asteroid

SpaceX launches Europe’s Hera asteroid mission ahead of Hurricane Milton

asteroid, Commercial space, Dart, european space agency, falcon 9, Federal Aviation Administration, hera, launch, planetary defense, Science, Space, spacex / Rejus Almole / October 7, 2024

The launch of another important mission, NASA’s Europa Clipper, is on hold due to Hurricane Milton.

The European Space Agency’s Hera spacecraft flies away from the Falcon 9 rocket’s upper stage a little more than an hour after liftoff Monday. Credit: SpaceX

Two years ago, a NASA spacecraft smashed into a small asteroid millions of miles from Earth to test a technique that could one day prove useful to deflect an object off a collision course with Earth. The European Space Agency launched a follow-up mission Monday to go back to the crash site and see the damage done.

The nearly $400 million (363 million euro) Hera mission, named for the Greek goddess of marriage, will investigate the aftermath of a cosmic collision between NASA’s DART spacecraft and the skyscraper-size asteroid Dimorphos on September 26, 2022. NASA’s Double Asteroid Redirection Test mission was the first planetary defense experiment, and it worked, successfully nudging Dimorphos off its regular orbit around a larger companion asteroid named Didymos.

But NASA had to sacrifice the DART spacecraft in the deflection experiment. Its destruction meant there were no detailed images of the condition of the target asteroid after the impact. A small Italian CubeSat deployed by DART as it approached Dimorphos captured fuzzy long-range views of the collision, but Hera will perform a comprehensive survey when it arrives in late 2026.

“We are going to have a surprise to see what Dimorphos looks like, which is, first, scientifically exciting, but also important because if we want to validate the technique and validate the model that can reproduce the impact, we need to know the final outcome,” said Patrick Michel, principal investigator on the Hera mission from Côte d’Azur Observatory in Nice, France. “And we don’t have it. With Hera, it’s like a detective going back to the crime scene and telling us what really happened.”

Last ride before the storm

The Hera spacecraft, weighing in at 2,442 pounds (1,108 kilograms), lifted off on top of a SpaceX Falcon 9 rocket at 10: 52 am EDT (14: 52 UTC) Monday from Cape Canaveral Space Force Station, Florida.

Officials weren’t sure the weather conditions at Cape Canaveral would permit a launch Monday, with widespread rain showers and a blanket of cloud cover hanging over Florida’s Space Coast. But the conditions were just good enough to be acceptable for a rocket launch, and the Falcon 9 lit its nine kerosene-fueled engines to climb away from pad 40 after a smooth countdown.

SpaceX’s Falcon 9 rocket lifts off from Cape Canaveral Space Force Station, Florida, with ESA’s Hera mission. Credit: SpaceX

This was probably the final opportunity to launch Hera before the spaceport shutters in advance of Hurricane Milton, a dangerous Category 5 storm taking aim at the west coast of Florida. If the mission didn’t launch Monday, SpaceX was prepared to move the Falcon 9 rocket and the Hera spacecraft back inside a hangar for safekeeping until the storm passes.

Meanwhile, at NASA’s Kennedy Space Center a few miles away, SpaceX is securing a Falcon Heavy rocket with the Europa Clipper spacecraft to ride out Hurricane Milton inside a hangar at Launch Complex 39A. Europa Clipper is a $5.2 billion flagship mission to explore Jupiter’s most enigmatic icy moon, and it was supposed to launch Thursday, the same day Hurricane Milton will potentially move over Central Florida.

NASA announced Sunday that it is postponing Europa Clipper’s launch until after the storm.

“The safety of launch team personnel is our highest priority, and all precautions will be taken to protect the Europa Clipper spacecraft,” said Tim Dunn, senior launch director at NASA’s Launch Services Program. “Once we have the ‘all-clear’ followed by facility assessment and any recovery actions, we will determine the next launch opportunity for this NASA flagship mission.”

