S-Branes Can Make Ekpyrotic Theory At least Somewhat Respectable (Quantum / Astronomy)

Guys, we know that we live in an expanding universe, in which galaxies and stars are flying away from us at an ever-increasing speed. Scientists can tell that by using different types of techniques to calculate how fast galaxies at different distances from us are moving away. We also have pictures of the baby universe, when it was just 380,000 years old.

Within that baby picture, we see interesting patterns — tiny splotches and blotches that reveal the existence of slight temperature and pressure differences in that young universe.

We are able to explain all these observations with what’s called ‘Big Bang cosmology’, plus an additional idea known as inflation, which is a process that we think happened when the universe was less than a second old. During that process, the universe became much, much larger, taking quantum differences and making them bigger in the process. Those differences eventually grew, as slightly denser patches had slightly stronger gravity, making them bigger. Over time, those differences became large enough to imprint themselves as splotches in the baby picture of the universe.

Big bang cosmology

Tired of the Big Bang Theory and want another version of cosmology? That’s fine, but we’ll have to explain things like the expansion of the universe and the splotches in the baby picture of cosmos. In other words, we have to do a better job at explaining the universe than inflation does.

This seems easy, but it isn’t. The pressure, density and temperature differences in the universe’s early years has bedeviled many alternative cosmologies, including one of the most popular let’s-go-bigger-than-the-big-bang ideas, known as Ekpyrotic universe. The word ekpyrotic comes from the Greek for word for “conflagration,” which refers to an ancient philosophical idea of a constantly repeating universe.

In the Ekpyrotic scenario, the universe … constantly repeats. Under that perspective, we are currently in a “bang” phase, which will eventually slow down, stop, reverse, and crunch back down to incredibly high temperatures and pressures. Then, the universe will somehow bounce back and re-ignite in a new big bang phase.

The trouble is, it’s hard to replicate the blotches and splotches in the baby picture of the universe in an Ekpyrotic universe. When we attempt to put together some vague physics to explain the crunch-bounce-bang cycle (and I do emphasize “vague” here, because these processes involve energies and scales that we aren’t even coming close to understanding with known physics), everything just comes out too … smooth. No bumps. No wiggles. No splotches. No differences in temperature, pressure or density.

And that doesn’t just mean the theories don’t match observations of the early universe. It means that these cosmologies don’t lead to a universe filled with galaxies, stars or even people.

So that’s kind of a bummer.

But, in the latest study, researchers tried attempt to overcome this hurdle and make Ekpyrotic cosmologies at least somewhat respectable, they invoke none other than the S-brane.

Right. S-branes. So you’ve heard of string theory, right? That’s the universe of fundamental physics where every particle is really a tiny, vibrating string. But a few years ago, theorists realized that the strings don’t have to be one-dimensional. And the name they give to a multidimensional string? A brane.

As for the “S” part? Well most branes in string theory can roam around freely through both space and time, but the hypothetical S-brane can exist only in one instant in time, under very special conditions.

In this new Ekpyrotic scenario, when the universe was at its smallest and densest configuration possible, an S-brane appeared, triggering the re-expansion of a cosmos filled with matter and radiation.. Yeah, a Big Bang and with small variations in temperature and pressure, it had given rise to the well-known splotches in the baby pictures of the universe. That’s what three physicists proposed in their new paper.

Is this idea correct? Who knows. String theory is on thin theoretical ice recently, as experiments like those at the Large Hadron Collider have failed to find any hints of a theory known as supersymmetry, which is a critical underpinning of String theory. And the concept of S-branes is itself a controversial idea within the String Theory community, as it’s not exactly known if branes would be allowed to exist only in one moment in time.

There’s also the fact that not only is the universe as we know it expanding, but it’s accelerating in its expansion, with no sign whatsoever of it slowing down (let alone collapsing) anytime soon. Figuring out what could make it hit the brakes and reverse course, then, is tricky.

Still, Ekpyrotic (and other) ideas are worth exploring, because the earliest moments of the universe provide some of the most puzzling and challenging questions to modern physics.


