Depending on your perspective, that result might seem surprising or it might produce a knowing nod. Either way, the result is contrary to past scholarly hypotheses. Many experts have surmised that knowing more, and having easier communication with medical providers, leads patients to follow instructions more closely.

The new study is based on over a decade of population-wide data from Sweden and includes suggestive evidence about why doctors and their families may ignore medical advice. Overall, the research shows that the rest of the population adheres to general medication guidelines 54.4 percent of the time, while doctors and their families lag 3.8 percentage points behind that.

“There’s a lot of concern that people don’t understand guidelines, that they’re too complex to follow, that people don’t trust their doctors,” says Amy Finkelstein, a professor in MIT’s Department of Economics. “If that’s the case, you should see the most adherence when you look at patients who are physicians or their close relatives. We were struck to find that the opposite holds, that physicians and their close relatives are less likely to adhere to their own medication guidelines.”

The paper, “A Taste of Their Own Medicine: Guideline Adherence and Access to Expertise,” is published this month in the American Economic Review: Insights. The authors are Finkelstein, the John and Jennie S. MacDonald Professor of Economics at MIT; Petra Persson, an assistant professor of economics at Stanford University; Maria Polyakova PhD ’14, an assistant professor of health policy at the Stanford University School of Medicine; and Jesse M. Shapiro, the George Gund Professor of Economics and Business Administration at Harvard University.

Millions of data points

To conduct the study, the scholars examined Swedish administrative data from 2005 through 2016, as applied to 63 prescription drug guidelines. The data enabled the researchers to determine who is a doctor; the study largely defined close relatives as partners, parents, and children. All told, the research involved 5,887,471 people to whom at least one of the medication guidelines applied. Of these people, 149,399 were doctors or their close family members.

Using information on prescription drug purchases, hospital visits, and diagnoses, the researchers could see if people were adhering to medication guidelines by examining whether prescription drug decisions matched these patients’ medical circumstances. In the study, six guidelines pertained to antibiotics; 20 involved medication use by the elderly; 20 focused on medication attached to particular diagnoses; and 17 were about prescription drug use during pregnancy.

Some guidelines recommended use of a particular prescription drug, like a preference of narrow-spectrum antibiotics for an infection; other guidelines were about not taking certain medications, such as the recommendation that pregnant women avoid antidepressants.

Out of the 63 guidelines used in the study, doctors and their families followed the standards less often in 41 cases, with the difference being statistically significant 20 times. Doctors and their families followed the guidelines more often in 22 cases, with the difference being statistically significant only three times.

“What we found, which is quite surprising, is that they [physicians] are on average less adherent to guidelines,” says Polyakova, who received her PhD from MIT’s Department of Economics. “So, in this paper we are also trying to figure out what experts do differently.”

Ruling out other answers

Since doctors and their close relatives adhere to medical guidelines less often than the rest of the population, what exactly explains this phenomenon? While homing in on an answer, the research team examined and rejected several hypotheses.

First, the lower compliance by those with greater access to expertise is unrelated to socioeconomic status. In society overall, there is a link between income and adherence levels, but physicians and their families are an exception to this pattern. As the scholars write in the paper, special “access to doctors is associated with lower adherence despite, rather than because of, the high socioeconomic status” of those families.

Additionally, the researchers did not find any link between existing health status and adherence. They also studied whether a greater comfort with prescription medication — due to being a doctor or related to one — makes people more likely to take prescription drugs than guidelines recommend. This does not appear to be the case. The lower adherence rates for doctors and their relatives were similar in magnitude whether the guidelines pertained to taking medication or, alternately, not taking medication.

“There are a number of first-order alternative explanations that we could rule out,” Polyakova says.

Resolving a medical mystery

Instead, the researchers believe the answer is that doctors possess “superior information about guidelines” for prescription drugs — and then deploy that information for themselves. In the study, the difference in adherence to guidelines between experts and nonexperts is largest in the case of antibiotics: Doctors and their families are 5.2 percentage points less in compliance than everyone else.

Most guidelines in this area recommend starting patients off with “narrow-spectrum” antibiotics, which are more targeted, rather than “broader-spectrum” antibiotics. The latter might be more likely to eradicate an infection, but greater use of them also increases the chances that bacteria will develop resistance to these valuable medications, which can reduce efficacy for other patients. Thus for things like a respiratory tract infection, guidelines call for a more targeted antibiotic first.