Europa Clipper must launch by November 6 in order to reach Jupiter and its moon Europa in 2030. ESA’s Hera mission had a similarly tight window to get off the ground in October and arrive at asteroids Didymos and Dimorphos in December 2026.

Returning to flight

The Falcon 9 did its job Monday, accelerating the Hera spacecraft to a blistering speed of 26,745 mph (43,042 km/hr) with successive burns by its first stage booster and upper stage engine. This was the highest-speed payload injection ever achieved by SpaceX.

SpaceX did not attempt to recover the Falcon 9’s reusable booster on Monday’s flight because Hera needed all of the rocket’s oomph to gain enough speed to escape the pull of Earth’s gravity.

“Good launch, good orbit, and good payload deploy,” wrote Kiko Dontchev, SpaceX’s vice president of launch, on X.

This was the first Falcon 9 launch in nine days—an unusually long gap between SpaceX missions—after the rocket’s upper stage misfired during a maneuver to steer itself out of orbit following an otherwise successful launch September 28 with a two-man crew heading for the International Space Station.

The upper stage engine apparently “over-burned,” and the rocket debris fell into the atmosphere short of its expected reentry corridor in the Pacific Ocean, sources said. The Federal Aviation Administration grounded the Falcon 9 rocket while SpaceX investigates the malfunction, but the FAA granted approval for SpaceX to launch the Hera mission because its trajectory would carry the rocket away from Earth, rather than back into the atmosphere for reentry.

“The FAA has determined that the absence of a second stage reentry for this mission adequately mitigates the primary risk to the public in the event of a reoccurrence of the mishap experienced with the Crew-9 mission,” the FAA said in a statement.

Members of the Hera team from ESA and its German prime contractor, OHB, pose with the spacecraft inside SpaceX’s payload processing facility in Florida. Credit: SpaceX

This was the third time the FAA has grounded SpaceX’s Falcon 9 rocket fleet in less than three months, following another upper stage failure in July that caused the destruction of 20 Starlink Internet satellites and the crash-landing of a Falcon 9 booster on an offshore drone ship in August. Federal regulators are responsible for ensuring commercial rocket launches don’t endanger the public.

These were the first major anomalies on any Falcon 9 launch since 2021.

It’s not clear when the FAA will clear SpaceX to resume launching other Falcon 9 missions. However, the launch of the Europa Clipper mission on a Falcon Heavy rocket, which uses essentially the same upper stage as a Falcon 9, is not licensed by the FAA because it is managed by NASA, another government agency. NASA will have final authority on whether to give the green light for the launch of Europa Clipper.

Surveying the damage

ESA’s Hera spacecraft is on course for a flyby of Mars next March to take advantage of the red planet’s gravity to slingshot itself on a trajectory to intercept its twin target asteroids. Near Mars, Hera will zoom relatively close to the planet’s asteroid-like moon, Deimos, to obtain rare closeups.

Then, Hera will approach Didymos and Dimorphos a little more than two years from now, maneuvering around the binary asteroid system at a range of distances, eventually moving as close as about a half-mile (1 kilometer) away.

Italy’s LICIACube spacecraft snapped this image of asteroids Didymos (lower left) and Dimorphos (upper right) a few minutes after the impact of DART on September 26, 2022. Credit: ASI/NASA

Dimorphos orbits Didymos once every 11 hours and 23 minutes, roughly 32 minutes shorter than the orbital period before DART’s impact in 2022. This change in orbit proved the effectiveness of a kinetic impactor in deflecting an asteroid that threatens Earth.

Dimorphos, the smaller of the two asteroids, has a diameter of around 500 feet (150 meters), while Didymos measures approximately a half-mile (780 meters) wide. Neither asteroid poses a risk to Earth, so NASA chose them as the objective for DART.

The Hubble Space Telescope spotted a debris field trailing the binary asteroid system after DART’s impact. Astronomers identified at least 37 boulders drifting away from the asteroids, material ejected when the DART spacecraft slammed into Dimorphos at a velocity of 14,000 mph (22,500 kmh).

