Orbital Debris is Getting Out of Control

In 1978, NASA scientists Donald J. Kessler and Burton G. Cour-Palais proposed a scenario where the density of objects in Low Earth Orbit (LEO) would be high enough that collisions between objects would cause a cascade effect. In short, these collisions would create debris that would result in more collisions, more debris, and so on. This came to be known as the Kessler Syndrome, something astronomers, scientists, and space environmentalists have feared for many decades. In recent years, and with the deployment of more satellites than ever, the warning signs have become undeniable.

Currently, there is an estimated 13,000 metric tons (14,330 US tons) of “space junk” in LEO. With the breakup and another satellite in orbit – the Intelsat 33e satellite – the situation will only get worse. This broadband communications satellite was positioned about 35,000 km (21,750 mi) above the Indian Ocean in a geostationary orbit (GSO). According to initial reports issued on October 20th, the Intelsat 33e satellite experienced a sudden power loss. Hours later, the U.S. Space Forces (USSF) confirmed that the satellite appeared to have broken up into at least 20 pieces.

While there are no confirmed reports about what caused the breakup, this is hardly the first time a satellite broke up in orbit. In recent years, satellites have been lost through accidental collisions, increased solar activity, or deliberate destruction (during tests of anti-satellite technology). What is known is that the Intelsat 33e satellite, manufactured by Boeing and operated by the multinational satellite services provider Intelsat, has suffered several issues since it was launched in August 2016, especially where its propulsion is concerned.

An artist rendering of the Mission Extension Vehicle docked to an Intelsat satellite.
Credit: Northrop Grumman

The first occurred less than a year after the satellite was launched when it reached its desired orbit three months later than anticipated. This delay was reportedly due to an issue with its primary thruster, which is responsible for controlling the satellite’s altitude and acceleration. Another occurred when it performed a special maneuver that ensures satellites can maintain the right altitude (a “station-keeping activity”). During the maneuver, Intelsat 33e burned more fuel than expected, which reduced the time it would spend in orbit by three and a half years.

In addition, another Intelsat satellite of the same model (a Boeing-built EpicNG 702 MP) failed in 2019. However, they are hardly alone regarding satellites breaking up and producing debris. In July, the Russian commercial satellite RESURS-P1 fractured in LEO, creating over 100 pieces of debris that could be tracked (and likely many more that were too small to detect). That same month, the decommissioned Defense Meteorological Satellite Program (DMSP) 5D-2 F8 satellite broke up in orbit.

On August 9th, 2024, the upper stage of a Long March 6A (CZ-6A) rocket fragmented in orbit, creating a cloud of at least 283 pieces of trackable debris. The geomagnetic storm that took place on February 3rd, 2022, coincided with the launch of 49 Starlink satellites, most of which were lost as a result. It is unclear how this latest incident will affect objects in orbit. Still, astronomers are hopeful that studying the resulting debris will provide insight into the growing problem of space junk.

According to the ESA Space Debris Office, an estimated 40500 objects in LEO are larger than 10 cm (3.9 inches) in diameter. Moreover, there are an additional 1.1 million objects measuring 1 and 10 cm (0.39 to 3.9 inches) in diameter and 130 million objects 1 mm to 1 cm (0.039 to 0.39 inches). Based on the Space Debris Office’s estimates, this adds up to more than 13,000 metric tons, consisting of pieces of spent rocket stages, satellites, and other objects launched into orbit since 1957 – when Sputnik-1 became the first artificial satellite launched into orbit.

In a 2009 paper, Kessler declared that the orbital situation had already reached the point of instability. As he wrote:

“Modeling results supported by data from USAF tests, as well as by a number of independent scientists, have concluded that the current debris environment is “unstable”, or above a critical threshold, such that any attempt to achieve a growth-free small debris environment by eliminating sources of past debris will likely fail because fragments from future collisions will be generated faster than atmospheric drag will remove them.”

In accordance with the 1972 Convention of International Liability for Damage Caused by Space Objects, the country that launched a satellite into space is responsible for its breakup and debris. However, this is only in cases where fault can be proven, and it has been enforced only once in the more than 50 years since it was signed. It is unclear if Intelsat will be fined by the Federal Communications Commission (FCC) for this latest incident. Regardless, this latest breakup highlights the need for a more robust framework for mitigating future collisions and addressing space debris.

In particular, tracking technology will need to evolve so that more objects can be tracked. At present, about 36,860 space objects are regularly tracked by Space Surveillance Networks (SSNs) worldwide and maintained in their catalogs. In addition, active measures to safely track and remove debris from LEO are being researched and developed, some of which have already been deployed. Examples include the ADRAS-J satellite, which launched on February 18th, 2024.

Developed by the Tokyo-based company AstroScale, ADRAS-J is the first mission to approach and survey a piece of space debris. The Clearsat-1 satellite is also being developed by the ESA and Swiss startup ClearSpace Today. NASA is also developing the Active Debris Removal Vehicle (ADRV), a lightweight, single-use vehicle that will remove debris with a mass of 1,000–4,000 kg (1.1 to 4.4 U.S. tons) and at an altitude of 200–2,000 km (124 to 1240 mi).

In the meantime, Intelsat continues to investigate the loss of both of its satellites. According to the latest update issued by the company, which was posted on October 21st, 2024:

“We are coordinating with the satellite manufacturer, Boeing, and government agencies to analyze data and observations. A Failure Review Board has been convened to complete a comprehensive analysis of the cause of the anomaly. Since the anomaly, Intelsat has been in active dialogue with affected customers and partners. Migration and service restoration plans are well underway across the Intelsat fleet and third-party satellites.”

Further Reading: Phys.org, Intelsat

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Webb Reveals a Steam World Planet Orbiting a Red Dwarf

The JWST has found an exoplanet unlike any other. This unique world has an atmosphere almost entirely composed of water vapour. Astronomers have theorized about these types of planets, but this is the first observational confirmation.

The unique planet is GJ 9827 d. It’s about twice as large as Earth and three times as massive, and it orbits a K-type star about 100 light years away. The Kepler Space Telescope first discovered it during its K2 extension. In 2023, astronomers studied it with the Hubble Space Telescope. They detected hints of water vapour and described it as an ocean world.

“This is the first time we’re ever seeing something like this.”

Eshan Raul, University of Wisconsin – Madison

However, the JWST results show that the atmosphere is almost completely comprised of water vapour.

The results are in new research published in The Astrophysical Journal Letters titled “JWST/NIRISS Reveals the Water-rich “Steam World” Atmosphere of GJ 9827 d.” The lead author is Caroline Piaulet-Ghorayeb from the University of Montréal’s Trottier Institute for Research on Exoplanets.

