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Saturn’s moon, Titan, is an anomaly among moons. No other moons have surface liquids, and aside from Earth, it’s the only other Solar System object with liquids on its surface. However, since Titan is so cold, the liquids are hydrocarbons, not water. Titan’s water is all frozen into a surface layer of ice.

New research suggests that under the surface, Titan is hiding another anomaly: a thick crust of methane.

The evidence for the methane comes mostly from craters. Observations have found few confirmed impact craters on the frigid moon, and the ones that have been observed are hundreds of meters shallower than the same-sized craters on other moons. If Titan’s crust was rock, the craters should be much deeper.

The new research, published in The Planetary Science Journal, is titled “Rapid Impact Crater Relaxation Caused by an Insulating Methane Clathrate Crust on Titan.” Lauren Schurmeier, from the Hawai’i Institute of Geophysics and Planetology at the University of Hawai’i at Manoa, is the lead author.

Titan stands apart from other moons for multiple reasons. Unlike any other natural satellites in the Solar System, it has a thick atmosphere. Its atmosphere is about 50% more dense than Earth’s and extends about 600 km into space. A haze made of complex organic molecules called tholins gives the atmosphere its characteristic orange colour. The atmosphere is so thick that it blocks optical light, making Titan’s surface features nearly inscrutable.

The Cassini spacecraft has given us our best looks at Titan. It used radar and infrared instruments to see the moon’s surface. The small Huygens probe that went to Saturn with Cassini was released into Titan in 2005 to study the atmosphere and surface. It’s thanks to Huygens that we have our best images of Titan’s surface.

The new research suggests a link between Titan’s unusual atmosphere, its shallow surface craters, and a layer of methane in the moon’s crust. The methane keeps the underlying layer of ice convective by insulating it and helps impact craters rebound quickly and remain shallow.

There’s no consensus on how many craters Titan has because its surface is veiled behind its thick atmosphere, but there is some data on the craters.

This graph shows crater candidate counts binned by latitude regions and certainty level. Craters of certainty level 1 have more lines of evidence pointing toward an impact crater origin; certainty level 4 is the least certain. Image Credit: Schurmeier et al. 2024.

The research centres on the fact that Titan displays few craters and that the ones we do see are shallow. This sets it apart from other moons.

These are Cassini SAR (synthetic aperture radar) images of Titan’s impact craters. Arrows indicate potential forms of crater modification processes, including dunes and sands (purple), channels (blue), and significant crater rim erosion (pink). Afekan crater is one of Titan’s largest impact craters at 115 km. Jupiter’s moon, Ganymede, which is about the same size as Titan, has way more craters, including 20 that are larger than Afekan. Image Credit: NASA/ Cassini

“This was very surprising because, based on other moons, we expect to see many more impact craters on the surface and craters that are much deeper than what we observe on Titan,” said lead author Schurmeier. “We realized something unique to Titan must be making them become shallower and disappear relatively quickly.”

A handful of processes have been proposed to explain Titan’s diminishing craters. Liquid hydrocarbon rainfall, aeolian sand infill, and topographic relaxation induced by insulating sand infill have all been discussed. “Here, we propose an additional mechanism: topographic relaxation due to an insulating methane clathrate crustal layer in Titan’s upper ice shell,” the authors write.

This simple schematic of Titan’s interior (not to scale) shows a methane clathrate crust over a convecting ice shell. The methane clathrate can insulate the ice below and keep it convective. That convection could explain why Titan’s craters are so few and so shallow. Image Credit: Schurmeier et al. 2024.
 

There’s very little new information coming from Titan, so researchers have to work with what they have. To try to understand its shallow craters, the researchers built a computer model. They used it to try to understand how Titan’s topography might respond to impacts if a layer of methane clathrate was trapped under the surface. A clathrate is a substance where one type of molecule is trapped within a structure of molecules of another type. In this case, methane is trapped in water ice.