The issue, however, is that what is good for the public in the long run — trying more targeted drugs first — may not work well for an individual patient. For this reason, doctors could be more likely to prescribe broader-spectrum antibiotics for themselves and their families.

“From a public-health perspective, what you want to do is kill it [the infection] off with the narrow-spectrum antibiotic,” Finkelstein observes. “But obviously any given patient would want to knock that infection out as quickly as possible.” Therefore, she adds, “You can imagine the reason doctors are less likely to follow the guidelines than other patients is because they … know there’s this wedge between what’s good for them as a patients and what’s good for society.”

Another suggestive piece of data comes from different types of prescription drugs that are typically avoided during pregnancies. For so-called C-Class drugs, where empirical evidence about the dangers of the drugs is slightly weaker, doctors and their families have an adherence rate 2.3 percentage points below other people (meaning, in this case, that they are more likely to take these medications during pregnancy). For so-called D-Class drugs with slightly stronger evidence of side effects, that dropoff is only 1.2 percentage points. Here too, doctors’ expert knowledge may be influencing their actions.

“The results imply that probably what’s going on is that experts have a more nuanced understanding of what is the right course of action for themselves, and how that might be different than what the guidelines suggest,” Polyakova says.

Still, the findings suggest some unresolved tensions in action. It could be, as Polyakova suggests, that guidelines about antibiotics should be more explicit about the public and private tradeoffs involved, providing more transparency for patients. “Maybe it’s better for the guidelines to be transparent and say they recommend this not because it is [always] the best course of action for you, but because it is the best for society,” she says.

Additional research could also aim to identify areas where lower expert adherence with guidelines may be associated with better health outcomes — to see how often doctors have a point, as it were. Or, as the researchers write in the paper, “An important avenue for further research is to identify whether and when nonadherence is in the patient’s best interest.”

The research was supported, in part, by the Population Studies and Training Center and the Eastman Professorship at Brown University, and the National Institute on Aging.

The published research in the December issue of the Monthly Notices of the Royal Astronomical Society offers a glimpse of what astronomers will find with Webb’s near-infrared camera. The instrument is designed to peer through clouds of interstellar dust that have previously blocked astronomers’ view of stellar nurseries, especially those that produce stars similar to Earth’s sun.

Reiter, an assistant professor of physics and astronomy, and co-authors from the California Institute of Technology, the University of Arizona, Queen Mary University in London and the United Kingdom’s Royal Observatory in Edinburgh, Scotland, analyzed a portion of Webb’s first images of the Cosmic Cliffs, a star-forming region in a cluster of stars known as NGC 3324.

“What Webb gives us is a snapshot in time to see just how much star formation is going on in what may be a more typical corner of the universe that we haven’t been able to see before,” said Reiter, who led the study.

Located in the southern constellation Carina, NGC 3324 hosts several well-known regions of star formation that astronomers have studied for decades. Many details from the region have been obscured by dust in images from the Hubble Space Telescope and other observatories. Webb’s infrared camera was built to see through dust in such regions and to detect jets of gas and dust that spew from the poles of very young stars.

Reiter and colleagues focused their attention on a portion of NGC 3324 where only a few young stars had previously been found. By analyzing a specific infrared wavelength, 4.7 microns, they discovered two dozen previously unknown outflows of molecular hydrogen from young stars. The outflows range in size, but many appear to come from protostars that will eventually become low-mass stars like Earth’s sun.

“The findings speak both to how good the telescope is and to how much there is going on in even quiet corners of the universe,” Reiter said.

Within their first 10,000 years, newborn stars gather material from the gas and dust around them. Most young stars eject a fraction of that material back into space via jets that stream out in opposite directions from their poles. Dust and gas pile up in front of the jets, which clear paths through nebular clouds like snowplows. One vital ingredient for baby stars, molecular hydrogen, gets swept up by these jets and is visible in Webb’s infrared images.

“Jets like these are signposts for the most exciting part of the star formation process,” said study co-author Nathan Smith of the University of Arizona. “We only see them during a brief window of time when the protostar is actively accreting.”

The accretion period of early star formation has been especially difficult for astronomers to study because it is fleeting — usually just a few thousand years in the earliest portion of a star’s multimillion-year childhood.