Scientists will use Hera, with its suite of cameras and instruments, to study how the strike by DART changed the asteroid Dimorphos. Did the impact leave a crater, or did it reshape the entire asteroid? There are “tentative hints” that the asteroid’s shape changed after the collision, according to Michael Kueppers, Hera’s project scientist at ESA.

“If this is the case, it would also mean that the cohesion of Dimorphos is extremely low; that indeed, even an object the size of Dimorphos would be held together by its weight, by its gravity, and not by cohesion,” Kueppers said. “So it really would be a rubble pile.”

Hera will also measure the mass of Dimorphos, something DART was unable to do. “That is important to measure the efficiency of the impact… which was the momentum that was transferred from the impacting satellite to the asteroid,” Kueppers said.

This NASA/ESA Hubble Space Telescope image of the asteroid Dimorphos was taken on December 19, 2022, nearly three months after the asteroid was impacted by NASA’s DART mission. Hubble’s sensitivity reveals a few dozen boulders knocked off the asteroid by the force of the collision. Credit: NASA, ESA, D. Jewitt (UCLA)

The central goal of Hera is to fill the gaps in knowledge about Didymos and Dimorphos. Precise measurements of DART’s momentum, coupled with a better understanding of the interior structure of the asteroids, will allow future mission planners to know how best to deflect a hazardous object threatening Earth.

“The third part is to generally investigate the two asteroids to know their physical properties, their interior properties, their strength, essentially to be able to extrapolate or to scale the outcome of DART to another impact should we really need it one day,” Kueppers said.

Hera will release two briefcase-size CubeSats, named Juventas and Milani, to work in concert with ESA’s mothership. Juventas carries a compact radar to probe the internal structure of the smaller asteroid and will eventually attempt a landing on Dimorphos. Milani will study the mineral composition of individual boulders around DART’s impact site.

“This is the first time that we send a spacecraft to a small body, which is actually a multi-satellite system, with one main spacecraft and two CubeSats doing closer proximity operations,” Michel said. “This has never been done.”

Artist’s illustration of the Hera spacecraft with its two deployable CubeSats, Juventas and Milani, in the vicinity of the Didymos binary asteroid system. The CubeSats will communicate with ground teams via radio links with the Hera mothership. Credit: ESA-Science Office

One source of uncertainty, and perhaps worry, about the environment around Didymos and Dimorphos is the status of the debris field observed by Hubble a few months after DART’s impact. But this is not likely to be a problem, according to Kueppers.

“I’m not really worried about potential boulders at Didymos,” he said, recalling the relative ease with which ESA’s Rosetta spacecraft navigated around an active comet from 2014 through 2016.

Ignacio Tanco, ESA’s flight director for Hera, doesn’t share Kuepper’s optimism.

“We didn’t hit the comet with a hammer,” said Tanco, who is responsible for keeping the Hera spacecraft safe. “The debris question for me is actually a source of… I wouldn’t say concern, but certainly precaution. It’s something that we’ll need to approach carefully once we get there.”

“That’s the difference between an engineer and a scientist,” Kuepper joked.

Scientists originally wanted Hera to be in the vicinity of the Didymos binary asteroid system before DART’s arrival, allowing it to directly observe the impact and its fallout. But ESA’s member states did not approve funding for the Hera mission in time, and the space agency only signed the contract to build the Hera spacecraft in 2020.

ESA first studied a mission like DART and Hera more than 20 years ago, when scientists proposed a mission called Don Quijote to get an asteroid deflection. But other missions took priority in Europe’s space program. Now, Hera is on course to write the final chapter of the story of humanity’s first planetary defense test.

“This is our contribution of ESA to humanity to help us in the future protect our planet,” said Josef Aschbacher, ESA’s director general.

