OSIRIS-Rex got to Know Bennu Really Well. Apparently, There’s now a 1-in-1,750 Chance That it’ll hit Earth by 2300

This mosaic image of asteroid Bennu is composed of 12 images collected on Dec. 2, 2018, by the OSIRIS-REx spacecraft's PolyCam instrument from a range of 15 miles (24 kilometers). Credit: NASA/Goddard/University of Arizona

Asteroid Bennu is one of the two most hazardous known asteroids in our Solar System. Luckily, the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer) spacecraft orbited Bennu for more than two years and gathered data that has allowed scientists to better understand the asteroid’s future orbit, trajectory and Earth-impact probability, and even rule out some future impact possibilities.

In the most precise calculations of an asteroid’s trajectory ever made, researchers determined Bennu’s total impact probability through the year 2300 is really small — about 1 in 1,750 (or 0.057%). The team’s paper says the asteroid will make a close approach to Earth in 2135, where Bennu will pose no danger at that time. But Earth’s gravity will alter the asteroid’s path, and the team identifies Sept. 24, 2182 as the most significant single date in terms of a potential impact, with an impact probability of 1 in 2,700 (or about 0.037%).

“The impact probability went up just a little bit, but it’s not a significant change,” said Davide Farnocchia, lead author of the paper, and scientist at the Center for Near Earth Object Studies at NASA’s Jet Propulsion Laboratory, speaking at a press briefing this week. Farnocchia added that means there is a 99.94% probability that Bennu is not on an impact trajectory.

“So, there is no particular reason for concern,” he said. “We have time to keep tracking the asteroid and eventually come to a final answer.”

101955 Bennu was discovered in 1999 by the Lincoln Near-Earth Asteroid Research Team. Since its discovery, Bennu has been extensively tracked with 580 ground-based optical astrometric observations. The asteroid made three relatively close passes of Earth in 1999, 2005, and 2011, during which the Arecibo and Goldstone radar stations collected a wealth of data about Bennu’s motion.

OSIRIS-REx discovered particles being ejected from asteroid Bennu shortly after arriving at the asteroid. Image Credit: NASA/Goddard/University of Arizona/Lockheed Martin

But OSIRIS-REx’s two-year reconnaissance and sample collection has provided crucial data about the 500-meter-wide asteroid, including some surprises. Scientists expected Bennu’s surface to be smooth and sandy, but the first images from OSIRIS-REx revealed a rugged boulder-field, littered with large rocks and loose gravel. The team also expected the asteroid to be geologically quiet, but just six days after arriving in orbit, the spacecraft observed the asteroid ejecting bits of rock, due to rocks on the asteroid cracking because of the day-night heat cycle. We also learned that Bennu has pieces of Vesta on it. The spacecraft also scooped up a sample of rock and dust from the asteroid’s surface in October of 2020, which it will deliver to Earth on Sept. 24, 2023, for further scientific investigation.

But OSIRIS-REx’s precise observations of Bennu’s motions and trajectory allowed for the best estimate yet of the asteroid’s future path.

“The OSIRIS-REx mission has provided exquisitely precise data on Bennu’s position and motion through space to a level never captured before on any asteroid,” said Lindley Johnson, planetary defense officer at NASA’s Planetary Defense Coordination Office at NASA.

The researchers took into account all kinds of small influences, including the tiny gravitational pull of more than 300 other asteroids, and the drag caused by interplanetary dust. They even checked to see if OSIRIS-REx pushed the asteroid off course when the spacecraft briefly touched its rocky surface with its Touch-And-Go (TAG) sample collection maneuver. But that event had a negligible effect, as expected.

The researchers especially focused on a phenomenon called the Yarkovsky effect, where an object in space would, over long periods of time, be noticeably nudged in its orbit by the slight push created when it absorbs sunlight and then re-emits that energy as heat. Over short timeframes, this thrust is minuscule, but over long periods, the effect on the asteroid’s position builds up and can play a significant role in changing an asteroid’s path.