Study co-author Jon Morse of the California Institute of Technology said jets like those discovered in the study “are only visible when you embark on that deep dive — dissecting data from each of the different filters and analyzing each area alone.

“It’s like finding buried treasure,” Morse said.

Reiter said the size of the Webb telescope also played a role in the discovery.

“It’s just a huge light bucket,” Reiter said. “That lets us see smaller things that we might have missed with a smaller telescope. And it also gives us really good angular resolution. So we get a level of sharpness that allows us to see relatively small features, even in faraway regions.”

The Webb Space Telescope program is led by NASA in partnership with the European Space Agency (ESA) and the Canadian Space Agency (CSA). The telescope’s science and mission operations are led by the Space Telescope Science Institute (STScI) in Baltimore.

The research was supported by NASA (NAS 5-0312, NAS 5-26555), STScI and a Dorothy Hodgkin Fellowship from the UK’s Royal Society.

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Materials provided by Rice University. Original written by Jade Boyd. Note: Content may be edited for style and length.

The findings, published Dec. 16 in the peer-reviewed journal Pediatrics, suggests that the Advancement via Individual Determination (AVID) program, aimed at increasing educational opportunities for under-represented and economically disadvantaged students, also significantly reduces substance use.

“Academic tracking” is a common practice in high schools through which lower-performing students are clustered with others of similar academic achievement. Although intended to tailor academic rigor to students’ level of preparation, the study findings suggest that this practice may be counterproductive by reinforcing risky behaviors that students pick up from their peers.

“Untracking” these students by mixing them in with higher-performing peers may lead to better physical and psychological health, said lead author Dr. Rebecca Dudovitz, associate professor of pediatrics and director of pediatric health services research at the David Geffen School of Medicine at UCLA.

“This is the first randomized controlled trial of AVID in the United States, so it’s really exciting to see that this program that was designed to help open up educational opportunities for kids, also improved their health,” Dudovitz said.

AVID works with high school students earning B or C grade averages who might not otherwise be placed in more rigorous college preparatory tracks. It operates in 5,400 secondary schools, including both middle and high school, in 46 states and exposes academically middling students to tougher courses than they would have been assigned to under normal circumstances. AVID helps students develop agency, relational capacity, and opportunity knowledge.

“We believe that surrounding students with a supportive community and providing them with the skills and resources they need to reach their goals within existing educational structures is how we make college and career readiness possible for every student,” said Thuan Nguyen, AVID’s CEO. “The findings of the UCLA study are not surprising because AVID educators invest so much in their students’ lives.”

The researchers randomized 270 students in five large public schools who were placed in either an AVID group or in usual school programs. Students completed surveys at the end of 8^th grade or beginning of 9^th grade, and again at the end of 9^th grade.

They found that students in the AVID group had lower odds of using substances — a 33% reduced risk compared to the control group — in addition to a 26% lower risk of associating with substance-using peers and about 1.7 times the odds of socializing with peers who were more involved with academics.

In addition, AVID males experienced lower stress and higher self-efficacy, determination and engagement with school than their peers who were assigned to the usual tracked academic program. These effects, however, were not seen among females, possibly because supportive academic environment have a greater effect on boys of color, the researchers write.

“AVID positively impacts social networks, health behaviors, and psycho-social outcomes suggesting academic untracking may have substantial beneficial spillover effects on adolescent health,” the researchers write.

The study has some limitations. The schools were all from a single school district and primarily serve low-income Latino students, and the findings were all from one school year, the researchers note. They did not directly observe how AVID was implemented or examine if the program actually increased college enrollment. In addition, it was not possible to blind the participants, meaning that students knew who was assigned to each group, which could have led them to respond to survey questions in ways that they thought the researchers would view favorably.

While more research is needed, the findings still provide important evidence that “ensuring schools have the resources and structures necessary to expand access to educational opportunities and facilitate healthy social connections, particularly in marginalized communities, may be key to achieving education and health equity more broadly,” the researchers write.

The Robert Wood Johnson Foundation Evidence for Action Program (Grant 74086) and National Institutes of Health (1K23DA040733-01A1) funded this research.

Study co-authors are Dr. Paul Chung, Kulwant Dosanjh, Meredith Phillips, Christopher Biely, Chi-Hong Tseng, and Dr. Mitchell Wong of UCLA; Joan Tucker of RAND Corporation; Mary Ann Pentz of USC; and Arzie Galvez and Guadalupe Arellano of Los Angeles Unified School District. Chung is also affiliated with Kaiser Permanente.