Nebra Sky Disk Could Be Younger than First Thought (Archeology)

Recent research done by German scientists says that, the Nebra sky disk, one of the oldest concrete depictions of cosmic phenomena, was created in the first millennium BCE, roughly 1,000 years later than previously assumed.

Fig: The Nebra sky disk. Image credit: Dbachmann / CC BY-SA 3.0.

The Nebra sky disk is a bronze disk of around 32 cm (12.6 inches) diameter and a mass of 2.2 kg, having a blue-green patina and inlaid with gold symbols.

The metal artifact was found in 1999 by illegal treasure hunters near Nebra, a small town in Saxony-Anhalt, Germany.

The Nebra disk was apparently developed in several stages. Its earliest version had 32 small round gold circles attached, a large circular gold plate, and a large crescent-shaped gold plate.

The circular plate may be interpreted as either the Sun or the full Moon, the crescent shape as the crescent Moon, or either the Sun or the Moon undergoing eclipse, and the dots as stars, with the cluster of seven dots likely representing the Pleiades.

Later, two arcs — constructed from gold of a different origin — were added at opposite edges of the disk. Given that the arcs seem to relate to solar phenomena, it is likely the circular gold plate represents the Sun, not the Moon.

Finally, another arc was added at the bottom. This arc is called the Sun boat and is also made of gold, but from a different origin. When the disk was buried it had 39-40 holes, each about 3 mm in diameter, perforated around its perimeter.

The Nebra disk is considered authentic and was initially dated to 1600 BCE based on associated finds: two bronze swords, a chisel, axe heads, and bracelets.

In the new research, they extensively analyzed all circumstances of the Nebra sky disk’s discovery and the results of previous studies.

Scientists said to science news that, “The site that was considered the discovery site until today and which was investigated in subsequent excavations is with high probability not the discovery site of the looters,” .

“Furthermore, there is no convincing evidence that the Bronze Age swords, axes and bracelets form an ensemble of common origins.”

“For this reason, it must be assumed that this is not a typical Bronze Age deposit and that the disk was not found together with the other objects in an original state at the excavation site.”

“This means that the disk must be regarded as an individual object in itself with regard to dating,” they said.

“Culturally and stylistically, the sky disk cannot be fitted into the Early Bronze Age motif world of the beginning of the second millennium BCE.”

“On the contrary, clearer references can be made to the motif world of the Iron Age of the first millennium BCE.”


References: Rupert Gebhard & Rüdiger Krause. Critical comments on the find complex of the so-called Nebra Sky Disk. Archäologische Informationen, published online September 3, 2020

Gaint Hogweed Is The Skin-Burning, DNA Attacking Plant Of Your Nightmares (Botany)

There’s something out there — something dangerous. It’s an invader, and it’s spreading faster than we humans can contain it. All it needs to do is touch you, and your skin will start to blister and peel. Even worse, it will attack the very building blocks of your DNA. But this isn’t John Carpenter’s “The Thing.” It’s just another deadly plant: the giant hogweed. Watch out!

Giant hogweed isn’t new in the United States, but it’s spreading. It has been here since 1917 when New Yorkers brought it over to the Big Apple to decorate their gardens. Sure, why not? What could go wrong? It’s not as if a pretty white flower can grow into a massive, flesh-mutating monstrosity, right? Right?

You already know where this is going, but let’s just run down the facts. Giant hogweed really puts the emphasis on “giant.” It looks a bit like Queen Anne’s Lace, but where that harmless plant is only 4 feet (1.2 meters) tall or so, giant hogweed can grow as high as 20 feet (6.1 meters). Of course, it’s not the size that makes the hogweed dangerous. It’s the sap. Brushing up against the plant can expose you to chemicals known as furocoumarins — they’re phototoxins, meaning they can be dangerous when exposed to light. If that happens, electrons from the toxins bind to the DNA bases thymine and cytosine, preventing them from enabling basic cellular function. Within 15 minutes, your skin can start to blister and peel as if from the worst sunburn of your life.