Astronomers have wondered if steam planets can exist. Some thought that life could exist on them in the cooler, higher layers of their atmospheres. Others think it’s extremely unlikely. But there was no evidence to go on until now.

“This is the first time we’re ever seeing something like this,” said Eshan Raul, who analyzed the JWST data of GJ 9827 d as an undergraduate student at the University of Michigan. “To be clear, this planet isn’t hospitable to at least the types of life that we’re familiar with on Earth. The planet appears to be made mostly of hot water vapor, making it something we’re calling a ‘steam world.'”

However, every exoplanet teaches us something. GJ 9827 d and its unique atmosphere will help scientists understand exoplanets better in general.

“If these are real, it really makes you wonder what else could be out there.”

Eshan Raul, University of Wisconsin – Madison

The researchers used transmission spectroscopy to detect the exoplanet’s atmosphere. As the planet passes in front of its star, the atmosphere absorbs certain wavelengths of light in the starlight’s spectrum. Different chemicals absorb different wavelengths and reveal their presence.

The observations show that GJ 9827 d’s atmosphere is more than 31% water vapour by volume and has very high metal enrichment. The observations also show that no hydrogen or helium is escaping.

The exoplanet’s atmosphere may be strange, but in other ways, the planet itself is common. It’s a sub-Neptune, a planet larger than Earth but smaller than Neptune. Sub-Neptunes are the most common type of exoplanet we’ve found in the Milky Way.

This discovery is about more than sub-Neptunes and steam worlds. It’s about one of the key challenges in exoplanet atmospheres: the clouds-metallicity degeneracy.

When astronomers use transmission spectroscopy to examine and characterize an exoplanet’s atmosphere, high metallicity and clouds can produce the same signal. High metallicity can produce smaller spectral features, and clouds can also mute and flatten spectral features. Clouds can also mask the presence of molecular absorbers below the cloud deck. As a result, when scientists see a relatively flat spectrum or muted features, they struggle to determine if they’re seeing a metal-rich atmosphere with intrinsically small features or a low-metallicity atmosphere that’s partially obscured by clouds.

This research has broken the stalemate between clouds and metallicity.

Piaulet-Ghorayeb and her co-authors combined previous Hubble Space Telescope observations of GJ 9827 d with JWST observations. The JWST used its NIRISS (Near-Infrared Imager and Slitless Spectrograph) and SOSS (Single Object Slitless Spectroscopy) to analyze the exoplanet’s atmosphere during two transits. This provided enough wavelength coverage and precision to break the clouds-metallicity degeneracy. This is the first conclusive observation of a high-metallicity and water-rich atmosphere.

“This is a crucial proving step towards detecting atmospheres on habitable exoplanets in the years to come.”

Ryan MacDonald, Astrophysicist, University of Wisconsin

This figure from the research shows GJ 9827 d’s two transits observed by the JWST. The broad wavelength coverage and the precision broke the clouds-metallicity degeneracy. Image Credit: Piaulet-Ghorayeb et al. 2024.

Almost all the exoplanet atmospheres that have been characterized are mostly made of the lighter elements hydrogen and helium. These atmospheres are similar to Jupiter and Saturn in our Solar System. They’re nothing like Earth and its life-friendly atmosphere.

“GJ 9827 d is the first planet where we detect an atmosphere rich in heavy molecules like the terrestrial planets of the solar system,” Piaulet-Ghorayeb said. “This is a huge step.”

Though GJ 9827 d isn’t habitable as far as our understanding of life goes, other exoplanets with similar metallicity are desirable targets in the search for life. Now that astronomers have broken the clouds-metallicity degeneracy, it changes our understanding of those planets and scientists’ ability to discern them. It’s all thanks to the JWST and its observing prowess.

Ryan MacDonald is a co-author of the new research and is a U-M astrophysicist and NASA Sagan Fellow. “Even with JWST’s early observations in 2022, researchers were discovering new insights into the atmospheres of distant gas giants,” MacDonald said, referring to the JWST’s spectroscopic characterizations of exoplanet atmospheres.

But those atmospheres were primarily composed of light gases, not heavier metals. These observations take us deeper into the atmospheres of sub-Neptunes. And though they’re the most common type of exoplanet in our galaxy, our Solar System is without one.

“Now we’re finally pushing down into what these mysterious worlds with sizes between Earth and Neptune, for which we don’t have an example in our own solar system, are actually made of,” MacDonald said. “This is a crucial proving step towards detecting atmospheres on habitable exoplanets in the years to come.”

The atmospheric steam didn’t jump out of the JWST observations. JWST produces an enormous amount of data, and to make sense of it, astronomers use modelling tools based on sampling algorithms and machine learning techniques. They typically employ several different models and work with all of the results to arrive at the most likely interpretation of the data.

The process of determining an atmosphere from data is called atmospheric retrieval. A 2023 paper presented a catalogue of 50 different atmospheric retrieval codes used by exoplanet scientists. The lead author of that paper is none other than Ryan MacDonald, a co-author of this new research. MacDonald wrote the software that analyzed and retrieved GJ 9827 d’s atmosphere, and co-author Raul used that software.

Raul generated millions of model atmospheres that matched the JWST observations before settling on the steam world model. In a sense, Raul was the first person to see proof that steam worlds exist.

“It was a very surreal moment,” said Raul, who is now working toward his doctorate at the University of Wisconsin-Madison. “We were searching specifically for water worlds because it was hypothesized that they could exist.”

“If these are real, it really makes you wonder what else could be out there.”

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NASA Wants to Move Heavy Cargo on the Moon

While new rockets and human missions to the Moon are in the press, NASA is quietly thinking through the nuts and bolts of a long-term presence on the Moon. They have already released two white papers about the lunar logistics they’ll require in the future and are now requesting proposals from companies to supply some serious cargo transportation. But this isn’t just for space transport; NASA is also looking for ground transportation on the Moon that can move cargo weighing as much as 2,000 to 6,000 kg (4,400 to 13,000 pounds.)

In a recent press release, NASA asked U.S. industry to submit proposals for logistics ideas and solutions to help the agency land and move cargo on the lunar surface during the upcoming Artemis missions.

“NASA relies on collaborations from diverse partners to develop its exploration architecture,” said Nujoud Merancy, deputy associate administrator, strategy and architecture in the Exploration Systems Development Mission Directorate at NASA Headquarters in Washington. “Studies like this allow the agency to leverage the incredible expertise in the commercial aerospace community.”