“The Yarkovsky effect will act on all asteroids of all sizes, and while it has been measured for a small fraction of the asteroid population from afar, OSIRIS-REx gave us the first opportunity to measure it in detail as Bennu travelled around the Sun,” said Steve Chesley, senior research scientist at JPL and study co-investigator, in a press release. “The effect on Bennu is equivalent to the weight of three grapes constantly acting on the asteroid – tiny, yes, but significant when determining Bennu’s future impact chances over the decades and centuries to come.”

A diagram showing OSIRIS-REx’s sampling maneuver on October 20th, 2020. Image Credit: NASA/GSFC/UA

They also were able to better determine how the asteroid’s orbit will evolve over time and whether it will pass through a “gravitational keyhole” during its 2135 close approach with Earth. These keyholes are areas in space that would set Bennu on a path toward a future impact with Earth if the asteroid were to pass through them at certain times, due to the effect of Earth’s gravitational pull.

The team wrote in their paper that “compared to the information available before the OSIRIS-REx mission, the knowledge of the circumstances of the scattering Earth encounter that will occur in 2135 improves by a factor of 20, thus allowing us to rule out many previously possible impact trajectories.”

“The orbital data from this mission helped us better appreciate Bennu’s impact chances over the next couple of centuries and our overall understanding of potentially hazardous asteroids – an incredible result,” said Dante Lauretta, OSIRIS-REx principal investigator and professor at the University of Arizona. “The spacecraft is now returning home, carrying a precious sample from this fascinating ancient object that will help us better understand not only the history of the solar system but also the role of sunlight in altering Bennu’s orbit since we will measure the asteroid’s thermal properties at unprecedented scales in laboratories on Earth.”

Further reading:
Paper published in Icarus
NASA press release

NASA has Approved a Space Telescope That Will Scan the Skies for Dangerous Near-Earth Asteroids

An artist's illustration of the NEO Surveyor, a space telescope designed to detect and catalogue NEOs. Image Credit: NASA/JPL

A lot of the threats humanity faces come from ourselves. If we were listing them, we’d include tribalism, greed, and the fact that we’re evolved primates, and our brains have a lot in common with animal brains. Our animalistic brains subject us to many of the same destructive emotions and impulses that animals are subject to. We wage war and become embroiled in intergenerational conflicts. There are genocides, pogroms, doomed boatloads of migrants, and horrible mashups of all three.

Isn’t humanity fun?

But not all of the threats we face are as intractable as our internal ones. Some threats are external, and we can leverage our technologies and our knowledge of nature in the struggle against them. Case in point: asteroids.

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Did Asteroid Impacts Provide Both the Heat and Raw Ingredients to Enable Life?

An artist's conception of an asteroid collision, which leads to how "families" of these space rocks are made in the belt between Mars and Jupiter. Credit: NASA/JPL-Caltech
An artist's conception of an asteroid collision, in the belt between Mars and Jupiter. Credit: NASA/JPL-Caltech

This is our Great Question: How did life begin on Earth? Anyone who says they have the answer is telling tall tales. We just don’t know yet.

While a definitive answer may be a long way off—or may never be found—there are some clever ways to nibble at the edges of that Great Question. A group of researchers at Kobe University in Japan are taking their own bites out of that compelling question with a question of their own: Did the heat from asteroid impacts help life get started?

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Extrasolar Object Interceptor Would be Able to Chase Down the Next Oumuamua or Borisov and Actually Return a Sample

Artist’s depiction of the Extrasolar Object Interceptor. Credit: Christopher Morrison

What if we had the ability to chase down interstellar objects passing through our Solar System, like Oumuamua or Comet Borisov? Such a spacecraft would need to be ready to go at a moment’s notice, with the capacity to increase speed and change direction quickly.

That’s the idea behind a new mission concept called the Extrasolar Object Interceptor and Sample Return spacecraft. It has received exploratory funding from NASA through its Innovative Advanced Concepts (NIAC) program.

“Bringing back samples from these objects could fundamentally change our view of the universe and our place in it,” says Christopher Morrison, an engineer from the Ultra Safe Nuclear Corporation-Tech (USNC-Tech) who submitted the proposal to NIAC.            