Stephen Clark is a space reporter at Ars Technica, covering private space companies and the world’s space agencies. Stephen writes about the nexus of technology, science, policy, and business on and off the planet.

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Armada to Apophis—scientists recycle old ideas for rare asteroid encounter

Apophis, asteroid, european space agency, NASA, osiris rex, planetary science, Ramses, Science, solar system, Space / Kris Guyer / July 20, 2024

Tick-tock —

“It will miss the Earth. It will miss the Earth. It will miss the Earth.”

Stephen Clark – Jul 20, 2024 12: 26 am UTC

This artist's concept shows the possible appearance of ESA's RAMSES spacecraft, which will release two small CubeSats for additional observations at Apophis. — Enlarge / This artist’s concept shows the possible appearance of ESA’s RAMSES spacecraft, which will release two small CubeSats for additional observations at Apophis.

For nearly 20 years, scientists have known an asteroid named Apophis will pass unusually close to Earth on Friday, April 13, 2029. But most officials at the world’s space agencies stopped paying much attention when updated measurements ruled out the chance Apophis will impact Earth anytime soon.

Now, Apophis is again on the agenda, but this time as a science opportunity, not as a threat. The problem is there’s not much time to design, build and launch a spacecraft to get into position near Apophis in less than five years. The good news is there are designs, and in some cases, existing spacecraft, that governments can repurpose for missions to Apophis, a rocky asteroid about the size of three football fields.

Scientists discovered Apophis in 2004, and the first measurements of its orbit indicated there was a small chance it could strike Earth in 2029 or in 2036. Using more detailed radar observations of Apophis, scientists in 2021 ruled out any danger to Earth for at least the next 100 years.

“The three most important things about Apophis are: It will miss the Earth. It will miss the Earth. It will miss the Earth,” said Richard Binzel, a professor of planetary science at MIT. Binzel has co-chaired several conferences since 2020 aimed at drumming up support for space missions to take advantage of the Apophis opportunity in 2029.

“An asteroid this large comes this close only once per 1,000 years, or less frequently,” Binzel told Ars. “This is an experiment that nature is doing for us, bringing a large asteroid this close, such that Earth’s gravitational forces and tidal forces are going to tug and possibly shake this asteroid. The asteroid’s response is insightful to its interior.”

It’s important, Binzel argues, to get a glimpse of Apophis before and after its closest approach in 2029, when it will pass less than 20,000 miles (32,000 kilometers) from Earth’s surface, closer than the orbits of geostationary satellites.

“This is a natural experiment that will reveal how hazardous asteroids are put together, and there is no other way to get this information without vastly complicated spacecraft experiments,” Binzel said. “So this is a once-per-many-thousands-of-years experiment that nature is doing for us. We have to figure out how to watch.”

This week, the European Space Agency announced preliminary approval for a mission named RAMSES, which would launch in April 2028, a year ahead of the Apophis flyby, to rendezvous with the asteroid in early 2029. If ESA member states grant full approval for development next year, the RAMSES spacecraft will accompany Apophis throughout its flyby with Earth, collecting imagery and other scientific measurements before, during, and after closest approach.

The challenge of building and launching RAMSES in less than four years will serve as good practice for a potential future real-world scenario. If astronomers find an asteroid that’s really on a collision course with Earth, it might be necessary to respond quickly. Given enough time, space agencies could mount a reconnaissance mission, and if necessary, a mission to deflect or redirect the asteroid, likely using a technique similar to the one demonstrated by NASA’s DART mission in 2022.

“RAMSES will demonstrate that humankind can deploy a reconnaissance mission to rendezvous with an incoming asteroid in just a few years,” said Richard Moissl, head of ESA’s planetary defense office. “This type of mission is a cornerstone of humankind’s response to a hazardous asteroid. A reconnaissance mission would be launched first to analyze the incoming asteroid’s orbit and structure. The results would be used to determine how best to redirect the asteroid or to rule out non-impacts before an expensive deflector mission is developed.”