In the two white papers, NASA outlined the “gaps” they have lunar logistics and mobility as part of its Moon to Mars architecture.  In the first paper, “Lunar Logistics Drivers, Needs,” NASA said that as the Artemis missions and goals are conceptualized and planned, it is imperative to accurately predict logistics and resupply needs, not only for mission goals but for the very important need of keeping the humans alive and healthy. They need to have a good plan and the ability to transport landed cargo and exploration items from where they are delivered to where they are used.

Graph showing approximate logistics item needs for representative lunar surface missions. Credit: NASA.

“The total amount of logistics items required to keep the crew alive and healthy, to maintain systems, and to perform productive science and utilization can be relatively large,” the authors wrote. “It can also heavily influence the design of the architecture and exploration missions. The architecture must therefore be based on comprehensive, accurate estimates of logistics item needs and include assessment of a suitable logistics sub-architectures to deliver those needs.”

How to provide various things like food, water, air, spare parts, and other similar products required to sustain life, as well as maintain all the various systems and structures are key to having productive science and utilization activities. NASA also expects they will need to move all these supplies around on the Moon, including to the lunar South Pole where they plan to send crews in the future. The paper outlines the importance of accurately predicting logistics resupply needs, as they can heavily influence the overall architecture and design of exploration missions.

An artist’s conception shows NASA’s generic concept for the Lunar Terrain Vehicle. (NASA Illustration)

NASA’ said their current planned lunar mobility elements, such as the Lunar Terrain Vehicle and Pressurized Rover, have a capability limit of about 1,760 pounds (800 kilograms) and will primarily be used to transport astronauts around the lunar surface. However, future missions could include a need to move cargo totaling around 4,400 to 13,000 pounds (2,000 to 6,000 kg). That’s why NASA wants input from companies who have experience in this area.

But to be able to move cargo around to various places on the Moon, NASA first needs to get the supplies to the lunar surface. The second white paper, “Lunar Surface Cargo,” looks at the lunar surface cargo delivery needs, compares those needs with current cargo lander capabilities, and outlines considerations for fulfilling this capability gap. NASA said that access to a diverse fleet of cargo landers would empower a larger lunar exploration footprint, and that a combination of international partnerships and U.S. industry-provided landers could supply the concepts and capabilities to meet this need.

“Given diverse cargo needs of varying size, mass, delivery cadence, and operational needs, a diverse portfolio of cargo lander capabilities will be necessary to achieve NASA’s Moon to Mars Objectives,” the paper says. “Encouraging the development of varied cargo lander concepts and capabilities will be key to establishing a long-term lunar presence for science and exploration.”

Planned and potential cargo to the lunar surface. Credit: NASA

While the request for proposals doesn’t explicitly seek new concepts for landing vehicles, it does ask for integrated assessments of logistics that can include transportation elements.

“We’re looking for industry to offer creative insights that can inform our logistics and mobility strategy,” said Brooke Thornton, industry engagement lead for NASA’s Strategy and Architecture Office. “Ultimately, we’re hoping to grow our awareness of the unique capabilities that are or could become a part of the commercial lunar marketplace.”

Got ideas? Check out NASA’s Request for Proposals.

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Learning More About Supernovae Through Stardust

Most of the diverse elements in the Universe come from supernovae. We are, quite literally, made of the dust of those long-dead stars and other astrophysical processes. But the details of how it all comes about are something astronomers strive to understand. How do the various isotopes produced by supernovae drive the evolution of planetary systems? Of the various types of supernovae, which play the largest role in creating the elemental abundances we see today? One way astronomers can study these questions is to look at presolar grains.

These are dust grains formed long before the formation of the Sun. Some of them were cast out of older systems as a star fired up its nuclear furnace and cleared its system of dust. Others formed from the remnants of supernovae and stellar collisions. Regardless of its origin, each presolar grain has a unique isotopic fingerprint that tells us its story. For decades, we could only study presolar grains found in meteorites, but missions such as Stardust have captured particles from comets, giving us a richer source for study. Observations from radio telescopes such as ALMA allow astronomers to look at the isotope ratios of these grains at their point of origin. We can now study presolar grains both in the lab and in space. A new study compares the two, focusing on the role of supernovae.

Pair of presolar grains from the Murchison meteorite. Credit: Argonne National Laboratory, Department of Energy

What they found was that the physical gathering of presolar grains will be crucial to understanding their origins. For example, Type II supernovae, also known as [core-collapse supernovae,](https://ift.tt/UIhGKdF) are known to produce Titanium-44, which is an unstable isotope. Through decay processes, this can create an excess of Calcium-44 in presolar grains. But grains cast off from young star systems also have a Calcium-44 excess. In the first case, the grains form with titanium, which then decays to calcium, while in the second case, the grains form with calcium directly. We can’t distinguish between the two just by looking at the isotope ratios. Instead, we have to look at the specific distribution of Calcium-44 within the grain. The team found that using nanoscale secondary ion mass spectrometry (NanoSIMS) they could distinguish the origin of grains found in meteorites. Similar complexities are seen with isotopes of silicon and chromium.

Overall, the study proves that we will need much more study to tease apart the origins of the presolar grains we gather. But as we better understand the grains we gather here on Earth, they should help us unravel a deeper understanding of how elements are forged in the nuclear furnaces of large stars.

Reference: Liu, Nan, et al. “Presolar grains as probes of supernova nucleosynthesis.” arXiv preprint arXiv:2410.19254 (2024).

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Amazing Reader Views of Comet A3 Tsuchinshan-ATLAS From Around the World

Comet C/2023 A3 Tsuchinshan-ATLAS survived perihelion to become a fine dusk object for northern hemisphere observers.

It was an amazing month for astronomy. Not only were we treated to an amazing second solar storm for 2024 that sent aurorae as far south as the Caribbean, but we had a fine naked eye comet: C/2023 A3 Tsuchinshan-ATLAS.

The comet on October 24th, along with the Milky Way over the Sea of Japan as seen from Yuzhno-Morskoy (Nakhodka) Russia. Credit: Filipp Romanov.

Discovered in early 2023, this one actually performed as expected, and topped out as the best comet for 2024. Southern hemisphere observers got a portent of things to come in September, as the comet threaded the dawn skies.

The evolution of the comet post-perihelion through October 25-28th. Credit: Eliot Herman

Peril at Perihelion

Then came the big wild card of perihelion. The comet passed just 58.6 million kilometers from the Sun on September 27th. At its maximum, the comet hit nearly -5th magnitude. The dust and plane crossing for the comet were both especially dramatic, as we saw a sharp spiky anti-tail trace out the comet’s orbital trail and appear to pierce the Sun as seen in views from SOHO’s LASCO C2 and C3 imagers.