Methane’s insulating properties are key.

“Methane clathrate is stronger and more insulating than regular water ice,” said Schurmeier. “A clathrate crust insulates Titan’s interior, makes the water ice shell very warm and ductile, and implies that Titan’s ice shell is or was slowly connecting.”

With their model, they tested clathrate crusts that were 5, 10, 15, or 20 km thick. They used craters that were 40, 85, 100, and 120 km in diameter, each with two initial depths based on Ganymede’s crater diameters and depths. The result?

“We find that all clathrate crustal thicknesses result in rapid topographic relaxation despite Titan’s cold surface temperature,” the researchers write. “The 5 km thick clathrate crust can reproduce nearly all of the observed shallow depths, many in under 1000 yrs.”

They also found that a 10 km clathrate crust can reproduce Titan’s observed crater depths over geologic timescales. “If relaxation is the primary cause of the shallow craters, then the clathrate thickness is likely 5–10 km thick,” they write.

Across all simulations, most of the crater relaxation occurred in 1,000 years. “This finding suggests that thin clathrate crusts cause crater shallowing in a geological instant, similar to a fast-flowing terrestrial glacier,” the authors explain. It could certainly explain why none of Titan’s craters are deep.

The researchers point out a couple of caveats, though. They assumed that Titan’s initial craters had depths similar to Ganymede’s. They could’ve formed at different depths and shapes. Their model also didn’t include heat generated by the impact itself or account for an impact-triggered discontinuity in the methane clathrate layer. “These thermal and dynamic changes might alter the morphological evolution of the crater,” they write.

Juno captured this image of Ganymede in July 2022. The moon’s impact craters are easily visible, including the crater Tros, which is prominent below the center at left. Image Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill

This research adds to Titan’s mystery and our fascination with the unusual moon. It also adds another element to comparisons with Earth. Earth and Titan both have surface liquid and are the only two objects in the Solar System that do. Earth also has methane clathrates in its polar regions.

“Titan is a natural laboratory to study how the greenhouse gas methane warms and cycles through the atmosphere,” said Schurmeier. “Earth’s methane clathrate hydrates, found in the permafrost of Siberia and below the arctic seafloor, are currently destabilizing and releasing methane. So, lessons from Titan can provide important insights into processes happening on Earth.”

In the end, their results are clear: “We conclude that if crater relaxation is the primary cause of Titan’s unexpectedly shallow craters, then the clathrate crust is 5–10 km thick,” the authors write.

The post Titan May Have a Methane Crust 10 Km Thick appeared first on Universe Today.

By applying an electric field, the movement of microswimmers can be manipulated. Scientists describe the underlying physical principles by comparing experiments and theoretical modeling predictions. They are able to tune the direction and mode of motion through a microchannel between oscillation, wall adherence and centerline orientation, enabling different interactions with the environment.

By applying an electric field, the movement of microswimmers can be manipulated. Scientists describe the underlying physical principles by comparing experiments and theoretical modeling predictions. They are able to tune the direction and mode of motion through a microchannel between oscillation, wall adherence and centerline orientation, enabling different interactions with the environment.

Researchers designed tiny particles that can be implanted at a cancer tumor site, where they deliver two types of therapy: heat and chemotherapy.

Mechanical engineers designed a 3D-printed femur that could help doctors prepare for surgeries to repair bones and develop treatments for bone tumors. The study, which focused on the middle section of the bone, establishes 3D-printing parameters for a femur for use in biomechanical testing. Researchers said more studies will be needed before the technology could be available for widespread use.

Approximately 50 percent of global final energy consumption is dedicated to heating. Yet, the utilization of solar power in this sector remains relatively low compared to fossil energy sources. An inherent problem limiting the widespread usage of solar energy is the intermittency of its direct availability. A promising solution comes in the form of molecular solar energy storage systems.

Scientists highlighted the potential for ultrasound to treat some of the more complex health conditions affecting the human brain.

