Extreme solar storms are a relatively rare event. However, as more and more of our critical infrastructure moves into space, they will begin to have more and more of an impact on our daily lives, rather than just providing an impressive light show at night. So it's best to know what's coming, and a new paper from an international team of researchers led by Kseniia Golubenko and Ilya Usoskin of the University of Oulu in Finalnd found a massive Extreme Solar Particle Event (ESPE) that happened 12350 years ago, which is now considered to be the most energetic on record. 

During an ESPE, the Sun releases a stream of particles that collide with Earth's atmosphere. This type of event isn't the same as probably the most famous "solar storm" of all time, the Carrington Event, which set fire to telegraph stations worldwide in 1859. The Carrington Event was a geomagnetic storm caused by a coronal mass ejection (CME) that directly interacted with Earth's magnetic field. It didn't have as much effect on the Earth's atmosphere, especially compared to the ancient ESPE.

ESPEs, as their name suggests, are caused by a massive influx of particles from the Sun. These particles interact directly with the Earth's atmosphere, and, importantly for the purposes of dating, have a noticeable impact on Carbon-14 levels. Specifically, the amount of C-14, as it's commonly known in chemistry, is increased dramatically compared to a baseline. Since living things like trees sequester carbon, we can tell when events like this happen to measure the amount of C-14 embedded in those previously living things using a technique called radiocarbon dating.

Fraser talks through the Carrington event and how it impacts our engineering designs now.

The paper does not describe new data—the tree rings they used to capture the 12350 BC event were found in southwestern Europe and described in a paper in 2023. The new work done in this paper was to apply a climatic model known as SOCOL:14C-Ex and use it to understand the impact the environment at the time had on the capture and sequestration of the C-14 isotopes from the ESPE. 

When the ESPE hit, the Earth was in an entirely different geological age, known as the Late Glacial period, at the end of the last Ice Age, as compared to the Holocene period that has existed for the last 10,000 years. That means there were pretty massive geological differences that could play a role in how the C-14 was captured in the rings.

The Earth had weaker geomagnetic shielding in 12350 BC, allowing more particles to enter the atmosphere than a similarly-sized event would have in the modern day. However, it also had lower CO2 levels, meaning there was less Carbon-12 (a more stable isotope) to be transmuted into C-14. The climate itself was different, and while it could have impacted the C-14 levels by changing the efficacy of carbon sinks or increasing how the C-14 particles moved about the atmosphere, the study found that it had a relatively limited impact on the differences between modern-day and the carbon levels back then.

Solar storms can get pretty bad, as Fraser explains.

To prove what "modern day" would have been like, the researchers used one of eight other known extreme ESPEs found in other tree rings. This one occurred in 775 and was previously the most intense ESPE known to science. Plenty of other tree rings from Germany, New Zealand, Argentina, the US, and elsewhere already had known C-14 levels that could be used as a calibration, in this case, a proof of concept.

The researchers tested SOCOL:14C-Ex to estimate the storm's intensity in 775 and proved the model worked then. They then adjusted some of the parameters based on the above considerations to calculate the ESPE intensity in 12350 BC. They found that it was about 18% stronger than the event in 775, making it the strongest known ESPE yet found.

Understanding how the Sun's extremes can affect us will continue to play a central role as we move more and more of our infrastructure off-planet. Engineers will have to plan for these extremes, and knowing the limits will only help us understand what we need to design. And who knows, there may be even more extreme events in the fossil record that SOCOL:14C-Ex will eventually find.

Learn More:

• K Golubenko et al - New SOCOL:14C-Ex model reveals that the Late-Glacial radiocarbon spike in 12350 BC was caused by the record-strong extreme solar storm
• UT - It's Been a Year Since the Most Powerful Solar Storm in Decades. What Did We Learn?
• UT - How Bad Can Solar Storms Get? Ask the Trees
• UT - New Research Indicates the Sun may be More Prone to Flares Than we Thought

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When the JWST came to life and began observations, one of its first jobs was to gaze back in time at the early Universe. The Assembly of Galaxies is one of the space telescope's four main science themes, and when it observed the Universe's first galaxies, it uncovered a mystery. Some of them appear to have supermassive black holes (SMBH) in their centers that are fuelling active galactic nuclei (AGN). However, they're not emitting X-rays, which is one of the hallmarks of AGN.

