[ad_1]
If the possibility of a asteroid called Bennu slamming on Earth a lifetime from now on kept you awake at night, NASA scientists believe you can rest a little easier.
that of the agency OSIRIS-REx spacecraft has spent more than two years in narrow orbit around space rock. And with this incredibly detailed view of the asteroid, experts studying the potential impacts of space rock with Earth were able to refine their existing models of Bennu’s future.
As a result, the scientists behind the new research now say they are convinced that the probability of the total impact of the asteroid up to 2300 is only 1 in 1750. Estimates produced before arrival of OSIRIS-REx in the space rock counted the cumulative probability of a Determination impact between the years 2175 and 2199 at 1 in 2,700, according to Nasa. While this is a slightly higher risk than previous estimates, it represents a tiny change from an already tiny risk, NASA said.
Related: NASA spacecraft leaves asteroid Bennu to bring pieces to Earth
Read more: How the OSIRIS-REx team creates these photos of the asteroid Bennu
Technically, it’s a small increase in risk, but the scientists behind the new research say they’re not worried about a potential impact. Plus, the lessons the research offers for calculating the trajectory of asteroids could reduce concerns about the potential impacts of other asteroids more than enough to compensate.
“The probability of impact has increased slightly, but it’s not a significant change, the probability of impact is about the same,” said lead author Davide Farnocchia, who works at the Center for Near Earth Object. NASA Studies in California, at a press conference. held Wednesday (August 11). “I think overall the situation has improved.”
Precision matters
I think overall the situation has improved.
– Davide Farnocchia, lead author of the study
OSIRIS-REx (formerly known as Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) launched in September 2016 and slipped into orbit around asteroid Bennu in December 2018.
After arriving, the spacecraft spent nearly two and a half years studying space rock from orbit, diving, hovering above, and inspecting the rock in every way possible.
“The trajectory of the spacecraft was really amazing – I compare it to a hummingbird,” said Dante Lauretta, a planetologist at the University of Arizona, OSIRIS-REx principal investigator and author of the new research, at the conference. press conference. . “We were able to enter orbit, we were able to leave orbit, we were able to enter a variety of imaging angles.”
Throughout this time, the spacecraft constantly recorded its position relative to the Earth and the asteroid. Using this data, the team behind the new research was able to refine their understanding of the location and movement of space rock for nearly two and a half years.
The spacecraft’s visit to the asteroid peaked in October 2020, when OSIRIS-REx ripped off a sample of Bennu to hide. In May, the spacecraft and its precious cargo bid farewell to the asteroid and turned back to Earth, where OSIRIS-REx will drop off the sample capsule in September 2023. The delivery will give scientists the opportunity rare to study asteroid material using all the sophisticated equipment. terrestrial laboratories have to offer.
But scientists don’t need to get their hands on this sample of material to dig within two and a half years of observations of the spacecraft. Add in the work of astronomers observing Bennu from the ground before OSIRIS-REx was even an idea and scientists have about 20 years of data to track a single rock in space.
Scientific models of asteroid trajectories always involve some degree of uncertainty, as a multitude of forces pull at a space rock as it shakes around inside. solar system. This uncertainty persists even in new and improved models of Bennu’s future trajectory, but with the OSIRIS-REx observations, scientists have been able to significantly reduce their uncertainty about Bennu’s fate.
Among other factors, the researchers were able to explain the tiny orbital changes that forcing like solar radiation, the impact of relativity and the gravity of hundreds of other relatively large asteroids passing through the vicinity.
In addition to factors like these that affect every object in the solar system (albeit to a tiny degree), the team was also able to verify the impact of two unusual characteristics of Bennu in particular: the plumes of dust that regularly shoot at the asteroid and the rock’s interaction with the spacecraft itself.
One factor of particular concern to scientists is 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.
“The Yarkovsky effect acting on Bennu is equivalent to the weight of three grapes,” Farnocchia said. “This is what really drives Bennu’s move into the future, because this acceleration is persistent, its effect accumulates over time and becomes very large by the time you reach 2135.”
However, despite scientists’ best efforts, predicting Bennu’s course after 2135 is still tricky. In September of that year, Bennu will pass in front of Earth – not close enough for there to be a risk of impact, but certainly close enough for Earth’s gravity to push the asteroid down its path a bit. The precision with which this dance takes place will shape Bennu’s trajectory over the next decades and centuries.
With this remaining uncertainty and other similar events likely to occur in the future, scientists now say the probability of Bennu’s total impact through 2300 is around 1 in 1750, according to one. NASA statement on the new research. During this period, the date of most concern is September 24, 2182; Even on that day, Bennu’s probability of impact is only 1 in 2,700.
Beyond Bennu
Of course, Bennu isn’t the only space rock scientists are worried about. Planetary Defense is dedicated to identifying all asteroids that could have a significant impact on Earth. One aspect of that work is finding as many near-Earth asteroids as possible – scientists have cataloged more than 26,000 to date, according to Nasa.
But to accurately identify which asteroids might actually pose a risk, scientists need to be able to calculate the trajectory of a space rock as accurately as possible. This trajectory is based on existing observations of an asteroid’s location, of course, but scientists have known for years that factors like the Yarkovsky effect can cloud their calculations.
New data from OSIRIS-REx quantifying this three-grape Yarkovsky effect should help scientists understand how the same effect also shapes the trajectories of other asteroids, the researchers say.
“We were able for the first time to test our models on an asteroid trajectory at levels never really tried before,” said Farnocchia. “The results are generally valid for all other asteroids, we can apply these models and be sure they are extremely accurate.”
The research is described in a paper published Tuesday (August 10) in the journal Icarus.
Email Meghan Bartels at [email protected] or follow her on Twitter @meghanbartels. follow us on Twitter @Spacedotcom and on Facebook.
[ad_2]
Source link