But would the comet remain bright for its evening encore? This time, luck was on our side, as the comet held at +1^st magnitude for about a week, and joined Venus in the dusk sky. As it began its rapid ascent, Comet ‘T-ATLAS’ unfurled its tail about a dozen degrees in length, all while keeping its remarkable anti-tail pointing sunward.

The comet from October 18th, still exhibiting a spiky ‘anti-tail. Credit: Efrain Morales.

A ‘Just Point-and-Shoot’ Comet

And then the pictures came pouring in. Comet T-ATLAS was at its photogenic best in early October, as it became an easy target against the starry backdrop. Usually, +2^nd magnitude or brighter is the cutoff for catching a comet along with foreground objects. This time, you could actually simply set your smartphone camera to night mode, and capture a decent handheld shot of the comet.

The comet from October 19th, as seen from Ottawa, Canada. Credit: Andrew Symes

Plus, light pollution didn’t seem to faze this comet. We saw shots of the comet from downtown Los Angeles and other urban areas, as folks were treated to the best comet in recent memory since the dawn apparition of F3 NEOWISE in 2020.

Venus, a meteor, an airplane trail, and Comet T-ATLAS from Malaysia. Credit: Shahrin Ahmad.

And to think: the last time a really brilliant comet swung by (C/1995 O1 Hale-Bopp a generation ago in 1997) digital imaging was in its infancy, and film still dominated the market… just think what we might manage to do with such a comet today?

“I drove north for more than three hours, and reached the seashore facing the Sea of Japan after sunset,” says astrophotographer Hisayoshi Kato on Flickr, “It was fortunate that the sky was clear at the site, and I could enjoy the comet sinking into the Sea of Japan (over) the weekend.”

Comet C/2023 A3 Tsuchinshan-ATLAS from October 26th. Credit: Hisayoshi Kato.

Awaiting Next ‘Great Comet’

To be sure, it’s only a matter of time before the next ‘Comet of the Century’ makes itself known. Right now, Comet T-ATLAS is still a decent +6th magnitude binocular object in Ophiuchus, outbound on its nearly quarter-of-a-million-year orbit. Alas, a second sungrazer encore for October never came to pass, as Comet C/2024 S1 ATLAS ended its cometary career at perihelion earlier this week…

An amazing parting shot of the comet from October 29th. Credit: Gianluca Masi.

“These days, we all had an extraordinary proof of the splendor of the night sky,” astronomer Gianluca Masi noted in a recent Facebook post. “Comet C/2023 A3 Tsuchinshan-ATLAS is still putting on a show… but the firmament is always a prodigy of emotions and wonders, as those who regularly turn their gaze to the stars know.”

Comet T-ATLAS from downtown Bristol, Tennessee. Credit: Dave Dickinson.

When’s the next one? Well, we do have the promise of a similar comet coming right up in January 2025. C/2024 G3 ATLAS may reach -1^st magnitude or brighter near perihelion.

Thanks to everyone that got out there and sent images to the Universe Today Flickr pool. Here’s to the next yet-to-be named bright comet, waiting in the wings to take center stage in the drama of the inner solar system and the skies of Earth.

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Astronomer Calculates When van Gogh Painted This

One of my favorite paintings is Starry Night by Vincent van Gogh — for obvious astronomical reasons. But another favorite of van Gogh’s works is Lane of Poplars at Sunset. This painting depicts the setting Sun perfectly aligned with a long lane of trees, casting long shadows.

The geometry of the Earth and Sun means that this scene had to be painted on one specific day of the year when the alignment would be possible. An astronomer has now used 19th-century maps to discover where the lane was, and then used astronomical calculations to determine which date the Sun would be in the exact position as the painting. His result? The painting depicts a stretch of road known as Weverstraat in the Dutch town of Nuenen, on November 13 or 14, 1884.

Professor Donald Olson is an astronomer and physics professor emeritus at Texas State University (TSU). He is no stranger to studying van Gogh paintings, as in the past he has uncovered clues to help date three other of the noted painter’s works: Moonrise (July 13, 1889), Road with Cypress and Star (May 1890) and White House at Night (June 1890).

Van Gogh produced more than 2,000 paintings, drawings, and sketches in his lifetime, and many include scenery from The Netherlands, the Dutch master’s home. Olson was originally inspired to determine the date of Lane of Poplars at Sunset because the scene shows something similar to what happens twice a year for New York City’s “Manhattanhenge,” where the setting sun aligns with Manhattan’s east–west streets on dates near May 29 and July 12.  

Manhattanhenge from 42nd Street shot at 8:23 p.m. on July 13, 2006, the building on the right is the Chrysler Building. Photo by Roger Rowlett, via Wikipedia.

The first thing Olson wanted to figure out was where the lane might be.

“If we could identify the lane on 19th-century maps, then we’d be able to establish the compass direction of the road appearing in the artworks,” Olson explained in a news release from TSU. “Next, we could use astronomical calculations to determine the date when the disk of the setting sun aligned as van Gogh portrayed it.”

Olson called in assistance from Louis Verbraak and Ferry Zijp, members of the Eindhoven Weather and Astronomy Club in the Netherlands. After an exhaustive search of maps and correlating historic and recent imagery, the team narrowed it down to three possible streets. Further investigations led them to determine that Weverstraat in Nuenen must be the street, as it contained a long straightaway of 1,200 feet, or 365 meters, more than long enough for the scene painted by van Gogh.

As for determining the date, Olson and team relied on historical information. All of van Gogh’s paintings assigned catalog numbers, in order by dates determined by art historians. Lane of Poplars at Sunset is assigned as F123. The previous painting in the catalog, F122, is called Lane of Poplars in the Autumn, which shows the same scenes with vivid fall colors, while the leaves are almost completely gone from the trees in the sunset depiction. That means the painting had to be done in late fall.

The painting “Line of Poplars in Autumn” by Vincent van Gogh (F122, Nueun 1884).

Art historians have also long depended on van Gogh’s many letters to his brother Theo to help date most of the artist’s work. A total of three letters, written by Vincent during late October and early November of 1884, describe the lovely autumn weather he was experiencing. One letter, dated on or about Oct. 25, 1884, includes a description that matches Lane of Poplars in the Autumn:

“The last thing that I made is a rather large study of a lane of poplars with the yellow autumn leaves, where the Sun makes glittering patches here and there on the fallen leaves on the ground, alternating with the long shadows cast by the trunks. At the end of the road is a peasant cottage, and above it the blue sky between the autumn leaves.”