In Virginia, where giant hogweed plants were discovered for the first time this year, a teenage landscaper was recently severely injured after he cut down a plant not knowing what it was. His recovery may take quite some time. As Alex Childress told People, “I can’t go out into the sun for anywhere from two to six months. My face could be sensitive to light for a year up to two years.” Of course, his was a quite severe case — if all you’ve done is brush against a plant, just wash the affected area with soap and cold water, and try to avoid the sun for two days.

The United States isn’t the only place where giant hogweed has been spreading like, well, a weed. The plant originated in the Caucuses, but spread across continental Europe, the British Isles, across the ocean to the States, and across another ocean to Australia and New Zealand (generally by gardeners without a lot of foresight). But once it’s established itself in a place, it spreads with impunity. Its giant size makes it take up a lot of resources that could have been used by its gentler competitors, and every giant hogweed produces more than 100,000 seeds per year. But that all begs the question: Why is there such a panic over giant hogweed right now?

It’s not the first time the plant has stepped into the spotlight as a threat to public health. Writing for The Guardian, Jane Perrone notes that a similar panic occurred in 1970, even though the plant had been a fixture of the English countryside since the 19th century. So where were all the reports of blistered unfortunates from the decades previous? Experts have a few ideas.

It could be that 1970 and 2015 (the year the article was written) were both “vintage years” for giant hogweed in the UK, meaning it was particularly widespread so more people could encounter it not knowing the risks. That seems to match up with what’s going on in the USA right now since the plant certainly seems to be booming this year as it expands its territory. There’s also the simple fact that modern people may have less botanical knowledge in general. Maybe the kids of those 1917 gardeners knew the risks that giant hogweed posed ahead of time and simply didn’t take their chances. In any case, one thing is clear: If you encounter a towering white flower on your next nature hike, steer clear.


Your Nightmares Might Be Helping You Survive (Biology)

How many times have you woken up in a panic, thinking you slept through an exam or an important meeting, only to check your phone and realize you were just dreaming? It turns out that nightmares like this are just the brain’s way of helping you avoid oversleeping. Dreams about stressful scenarios like sleeping through class, fighting with your significant other, or even being chased by a mysterious figure might have evolved to help us to work through our anxieties in a risk-free environment, better preparing us to face our fears in real life.

Our ancestors had nightmares of their own, though their dreams likely featured lions and tigers rather than textbooks and alarm clocks. After noticing that most dreams tend to have more negative emotions than positive emotions, Finnish neuroscientist Antti Revonsuo developed a hypothesis to understand why nightmares evolved. He called it the threat simulation theory.

Revonsuo’s threat simulation theory says that dreams often take us through stressful or scary events as a way to prepare for the real thing. By rehearsing threat perception and avoidance in our sleep, we have a better chance of successfully reacting to threats in our waking lives, whether that means running from a hungry animal or making it to 9 a.m. biology.

The threat simulation theory also helps explain why even modern urbanites have the occasional nightmare about being chased through the woods. Over time, humans have learned to fear dangerous animals (and hostile humans), extreme weather events, and social ostracization, all of which pose threats to their survival. Our fear systems have evolved to be especially sensitive to such threats, so these deep-rooted fears are likely to show up in our dreams.

Your waking life also has an effect on what kinds of threats you face in your dreams. Dreaming of failing an exam is a distinctly modern fear that couldn’t have appeared in our ancestors’ nightmares, for instance. In a 2005 study, Revonsuo and fellow neuroscientist Katja Valli took this one step further to see if real threatening events someone experiences while they’re awake would affect how frequent and severe their dream threats were.

When they analyzed the dream reports of traumatized and non-traumatized children, they found that real-life trauma does, in fact, impact dream threats. Compared to a group of Finnish children who had been raised in a relatively safe environment, Kurdish children from Northern Iraq who faced regular military violence studied reported a greater number of threats in their dreams. Not only were threats they encountered in dreams more severe, but they also recalled more dreams in general. One explanation for this could be that trauma led to increased activation of the children’s threat simulation system, which would work as a form of protection against the increased threats in their waking environment.

Animal studies support the idea that dreaming improves survival instincts. A study of REM-deprived rats from 2004 demonstrated that animals who went without dream sleep struggled with survival-related tasks like finding their way through a maze and avoiding dangerous areas in their environment.

