period?
The DART investigation team recently confirmed that the impact of DART altered Dimorphos’ orbit around Didymos by 32 minutes. As a result, the orbital period of Dimorphos has been shortened to 11 hours and 23 minutes. According to NASA, the margin of error is plus or minus two minutes.
Before the collision, the space agency had defined a change of 63 seconds in orbital period as a minimum successful orbital period change. Surprisingly, DART has surpassed the minimum benchmark by more than 25 times.
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In a statement released by the space agency, NASA Administrator Bill Nelson said the mission shows that NASA is trying to be ready for whatever the universe throws at Earth. He added that this is a watershed moment for planetary defence and all of humanity.
Lori Glaze, director of NASA’s Planetary Science Division at NASA Headquarters, Washington, said the result is an important step toward understanding the full effect of DART’s impact with its target asteroid. She added that as new data come in each day, astronomers will be able to better assess how a mission like DART could be used in the future to help protect Earth from a collision with an asteroid if one is ever headed our way.
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How was the ejecta from the asteroid useful?
According to NASA, the investigation team is acquiring data with ground-based observatories around the world, and with radar facilities at NASA’s Jet Propulsion Laboratory and the National Science Foundation’s Green Bank Observatory in West Virginia.
Next, the team aims to shift toward measuring the efficiency of momentum transfer from DART’s roughly 22,530-kilometre per hour collision with Dimorphos. The ejecta, or the tons of asteroidal rock displaced and launched into space by the impact, will be analysed further.
The recoil from the blast of debris enhanced DART’s push against Dimorphos, similar to the way in which a jet of air streaming out of a balloon sends the balloon in the opposite direction.
What is next for NASA’s DART Mission?
More information on the asteroid’s physical properties is needed to successfully understand the effect of the recoil from the ejecta. These properties include the characteristics of the asteroid’s surface, and how strong or weak it is.
Nancy Chabot, the DART coordination lead from the Johns Hopkins Applied Physics Laboratory, Maryland, said DART has provided some fascinating data about both asteroid properties and the effectiveness of a kinetic impactor as a planetary defence technology. She added that the DART team is continuing to work on the rich dataset to fully understand this first planetary defence test of asteroid deflection.
In order to analyse the effectiveness of DART, and the properties of Dimorphos, astronomers will continue to study imagery of the asteroid from DART’s terminal approach and from the Light Italian CubeSat for Imaging of Asteroids (LICIACube), provided by the Italian Space Agency.
All this would help approximate Dimorphos’ mass and shape. In 2026, the European Space Agency’s Hera project will conduct detailed surveys of both Dimorphos and Didymos, and focus on the crater left by DART’s collision. Hera will also make a precise measurement of Dimorphos’ mass.
Hera mission, which is scheduled to be launched in October 2024, has the goals of planetary defence, technology demonstration, and performing bonus science experiments.
The Hera spacecraft is designed to undertake a detailed survey of the consequences of DART’s collision.