“White House at Night” by Vincent van Gogh. (F766 Auvers-sur-Oise, 1990).

A subsequent letter dated on or about Nov. 14, 1884, van Gogh indicated that freezing weather forced him to abandon painting outdoors for the rest of the season. Additional letters helped establish a time frame between Nov. 5-Nov. 14 for van Gogh to have painted Lane of Poplars at Sunset. Within this range of dates, planetarium software shows that the sun set in the southwest, in the range of azimuths, or compass direction of a celestial object, between 240° and 244°.

Then using astronomical calculations, Olson and team determined the setting sun would’ve been visible setting over Weverstraat on Nov. 13 or 14, 1884. Historical weather records indicate these dates fall within a five-day span where the area experienced unseasonably clear weather.

Olson said that because van Gogh rarely painted from memory and preferred to have his subject in front of him, Nov. 13 or 14, 1884, are the only possible dates for the creation of Lane of Poplars at Sunset.

“Today, we can still gaze down the same stretch of road where van Gogh walked on a chilly autumn afternoon and ponder how the artist, in his native Netherlands, was already interested in portraying sky phenomena, four years before he began to create his famous starry nights in the south of France,” Olson said.

Read more details about the search at TSU.

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Artemis V Astronauts Will be Driving on the Moon

In the summer of ’69, Apollo 11 delivered humans to the surface of the Moon for the first time. Neil Armstrong and Buzz Aldrin spent just over two hours exploring the area near their landing site on foot. Only during Apollo 15, 16, and 17 did astronauts have a vehicle to move around in.

Artemis astronauts on the Moon will have access to a vehicle right away, and NASA is starting to test a prototype.

Momentum is building behind NASA’s Artemis program despite some setbacks. Artemis astronauts will explore the Moon far more thoroughly than the Apollo astronauts did, and technology is behind the improvement. Surface mobility is a key piece of Artemis. In April of 2024, NASA selected three vendors as part of their Lunar Terrain Vehicle Services contract.

NASA engineers at the Johnson Space Center are designing an unpressurized rover prototype known as the Ground Test Unit. It’s a human-rated, unpressurized LTV (Lunar Terrain Vehicle). The unit is being designed and built as a platform to evaluate rover designs being developed by three private companies: Intuitive Machines, Lunar Outpost, and Venturi Astrolab.

Intuitive Machines is known for its IM-1 mission with its Nova-C Lander. They were the first private company to land a spacecraft on the Moon.

Intuitive Machines’ Nova-C lunar lander was the first private spacecraft to land on the Moon. Image Credit: By NASA Marshall Space Flight Center / Intuitive Machines Photo ID: IM_00309., Public Domain, https://ift.tt/PIz3HZu

Lunar Outpost is known for its Mobile Autonomous Prospecting Platform (MAPP) rover (MAPP) rover. MAPP will be used on Intuitive Machines’ IM-2 and IM-3 missions and will demonstrate aspects of In-Situ Resource Utilization.

Venturi Astrolab is known for developing hyper-deformable wheels and batteries for lunar rovers. They’re also developing their FLEX rover, a larger vehicle designed to be modular to meet different objectives.

The LTV will be used to test the technologies these three companies develop. It’ll be used to evaluate crew compartment design, rover maintenance, science payload, and many other aspects of their rovers.

“The Ground Test Unit will help NASA teams on the ground, test and understand all aspects of rover operations on the lunar surface ahead of Artemis missions,” said Jeff Somers, engineering lead for the Ground Test Unit. “The GTU allows NASA to be a smart buyer, so we are able to test and evaluate rover operations while we work with the LTVS contractors and their hardware.”

Two engineers in suits sit on the prototype during testing at the Johnson Space Center. Image Credit: NASA/Bill Stafford

NASA has some requirements that the three selected companies need to meet. The rover must support two crew members and be able to be operated remotely. It can use multiple control concepts, such as supervised autonomy, different drive modes, and self-levelling.

NASA used its ‘Moon Buggy’ or Lunar Roving Vehicle (LRV) on Apollo 15, 16, and 17 in 1971 and 1972. It could carry 440 kg, including two astronauts, and had a top speed of 18 km/h. Though it provided range and mobility, it never travelled further than walking distance from the landers in case of breakdown. Image Credit: By NASA/Dave Scott; Public Domain, https://ift.tt/ydriJYF

By supplying the Ground Test Unit, NASA is making it easier to test the designs from the three companies. It also helps build private sector capacity by enabling testing and iterative design without the separate companies needing to spend money on a GTU. Ground testing also allows for a safer testing environment.

An artist’s illustration of astronauts at the lunar south pole. Image Credit: NASA

When Apollo 11 reached the Moon, it was a civilization-defining moment. There was no reason to explore beyond the landing site since it was as unexplored as the rest of the Moon. But things are much different now.

Thanks to other missions and satellites that orbit the Moon, we have an almost encyclopedic knowledge of our natural satellite compared to the Apollo days. We know what questions we want answered, where we can do the best science, and where useful resources like water ice is. The idea behind Artemis is to go to the Moon and create an infrastructure that will allow us to maintain a presence there.

The Artemis lunar missions will rely on mobility to meet their goals. The LTV will be critical to Artemis’ success by allowing each mission to explore and develop a larger area. NASA intends to use the new rovers starting in Artemis V, which will launch no sooner than 2030.

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Tiny Fragments of a 4-Billion Year Old Asteroid Reveal Its History

In June 2018, Japan’s Hayabusa 2 mission reached asteroid 162173 Ryugu. It studied the asteroid for about 15 months, deploying small rovers and a lander, before gathering a sample and returning it to Earth in December 2020.

The Ryugu sample contains some of the Solar System’s most ancient, primitive, and unaltered material, opening a window into its earliest days about 4.6 billion years ago.

The Ryugu sample is small, only about 5.4 grams (0.19 oz). However, scientific instruments that examine the sample’s chemical characteristics don’t need a large sample.

In new research, scientists examined tiny fragments of Ryugu using the Argonne National Laboratory’s Advanced Photon Source (APS). The APS is a particle accelerator that accelerates photons to nearly the speed of light. These photons release X-rays that are used in a wide variety of scientific endeavours. (The APS was even involved in developing COVID-19 vaccines.) In this research, the APS X-rays were used in a special technique called Mössbauer spectroscopy that can determine the oxidation rate of iron in the Ryugu sample.