But that’s in rats. What about in humans? Well, a 2014 study of medical students led by neurologist Isabelle Arnulf looked at a more relatable scenario: the all-too-familiar test anxiety dream. Sixty percent of the students surveyed said they dreamed of the medical school entrance exam the night before the test. Most of these dreams qualified as nightmares, riddled with fear of failing the test, being late, or forgetting answers. No surprise there. But get this: Students who dreamed of the exam actually performed better on test day. It turns out dreams probably do improve our ability to face threats, whether they’re saber-toothed or multiple choice.


Your Stress Can Spread To Your Dog (Neuroscience)

Most dog owners find their pets to be great stress busters. Curling up on the couch with your pug or playing catch with your Labradoodle is a great way to unwind and let the cares of the day slip away. But new science has some bad news for dog owners. Dogs might ease your stress, but they can also catch it.

It’s an old joke that dogs resemble their owners, but according to this new study out of Linkoping University in Sweden, it’s actually true in one less funny way: Stressed out owners have stressed out dogs.

To figure this out, the researchers took hair samples from 25 border collies and 33 Shetland sheepdogs, as well as their female owners. For both humans and dogs, hair records the level of the stress hormone cortisol in the body over time. So by analyzing these hairs, the team could figure out just how much stress both the owners and their pets were under long-term.

The study found the stress levels of the dogs and their owners matched up: Higher levels of stress among owners showed up as higher levels of stress in their dogs. The effect was even more pronounced if the dog was female or if it took part in agility competitions with its owner.

Previous research has found that cortisol in humans and their dogs can rise together in the short-term, especially when competing. But this finding was something new. “This is the first time we’ve seen a long-term synchronization in stress levels between members of two different species. We haven’t seen this between humans and dogs before,” lead researcher Lina Roth told the Guardian.

And what about a pooch’s lifestyle? Did limited opportunities for play or more time spent alone stress out the dogs? Not nearly as much as belonging to a human with high cortisol levels. The personality of the owner seemed to play a role too, although that varied with the sex of the dog. Female dogs whose owners had higher scores in the Big Five traits of neuroticism, openness, and conscientiousness had higher cortisol levels, while the same was true of male dogs whose owners scored high in agreeableness.

This will not come as a huge surprise to many observant folks who have noticed that highly strung people often have highly strung dogs. But should scientific confirmation of this connection between owners and their dogs put you off having a pet if you’re anxiety-prone? Or if you’re under a lot of stress and already a pet owner, should you feel guilty?

Nope, replies Roth. “I don’t think you should be anxious that, if you’re stressed, you might harm your dog,” she told NPR. “Instead, your dog is a social support for you, and you are a social support for the dog.” Your stressed-out state can be more than made up for by extra pats, belly rubs, and tennis ball throws.

Though if you do lean towards the anxious side, you might want to think carefully about choosing a more laid back and resilient type of dog. Just which breeds are best is still an open question, one Roth and her collaborators hope to look into next.

It may “be possible to match dog and owner in a way that is better for both, from a stress-management point of view,” she says. “It may be that certain breeds are not so deeply affected if their owner has a high stress level.”


Lying Makes It Harder To Read The Emotions Of Others (Psychology)

Dishonesty diminishes a person’s ability to read others’ emotions, or “interpersonal cognition,” according to new research.

And here’s one of the other key findings: The consequences snowball. One dishonest act can set in motion even more dishonesty.

“It can be a vicious cycle,” says Ashley E. Hardin, assistant professor of organizational behavior at the Olin Business School at Washington University in St. Louis. “Sometimes people will tell a white lie and think it’s not a big deal. But a decision to be dishonest in one moment will have implications for how you interact with people subsequently.”

It’s no surprise that liars and cheaters can hurt the workplace, as well.

“Given the rise of group work in organizations, there’s a heightened awareness of the importance of understanding others’ emotions,” Hardin says. Also, a person’s ability to read emotions is crucial in negotiations and in building relationships.

Dishonesty has repercussions beyond harming trust and one’s reputation if others become aware of it, according to the study.