“The amount and location of hemoglobin in the body provide critical information about blood perfusion or accumulation in specific locations. Our device shows great potential in close monitoring of high-risk groups, enabling timely interventions at urgent moments,” said Sheng Xu, a professor of nanoengineering at UC San Diego and corresponding author of the study.

The paper, “A photoacoustic patch for three-dimensional imaging of hemoglobin and core temperature,” is published in the December 15, 2022 issue of Nature Communications.

Low blood perfusion inside the body may cause severe organ dysfunctions and is associated with a range of ailments, including heart attacks and vascular diseases of the extremities. At the same time, abnormal blood accumulation in areas such as in the brain, abdomen or cysts can indicate cerebral or visceral hemorrhage or malignant tumors. Continuous monitoring can aid diagnosis of these conditions and help facilitate timely and potentially life-saving interventions.

The new sensor overcomes some significant limitations in existing methods of monitoring biomolecules. Magnetic resonance imaging (MRI) and X-ray-computed tomography rely on bulky equipment that can be hard to procure and usually only provide information on the immediate status of the molecule, which makes them unsuitable for long-term biomolecule monitoring.

“Continuous monitoring is critical for timely interventions to prevent life-threatening conditions from worsening quickly,” said Xiangjun Chen, a nanoengineering PhD student in the Xu group and study co-author. “Wearable devices based on electrochemistry for biomolecules detection, not limited to hemoglobin, are good candidates for long-term wearable monitoring applications. However, the existing technologies only achieve the ability of skin-surface detection.”

The new, flexible, low form-factor wearable patch comfortably attaches to the skin, allowing for noninvasive long-term monitoring. It can perform three-dimensional mapping of hemoglobin with a submillimeter spatial resolution in deep tissues, down to centimeters below the skin, versus other wearable electrochemical devices that only sense the biomolecules on the skin surface. It can achieve high contrast to other tissues. Due to its optical selectivity, it can expand the range of detectable molecules, integrating different laser diodes with different wavelengths, along with its potential clinical applications.

The patch is equipped with arrays of laser diodes and piezoelectric transducers in its soft silicone polymer matrix. Laser diodes emit pulsed lasers into the tissues. Biomolecules in the tissue absorb the optical energy, and radiate acoustic waves into surrounding media.

“Piezoelectric transducers receive the acoustic waves, which are processed in an electrical system to reconstruct the spatial mapping of the wave-emitting biomolecules,” said Xiaoxiang Gao, a postdoctoral researcher in Xu’s lab and co-author of the study.

“With its low-power laser pulses, it is also much safer than X-ray techniques that have ionizing radiation,” said Hongjie Hu, a postdoctoral researcher in the Xu group and study coauthor.

Based on its success so far, the team plans to further develop the device, including shrinking the backend controlling system to a portable-sized device for laser diode driving and data acquisition, greatly expanding its flexibility and potential clinical utility.

They also plan to explore the wearable’s potential for core temperature monitoring. “Because the photoacoustic signal amplitude is proportional to the temperature, we have demonstrated core temperature monitoring on ex-vivo experiments,” Xu said. “However, validating the core temperature monitoring on the human body requires interventional calibration.”

They are continuing to work with physicians to pursue more potential clinical applications.

The work was supported in part by Air Force Research Laboratory under agreement number FA8650-18-2-5402, and the National Institutes of Health grants 1R21EB025521-01 (S.X.), 1R21EB027303-01A1 (S.X.), and 3R21EB027303-02S1 (S.X.).

Their work has numerous potential impacts, especially in the context of understanding and responding to autoimmune disorders and inflammation.

While our immune system serves a very important function protecting us from infection and injury, when immune responses become too aggressive this can lead to damaging inflammation, which occurs in conditions such as rheumatoid arthritis and psoriasis. Inflammation is triggered when our bodies produce “alarm proteins” (interleukins), which ramp up our defenses against infection and injury by switching on different components of our immune system.

Understanding how and when such alarm proteins are produced and how they activate our immune system has led to major breakthroughs in the treatment of many immune conditions.