The research is titled “Formation and evolution of carbonaceous asteroid Ryugu: Direct evidence from returned samples.” It’s published in the journal Science, and the lead author is Tetsuya Nakamura from Tohoku University in Sendai, Japan.

Ryugu is a rare type of asteroid. As a Cb spectral type, it has characteristics of both C-type carbonaceous asteroids, the most common type by far, and B-type asteroids, a more uncommon type of carbonaceous asteroid.

5.4 grams is not a large sample, but it’s large enough to reveal the nature and history of asteroid Ryugu. Image Credit: Yada et al./Nature Astronomy 2021

JAXA, the Japan Aerospace Exploration Agency, chose Ryugu for their sampling mission for several reasons. As a Near-Earth Asteroid (NEA), Ryugu was easier to reach. It’s also classified as a primitive, carbon-rich asteroid, so they hoped it would contain organic chemicals that hold clues about the early Solar System. Ryugu is also relatively small (900 metres) and rotates slowly, making sampling easier. The asteroid’s orbit also brings it close to Earth, making it easier to return the sample.

Ryugu could answer certain questions, all related to the history of the Solar System. Ryugu’s structure and composition, including the presence of water and organic matter, can reveal details about how planets and asteroids formed and how these essential materials for life may have been delivered to Earth. Scientists also hoped to classify Ryugu in more detail and understand its internal structure and how it might have evolved. Researchers also wondered about the asteroid’s resource potential.

Scientists working with the samples have already learned a lot. They’ve found that the asteroid is rich in organic matter, which supports the idea that asteroids could have delivered these materials to Earth. Ryugu contains water-bearing minerals, which is evidence that it held more water or water ice in the past. Scientists have also detected the effects of space weathering on the asteroid’s surface and solar wind particles trapped within its grains.

Artist’s impression of the Hayabusa2 taking samples from the surface of the asteroid Ryugu. Credit: Akihiro Ikeshita/JAXA

This new research added to the bounty of knowledge provided by the tiny 5.4-gram sample. The researchers analyzed 17 Ryugu particles, ranging in size from 1 to ~8 mm. They were mostly interested in uncovering a more detailed understanding of the asteroid’s history. They wanted to find answers to several specific questions:

1. When and where did Ryugu’s parent body form?
2. What is the original mineralogy, elemental abundances as a whole, and chemical compositions of the accreted materials, including their ice content?
3. How did these materials evolve through chemical reactions?
4. How was Ryugu ejected from its parent?

The APS and its Mossbauer Spectroscopy revealed more detail about Ryugu, and the researchers used impact simulators and other tools to piece together the history of the asteroid and its parent.

The researchers found carbon dioxide-bearing water inclusions in a certain type of crystal. This is evidence that Ryugu’s parent body formed in the outer Solar System, where cold temperatures allowed water ice to be incorporated. APS also identified a large concentration of pyrrhotite in the sample. Pyrrhotite is an iron sulphide found nowhere in meteorite fragments that resemble Ryugu. This helps limit the location and temperature of the parent body when it formed. The research team says that the parent body formed about 1.8 million to 2.9 million years after the beginning of Solar System formation.

In the outer Solar System, materials that form at low temperatures are dominant, and Ryugu’s parent was largely made of ice. The parent body formed beyond the H₂O and CO₂ snow lines and possibly beyond Jupiter.

The samples are porous and fine-grained, indicating that the parent contained ice that melted over a long period of time. The researchers say that radioactive heating in the parent body’s interior melted the water ice about three million years ago. Over time, reactions between the water and rock slowly changed the asteroid’s initial anhydrous mineralogy to a largely hydrous mineralogy.

The material was initially less altered at shallow depths and more hydrous at deeper depths. After about five million years, all of the material in the parent body reached its maximum temperature, and aqueous alteration continued.

The catastrophic head-on collision that blasted Ryugu’s parent happened about one billion years ago. The parent was about 50km in diameter, and the impactor was about 6 km. Ryugu isn’t a single chunk of its parent. Instead, it’s a rubble pile asteroid, a collection of debris dislodged from its parent body by the impact. Ryugu’s material originated at different depths on the opposite side of its parent from the impact and then coagulated into Ryugu.

This research helps paint a timeline of Ryugu’s parent and Ryugu itself on its long journey through the Solar System.

Ryugu itself began its journey as part of a larger body only about two million years after the birth of the Solar System. After billions of years as part of its parent body, it was created in the aftermath of a collision. After a long time, it made its way into its near-Earth orbit, and in the last blink of an eye, humanity arose and built a technological civilization. We’ve reached out and sampled this messenger from the past, and it’s taught us a lot about our Solar System’s history.

Hayabusa 2 is now on an extended mission to visit two other asteroids. In 2026, it will perform a high-speed fly-by of the S-type asteroid 98943 Torifune. In 2031, it will rendezvous with 1998 KY26, a small 30m asteroid that is a fast rotator.

Hayabusa 2 won’t sample either of these asteroids, but its observations will add to its already impressive contribution.

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Astronomers Have Found the Fastest Spinning Neutron Star

Neutron stars are as dense as the nucleus of an atom. They contain a star’s worth of matter in a sphere only a dozen kilometers wide. And they are light-years away. So how can we possibly understand their interior structure? One way would be to simply spin it. Just spin it faster and faster until it reaches a maximum limit. That limit can tell us about how neutron stars hold together and even how they might form. Obviously, we can’t actually spin up a neutron star, but it can happen naturally, which is one of the reasons astronomers are interested in these maximally spinning stars. And recently a team has discovered a new one.

All neutron stars rotate on their axes. They form from the collapse of a massive star’s core, and just as an ice skater spins faster as they pull in their arms, a neutron star spins up as it forms. Young neutron stars can rotate hundreds of times a second, though they generally slow down as they age. Interactions between their magnetic fields and interstellar space cause their rate of rotation to decay. This is why, for example, we can observe pulsars gradually slow down over time.

But many neutron stars have a binary companion. If their companion happens to be a closely orbiting regular star, the neutron star can pull off some of the companion’s outer layer and capture it. The slow exchange of matter can cause the neutron star to speed up as it essentially steals some of the orbital angular momentum of the companion. They are known as millisecond pulsars because they emit a radio pulse every few milliseconds. They are the fastest-rotating stars in the cosmos.

So, just how fast can these neutron stars spin? The record for the fastest spinning pulsar is held by PSR J1748–2446ad. Observations in 2004 and 2005 confirmed it rotates 716 times per second. That’s a bit faster than number two, which rotates at 707 times a second. This new study has found another neutron star rotating at 716 times a second, and it’s interesting because it isn’t a pulsar.

