In the vast expanse between Uranus and Neptune, a team of researchers have uncovered something really quite extraordinary, a minor planet that has been locked in precise gravitational manouevres with Uranus for at least a million years. This discovery sheds new light on the complex dynamics that govern our Solar System's outer reaches.

The object in question, designated 2015 OU₁₉₄, belongs to a class of small bodies called Centaurs, rocky and icy objects that orbit between Jupiter and Neptune. What makes this particular Centaur special is its remarkably stable relationship with Uranus, locked in what is known as a 3:4 mean motion resonance. This means that for every three orbits 2015 OU₁₉₄ completes around the Sun, Uranus completes exactly four. This precise mathematical relationship creates a gravitational partnership that keeps the two objects in a stable dance, preventing them from colliding or drifting apart.

Uranus, the 7th planet in the Solar System seems to have an asteroid tagging along.

(Credit : NASA)

The discovery came about through detective work with archival observations. Researchers led by Daniel Bamberger from the Northolt Branch Observatories in Germany, located additional observations of 2015 OU₁₉₄ from 2017 and 2018, extending the object's data points from just one year to 3.5 years. This longer observation period was crucial for understanding the object's true orbital behavior.

Computer simulations revealed the remarkable stability of this relationship. The resonance has remained stable for at least 1,000 years in the past, probably even 1 million years and is predicted to continue for another 500,000 years into the future. This longevity suggests that the gravitational partnership formed early in our Solar System's history and has persisted through countless changes.

What makes this discovery particularly significant is that no objects has previously been found in resonance between the orbits of Uranus and Neptune. It’s a region of space, while containing many small bodies, that appears to lack the kind of stable orbital relationships commonly found elsewhere in the Solar System.

The asteroids of the inner Solar System, where they are far more numerous than the outer Solar Sytem, are plotted on this diagram.

(Credit : MDF)

The researchers didn't stop with just one object though. Their investigation uncovered additional candidates, including 2013 RG₉₈, which also appears to maintain this same 3:4 resonance with Uranus for several hundred thousand years. A third candidate, 2014 NX₆₅, shows strong gravitational influence from Neptune, suggesting the complex interplay of forces in this region.

The existence of these Uranus resonant objects suggests that similar relationships may be more common than previously thought. As our survey capabilities improve and we discover more objects in the outer Solar System, we may find that these gravitational partnerships are common and fundamental to understanding how small bodies are distributed throughout the region.

Source : 

• A minor planet in an outer resonance with Uranus

From one perspective, the Sun is a benevolent orb of plasma and its warmth makes Earth habitable and has kept if habitable for billions of years, allowing complex things like human beings to evolve. From another perspective, it's a malevolent orb that sends deadly UV radiation our way, and sometimes erupts and hurls massive blobs of plasma toward Earth. The truth is somewhere in the middle, and NASA launched the Parker Solar Probe to flesh out that truth.

NASA launched the Parker Solar Probe (PSP) in 2018 and its mission is to examine the Sun's coronal plasma and its magnetic field. To do this, it has to get close. NASA describes it as a mission to "touch the Sun," and that's pretty accurate. Throughout its mission it has gotten progressively closer, setting a new record each time for closest approach to the Sun. On Dec. 24, 2024, the spacecraft flew just 6.1 million km (3.8 million miles) from the solar surface.

That is incredibly close, but luckily, the spacecraft has several layers of protection. The PSP is also the fastest-moving spacecraft ever built. It was travelling at 692,000 km/h (430,000 mph) during its 2024 flyby, and didn't spend much time that close to the star.

The result of this daring piece of coronal navigation is the closest images yet of our star. The PSP carries four main instruments, and one of them is WISPR, the Wide-field Imager for Solar Probe. WISPR has two radiation-hardened cameras that can withstand the Sun's power. It's job is to image the corona, the solar wind, and other phenomena near the Sun. On the last flyby, WISPR showed us the solar corona and the solar wind in a way we've never seen before.

“Parker Solar Probe has once again transported us into the dynamic atmosphere of our closest star,” said Nicky Fox, associate administrator, Science Mission Directorate at NASA Headquarters in Washington. “We are witnessing where space weather threats to Earth begin, with our eyes, not just with models. This new data will help us vastly improve our space weather predictions to ensure the safety of our astronauts and the protection of our technology here on Earth and throughout the solar system.”

