NASA boosts impact risk from ‘potentially hazardous’ asteroid Bennu
Potentially hazardous asteroid Bennu just became slightly more potentially dangerous.
Over a century from now, in 2135, a half-kilometre-wide asteroid named 101955 Bennu will pass between the Earth and the Moon. While there is absolutely no chance of an impact with Bennu at that time, the close encounter throws uncertainty into the predictions. As a result, there’s no saying for sure that Earth will be safe from Bennu afterward.
Before NASA sent their OSIRIS-REx spacecraft to Bennu, astronomers tracked asteroid Bennu using telescopes. Their observations gave us very accurate calculations of Bennu’s orbit. The relatively close passes of Bennu in 1999, 2005 and 2011 helped with this. Although it was officially classified as a “Potentially Hazardous Asteroid” (PHA), NASA could rule out any possibility of a Bennu impact for the next 100+ years.
However, the September 2135 encounter added an extra complication. The asteroid comes very close to Earth at that time. On September 24 of that year, its absolute minimum distance could be around 110,000 km from the planet’s surface or less than one-third the distance to the Moon. As it flies past, it will encounter one of several ‘gravitational keyholes’. As it passes through one of these tiny points in space, Earth’s gravity will tug on the asteroid and alter its orbit around the Sun.
Bennu Sept 2135 keyholes – NASA/Goddard
This screenshot of an animation used during the NASA press briefing on Wednesday, August 11, 2021, shows the potential paths of Bennu during the 2135 flyby, based on the most up-to-date telescope observations, with a separate ‘gravitational keyhole’ for each path. Credit: NASA/Goddard
Even with the carefully plotted orbit of Bennu, the minor uncertainties made it challenging to tell which ‘keyhole’ it would pass through during that 2135 flyby. Thus, there was no way to know with any certainty which orbit it would end up on afterward.
This was of great concern to scientists because it introduced over 150 possible impacts, with a cumulative 1 in 2,700 impact chance between 2135 and 2300. The most likely impact would be on September 24, 2182.
Bennu Sept 2182 potential impact – NASA/Goddard
The effects of one particular ‘gravitational keyhole’ could have disastrous results in 2182. Credit: NASA/Goddard
With OSIRIS-REx following along with the asteroid for over two years, though, it gave scientists an unprecedented chance to closely track the influence of the Yarkovsky effect.
The Yarkovsky effect is a tiny, constant ‘push’ that an asteroid receives as it radiates heat into space.
Watch below: How the Sun pushes asteroids around the solar system
According to Davide Farnocchia from the Center for Near Earth Object Studies (CNEOS) at NASA’s Jet Propulsion Lab, who is the lead author of a new study published this week, the force of this ‘push’ on Bennu is equivalent to about the weight of three grapes.
“Think about that, just three grapes,” Farnocchia said in a NASA teleconference on Wednesday. “Because this acceleration is persistent, its effect builds up over time, and it becomes very significant by the time we get to 2135.”
“The OSIRIS-REx data give us so much more precise information, we can test the limits of our models and calculate the future trajectory of Bennu to a very high degree of certainty through 2135,” Farnocchia said in a NASA press release. “We’ve never modelled an asteroid’s trajectory to this precision before.”
Based on their study of the Yarkovsky effect on Bennu, Farnocchia and his colleagues calculated an updated cumulative probability of a Bennu impact between 2135 and 2200. Instead of 1 in 2,700, the chance is now just 1 in 1,750. The individual chance of an impact on September 24, 2182, is now 1 in 2,700.
It should be noted that these probabilities are tiny.
A 1 in 1,750 chance is equal to a 0.057 per cent impact probability, while 1 in 2,700 is equivalent to 0.037 per cent. That means there’s over a 99.94 per cent chance that Bennu will miss Earth on all the potential encounters it has towards the end of the 22nd century. Specifically for September 2182, there’s a 99.96 per cent chance of a miss.
During their research, Farnocchia and the others accounted for every conceivable force that could affect Bennu’s orbit. They even considered whether the Touch-and-Go (TAG) maneuver that netted NASA a sample of the asteroid was enough to alter its trajectory.
Watch below: NASA’s OSIRIS-REx tags asteroid Bennu
“The force exerted on Bennu’s surface during the TAG event were tiny even in comparison to the effects of other small forces considered,” Rich Burns, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center, said in the press release. “TAG did not alter Bennu’s likelihood of impacting Earth.”
The next steps in determining Bennu’s true potential as a threat to Earth will come in 2023 and 2037.
In 2023, OSIRIS-REx will swing past Earth. On its way past, it will drop off the sample it collected from Bennu’s surface back in the Fall of 2020. As scientists examine these samples in the laboratory, we will learn more about Bennu’s composition. This might provide information about how we could deflect such an asteroid on an impact trajectory.
In 2037, Bennu will be making its next close (but safe) flyby past Earth. During this pass, radio telescopes can gather radar data on the asteroid. These readings will help confirm the calculations made based on OSIRIS-REx’s data and give us an even better estimate of its exact path for that 2135 encounter.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