X-ray burst showing the 716 Hz oscillation. Credit: Jaisawal, et al

Known as 4U 1820-30, it is part of a binary X-ray system. As the neutron star captures material from its companion, part of its surface will heat up to such a degree that it emits X-rays. As the neutron star rotates, the hot-spot swings in and out of view, and we observe a periodic pulsation of X-rays. Using NASA’s NICER X-ray telescope, the team observed the binary from 2017 to 2021 and captured data on 15 powerful X-ray bursts. One of these bursts had a clear periodicity of 716 Hz. This strongly suggests the neutron star rotates at that rate.

While it could just be a statistical fluke, the fact that we now have two 716 Hz neutron stars found in two different ways suggests they may be near the maximal rotation limit for a neutron star.

Reference: Jaisawal, Gaurava K., et al. “A Comprehensive Study of Thermonuclear X-Ray Bursts from 4U 1820–30 with NICER: Accretion Disk Interactions and a Candidate Burst Oscillation.” The Astrophysical Journal 975.1 (2024): 67.

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Astronomers Discover Potential New Building Block of Organic Matter in Interstellar Space

Carbon is the building block for all life on Earth and accounts for approximately 45–50% of all dry biomass. When bonded with elements like hydrogen, it produces the organic molecules known as hydrocarbons. When bonded with hydrogen, oxygen, nitrogen, and phosphorus, it produces pyrimidines and purines, the very basis for DNA. The carbon cycle, where carbon atoms continually travel from the atmosphere to the Earth and back again, is also integral to maintaining life on Earth over time.

As a result, scientists believe that carbon should be easy to find in space, but this is not always the case. While it has been observed in many places, astronomers have not found it in the volumes they would expect to. However, a new study by an international team of researchers from the Massachusetts Institute of Technology (MIT) and the Harvard-Smithsonian Center for Astrophysics (CfA) has revealed a new type of complex molecule in interstellar space. Known as 1-cyanoprene, this discovery could reveal where the building blocks of life can be found and how they evolve.

The research was led by Gabi Wenzel, a postdoctoral researcher from the Department of Chemistry at MIT. She was joined by researchers from the CfA, the University of British Columbia, the University of Michigan, the University of Worchester, the University of Virginia, the Virginia Military Institute (VMI), the National Science Foundation (NSF), the National Radio Astronomy Observatory (NRAO), and the Astrochemistry Laboratory at NASA’s Goddard Space Flight Center (GSFC). The paper that describes their findings recently appeared in the journal Science.

Artist’s impression of complex organic molecules in space. Credit: NSF/NSF NRAO/AUI/S. Dagnello

For their study, the team relied on the NSF Green Bank Telescope (GBT), the most accurate, versatile, and largest fully-steerable radio telescope in the world, located at the Green Bank Observatory in West Virginia. This sophisticated instrument allowed the team to detect the presence of 1-cyanopyrene based on its unique rotational spectrum. 1-cyanoprene is a complex molecule composed of multiple fused benzene rings and belongs to the polycyclic aromatic hydrocarbon (PAHs) class of molecules. On Earth, they are created by burning fossil fuels or other organic materials, like charred meat or burnt bread.

By studying PHAs, astronomers hope to learn more about their lifecycles and how they interact with the ISM and nearby celestial bodies. As co-author Harshal Gupta, the NSF Program Director for the GBO and a Research Associate at the CfA, explained in a recent CfA press release:

“Identifying the unique rotational spectrum of 1-cyanopyrene required the work of an interdisciplinary scientific team. This discovery is a great illustration of synthetic chemists, spectroscopists, astronomers, and modelers working closely and harmoniously.”

This was an impressive feat due to the difficulty (or even impossibility) of detecting these molecules due to their large size and lack of a permanent dipole moment. “These are the largest molecules we’ve found in TMC-1 to date. This discovery pushes the boundaries of our understanding of the complexity of molecules that can exist in interstellar space,” added co-author MIT professor Brett McGuire, who is also an adjunct astronomer at the NSF and the NRAO.

Previously, these molecules were believed to form only in high-temperature environments, like the region surrounding older stars. This concurs with what astronomers have known for a long time about certain carbon-rich stars, which produce massive amounts of small molecular sheets of carbon that they then distribute into the interstellar medium (ISM). In addition, previous research has suggested that the infrared fluorescence of PAHs – caused by the absorption of ultraviolet radiation from nearby stars – could be responsible for infrared bands observed in many celestial objects.

Artist’s impression of Green Bank Telescope conducting radio astronomy with the help of AI algorithms. Credit: Breakthrough Listen/Danielle Futselaar.

The intensity of these bands has led some astronomers to theorize that PAHs could account for a significant fraction of carbon in the ISM. Other astronomers have maintained that these carbon-rich molecules could not survive the harsh conditions of interstellar space because temperates in the ISM are far too low – averaging about 10 K (-263 °C; -442 °F). However, the 1-cyanopyrene molecules Wenzel and her colleagues observed were located in the nearest star-forming region to Earth, the cold interstellar cloud known as Taurus Molecular Cloud-1 (TMC-1).

Since this Nebula has not yet started forming stars, its temperature is the same as that of the ISM. “TMC-1 is a natural laboratory for studying these molecules that go on to form the building blocks of stars and planets,” said Wenzel. These observations suggest that PHAs like 1-cyanopyrene may have a different formation mechanism entirely and/or can survive the harsh environment of space. In the meantime, detecting cyanopyrene can provide indirect evidence of even larger and more complex molecules in future observations. 

This research was supported by measurements and analysis conducted by the molecular spectroscopy laboratory of Dr. Michael McCarthy at the CfA. As he indicated:

“The microwave spectrometers developed at the CfA are unique, world-class instruments specifically designed to measure the precise radio fingerprints of complex molecules like 1-cyanopyrene. Predictions from even the most advanced quantum chemical theories are still thousands of times less accurate than what is needed to identify these molecules in space with radio telescopes, so experiments in laboratories like ours are indispensable to these ground-breaking astronomical discoveries.”

Further Reading: CfA

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There’s Another Ocean Moon Candidate: Uranus’ Tiny Moon Miranda

The Solar System’s hundreds of moons are like puzzle pieces. Together, they make a picture of all the forces that can create and modify them and the forces that shape our Solar System. One of them is Miranda, one of 28 known moons that orbit the ice giant Uranus. Miranda is its smallest major moon, at 471 km in diameter.