Shaking off the cobwebs

In order to make a 2028 launch feasible for RAMSES, ESA will reuse the design of a roughly half-ton spacecraft named Hera, which is scheduled for launch in October on a mission to survey the binary asteroid system targeted by the DART impact experiment in 2022. Copying the design of Hera will reduce the time needed to get RAMSES to the launch pad, ESA officials said.

“Hera demonstrated how ESA and European industry can meet strict deadlines and RAMSES will follow its example,” said Paolo Martino, who leads ESA’s development of Ramses, which stands for the Rapid Apophis Mission for Space Safety.

ESA’s space safety board recently authorized preparatory work on the RAMSES mission using funds already in the agency’s budget. OHB, the German spacecraft manufacturer that is building Hera, will also lead the industrial team working on RAMSES. The cost of RAMSES will be “significantly lower” than the 300-million-euro ($380 million) cost of the Hera mission, Martino wrote in an email to Ars.

“There is still so much we have yet to learn about asteroids but, until now, we have had to travel deep into the Solar System to study them and perform experiments ourselves to interact with their surface,” said Patrick Michel, a planetary scientist at the French National Center for Scientific Research, and principal investigator on the Hera mission.

“For the first time ever, nature is bringing one to us and conducting the experiment itself,” Michel said in a press release. “All we need to do is watch as Apophis is stretched and squeezed by strong tidal forces that may trigger landslides and other disturbances and reveal new material from beneath the surface.”

Assuming it gets the final go-ahead next year, RAMSES will join NASA’s OSIRIS-APEX mission in exploring Apophis. NASA is steering the spacecraft, already in space after its use on the OSIRIS-REx asteroid sample return mission, toward a rendezvous with Apophis in 2029, but it won’t arrive at its new target until a few weeks after its close flyby of Earth. The intricacies of orbital mechanics prevent a rendezvous with Apophis any earlier.

Observations from OSIRIS-APEX, a larger spacecraft than RAMSES with a sophisticated suite of instruments, “will deliver a detailed look of what Apophis is like after the Earth encounter,” Binzel said. “But until we establish the state of Apophis before the Earth encounter, we have only one side of the picture.”

Enlarge / At its closest approach, asteroid Apophis will closer to Earth than the ring of geostationary satellites over the equator.

Scientists are also urging NASA to consider launching a pair of mothballed science probes on a trajectory to fly by Apophis some time before its April 2029 encounter with Earth. These two spacecraft were built for NASA’s Janus mission, which the agency canceled last year after the mission fell victim to launch delays with NASA’s larger Psyche asteroid explorer. The Janus probes were supposed to launch on the same rocket as Psyche, but problems with the Psyche mission forced a delay in the launch of more than one year.

Despite the delay, Psyche could still reach its destination in the asteroid belt, but the new launch trajectory meant Janus would be unable to visit the two binary asteroids scientists originally wanted to explore with the probes. After spending nearly $50 million on the mission, NASA put the twin Janus spacecraft, each about the size of a suitcase, into long-term storage.

At the most recent workshop on Apophis missions in April, scientists heard presentations on more than 20 concepts for spacecraft and instrument measurements at Apophis.

They included an idea from Blue Origin, Jeff Bezos’s space company, to use its Blue Ring space tug as a host platform for multiple instruments and landers that could descend to the surface of Apophis, assuming research institutions have enough time and money to develop their payloads. A startup named Exploration Laboratories has proposed partnering with NASA’s Jet Propulsion Laboratory on a small spacecraft mission to Apophis.

“At the conclusion of the workshop, it was my job to try to bring forward some consensus, because if we don’t have some consensus on our top priority, we may end up with nothing,” Binzel said. “The consensus recommendation for ESA was to more forward with RAMSES.”

Workshop participants also gently nudged NASA to use the Janus probes for a mission to Apophis. “Apophis is a mission in search of a spacecraft, and Janus is a spacecraft in search of a mission,” Binzel said. “As a matter of efficiency and basic logic, Janus to Apophis is the highest priority.”