There are important implications for understanding or misunderstanding the solar wind and coronal mass ejections (CME). They're ever present forces in the Solar System. The wind is a stream of charged particles that constantly flows outward from the Sun. It's responsible for the gorgeous aurorae that we love to gaze it, but it's also responsible for damaging power grids and satellites. As we expand into cislunar space and crowd more satellites into Low-Earth Orbit, it's important that we understand not only the solar wind, but everything that flows from the Sun, including coronal mass ejections (CME).

While the solar wind is a continuous phenomenon, coronal mass ejections are episodic. They're ejections of plasma that can reach Earth. CMEs can contain billions of tons of plasma moving at high speeds. Only a small number of them reach Earth, but when they do, they can also cause geomagnetic storms that can damage power grids and other equipment.

The Parker Solar Probe is named after the American heliophysicist Eugene Parker, who coined the term 'solar wind in 1958. His theories, though they faced stiff resistance at the time, revolutionized our scientific understanding of the Sun. Multiple spacecraft have been launched to study the Sun and the solar wind, but the Parker Solar Probe has outdone them all.

Each mission has revealed more about the Sun and the solar wind, but none have come as close to the star as the PSP. It also has the advantage of the most modern technologies and instruments. One of the things its revealed is the nature of so-called switchbacks.

When measured near Earth, the solar wind is pretty much constant. But closer to the Sun, things are more chaotic. The Sun has extremely powerful magnetic fields, and when the PSP came within 14.7 million miles of the Sun, it showed us that some of those fields zig-zag. These zig-zagging fields are called switchbacks. The PSP also showed us that these switchbacks are more common than thought, and that they come in clumps.

As the PSP got progressively closer and travelled through the Sun's corona, it noticed that the corona's boundary was uneven and complex. Getting even closer in subsequent flybys, it was able to pinpoint the source of the switchbacks. The source is patches on the Sun where magnetic funnels form and images showed that the switchbacks are partly responsible for the fast solar wind, one of the wind's two components.

“The big unknown has been: how is the solar wind generated, and how does it manage to escape the Sun’s immense gravitational pull?” said Nour Rawafi, the project scientist for Parker Solar Probe at the Johns Hopkins Applied Physics Laboratory. “Understanding this continuous flow of particles, particularly the slow solar wind, is a major challenge, especially given the diversity in the properties of these streams — but with Parker Solar Probe, we’re closer than ever to uncovering their origins and how they evolve.”

The slow solar wind is twice as dense as the fast solar wind, and interplay between the two seems to create moderately strong conditions on Earth that can rival conditions generated by CMEs. The slow solar wind appears to originate from the Sun's equatorial regions, but scientists are still debating what structures they originate in and how the material is released.

“We don’t have a final consensus yet, but we have a whole lot of new intriguing data,” said Adam Szabo, Parker Solar Probe mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

We've learned a lot about the Sun in recent decades, and the PSP is poised to show us more and hopefully provide answers to our most probing questions. It's next perihelion will be in September, 2025, when it will again fly through the solar corona. That approach will gather even more data on the slow solar wind and other facets of the Sun.

It will also give us more stunning images.

Astrobiology can be split into two very distinct fields. There’s the field that astronomers are likely more familiar with, involving large telescopes, exoplanets, and spectroscopic signals that are pored over to debate whether they show signs of life. But there is another camp, collective known as the Origins researchers that focus on developing a scientific understanding of how life originally developed on Earth. A new paper from Cole Mathis at Arizona State and Harrison B. Smith at the Institute of Science in Tokyo suggests a new path forward to tackling those challenges - set them up as competitions and let a hefty prize motivate scientific teams and individuals to pursue them.

The paper, which was published on arXiv, is a response to NASA’s Decadal Astrobiology Research and Exploration Strategy (DARES) call for community input. It calls on the “challenge” funding model popularized by organizations like the X Prize, and the Defense Research Advanced Projects Agency (DARPA), whose early autonomous driving challenges inspired the self-driving cars that are finally starting to navigate public roadways.

A similar method could be used to stimulate research into specific, measurable, and important “origins” research according to Drs. Mathis and Smith. They point out that one hurdle holding back development in this field is a lack of consensus on even simple definitions, such as “what is life?”. However, they lay out five different “finish lines” that, though some of them would prove certain theories, lack of progress towards them could also be held up as proof of opposing theories.

One finish line will attempt to solve the debate of whether metabolism or genetics were developed first in the course of life. It focuses on creating a biological pathway known as the pentose phosphate pathway (PPP) using abiotic chemistry. If possible, it would make a strong case that the “metabolism first” camp is correct.

