Scientists analyzing images from NASA’s Double Asteroid Redirection Test (DART) mission have found the first visual evidence that small asteroids exchange rocks and dust in a slow process that reshapes their surfaces over millions of years.
Photos taken at the end of 2022 by DARTS spacecraft – an experiment that tested asteroid deflection technology – moments before that hit the asteroid deliberately The moon Dimorphos revealed faint, fan-shaped streaks across its rocky surface, according to a new study.
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“At first we thought there was something wrong with the camera, and then we thought there might have been something wrong with our image processing,” said study lead author Jessica Sunshine of the University of Maryland. statement.
However, further analysis showed that the streaks were consistent with mild, low-velocity impacts from material drifting through space, “like throwing ‘cosmic snowballs,'” Sunshine said.
“We had the first direct evidence of recent material transport in a binary asteroid system.”
The findings, described in paper published March 6 in The Planetary Science Journal, came as another team of researchers confirmed that DART not only changed Dimorphos’ orbit around its companion asteroid, but also slightly the entire orbit of the binary system around the sun.
The shift in the system’s orbital velocity was about 11.7 microns per second, or about 1.7 inches per hour, researchers reported in another paper published March 6 in the journal Science Advances.
“Over time, such a small change in an asteroid’s motion can make the difference between a dangerous object hitting or missing our planet,” Rahil Makadia, a planetary defense scientist at the University of Illinois Urbana-Champaign who led the Science Advances paper, said in a separate statement.
About 15% of near-Earth asteroids are estimated to be binary systems, in which a smaller asteroid orbits a larger companion. These systems can host surprisingly complex processes, in part because sunlight can gradually speed up the rotation of small asteroids until loose material breaks loose from their surfaces.
This phenomenon, known as YORP effectoccurs when an asteroid absorbs sunlight and re-emits that energy as thermal radiation, creating a small but continuous thrust that can slowly spin the space rock faster.
Evidence of this process has been seen elsewhere in the solar system. Observations from NASA Spacecraft Lucyfor example revealed ridges around equators of the asteroid Dinkinesh and its moon Selam — features that scientists believe formed as material migrated and accumulated during such spin-ups. Similar ridges appear along the equators of Dimorphos and Didymos, likely formed by material ejected from the spinning asteroids that later settled back on their surfaces.
In the new study, Sunshine and her team identified the fan-shaped streaks by developing sophisticated image processing techniques to remove shadows cast by boulders and correct for uneven illumination across the surface, the statement said.
“As we refined our 3D model of the moon, the fan-shaped streaks became clearer, not fainter,” study co-author Tony Farnham, a researcher at the University of Maryland, said in the statement. “It confirmed for us that we were working with something real.”
The team found that debris was leaving Didymos at about 30.7 centimeters (12.1 inches) per second — so slowly that the impacts would create deposits instead of craters. The streaks are also clustered around the moon’s equator, consistent with models that predict where the material spun off from Didymos is most likely to land, researchers say.
Scientists are eager to see what the transformed Dimorphos now looks like up close. That opportunity could come as soon as December, when the European Space Agency Hera spacecraft arrives in the Dimorphos-Didymos system.
The $398 million Hera mission will conduct a detailed post-impact survey of Dimorphos and may reveal whether the fan-shaped streaks survived the collision, researchers say. It can also detect new jet-like patterns created by boulders knocked loose during the impact, providing new clues about how asteroids evolve and which ones may pose a threat to the earth.
“These new details emerging from this research are critical to our understanding of near-Earth asteroids and how they evolve,” Sunshine said in the statement. “We now know that they are far more dynamic than previously thought, which will help us improve our models and our planetary defense measures.”