A matter of money

But NASA’s science budget, and especially funding for its planetary science vision, is under stress. Earlier this week, NASA canceled an already-built lunar rover named VIPER after spending $450 million on the mission. The mission had exceeded its original development cost by greater than 30 percent, prompting an automatic cancellation review.

The funding level for NASA’s science mission directorate this year is nearly $500 million less than last year’s budget, and $900 million below the White House’s budget request for fiscal year 2024. Because of the tight budget, NASA officials have said, for now, they are not starting development of any new planetary science missions as they focus on finishing projects already in the pipeline, like the Europa Clipper mission, the Dragonfly quadcopter to visit Saturn’s moon Titan, and the Near-Earth Object (NEO) Surveyor telescope to search for potentially hazardous asteroids.

These grainy radar views of asteroid Apophis were captured using radars at NASA's Goldstone Deep Space Communications Complex in California and Green Bank Telescope in West Virginia. — Enlarge / These grainy radar views of asteroid Apophis were captured using radars at NASA’s Goldstone Deep Space Communications Complex in California and Green Bank Telescope in West Virginia.

NASA has asked the Janus team to look at the feasibility of launching on the same rocket as NEO Surveyor in 2027, according to Dan Scheeres, the Janus principal investigator at the University of Colorado. With such a launch in 2027, Janus could capture the first up-close images of Apophis before RAMSES and OSIRIS-APEX get there.

“This is something that we’re currently presenting in some discussions with NASA, just to make sure that they understand what the possibilities are there,” Scheeres said in a meeting last week of the Small Bodies Advisory Group, which represents the asteroid science community.

“These spacecraft are capable of performing future scientific flyby missions to near-Earth asteroids,” Scheeres said. “Each spacecraft has a high-quality Malin visible imager and a thermal infrared imager. Each spacecraft has the ability to track and image an asteroid system through a close, fast flyby.”

“The scientific return from an Apophis flyby by Janus could be one of the best opportunities out there,” said Daniella DellaGiustina, lead scientist on the OSIRIS-APEX mission from the University of Arizona.

Binzel, who has led the charge for Apophis missions, said there is also some symbolic value to having a spacecraft escort the asteroid by Earth. Apophis will be visible in the skies over Europe and Africa when it is closest to our planet.

“When 2 billion people are watching this, they are going to ask, ‘What are our space agencies doing?’ And if the answer is, ‘Oh, we’ll be there. We’re getting there,’ which is OSIRIS-APEX, I don’t think that’s a very satisfying answer,” Binzel said.

“As the international space community, we want to demonstrate on April 13, 2029, that we are there and we are watching, and we are watching because we want to gain the most knowledge and the most understanding about these objects that is possible, because someday it could matter,” Binzel said. “Someday, our detailed knowledge of hazardous asteroids would be among the most important knowledge bases for the future of humanity.”

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How the perils of space have affected asteroid Ryugu

asteroid, astronomy, magneticsm, planetary science, Ryugu, Science / Paul Patrick / May 19, 2024

Magnets: how do they stop working? —

Ryugu’s parent body appears to have had a fair amount of water present, too.

Elizabeth Rayne – May 19, 2024 11: 55 am UTC

Grey image of a complicated surface composed of many small rocks bound together by dust. — Enlarge / The surface of Ryugu. Image credit: JAXA, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Chiba Institute of Technology, Meiji University, Aizu University, AIST

An asteroid that has been wandering through space for billions of years is going to have been bombarded by everything from rocks to radiation. Billions of years traveling through interplanetary space increase the odds of colliding with something in the vast emptiness, and at least one of those impacts had enough force to leave the asteroid Ryugu forever changed.