Asteroids that regularly fly between Earth, Venus and Mars could provide radiation shielding for human missions to explore neighbouring planets

We get about a quarter of our calories from snacks and new research shows that this isn't necessarily bad for us. Done right, snacking can boost our health

A research team has developed a deep skin-stimulating LED mask which has been verified in clinical trials to improve dermis elasticity by 340%.

A study developed a new technique to accurately analyse the properties of cancer cells and the surrounding tissue at the level of individual cells. This innovation enables a more comprehensive assessment of prognoses and treatment responses in the head and neck cancers, and paves the way for more accurate diagnostics.

Using state-of-the-art microscopy and simulation techniques, an international research team systematically observed how iron atoms alter the structure of grain boundaries in titanium. They were in for a surprise.

New research shows that not all standing positions in airport smoking lounges are created equal. Scientists found that the thermal environment and positioning of smokers influences how particles settle in the room. Additionally, smokers seated farther from ventilation inlets experience the lowest levels of pollution in the room. The researchers created a smoking room using computational models and placed heated and unheated manikins in the room to simulate smokers. They also modeled the ventilation system with three exhaust air diffusers.

Researchers overcame the tradeoff between plastic toughness and degradability by developing plastics with movable crosslinks. The crosslinks both increased toughness by over eight times and increased enzymatic degradability by over twenty times compared with those of a reference plastic without movable crosslinks. These advanced biodegradable plastics bring us one step closer to achieving a resource-circulating society.

Sungrazer C/2024 S1 ATLAS broke apart at perihelion.

Alas, a ‘Great Halloween Comet’ was not to be. The Universe teased us just a bit this month, with the potential promise of a second naked eye comet in October: C/2024 S1 ATLAS. Discovered on the night of September 27th by the Asteroid Terrestrial Last-alert impact System (ATLAS) all-sky survey, this inbound comet was surprisingly bright and active for its relative distance from the Sun at the time of discovery. This gave the comet the potential to do what few sungrazers have done: survive a blisteringly close perihelion passage near the Sun.

S1 ATLAS on final solar approach. NASA/ESA/SOHO Perishing at Perihelion

But as perihelion day approached yesterday on October 28th, things started to look grim. S1 ATLAS began to resemble a garden variety Kreutz sungrazer more and more. Little more than an icy rumble pile on final approach, the comet went in the inner field of view of the Solar Heliospheric Observatory’s (SOHO) LASCO C2 imager and behind the central occulting disk yesterday morning… and failed to exit.

Comet S1 ATLAS ends its days, as seen via SOHO’s LASCO C2 imager. NASA/SOHO

Perihelion distance (and time of expiry) for the comet was 330,600 miles/532,000 kilometers from the surface of the Sun yesterday, at around 7:30 AM EDT/11:30 Universal Time. Curiously, the final estimates for the comet put its orbital period at 953 years, suggesting that this may not have been its first passage through the inner solar system.

The finale for Comet S1 ATLAS, just hours prior to perihelion. ESA/NASA/SOHO/NRL

The comet gave us a few tell-tale signs that it was under-performing leading up to perihelion. After a brief outburst around its discovery 1.094 Astronomical Units (AU) from the Sun, the comet then faded considerably in early October. The lackluster performance was confirmed as it entered the field of view of SOHO’s LASCO C3 viewer this weekend. Still, its final solar dive put on a good show.

As I’m sure you’re aware, little comet ATLAS didn’t make it. ? It was clearly already a pile of rubble by the time it reached the LASCO field of view, and solar radiation took care of the clean-up for us. ???? pic.twitter.com/s8HrchtWnF

— Karl Battams (@SungrazerComets) October 28, 2024

A Brief History of Sungrazers

The demise of Comet S1 ATLAS yesterday brought to mind memories from early on in my Universe Today writing career of another great comet that wasn’t: C/2012 S1 ISON. That particular comet met its end on U.S. Thanksgiving Day 2013. The last great surprise for sungrazers was Comet W3 Lovejoy in 2011-2012, which survived a perihelion just 87,000 miles/140,000 kilometers from the surface of the Sun (!), and went on to become a great comet. Another example showing us what is possible was Comet Ikeya-Seki, which survived perihelion 280,000 miles/450,000 miles from the Sun in 1965 and became one of the great comets of the 20th century.