Scientists estimate that this behavior comes at a $3.7 trillion cost annually worldwide. Lying and cheating is “not only is financially costly (as in the case of stealing from a company, for example, or increasing the risk of costly lawsuits) but also can harm interpersonal relationships through a particular channel: individuals’ ability to detect others’ emotions,” even when those others are not the victims of the wrongdoing.

In all, the researchers conducted eight studies involving more than 1,500 adults to gauge lying and cheating in various scenarios. The findings support the following:

• A connection exists between dishonest behavior and our ability to accurately read and empathize with others’ emotions.
• Bad actors are less likely than others to define themselves in terms of close relationships, for example as a sister or a mentor.
• Dishonest behavior leads to damage downstream; the first transgression is a catalyst to dehumanize others and perform even more dishonest acts.
• People who are more socially attuned are less likely to behave dishonestly.

“When individuals are lacking their physiological capacity for social sensitivity, they may be more susceptible to the social distancing effects of engaging in dishonest behavior,” the researchers write.

The findings fundamentally challenge views that lump morality and empathy into a single construct, Hardin says. Social psychology research has long argued that empathy is a moral sentiment that triggers prosocial behavior. But empathy toward others can also lead employees to cross ethical boundaries.

A 2010 study, for example, highlighted the importance of social context in ethical decision-making. Researchers found that employees doing emissions checks helped customers with standard vehicles, as opposed to luxury cars, by illegally passing the cars. The results suggest that empathy toward others with a similar economic status can motivate dishonest behavior.

“Our work adds to this dynamic tension between dishonesty and empathy by showing… that one’s empathic accuracy can be affected by the specific psychological state produced by one’s dishonest behavior,” the researchers write.

The study appears in the Journal of Experimental Psychology: General. Additional researchers from the University of Michigan; the University of Virginia; and Harvard University contributed to the work.


Want To Remember More Of Your Dreams? I Know How (Neuroscience)

Whether they involve flying through the clouds with Danny DeVito, battling witches on broomsticks with Optimus Prime, or having a tearful heart to heart with a departed loved one, it’s always fun to remember your dreams. Why is it that some people seem to always remember their dreams and others don’t? And is there a way to get a better memory for your nighttime reveries?

Dreams are still mysterious to scientists and dreamers alike, but research reveals that there could be some fundamental differences between those who remember their dreams and those who don’t.

First of all, there’s gender. Researchers aren’t sure why, but Harvard psychology professor and author of “The Committee of Sleep” Dr. Deirdre Leigh Barrett told Mental Floss in 2018 that women tend to recall their dreams more often than men. This could be due to gendered differences when it comes to interest in dreams, or it could be due to hormonal or biological differences. Age is also a factor: Just like with déjà vu, dream recall tends to peak in your twenties and then drop off as you get older.

And then there’s personality. “More psychologically minded people tend to have higher dream recall, and people who are more practical and externally focused tend to have lower recall,” Dr. Barrett says. But some factors in dream recall might be less determined by who you are, and more influenced by how you sleep.

According to an article in “On the Brain” from Harvard Medical School, those who fall asleep and wake up slowly are more likely to remember their dreams. When you fall asleep gradually, you enter hypnagogia, a period of “dreamlike visual, auditory, and physical hallucinations that occur just at the onset of sleep.” A more regular dreaming period occurs when a sleeper enters REM sleep, a dream-ready phase that comes with physiological changes in heart rate, blood pressure, and breathing. Near the end of REM, the body prepares to wake up or cycle through the sleep stages again. Those who wake up toward the end of a REM phase are more likely to remember their dreams.

For a study published in Frontiers in Psychology in 2013, researchers gave 36 people a questionnaire about dream recall, then analyzed their brain activity while they were awake and asleep. During the analysis, the participants listened to various musical tones and occasionally heard their own names. The results showed that “high recallers” (people who remember their dreams almost every day) and “low recallers” (people who remember only one to two dreams per month) might be different even when they’re awake.

When asleep, both high and low recallers showed similar changes in brain activity in response to hearing their names. When awake, however, high recallers showed a greater decrease in alpha wave response to their names. Scientists think this decrease in alpha waves mean high recallers’ brains become more active when they hear their names while awake, suggesting their brains might be more reactive to sounds and other stimuli overall.