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If you Want to Move an Asteroid, you Need the Right Kind of Nuclear Explosion

Artist's concept of a large asteroid passing by the Earth-Moon system. Credit: A combination of ESO/NASA images courtesy of Jason Major/Lights in the Dark.

Using nuclear devices to deflect or disrupt an asteroid. Sounds a bit crazy, no? Maybe a little too Hollywood? And yet, detonating nukes in space may be necessary someday for the sake of planetary defense. In order for this method to be effective, scientists need to work out all the particulars in advance. That means knowing how much force will be necessary depending on the mass and trajectory of the asteroid.

Recently, a research collaboration between Lawrence Livermore National Laboratory (LLNL) and the Air Force Institute of Technology (AFIT) investigated how the energy output of a nuclear detonation could affect the path of an asteroid. This consisted of modeling different nuclear reactions (fission or fusion) to determine the neutron energy generated, which could potentially pave the way for a new type of asteroid redirect mission (ARM).

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100-meter Asteroid Created a Strange Impact Event in Antarctica 430,000 Years Ago

Mocked up illustration of touchdown impact on Antarctica. Credit: Mark A. Garlick.

The effects of ancient asteroid impacts on Earth are still evident from the variety of impact craters across our planet. And from the Chelyabinsk event back in 2013, where an asteroid exploded in the air above a Russian town, we know how devastating an “airburst” event can be.

Now, researchers in Antarctica have discovered evidence of a strange intermediate-type event – a combination of an impact and an airburst. The event was so devastating, its effects are still apparent even though it took place 430,000 years ago.

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Earth Gains 5,200 Tons of Dust From Space Every Year

Electron micrograph of a Concordia micrometeorite extracted from Antarctic snow at Dome C. Credit and copyright: Cécile Engrand/Jean Duprat.

Whenever I wipe the dust off my coffee table or catch a glimpse of dust motes floating in sunlight, my spacey mind always wonders, is any of that cosmic dust?

It just might be. But the amount of space dust that lands on our planet every year might surprise you.

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OSIRIS-REx Did One Last Close Flyby of Asteroid Bennu. It’s Almost Time to Come Home

After more than two years in orbit around asteroid Bennu, NASA’s OSIRIS-REx spacecraft is ready to come home. It’s bringing with it a pristine sample of space rocks that geologists here on Earth are eager to study up close. The sample will arrive in September 2023, but we won’t have to wait nearly that long for new data from OSIRIS-REx. Last week, the probe carried out one final flyby of Bennu, in an effort to photograph the sample collection site. The photographs are being downlinked now, and should be here by midweek.

If you’ve been following the OSIRIS-REx mission, you probably already know why scientists are keen to see these photographs, but if you haven’t, hold on to your hats – it’s a wild story.

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Primordial Asteroids That Never Suffered Massive Collisions all Seem to be Larger Than 100 km. Why?

2004 EW95, seen in this artist view, may be a primordial asteroid. Credit: M. Kornmesser/European Southern Observatory

Planetary systems form out of the remnant gas and dust of a primordial star. The material collapses into a protoplanetary disk around the young star, and the clumps that form within the disk eventually become planets, asteroids, or other bodies. Although we understand the big picture of planetary formation, we’ve yet to fully understand the details. That’s because the details are complicated.

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Careful Calculations Show That Earth is Safe From Asteroid Apophis for at Least 100 Years

These images of asteroid Apophis were recorded by radio antennas at the Deep Space Network’s Goldstone complex in California and the Green Bank Telescope in West Virginia. The asteroid was 10.6 million miles (17 million kilometers) away, and each pixel has a resolution of 127 feet (38.75 meters). Credit: NASA/JPL-Caltech and NSF/AUI/GBO

If you’re looking for doomsday, you can forget about asteroid Apophis. The latest radar observations have effectively ruled out any possibility of this near-Earth object (NEO) hitting Earth for the foreseeable future. 

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