Little Red Dot (LRD) galaxies are small, red galaxies that formed about 600 million years after the Big Bang. The JWST has found more than 300 of them, but they remain a mystery collectively. Their brightness indicated they're more massive and swollen with stars than they should be at an early age. Our models suggest there wasn't enough time for them to grow so massive.

Astronomers then discovered AGN signatures that could explain the excess light. Rather than only stars, the LRD's excess light came from AGN. That would mean that the LRDs wouldn't need to be so massive to emit all that light, and their size wouldn't challenge our galaxy evolution models.

Unfortunately, that potential conclusion causes another problem. AGN emit powerful X-rays as the material swirling around in their accretion disks heats up. However, according to new research, LRDs appear to emit no X-rays.

The new research, titled "Chandra Rules Out Super-Eddington Accretion For Little Red Dots," has been submitted to The Astrophysical Journal. The authors are Andrea Sacchi and Akos Bogdan, both from the Harvard and Smithsonian Centers for Astrophysics. The paper is currently available at arxiv.org.

"A key feature of LRDs is their extreme X-ray weakness: analyses of individual and stacked sources have yielded non-detections or only tentative, inconclusive X-ray signals, except for a handful of individual cases," the authors write.

The lack of X-rays winds everything backward. If there are no X-rays, there can't be AGN with accretion disks. If there are no accretion disks, then LRD's powerful brightness can't come from SMBHs. If it can't come from SMBHs, it has to come from stars. Then we're back to square one: trying to explain how early galaxies were so massive and swollen with stars.

This Chandra image from the research shows the 55 LRDs in the Chandra Deep Field South in the 0.3 − 7 keV X-ray band. This range encompasses both soft X-rays and a good portion of the hard X-ray band. It's a broad and informative band for astrophysical observations, yet it turned up no X-ray detections.

Image Credit: Sacchi and Bogdan, 2025, The Astrophysical Journal.

Some researchers have suggested another solution. They say that the SMBHs are experiencing super-Eddington accretion rates.

SMBH black hole accretion is governed by the Eddington limit. The Eddington limit is a fundamental concept in astrophysics that explains the maximum brightness and accretion rates for astrophysical objects like SMBH. An object reaches the Eddington limit when two forces are balanced: outward radiation and inward gravitation. If one of these forces is too powerful, the object either expels its outer layers or ceases further accretion.

Astrophysicists know that the Eddington limit influences SMBH growth. However, they've proposed what's called super-Eddington accretion to explain how these massive objects became so massive so early in the Universe. Objects can exceed the Eddington limit for periods of time and experience super-Eddington accretion. Can that explain why LRDs are so bright while also being so weak in X-rays?

The authors point out that the only other explanation for the lack of X-rays is obscuration, and that explanation hasn't held up.

"As the most natural explanation, high obscuration, is disfavored by JWST spectroscopic evidence, several authors have suggested that the X-ray weakness of LRDs is intrinsic, due to super-Eddington accretion rates," the authors write. "In this work, we test that scenario by stacking X-ray data for 55 LRDs in the Chandra Deep Field South, accumulating a total exposure time of nearly 400 Ms."

400 megaseconds is the cumulative observing time for the 55 LRDs combined, not the total telescope observing time. That's an impressive depth of observation for the 55 objects. If super-Eddington accretion were occurring, that would explain the lack of X-rays.

Super-Eddington accretion still creates X-rays. However, those photons can get trapped in the accretion flow. They can also be absorbed or scattered by outflows and winds, or obscured by the thick disk or envelope around the SMBH. Current models show that super-Eddington accretion still emits X-rays, but as lower-energy soft X-rays. 400 megaseconds of stacked X-ray observations should detect them.

However, they didn't.

The Chandra X-ray Observatory is the world's most powerful X-ray telescope. It has eight times greater resolution and can detect sources more than 20 times fainter than any previous X-ray telescope. 400 megaseconds of stacked observing time should've detected X-rays if they were being emitted.