When the Japanese Space Agency’s Hayabusa2 spacecraft touched down on Ryugu, it collected samples from the surface that revealed that particles of magnetite (which is usually magnetic) in the asteroid’s regolith are devoid of magnetism. A team of researchers from Hokkaido University and several other institutions in Japan are now offering an explanation for how this material lost most of its magnetic properties. Their analysis showed that it was caused by at least one high-velocity micrometeoroid collision that broke the magnetite’s chemical structure down so that it was no longer magnetic.

“We surmised that pseudo-magnetite was created [as] the result of space weathering by micrometeoroid impact,” the researchers, led by Hokkaido University professor Yuki Kimura, said in a study recently published in Nature Communications.

What remains…

Ryugu is a relatively small object with no atmosphere, which makes it more susceptible to space weathering—alteration by micrometeoroids and the solar wind. Understanding space weathering can actually help us understand the evolution of asteroids and the Solar System. The problem is that most of our information about asteroids comes from meteorites that fall to Earth, and the majority of those meteorites are chunks of rock from the inside of an asteroid, so they were not exposed to the brutal environment of interplanetary space. They can also be altered as they plummet through the atmosphere or by physical processes on the surface. The longer it takes to find a meteorite, the more information can potentially be lost.

Once part of a much larger body, Ryugu is a C-type, or carbonaceous, asteroid, meaning it is made of mostly clay and silicate rocks. These minerals normally need water to form, but their presence is explained by Ryugu’s history. It is thought that the asteroid itself was born from debris after its parent body was smashed to pieces in a collision. The parent body was also covered in water ice, which explains the magnetite, carbonates, and silicates found on Ryugu—these need water to form.

Magnetite is a ferromagnetic (iron-containing and magnetic) mineral. It is found in all C-type asteroids and can be used to determine their remanent, or remaining, magnetization. The remanent magnetization of an asteroid can reveal how intense the magnetic field was at the time and place of the magnetite’s formation.

Kimura and his team were able to measure remanent magnetization in two magnetite fragments (known as framboids because of their particular shape) from the Ryugu sample. It is proof of a magnetic field in the nebula our Solar System formed in, and shows the strength of that magnetic field at the time that the magnetite formed.

However, three other magnetite fragments analyzed were not magnetized at all. This is where space weathering comes in.

…and what was lost

Using electron holography, which is done with a transmission electron microscope that sends high-energy electron waves through a specimen, the researchers found that the three framboids in question did not have magnetic chemical structures. This made them drastically different from magnetite.

Further analysis with scanning transmission electron microscopy showed that the magnetite particles were mostly made of iron oxides, but there was less oxygen in those particles that had lost their magnetism, indicating that the material had experienced a chemical reduction, where electrons were donated to the system. This loss of oxygen (and oxidized iron) explained the loss of magnetism, which depends on the organization of the electrons in the magnetite. This is why Kimura refers to it as “pseudo-magnetite.”

But what triggered the reduction that demagnetized the magnetite in the first place? Kimura and his team found that there were more than a hundred metallic iron particles in the part of the specimen that the demagnetized framboids had come from. If a micrometeorite of a certain size had hit that region of Ryugu then it would have produced approximately that many particles of iron from the magnetite framboids. The researchers think this mystery object was rather small, or it would have had to have been moving incredibly fast.

“With increasing impact velocity, the estimated projectile size decreases,” they said in the same study.

Pseudo-magnetite might sound like an imposter, but it will actually help upcoming investigations that seek to find out more about what the early Solar System was like. Its presence indicates the former presence of water on an asteroid, as well as space weathering, such as micrometeoroid bombardment, that affected the asteroid’s composition. How much magnetism was lost also affects the overall remanence of the asteroid. Remanence is important in determining an object’s magnetism and the intensity of the magnetic field around it when it formed. What we know of the Solar System’s early magnetic field has been reconstructed from remanence records, many of which come from magnetite.

Some magnetic properties of those particles might have been lost eons ago, but so much more could be gained in the future from what remains.

Nature Communications, 2024. DOI: 10.1038/s41467-024-47798-0

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