A second finish line utilizes the concept of “assembly theory”, a framework developed by Leroy Cronin and Sara Walker, that quantifies the complexity of organic molecules, and draws a distinct line at a certain complexity level, showing that anything more complex must be made within a biological system. The challenge the authors put forward is to create a sufficiently complex molecule using only abiotic chemistry.

The third challenge attempts to settle the debate between “determinism” and “contingency”. In the determinism world view, if we manage to rewind life back to its early beginnings, would the same process happen in the same way all over again if given the same starting conditions? Or, according to the “contingency” theory, would small differences in the chemistry makeup of early life lead to massive differences in the biochemistry of later lifeforms. The challenge itself is to design an organic chemistry experiment where exactly the same initial conditions can lead to different products. If someone manages to do this, it would prove the “contingency” theory of early life formation.

The fourth challenge tackles self-replication, by requiring a team to make polymers that can self-replicate but still overcome “Eigen’s error threshold”. According to the information theory developed by Manfred Eigen that goes along with replicators passing data to the new copies of themselves, early replicators would have to be much smaller than would be necessary to contain any error-correcting biological machinery common when our cells copy their own DNA during the replication process. Understanding how early life got through this bottle neck to develop reliable error checking systems without losing all their information once they cross the threshold in terms of size is at the problem at the heart of this challenge.

Scientists have long thought that, somewhere in the process of evolution, there was a transition from RNA to DNA. However, that has never actually been proven, and the fifth and final challenge pushes researchers to prove that the RNA to DNA jump can be made gradually. If such a jump is infeasible, that would call into question the significance of RNA in the overall scheme of the development of life on Earth.

These challenges are well defined, measurable, and have an obvious tie back to the fundamental challenge of understanding where life originally came from. Whether or not NASA, especially with its own current funding challenges, would be willing to back a challenge-based structure to pursue these efforts remains to be seen. But there are plenty of other challenge-based funding supporters out there, such as the team around the Evolution 2.0 challenge and the X Prize itself. Astrobiology research remains key to understanding our place in the universe - it might be time to consider a different path to how we approach it.

Learn More:

• C. Mathis & H. B. Smith - Challenge-Based Funding to Spark Origins Breakthroughs
• UT - Astrobiology: Why study it? How to study it? What are the challenges?
• UT - NASA's Future Telescope Could Solve the Mystery of Life's Origins
• UT - Is There a Fundamental Logic to Life?

There's very little scientific debate about the existence of surface water on Mars in its past. The evidence at this point is overwhelming. Orbiter images clearly show river channels and deltas, and rovers have found ample minerals that only form in the presence of water. Now the scientific debate has moved on. Scientists are trying to learn the extent of Martian surface water, both on the planet's surface and through time.

NASA's Mars Reconnaissance Orbiter (MRO) is a prolific purveyor of images of Mars' surface. One of its most well-known image shows Jezero Crater, the landing site of the Mars Perseverance rover. Jezero Crater is an ancient paleolake filled by an ancient river that created a delta of sediments. The orbiter also identified clays and carbonate salts, minerals that were altered by water in the planet's past.

This image of Jezero Crater is one of the MRO's most well-known images. It shows clear evidence of flowing water. The colours map the location of different minerals, including water-altered clays and carbonate salts.

Image Credit: NASA/ JPL-Caltech/ MSSS/ JHU-APL.

There are two schools of thought around Mars' watery past. One says that water was stable on the Martian surface for long periods of time, while the other states that the water channels were carved during geologically brief periods of time when climate shifts caused ice sheets to melt. Call the first one the 'warm and wet' theory and the second one the 'cold and dry' theory. Both theories are well developed, and make predictions about what scientists will find when they dig deeper.

Some research into Noachis Terra supports the idea that water features there were carved by ice-related processes during short-lived periods of wetness, the cold and dry theory. This 2016 paper illustrates that point of view. "Our studied valleys' association with ice-rich material and abundant evidence for erosion caused by downslope flow of ice-rich material are consistent with a cold, wet Mars hypothesis where accumulation, flow, and melting of ice have been dominant factors in eroding crater valleys," those researchers concluded.

Not all regions of Mars have been studied equally, and the Noachis Terra is not as well-studied as some other regions. The 'warm and wet' climate theory predicts that Noachis Terra would've had high levels of precipitation. However, there's an overall lack of Valley Networks (VNs) in the region. Valley Networks are similar to Earth's river drainage basins and are compelling evidence of Mars' watery past.

This map of Mars shows important surface features, as well as all of the planet's surface regions. Noachis Terra is a southern highland region of heavily cratered ancient terrain.

