How precisely that dance plays out will shape Bennu's trajectory over the next decades and centuries. In September of that year, Bennu will swing past Earth - not close enough that there's any risk of an impact, but certainly close enough that Earth's gravity could nudge the asteroid a bit on its path. However, despite the scientists' best efforts, predicting Bennu's course after 2135 is still tricky.
"That's what's really driving the motion of Bennu into the future, because this acceleration is persistent, its effect builds up over time, and it becomes very significant by the time you get to 2135." "The Yarkovsky effect acting on Bennu is equivalent to the weight of three grapes," Farnocchia said.
One factor that scientists were particularly concerned about is called the Yarkovsky effect, which is triggered by the constant temperature fluctuations that occur as regions of the asteroid pass in and out of daylight, gently pushing the asteroid. In addition to factors like these that affect all solar system objects (albeit to a tiny degree), the team was also able to check the impact of two unusual characteristics of Bennu specifically: the plumes of dust that regularly shoot off the asteroid and the rock's interaction with the spacecraft itself. That uncertainty remains even in the new and improved models of Bennu's future path, but with the OSIRIS-REx observations, scientists were able to dramatically reduce their uncertainty about Bennu's fate.Īmong other factors, the researchers were able to account for the tiny orbital changes that forces like radiation from the sun, the impact of relativity and the gravity of hundreds of other relatively large asteroids whizzing through the neighborhood. Scientists' models of asteroid trajectories always include some degree of uncertainty, since a multitude of forces tug at a space rock as it rattles around the inner solar system. Add in astronomers' work observing Bennu from the ground before OSIRIS-REx was even an idea and scientists have about 20 years of data tracking a single space rock.
The delivery will give scientists the rare opportunity to study asteroid material using all the sophisticated equipment terrestrial laboratories have to offer.īut scientists don't need to get their hands on that sample material to dig into the spacecraft's two and a half years of observations. In May, the spacecraft and its precious cargo bid farewell to the asteroid and turned back for Earth, where OSIRIS-REx will deposit the sample capsule in September 2023. The spacecraft's visit to the asteroid culminated in October 2020, when OSIRIS-REx snatched a sample of Bennu to stash away. Using that data, the team behind the new research were able to fine-tune their understanding of the space rock's location and movement for nearly two and a half years. Throughout that time, the spacecraft constantly logged its location with respect to Earth and to the asteroid. "We were able to go into orbit, we were able to leave orbit, we were able to get into a variety of imaging angles." "The trajectory of the spacecraft was really amazing - I compare it to a hummingbird," Dante Lauretta, a planetary scientist at the University of Arizona, the principal investigator for OSIRIS-REx and an author on the new research, said during the news conference. OSIRIS-REx (formally known as Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) launched in September 2016 and slipped into orbit around the asteroid Bennu in December 2018.Īfter its arrival, the spacecraft spent nearly two and a half years studying the space rock from orbit, swooping in, hovering overhead and inspecting the rock in every way possible. I think that, overall, the situation has improved. "I think that, overall, the situation has improved." Precision counts "The impact probability went up just a little bit but it's not a significant change, the impact probability is pretty much the same," lead author Davide Farnocchia, who works at NASA's Center for Near Earth Object Studies in California, said during a news conference held Wednesday (Aug.
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