Hubble captures movie of DART asteroid impact debris

Hubble captures movie of DART asteroid impact debris
by Staff Writers
Munich, Germany (SPX) Mar 06, 2023

The NASA/ESA Hubble Space Telescope captured a series of photos of rapid changes to the asteroid Dimorphos when it was deliberately hit by a 545-kilogram spacecraft on 26 September 2022. The primary objective of the NASA mission, called DART (Double Asteroid Redirection Test), was to test our ability to alter the asteroid's trajectory as it orbits its larger companion asteroid, Didymos. Though Dimorphos poses no threat to Earth, data from the mission could help inform researchers how to potentially change an asteroid's path away from Earth, if ever necessary.

Hubble's resulting time-lapse movie of the aftermath of the collision reveals surprising and remarkable changes as dust and chunks of debris were flung into space from the wounded asteroid. Smashing head-on into the asteroid at 21 000 kilometres per hour, the DART impactor blasted over 900 000 kilograms of dust off of the asteroid.

The Hubble movie provides invaluable new clues into how the debris was dispersed into a complex pattern in the days following the impact.

The movie shows three overlapping stages of the aftermath of the crash: the formation of an ejecta cone, the spiral swirl of debris caught up along the asteroid's orbit about its companion asteroid, and the tail swept behind the asteroid by the pressure of sunlight.

The Hubble movie starts at 1.3 hours before impact. In this view both Didymos and Dimorphos are within the central bright spot; even Hubble can't resolve the two asteroids separately. The thin, straight spikes projecting away from the centre (and seen in later images) are artefacts of Hubble's optics. The first post-impact snapshot is two hours after the event. Debris flies away from the asteroid, moving in with a range of speeds faster than four miles per hour (fast enough to escape the asteroid's gravitational pull, so it does not fall back onto the asteroid). The ejecta forms a largely hollow cone with long, stringy filaments.

At about 17 hours after the collision the debris pattern entered a second stage. The dynamic interaction within the binary system started to distort the cone shape of the ejecta pattern. The most prominent structures are rotating, pinwheel-shaped features. The pinwheel is tied to the gravitational pull of the companion asteroid, Didymos.

Hubble next captures the debris being swept back into a comet-like tail by the pressure of sunlight on the tiny dust particles. This stretches out into a debris train where the lightest particles travel the fastest and farthest from the asteroid. Hubble also recorded the tail splitting in two for a few days.

Due to launch in October 2024, ESA's Hera mission will perform a detailed post-impact survey of the target asteroid Dimorphos. Hera will turn the grand-scale experiment into a well-understood and repeatable planetary defence technique that might one day be used for real.

Just like Hubble and the NASA/ESA/CSA James Webb Space Telescope, NASA's DART and ESA's Hera missions are great examples of what international collaboration can achieve; the two missions are supported by the same teams of scientists and astronomers, and operate via an international collaboration called AIDA - the Asteroid Impact and Deflection Assessment.

NASA and ESA worked together in the early 2000s to develop asteroid monitoring systems, but recognised there was a missing link in the chain between asteroid threat identification and ways of addressing that threat. In response NASA oversaw the DART mission while ESA developed the Hera mission to gather additional data on DART's impact. With the Hera mission, ESA is assuming even greater responsibility for protecting our planet and ensuring that Europe plays a leading role in the common effort to tackle asteroid risks. As Europe's flagship planetary defender, Hera is supported through the Agency's Space Safety programme, part of the Operations Directorate.

Unistellar Citizen Science Network and SETI Institute contribute to planetary defense
SETI Institute
Citizen scientists worldwide made decisive contributions to defend our planet by recording accurate and meaningful observations supporting the NASA DART (Double Asteroid Redirection Test) mission. The team, including eight SETI Institute astronomers and led by SETI Institute postdoctoral fellow Ariel Graykowski published their results in Nature on March 1.

NASA's first test mission for planetary defense, DART, which seeks to test and validate a method to protect Earth in case of an asteroid strike, reached

Dimorphos, a moon of the near-Earth asteroid Didymos on September 26, 2022. Unistellar citizen scientists were mobilized by SETI Institute researchers to observe the impact live, which was only visible from parts of Africa. Several observers in Kenya and Reunion Island successfully recorded the event with their smart telescope, witnessing the first successful deflection of an astronomical object using human technology.

"Our citizen astronomers were excited to witness with their Unistellar telescopes the impact of DART, the first ever attempt to divert an asteroid. It's commendable that we are the only group that has reported a scientific analysis of the impact, showing the ejecta cloud and the aftermath for a month. There is always a clear starry night somewhere in the Unistellar network, and that's without doubt the strength of our network; we can see any part of the sky at any time," said Marchis.

The paper led by Graykowski was published in Nature along with four others describing the aftermath of the impact and confirming the deflection of the moon of Didymos. This publication stands out due to the involvement of citizen science as the driving force behind the study, including four observations taken at the time of impact.

All the 31 citizen scientists of the Unistellar network involved in this study are co-authors of this scientific paper. Four of them (Patrice Huet, Matthieu Limagne, Bruno Payet from Reunion Island, and the Traveling telescope team in Kenya) observed the impact. Eight scientists from the SETI Institute (Ariel Graykowski, Ryan Lambert, Franck Marchis, Dorian Cazeneuve, Paul Dalba, Thomas Esposito, Daniel Peluso, and Lauren Sgro) have contributed to this research.

The SETI Institute is Unistellar's scientific partner, working with Unistellar to mobilize teams to conduct observations leading to significant scientific discoveries and contributions.

Research Report:Light Curves and Colors of the Ejecta from Dimorphos after the DART Impact

Research Report:Ejecta from the DART-produced active asteroid Dimorphos