The Great Enigma of Titan: Why the Moon’s Rivers Are Missing Deltas

Titan, Saturn’s largest moon, is a geological treasure trove that has long fascinated planetary scientists. With its thick atmosphere, liquid methane and ethane seas, and rivers that flow across its surface, Titan offers a unique window into the moon’s history and evolution. However, a new study published in the Journal of Geophysical Research: Planets reveals a surprising absence of river deltas on Titan – a feature that is common on Earth but mysteriously missing on this alien world.

“As a geomorphologist, it’s kind of disappointing to see that Titan doesn’t have the same type of deltas as we do on Earth,” said Sam Birch, an assistant professor in Brown University’s Department of Earth, Environmental and Planetary Sciences who led the work. “But at the same time, it raises a host of new questions.”

Titan’s liquid methane and ethane rivers should be perfectly capable of carrying and depositing sediment, forming deltas at their mouths. However, when Birch and his colleagues analyzed Cassini SAR data, they found that only about 1.3% of Titan’s large rivers have deltas – a stark contrast to the nearly 100% delta formation on Earth.

“It’s not entirely clear why Titan generally lacks deltas,” Birch said. “The fluid properties of Titan’s rivers should make them perfectly capable of carrying and depositing sediment.”

The researchers suggest that rapid changes in sea levels, winds, and tidal currents along Titan’s coasts may prevent delta formation. However, more research is needed to fully understand this phenomenon.

“This is really not what we expected,” Birch said. “But Titan does this to us a lot. I think that’s what makes it such an engaging place to study.”

The new analysis of Cassini SAR data also revealed pits of unknown origin deep within lakes and seas on Titan, as well as deep channels on the floors of these seas that seem to have been carved by river flows – but it’s not clear how they got there.

All of these surprises will require more research to fully understand. As Birch said, “This is really not what we expected, but Titan does this to us a lot. I think that’s what makes it such an engaging place to study.”

The long-standing debate over the origin of water on Earth has finally been put to rest by a team of researchers at the University of Oxford. Using a rare type of meteorite known as an enstatite chondrite, which has a composition analogous to that of the early Earth (4.55 billion years ago), they have uncovered crucial evidence for the origin of water on our planet.

The research team analyzed the elemental composition of a meteorite known as LAR 12252, originally collected from Antarctica. They used an elemental analysis technique called X-Ray Absorption Near Edge Structure (XANES) spectroscopy at the Diamond Light Source synchrotron at Harwell, Oxfordshire. This powerful tool allowed them to search for sulphur-bearing compounds in the meteorite’s structure.

When scanning the sample, the team focussed their efforts on the non-crystalline parts of the chondrules, where hydrogen had been found before. However, serendipitously, they discovered that the matrix itself was incredibly rich in hydrogen sulphide. In fact, their analysis found that the amount of hydrogen in the matrix was five times higher than that of the non-crystalline sections.

This finding suggests that the material which our planet was built from was far richer in hydrogen than previously thought. Without hydrogen, a fundamental elemental building-block of water, it would have been impossible for our planet to develop the conditions to support life.

The research team’s discovery contradicts the popular theory that water on Earth originated from asteroids bombarding its surface. Instead, their findings suggest that Earth had the hydrogen it needed to create water from when it first formed. This supports the idea that the formation of water on Earth was a natural process, rather than a fluke of hydrated asteroids bombarding our planet after it formed.

Tom Barrett, DPhil student in the Department of Earth Sciences at the University of Oxford, who led the study, said: “We were incredibly excited when the analysis told us the sample contained hydrogen sulphide — just not where we expected! Because the likelihood of this hydrogen sulphide originating from terrestrial contamination is very low, this research provides vital evidence to support the theory that water on Earth is native — that it is a natural outcome of what our planet is made of.”

Co-author Associate Professor James Bryson (Department of Earth Sciences, University of Oxford) added: “A fundamental question for planetary scientists is how Earth came to look like it does today. We now think that the material that built our planet — which we can study using these rare meteorites — was far richer in hydrogen than we thought previously. This finding supports the idea that the formation of water on Earth was a natural process, rather than a fluke of hydrated asteroids bombarding our planet after it formed.”

The discovery of this hidden secret to Earth’s water origin has significant implications for our understanding of the planet’s history and evolution. It suggests that the conditions necessary for life to arise were present from the very beginning, and that the formation of water was an integral part of the process.

The movement of comets and their associated meteoroid streams has long been a topic of interest for astronomers. Researchers at the SETI Institute have made a groundbreaking discovery that sheds new light on this phenomenon. In a recent study published in the journal Icarus, the team found that the Sun’s motion around the solar system barycenter plays a crucial role in the orbital evolution of long-period comets.

The solar system barycenter is the point where the Sun and planets all orbit together, serving as a reference frame for understanding their movements. Traditionally, astronomers have placed the Sun at the center of our solar system due to its massive size and gravitational influence. However, this perspective can be misleading when it comes to understanding the complex interactions between comets and the Sun.

Lead author Stuart Pilorz explained that long-period comets spend most of their time far away from the solar system, where they are affected by the Sun’s motion around the barycenter. As these comets approach Jupiter’s orbit, they come under the influence of the Sun, leading to a change in their orbital plane and inclination.

Pilorz noted that this phenomenon is similar to bouncing a tennis ball off the front or back of a moving train. The Sun’s motion provides a gravitational boost or braking effect on the comets, which can cause them to disperse over time. This randomness is primarily due to the Sun’s position and velocity in its orbit around the barycenter when each meteoroid encounters it.

The researchers’ findings have significant implications for predicting meteor showers. By taking into account the Sun’s motion around the barycenter, astronomers can better understand how comets and their associated meteoroid streams disperse over time. This knowledge can be used to search for parent comets of long-period comet meteoroid streams.

In addition, the study has shed new light on the relationship between planetary forces and the precession of comet orbits. The team’s calculations suggest that the measured shower dispersions can be used to determine the ages of over 200 long-period comet meteoroid streams.

The discovery made by the SETI Institute researchers highlights the importance of considering the Sun’s motion around the barycenter in understanding complex astronomical phenomena. Their work demonstrates the value of interdisciplinary research and collaboration, and it has paved the way for further studies on the orbital evolution of comets and the resulting meteor showers.