Now, scientists from the Smurfit Institute of Genetics at Trinity College Dublin, led by Seamus Martin, Smurfit Professor of Genetics, have found that Interleukin-37 has an unexpected function as an immune-activating molecule, as previous studies suggested that this interleukin instead served as an “off switch” for the immune system.

Professor Martin said:

“Interleukins play key roles in regulating our immune systems in response to bacterial and fungal infections. However, Interleukin-37 has long remained an enigma, as it isn’t found in mammals such as mice. This has presented a major obstacle to figuring out what it does as much of what we know about the human immune system has first been discovered in model organisms whose biological make-ups are similar to ours.”

Prior to the new study, Interleukin-37 was thought to have immune-suppressive functions but how exactly it switched off inflammation was hotly debated. However, the Trinity scientists now report that, when activated in the correct way, Interleukin-37 displays potent pro-inflammatory activity.

Professor Martin added:

“This pro-inflammatory impact was highly unexpected. Our work shows that the protein binds to an interleukin receptor in the skin that is known to play a key role in driving psoriasis. And, to add further intrigue to the story, this brings the total number of immune alarm molecules that signal via this particular interleukin receptor to four.

“Why there are so many interleukins that bind to the same receptor is a mystery, but if we were to speculate it may be because this receptor serves a very important sentinel function in our skin, and that one alarm protein may simply not be enough to respond to the many different infectious agents that our skin encounters. Our skin is the major barrier between our bodies and the outside world that microbes must breach if they are to gain entry to our bodies and, in many respects, represents the first line of defense in our immune systems.”

As such, Interleukin-37 and other immune alarm proteins may have evolved to become distinct variations on the same theme that enable our bodies to detect different types of infection by becoming activated by enzymes that are distinct to each infectious agent.

The research has just been published in the journal, Science Immunology, and was a collaboration between several Trinity research groups led by Professor Martin’s team, which included post-doctoral scientists Dr Graeme Sullivan and Dr Pavel Davidovich, along with research groups led by Professor Ed Lavelle (School of Biochemistry and Immunology) and Professor Pat Walsh (School of Clinical Medicine).

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The discovery makes it possible to ‘derive’ any Sanskrit word — to construct millions of grammatically correct words including ‘mantra’ and ‘guru’ — using Pāṇini’s revered ‘language machine’ which is widely considered to be one of the great intellectual achievements in history.

Leading Sanskrit experts have described Rajpopat’s discovery as ‘revolutionary’ and it could now mean that Pāṇini’s grammar can be taught to computers for the first time.

While researching his PhD, published today, Dr Rajpopat decoded a 2,500 year old algorithm which makes it possible, for the first time, to accurately use Pāṇini’s ‘language machine’.

Pāṇini’s system — 4,000 rules detailed in his greatest work, the Aṣṭādhyāyī, which is thought to have been written around 500BC — is meant to work like a machine. Feed in the base and suffix of a word and it should turn them into grammatically correct words and sentences through a step-by-step process.

Until now, however, there has been a big problem. Often, two or more of Pāṇini’s rules are simultaneously applicable at the same step leaving scholars to agonise over which one to choose.

Solving so-called ‘rule conflicts’, which affect millions of Sanskrit words including certain forms of ‘mantra’ and ‘guru’, requires an algorithm. Pāṇini taught a metarule* to help us decide which rule should be applied in the event of ‘rule conflict’ but for the last 2,500 years, scholars have misinterpreted this metarule meaning that they often ended up with a grammatically incorrect result.

In an attempt to fix this issue, many scholars laboriously developed hundreds of other metarules but Dr Rajpopat shows that these are not just incapable of solving the problem at hand — they all produced too many exceptions — but also completely unnecessary. Rajpopat shows that Pāṇini’s ‘language machine’ is ‘self-sufficient’.

Rajpopat said: “Pāṇini had an extraordinary mind and he built a machine unrivalled in human history. He didn’t expect us to add new ideas to his rules. The more we fiddle with Pāṇini’s grammar, the more it eludes us.”

Traditionally, scholars have interpreted Pāṇini’s metarule as meaning: in the event of a conflict between two rules of equal strength, the rule that comes later in the grammar’s serial order wins.

Rajpopat rejects this, arguing instead that Pāṇini meant that between rules applicable to the left and right sides of a word respectively, Pāṇini wanted us to choose the rule applicable to the right side. Employing this interpretation, Rajpopat found Pāṇini’s language machine produced grammatically correct words with almost no exceptions.