Light curve magnitude comparisons of comets Ikeya-Seki, W3 Lovejoy and S1 ATLAS in the lead up to their respective perihelia. Credit: Jakub Cerný

Astronomer Heinrich Kreutz discovered the existence on the Kreutz family of sungrazing comets in the 1890s. The earliest documented report of a sungrazer was from Greece by Aristotle and contemporary historian Ephorus in 371 BC. Prior to 1979, only nine confirmed sungrazers were known of… the launch of the joint NASA European Space Agency’s SOHO mission in 1995 changed the game considerably. Now, SOHO’s sungrazer tally after over a quarter of a century in space is 5,065 comets and counting. It turns out, we were still missing lots of what was passing through the inner solar system, all this time.

More in Store?

Last week, the NOAA revealed the successor for SOHO’s coronagraph aboard its GOES-19 satellite. The CCOR-1 (Compact Coronagraph) should start releasing public images in early 2025.

This comes as the ‘other’ October comet, C/2023 A3 Tsuchinshan-ATLAS fades from view. A3 T-ATLAS is now outbound at +6th magnitude in the constellation Ophiuchus. The comet had a decent evening apparition post perihelion a few weeks ago. The spiky ‘anti-tail’ provided an amazing view.

Are there any great comets on tap for 2025? Well, as of writing this, there’s only one comet with real potential to reach naked eye visibility in 2025: Comet C/2024 G3 ATLAS. This comet reaches perihelion 0.094 AU from the Sun on January 13th. G3 ATLAS and ‘may’ top -1st magnitude or brighter.

S1 ATLAS may have joined the ranks of comets that failed to live up to expectations… but you just never know. Its fast-paced story from discovery to demise shows us just how quickly the next bright comet could make itself known. Keep watching the skies: its only a matter of time.

The post Death of a Comet: S1 Didn’t Survive its Sungrazing Plummet appeared first on Universe Today.

Antibiotics can reduce diversity in the gut microbiome, raising the risk of infections that cause diarrhoea - and the effects may last years

Recent research shows that anti-inflammatory diets are not as faddish as they might sound, with the power to reduce the risk of heart attacks and some cancers

A specialised algorithm could help autonomous vehicles track hidden objects, such as a pedestrian, a bicycle or another vehicle concealed behind a parked car

I’ve always longed to go to Zion National Park in Utah, as it’s renowned for its beauty. My friend Phil Ward and I drove there for most of the day yesterday. First, a bit about its geology from Wikipedia:

The nine known exposed geologic formations in Zion National Park are part of a super-sequence of rock units called the Grand Staircase. Together, these formations represent about 150 million years of mostly Mesozoic-aged sedimentation in that part of North America. The formations exposed in the Zion area were deposited as sediment in very different environments:

• The warm, shallow (sometimes advancing or retreating) sea of the Kaibab and Moenkopi formations
• Streams, ponds, and lakes of the Chinle, Moenave, and Kayenta formations
• The vast desert of the Navajo and Temple Cap formations
• The dry near-shore environment of the Carmel Formation

Uplift affected the entire region, known as the Colorado Plateaus, by slowly raising these formations more than 10,000 feet (3,000 m) higher than where they were deposited.[54] This steepened the stream gradient of the ancestral Virgin and other rivers on the plateau.

Click the photos to enlarge them. You will find that there are more pictures of chipmunks and people feeding them than there are of the landscapes. Shoot me–I love chipmunks (and all animals).