If you want to remember your dreams and never have before, hope is not lost. Scientists think some simple tricks might help you become a high recaller.

In 2017, Harvard Medical School professor and sleep expert Robert Stickgold made some pretty bold claims about dreaming to the New York Times. By following his regimen for dream memory, Stickgold said, “I would predict that 80 percent of people who initially said they never dream would say they do now.” Here are the three main things he recommended:

1. Drink three full glasses of water — but not beer or wine since they suppress REM — and then go to sleep. You’ll wake up more frequently, and as we know, that could help you remember your dreams.
2. Put dreaming on your to-do list. Repeat the phrase “I’m going to remember my dreams” three times before zonking out. Your brain likes to work on important things before sleep, and this habit reinforces dreaming as a priority. Make sure you have a pen and paper next to your bed in case you need to remember what you just dreamed.
3. Wake up slowly! The worst thing you can do is wake up, turn to your partner, and say, “I just had the coolest dream.” Do that, and you might forget it forever. Instead, stay half-asleep and replay your dreams as best you can. Replaying will help you store the memory differently so you’ll remember it for a long time.

If mantras and frequent wake-ups aren’t your thing, science also shows you can make small changes to improve your dream recall. First of all, the most important part of dreaming is being asleep. The longer you sleep, the more REM time you have, and the more opportunities you have to dream and remember. Don’t forget that REM periods get longer through the night, so if you sleep for four hours instead of eight, you’re missing out on 80 percent of your dream time. Try waking up as late as possible and skipping an episode or two on Netflix before bed.

Dr. Barrett says becoming a high recaller can even be as simple as thinking about it. Read a book on dreams — or, hey! Just read this article. Looks like you’re good to go!


This One Question Can Help Make An Insure Partner Feel Loved (Psychology)

Loving an insecure person can be frustrating. You always feel like you have to offer praise or reassurance. Not only can that be exhausting, but in trying to do what you think is helpful, you might actually be making matters worse.

When people with insecurities hear something good about themselves, they tend to doubt or even dismiss it, as much research shows. This means, quite perplexingly, that hearing positive feedback can often raise their anxieties, because it may clash with the more pessimistic views they hold of themselves.

Insecure people may wonder whether their partner truly knows them, or worry that they cannot live up to the partner’s expectations. At times, praise can even lead their minds to argue back; it can trigger unfavorable thoughts about themselves that contradict the praise.

What can loving partners do instead? Try conveying genuine curiosity, rather than compliments. Asking a simple question — “How was your day?” — can show concern without triggering a negative self-assessment.

At the University of Waterloo, Cortes & Wood recently conducted a series of studies showing that asking this simple question can make insecure people feel cared for. They ran two survey studies involving 359 adults (aged 18 to 66) across the United States who were in romantic relationships.

To determine their research participants’ level of security and trust in their partner’s love, they gave them a questionnaire assessing how confident they were that their partner loves them, is committed to them, and will be responsive to them in times of need. Another questionnaire tapped into their relationship satisfaction.

In two studies, they found that the satisfaction reported by those who usually felt more insecure in their relationships actually increased when their partners asked them about their day.

For people higher in security, who were already high in relationship satisfaction, being asked “How was your day?” was rarely the boost that it was for people lower in security.

Why is asking “How was your day?” effective? They anticipated that this expression of interest, if it is genuine, signals caring.

To test the idea, they conducted another study. Participants read a scenario in which a couple, Mike and Sarah, had a pleasant, brief conversation after Sarah arrived home from work. Participants in one group read that during that conversation, Mike asked Sarah about her day. Participants in a second group were not given this detail.

Those who read that Mike asked Sarah about her day predicted that Sarah felt more cared for than participants who were not given this detail. The benefit did not derive from Sarah describing her day; when participants read a scenario about Sarah describing her day, even though Mike had not asked, participants thought Sarah would not feel as cared for as when Mike asked her directly.

They suspect that this care signal works especially well for people low in security because it is subtle and nonthreatening. It does not make them question why a partner is asking or whether they deserve it. Thus, asking about a partner’s day may fly under the insecure person’s radar.