Image Credit: By Jim Secosky modified NASA image. - http://planetarynames.wr.usgs.gov/images/mola_regional_boundaries.pdf, Public Domain,

New research presented at the Royal Astronomical Society's National Astronomy Meeting presented a different sort of evidence to support the high levels of precipitation predicted in Noachis Terra by the warm and wet theory. It's titled "The Fluvial History of Noachis Terra, Mars," and the lead researcher is Adam Losekoot. Losekoot is a PhD student at the Open University, a public research university in the UK.

"Studying Mars, particularly an underexplored region like Noachis Terra, is really exciting because it's an environment which has been largely unchanged for billions of years. It's a time capsule that records fundamental geological processes in a way that just isn't possible here on Earth," Losekoot said in a press release.

The evidence Losekoot and his fellow researchers uncovered is in the form of Fluvial Sinuous Ridges.

"Noachis Terra, in Mars’ southern highlands, is a region where ‘warm, wet’ climate models predict high rates of precipitation, but is poorly incised by VNs," Losekoot explained. "We searched instead for Fluvial Sinuous Ridges (FSRs, aka inverted channels) here as they provide alternate evidence to VNs for stable surface water."

FSRs are winding, elevated features left behind from Mars' watery past. They form when water flows across the surface carrying sediment with it. The sediment deposits become harder than the rock in the surrounding terrain due to compaction and mineral precipitation. When Mars' water disappeared, aeolian erosion ate away at the softer, surrounding rock, leaving the elevated FSRs behind.

To find the FSRs in Noachis Terra, Losekoot and his co-researchers turned to NASA's MRO. No other mission has done more to reveal Mars' past than the MRO. They used data from its HiRISE and other instruments, as well as data from the Mars Orbital Laser Altimeter on the Mars Global Surveyor, to identify FSRs.

Losekoot and his co-researchers found 15,000 km of FSRs in Noachis Terra. "We find FSRs to be common across Noachis Terra, with a cumulative length of more than 15,000 km. These are often isolated segments, but some systems are hundreds of km in length," Losekoot writes.

This HiRISE image shows two branches of an FSR. The river split into two then rejoined outside of the image. The lower branch is heavily eroded and quite spread out, the upper branch is narrower but more clearly preserved. They could've had different exposure times or undergone different geological processes. Or they could be from different periods of water activity. There are remnants of an infilling material within the ridge and a meander where the branch turns back towards the lower trunk. The mesa in between the branches could be a crater that was filled with the same sediment as the FSR.

Image Credit: HiRISE Image: ESP_085519_1585 NASA/JPL/University of Arizona. Licence type: Attribution (CC BY 4.0)

The FSRs are broadly distributed across Noachis Terra, and some are tens of meters tall. That means the water flowed for a long time.

"The broad distribution of FSRs suggests a broadly distributed source of water," Losekoot writes. "The most likely candidate is precipitation, suggesting a benign surface environment. For FSRs to have formed mature, interconnected systems, up to tens of meters high, these conditions must also have been relatively long-lived."

"This suggests that ~3.7 Ga, Noachis Terra experienced warm and wet conditions for a geologically relevant period," Losekoot explained.

This HiRISE image shows narrow FSR with a pointed pinnacle ridge. The pointed could indicate that this FSR has suffered heavy erosion for a long time until only a narrow peak remained, or it may be that only a narrow part of the original river infill has been preserved.

Image Credit: HiRISE Image: ESP_067439_1505 NASA/JPL/University of Arizona. Licence type: Attribution (CC BY 4.0)

The way the FSRs are distributed across Noachis Terra and their extent suggests that precipitation is responsible. They also form large, interconnected systems, which suggests the watery period was long-lived. This work supports the idea that Mars was warm and wet for a long time, rather than just for bursts of time when ice sheets melted.

This MRO CTX image gives an oblique view of part of a system of FSRs in Noachis Terra. It shows river tributaries that were probably active at the same time. The rivers meandered, and there are areas where the river banks burst and deposited fine layers of sediment. At the top of the image is a really clear example of an area where two FSRs intersect with an infilled crater. This is likely where the river flowed into the crater, filling it up and then breaching the other side to continue through the crater and down to the bottom of the image.

CTX image: MurrayLab_V01_E020_N-20_Mosaic. Image Credit: NASA/JPL/MSSS/The Murray Lab. Licence type: Attribution (CC BY 4.0)

"Our work is a new piece of evidence that suggests that Mars was once a much more complex and active planet than it is now, which is such an exciting thing to be involved in," said Losekoot.