First, I affirm my credentials as a Zionist. I’m wearing a hat that someone gave me, and it reads, à la the Larry David show, “Curb Your Antisemitism”:

The landscape is stunning, so let’s just look at some photos.

Sandstone cliffs, red but topped with some white sediments:

Even though it’s dry here, plants and even trees manage to eke out a living on the bare rock:

Some of the cliffs are topped with plateaus:

A panoramic view. Definitely click once or several times to enlarge:

There are all kinds of wave patterns in the sedimentary layers:

We had a mild hike up Canyon Overlook Trail (1 mile long) to get to this stunning viewpoint looking down into Zion Canyon.

Below, my friend Phil Ward at the overlook. He’s a Professor of Entomology at the University of California at Davis, and I’ve known him since he arrived there in the early 1980s.  His speciality is ants, and although one is not allowed to collect in National Parks without a permit (I used to get one to collect flies in Death Valley), he never leaves home without his ant-collecting kit, which includes ant bait, and that includes cookie crumbs.  It turns out that although we couldn’t collect ants, we used the bait to collect chipmunks (see below).

There were at least four species of flowers along the trail. This one is a California fuchsia (Epilobium canum):

Life is ubiquitous and tenacious, even in environments as dry and hostile as Zion.  Where water seeps through the rocks, plants and mosses about, and I think this is maidenhair fern (Adiantun pedatum aleuticum).

A great treat awaited us at the overlook. Because many tourists linger there for the view, the local chipmunks have learned to hang out there to beg for noms. They are lovely, tame, as fast as quicksilver, and will even dive into your backpack if you leave it open.  Phil gave me some ant bait (crumbled cookies), and, sure enough, the chipmunks went all over me to get them. (This reminds me of the Botany Pond Squirrels climbing up m leg for nuts.)

There are three species of chipmunk in Zion; I believe this one is the Uinta chipmunk (Neotamias umbrinus). It’s related to the East’s common Eastern chipmunk  (Tamias striatus), and used to be considered the same species, but now it’s been placed in a different genus.

The visitors were entranced by these rodents (they are as light as a feather, and when they climb upon you, it’s barely detectable). And so people pulled out their hiking food and gave some to the ‘munks. Sometimes three or four chipmunks would climb on a person at once. This woman is obviously delighted.

I love people being happy when interacting with animals.

A close-up of a nomming chipmunk:

This woman was part of a group of visiting British tourists. Since chipmunks are exclusively North American, it’s likely that this is her first close encounter with one. Like everyone, she was delighted when they took food. (And yes, I know you’re not supposed to feed the wildlife, but seriously, how can you resist?)

A two-fisted feed:

Look how happy she is! (And, I’m sure, so were the chipmunks.)

A closeup.  Phil and I discussed the evolutionary significance of the striping pattern; Phil thought it may be camouflage, but it seemed to me to not yield a very cryptic pattern. Perhaps, I thought, it was for members of the species to recognize each other, but I’ve always been wary of “species recognition” traits because it’s hard to see how they’d evolve (the trait and recognition of the trait must evolve simultaniously). In the end, we decided, “Well, we’re evolutionary biologists, and we could make up a hundred explanations, but how would we test them?”

Look at these little beauties, with their racing stripes, fluffy tails, and huge black eyes!

And a top view. As I said, they are so light—Uitna chipmunks weigh about 67 g, or 2.4 ounces—that you can barely feel them when they climb on you. And, like squirrels, when they take a tidbit from your hand you can feel their tiny claws.

Today, we go to Bryce Canyon National Park, famous for its geological “hoodoes“, tall and thin pillars of rock very different from what you see in Zion. Here’s a picture from Wikipedia:

Attribution: I, Luca Galuzzi; Creative Commons Attribution-Share Alike 2.5 Generic license.

Peaks in appetite and metabolism driven by our body's inbuilt clocks mean that eating at the wrong time can have consequences for our health and waistline