There is nothing special about the four words, “How was your day?” Rather, showing genuine interest is special.

In a final study, they brought 162 romantic couples (undergraduates or from the community, between 17 and 47 years of age) into the laboratory and separated them, ostensibly to work on different tasks.

They led participants to believe that their partner had written a note to them. In one group, the partners simply described their own experiences, whereas in the other group, partners described their own experiences, but also asked, “How did your task go? Did you enjoy it?”

Partners lower in security who received the note that asked about their experiences felt more cared for by their partners than those who were not asked. In contrast, for people higher in security, being asked did not matter. They suspected that people high in security don’t need the signal of interest to feel valued.

They’re not suggesting us to stop praising our insecure partner altogether. The complete absence of praise could be harmful, especially if your partner asks for praise or reassurance. But praise may not accomplish what we want it to. Don’t count on reassurance to convince our partner that we care.

Instead, show interest in him or her by asking, “How was your day?” Showing attention and interest in someone, especially in a society as filled with distractions as ours, can be the most important signal of caring there is.


Researchers Determined Geologic Age Of Finsen Crater, Present On The Far Side Of Moon (Planetary Science)

Sheng Gou and colleagues using crater counting method, determined the absolute model age (AMA), or geologic age of Finsen crater on the moon’s far side and found that it is about 3.5 billion years.

Finsen Crater

Based on this model age, the regolith growth rate at the Chang’e-4 landing site and the crater degradation rate within Finsen crater have also been estimated.

China’s Chang’e-4 probe, including a lander and a rover, successfully touched down the floor of Von Kármán crater within the South Pole-Aitken (SPA) basin on the far side of the moon on January 3, 2019. Since then, Chang’e-4 rover has been traversing on the floor of Von Kármán crater and has carried out a string of in situ measurements with equipped scientific payloads.

Although multiple studies have revealed that Finsen crater ejecta is the primary source of materials measured inside of Von Kármán crater, where Chang’e-4 rover landed, the formation age of Finsen crater, which has significant geologic implications, is still debated within the planetary community.

The team used Chang’e-2 digital orthophoto map (DOM) and digital elevation model (DEM) data in their research. They outlined a flat and homogenous area on the floor of Finsen as crater count area, and manually mapped craters in the outlined area.

Finally, the AMA of Finsen crater was determined by fitting the obtained crater size-frequency distribution (CSFD) to standard lunar cratering chronology. Both cumulative and differential fits revealed an AMA of ~3.5 Ga, indicating Finsen crater was Imbrium-aged.

Context map of Chang’e-4 landing site. Credit: AIR

Radar images indicated that the thickness of the Finsen crater ejecta-sourced fine-grained regolith at Chang’e-4 landing site was about 12 m. The team thus estimated the average regolith growth rate at the Chang’e-4 landing site was about 3.4 m/Gyr.

Compared with Apollo landing sites of similar age, the regolith growth rate at Chang’e-4 landing site was greater, except for Apollo 16, suggesting a low weathering resistivity of Finsen crater ejecta to the harsh space environment.

There are many simple craters on the floor of Finsen crater, which are easily degraded by erosion of crater rim and infilling of crater interior through geologic processes. The team further calculated the current depth of 25 largest craters within the outlined area through a profile-average-depth method and the estimated crater degradation rate within Finsen was about 21 ± 3 m/Gyr.

This degradation rate has the same order of magnitude to that on the lunar maria (about 32 m/Gyr), indicating lunar craters might have a similar degradation rate on a global scale.

However, the rate is much slower than that on other airless rocky bodies, for example, average degradation rate on Vesta is 350 m/Gyr, and on Gaspra is 100-1000 m/Gyr. One of the most likely reasons is that craters on asteroids are easily degraded or even erased by mass movements caused by impact-induced global seismic shaking.


References: Sheng Gou et al. Absolute model age of lunar Finsen crater and geologic implications, Icarus (2020), vol. 354. DOI: 10.1016/j.icarus.2020.114046 link: https://www.sciencedirect.com/science/article/pii/S0019103520304000?via%3Dihub