Image Credit: NASA/CXC & J. Vaughan

"Despite reaching unprecedented X-ray depths, our stack still yields a non-detection," the authors write. "The corresponding upper limits are deep enough to rule out current super-Eddington accretion models, and are compatible only with extremely high levels of obscuration."

The authors say we're left with only one explanation: "To explain the X-ray weakness of LRDs, we therefore speculate that the SMBHs in these systems are neither as massive nor as luminous as currently believed. " Other researchers have also suggested this.

So what's going on if observations show no X-rays, and if the JWST shows that dust obscuration is responsible?

"If the bolometric luminosities are overestimated by an order of magnitude, much lower levels of obscuration can hide the X-ray emission from accreting SMBHs without invoking super-Eddington accretion," the authors conclude.

The JWST has fulfilled its promise by revealing the Universe's earliest galaxies. That the results go against our models isn't surprising. Every new mission and telescope delivers some surprises, and scientists often look forward to surprising results.

For now, the LRD galaxies are unexplained. In fact, the mystery has deepened.

Examine just about any extraterrestrial body in the Solar System, and you will find that they all have the same thing in common: a long history of impacts. Whether it is the Moon, Mercury, Mars, or virtually all of the icy moons of the outer Solar System, the surface of these objects is pockmarked with craters. These craters tell a story about the evolution of these bodies and the kinds of forces that shaped them. Now, a team of researchers led by Brown University has determined that craters can be used to determine a body's subsurface composition.

The team was led by Aleksandra Sokolowska, a UKRI Fellow with the Department of Earth Science and Engineering (DESE) at Imperial College London. She was joined by Gareth S. Collins, a DESE Professor at Imperial, Ingrid J. Daubar, an Associate Professor with the Department of Earth, Environmental and Planetary Sciences (DEEPS) at Brown University, and Dr. Martin Jutzi, a Privatdozent with the Physics Institute at the University of Bern. Their research was published in the Journal of Geophysical Research: Planets. 

For decades, scientists have examined the size and shape of craters on extraterrestrial bodies to learn about what lies beneath the surface. According to Sokolowska's research, the rock layers and other ejecta produced by an impact can vary in size depending on the composition of materials beneath the impact point. Several factors play a role in altering a crater's characteristics, including the strength of the subsurface material and its porousness. This allows scientists to study planetary interiors from orbit without having to land and take drill samples.

Sokolowska performed the work with Dauba as a postdoctoral researcher at Brown University. This technique could allow scientists to spot patches of subsurface ice on Mars and other bodies based on data collected by orbiting missions. As Sokolowska indicated in a Brown University news release:

“Historically, researchers have used the size and shape of impact craters to infer the properties of materials in the subsurface. But we show that the size of the ejecta blanket around a crater is sensitive to subsurface properties as well. That gives us a new observable on the surface to help constrain materials present underground.”

For their study, Sokolowska and her colleagues sought to determine if crater ejecta could provide another source of information. This consisted of running models co-developed by Collins that simulate the physics of planetary impacts. The simulations also allowed them to vary the characteristics of the materials beneath the surface (single, layered, mixed) and the materials themselves (bedrock, sediment, loose rock with ice, solid glacial ice). The simulations showed that these characteristics produced a wide range of ejecta patterns.

The team then tested their results by examining two fresh impact craters on Mars, which were already known to have taken place over bedrock and subsurface ice. Since the ejected materials were young, they had not yet eroded much, making it easy to measure their distance from the impact site. They found that the ejecta pattern over the bedrock site was much larger than the one over subsurface ice. This was consistent with model predictions, confirming that differences in ejecta radius reflect subsurface properties. 

"The differences in ejecta radius can be quite large, and we predict that they could be measured from orbit with the HiRISE camera onboard Mars Reconnaissance Orbiter." Said Sokolowska. "Once the method is thoroughly tested, it could become a promising new tool for investigating subsurface properties. Turning this proof-of-concept work into a tool is the subject of my current fellowship at Imperial."