New research shows that this relatively small, distant moon may be hiding something: a subsurface ocean.

Miranda stands out from the other moons for one reason: its surface is a bizarre patchwork of jumbled terrain. There are cratered areas, rough scarps, and grooved regions. It may have the tallest cliff in the Solar System, a 20 km drop named Verona Rupes. Many researchers think its surface is deformed by tidal heating from gravitational interactions with some of the Uranus’ other moons.

New research in The Planetary Journal set out to explain Miranda’s jumbled geology. It’s titled “Constraining Ocean and Ice Shell Thickness on Miranda from Surface Geological Structures and Stress Modeling.” The lead author is Caleb Strom, a graduate student at the University of North Dakota.

“To find evidence of an ocean inside a small object like Miranda is incredibly surprising,”

Tom Nordheim, co-author and planetary scientist at the Johns Hopkins Applied Physics Laboratory

Scientists don’t have much to go on when it comes to Miranda. The only spacecraft to image it was Voyager 2 in 1986. Even then, the flyby was brief, and the spacecraft only imaged the moon’s southern hemisphere. But that was enough to reveal the moon’s bizarre and complex geological surface features. Miranda’s strange surface coronae attracted a lot of attention.

This figure from the study shows some of Miranda’s surface features. The moon is known for its coronae features, two of which are labelled here. Image Credit: Strom et al. 2024.

When the images were first received, scientists were baffled by Miranda’s complexity. Some called it a “patchwork planet,” and there was much healthy speculation about what created it. Attempts to understand the moon are still limited by the amount of data that Voyager 2 provided. However, modern scientists have access to a more powerful tool than scientists did in the 80s: computer models and simulations.

Strom and his co-researchers used a computer model to work backward from Miranda’s current surface. They started by mapping Miranda’s surface features, including its cracks, ridges, and unique trapezoidal coronae, and then reverse-engineered it. They tested different models of the moon’s interior to see what could account for the varied surface.

This simple schematic shows the four-layer model Strom and his co-researchers worked with. Image Credit: Strom et al. 2024.

The model that best matched the surface was one where Miranda had a vast ocean under its surface some 100-500 million years ago. The icy crust is probably 30 km thick or less, and the ocean could be up to 100 km thick.

“Our results show that a thin crust (?30 km) is most likely to result in sufficient stress magnitude to cause brittle failure of ice on Miranda’s surface,” the authors explain in their research. “Our results also suggest the plausible existence of a ?100 km thick ocean on Miranda within the last 100–500 million yr.”

“To find evidence of an ocean inside a small object like Miranda is incredibly surprising,” said Tom Nordheim, a planetary scientist at the Johns Hopkins Applied Physics Laboratory (APL) in Laurel, Maryland, a study co-author, and the principal investigator on the project that funded the study. “It helps build on the story that some of these moons at Uranus may be really interesting — that there may be several ocean worlds around one of the most distant planets in our solar system, which is both exciting and bizarre.”

Tidal heating is responsible for this, and it came from gravitational relationships between Miranda and Uranus’ other moons. Moons tug on each other, and when they’re in an orbital resonance with one another, where each moon’s period around a planet is an exact integer of the others’ periods, those tugs are amplified. These forces can periodically deform the moons, and as they’re squeezed, they heat up, keeping subsurface oceans warm and liquid.

Miranda and other moons of Uranus were likely in resonance in the past, which could’ve created surface fractures and related terrain.

A digital elevation model (DEM) of Miranda’s Inverness Coronae. The relative elevation ranges from 0 km (purple) to 4 km (red). Image Credit: Beddingfield et al. 2022.

However, resonances don’t last forever, and the researchers think that some time ago, Miranda left orbital resonance, and its interior began to cool. They don’t think it’s completely cooled yet because if the ocean had completely frozen, it would’ve expanded and displayed telltale surface cracks. So, the interior ocean likely still exists but is probably much thinner than in the past. “But the suggestion of an ocean inside one of the most distant moons in the solar system is remarkable,” Strom said.

Nobody predicted that Miranda would have an ocean. As far as scientists could tell, it was a frozen ball. But they’ve been wrong about moons before.

Researchers used to think that Saturn’s moon, Enceladus, the most reflective object in the Solar System, was just a ball of ice. After all, its surface is smooth and clearly frozen solid. However, the Cassini mission showed us that it may not be totally frozen. There’s a bevy of evidence that Enceladus has a warm ocean under a layer of ice.

This false-colour image of the plumes erupting from Enceladus is easily recognizable to many. Enceladus and Miranda are similar in important ways. Could Miranda also be geologically active? Image Credit: NASA/ESA

“Few scientists expected Enceladus to be geologically active,” said co-author Alex Patthoff. “However, it’s shooting water vapour and ice out of its southern hemisphere as we speak.”

Since both Enceladus and Miranda are roughly the same size and may have similar ice shells, it increases the chances that Miranda also has an ocean. Other moons, like Saturn’s Europa, may also be icy ocean moons. Now, scientists think these moons and their warm oceans are the best targets in the search for life in our Solar System.

Other recent research suggests that Miranda could be more like Enceladus than thought. One 2023 study showed that the moon may be releasing material into space like Enceladus does. The ESA and NASA are both sending probes to Jupiter to study Europa and other potential ocean moons. Should we expand that search to distant Uranus and its small moon Miranda?

An artist’s impression of Uranus and its five largest moons (innermost to outermost): Miranda, Ariel, Umbriel, Titania and Oberon. A 2023 paper showed that Ariel and/or Miranda could be releasing material into space. Image Credit: NASA/Johns Hopkins APL/Mike Yakovlev

“We won’t know for sure that it even has an ocean until we go back and collect more data,” said study co-author Nordheim. “We’re squeezing the last bit of science we can from Voyager 2’s images. For now, we’re excited by the possibilities and eager to return to study Uranus and its potential ocean moons in depth.”

For now, all we have is decades-old Voyager 2 data. However, the data and the computer models the team employed shed new light on Miranda.

“We interpret the tidal stress model results to indicate that at some point in Miranda’s geologic past, it experienced an intense heating event that resulted in a thin crust (?30 km). Such a thin crust would also have resulted in a ?100 km thick ocean to account for the molten part of the hydrosphere. This thin ice crust and thick ocean could have allowed for intense tidal stress leading to significant geologic deformation in the form of brittle deformation at Miranda’s surface,” the authors explain.

“In conclusion, our results suggest that Miranda could have had a subsurface ocean in the geologically recent past from an intense heat pulse, consistent with dynamical modelling results of previous studies,” they conclude.

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