The team indicates that this method could be useful for current and future missions as they continue to explore Mars for clues about its past and where crewed missions could land someday. However, the team's findings have applications in the study of other astronomical bodies in the Solar System. This includes the double asteroid system Didymos, which the ESA's Hera spacecraft will rendezvous with in February 2026. In September 2022, NASA's Double Asteroid Redirect Test (DART) conducted the first kinetic impact test with Dimorphos, the small satellite that orbits Didymos.

When it arrives, Hera will examine the crater created by the impact to learn more about the asteroid's interior. Sokolowska said that examining the ejecta pattern could assist in this objective: "Our work suggests that ejecta that did not escape from the asteroid and blanketed its surface could hold valuable information about the asteroid's interior."

Further Reading: 

• Brown University, 
• JGR Planets

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On March 15th, 2024, the Sun released a powerful solar flare that coincided with a heightened period of solar activity. This was accompanied by a coronal mass ejection (CME), a massive cloud of solar energetic particles (SEP) that led to auroras all across the Solar System. This included Mars, where NASA's Perseverance rover made history by capturing a visible light image of the event with its Mastcam-Z instrument. This was the first time that an aurora was witnessed from the surface of another planet.

On Earth, auroras are a common phenomenon that occurs whenever solar particles interact with the global magnetic field. This field channels these energetic particles towards the poles, where they interact with atmospheric gases to produce the famous Northern Lights (Aurora Borealis) and Southern Lights (Aurora Australis). While Mars does not have a global magnetic field like Earth, it has localized magnetic fields and a very thin atmosphere by comparison (less than 1% of the atmospheric pressure).

On Earth, the most common color associated with auroras is green, which is caused by the excitation of oxygen atoms. For years, scientists predicted that Mars might also experience green light auroras, except they would be far fainter and more difficult to image. Hence why all previous observations of auroras on Mars have been by orbiters in ultraviolet wavelengths. This includes NASA's Mars Atmosphere and Volatile EvolutioN (MAVEN), which observed an SEP aurora from orbit in 2014.

Consequently, capturing this image required serious coordination and timing. Elise Knutsen, a postdoctoral researcher at the University of Oslo in Norway, was the lead author of the study that reported the detection, which recently appeared in Science Advances. Since SEPs typically occur during solar storms, especially during the peak of the Sun's eleven-year solar cycle (aka solar maximum), Knutsen and her team planned their observations to coincide with the peak of the Sun's current solar cycle.

They also created models that determined the optical angle for the Perseverance rover's SuperCam spectrometer and Mastcam-Z camera to observe it. The next step consisted of waiting for the right type of CME to happen. This task fell to NASA's Moon to Mars (M2M) Space Weather Analysis Office and the Community Coordinated Modeling Center (CCMC) at NASA's Goddard Space Flight Center. The former provides real-time analysis of solar eruptions to the CCMC, which uses the data to run simulations of CMEs and determine if they could impact NASA missions.

When their simulations predict a potentially hazardous CME, the M2M team sends out of alert. As Knutsen explained in a NASA press release:

"The trick was to pick a good CME, one that would accelerate and inject many charged particles into Mars' atmosphere. When we saw the strength of this one, we estimated it could trigger [an] aurora bright enough for our instruments to detect. This exciting discovery opens up new possibilities for auroral research and confirms that auroras could be visible to future astronauts on Mars' surface."

The team included researchers from Colorado's Laboratory for Atmospheric and Space Physics (LASP), UC Berkeley, NASA's Goddard Space Flight Center, and Jet Propulsion Laboratory, which collaboratively oversee NASA's MAVEN mission. By coordinating Perseverance's observations with measurements from MAVEN's SEP instrument, the teams helped determine that the light detected was the same emission line as green auroras on Earth.

"Perseverance's observations of the visible-light aurora confirm a new way to study these phenomena that's complementary to what we can observe with our Mars orbiters," said Katie Stack Morgan, acting project scientist for Perseverance at NASA's Jet Propulsion Laboratory. "A better understanding of auroras and the conditions around Mars that lead to their formation are especially important as we prepare to send human explorers there safely."

What's more, future astronauts are likely to be able to see this type of aurora from the Martian surface. While most will be difficult to see, mission crews could spend up to a year on the surface,

Further Reading: 

• NASA