Take ‘mantra’ and ‘guru’ as examples. In the sentence ‘devāḥ prasannāḥ mantraiḥ’ (‘The Gods [devāḥ] are pleased [prasannāḥ] by the mantras [mantraiḥ]’) we encounter ‘rule conflict’ when deriving mantraiḥ ‘by the mantras’. The derivation starts with ‘mantra + bhis’. One rule is applicable to left part ‘mantra’ and the other to right part ‘bhis’. We must pick the rule applicable to the right part ‘bhis’, which gives us the correct form ‘mantraiḥ’.

And in the the sentence ‘jñānaṁ dīyate guruṇā’ (‘Knowledge [jñānaṁ] is given [dīyate] by the guru [guruṇā]’) we encounter rule conflict when deriving guruṇā ‘by the guru’. The derivation starts with ‘guru + ā’. One rule is applicable to left part ‘guru’ and the other to right part ‘ā’. We must pick the rule applicable to the right part ‘ā’, which gives us the correct form ‘guruṇā’.

Eureka moment

Six months before Rajpopat made his discovery, his supervisor at Cambridge, Vincenzo Vergiani, Professor of Sanskrit, gave him some prescient advice: “If the solution is complicated, you are probably wrong.”

Rajpopat said: “I had a eureka moment in Cambridge. After 9 months trying to crack this problem, I was almost ready to quit, I was getting nowhere. So I closed the books for a month and just enjoyed the summer, swimming, cycling, cooking, praying and meditating. Then, begrudgingly I went back to work, and, within minutes, as I turned the pages, these patterns starting emerging, and it all started to make sense. There was a lot more work to do but I’d found the biggest part of the puzzle.”

“Over the next few weeks I was so excited, I couldn’t sleep and would spend hours in the library including in the middle of the night to check what I’d found and solve related problems. That work took another two and half years.”

Significance

Professor Vincenzo Vergiani said: “My student Rishi has cracked it — he has found an extraordinarily elegant solution to a problem which has perplexed scholars for centuries. This discovery will revolutionise the study of Sanskrit at a time when interest in the language is on the rise.”

Sanskrit is an ancient and classical Indo-European language from South Asia. It is the sacred language of Hinduism, but also the medium through which much of India’s greatest science, philosophy, poetry and other secular literature have been communicated for centuries. While only spoken in India by an estimated 25,000 people today, Sanskrit has growing political significance in India, and has influenced many other languages and cultures around the world.

Rajpopat said: “Some of the most ancient wisdom of India has been produced in Sanskrit and we still don’t fully understand what our ancestors achieved. We’ve often been led to believe that we’re not important, that we haven’t brought enough to the table. I hope this discovery will infuse students in India with confidence, pride, and hope that they too can achieve great things.”

A major implication of Dr Rajpopat’s discovery is that now we have the algorithm that runs Pāṇini’s grammar, we could potentially teach this grammar to computers.

Rajpopat said: “Computer scientists working on Natural language Processing gave up on rule-based approaches over 50 years ago.

“So teaching computers how to combine the speaker’s intention with Pāṇini’s rule-based grammar to produce human speech would be a major milestone in the history of human interaction with machines, as well as in India’s intellectual history.”

Reference

R.A. Rajpopat, ‘In Pāṇini We Trust: Discovering the Algorithm for Rule Conflict Resolution in the Aṣṭādhyāyī’,PhD thesis (University of Cambridge, 2022).DOI: 10.17863/CAM.80099

Notes:

* Dr Rishi Rajpopat names Pāṇini’s metarule ‘1.4.2 vipratiṣedhe paraṁ kāryam’

Pāṇini is thought to have lived in a region in what is now north-west Pakistan and south-east Afghanistan.

The research, led by UCLA planetary scientists and published in two papers in Geophysical Research Letters, could also indicate that alternating layers of volcanic and sedimentary rocks lie beneath the surface.

The 4.7 magnitude earthquake, or marsquake, happened in May 2022 and lasted more than four hours, releasing five times more energy than any previously recorded quake. Though moderate by Earth standards, the temblor was nonetheless powerful enough to send seismic surface waves completely around the planet’s circumference, the first time this phenomenon has been observed on Mars.

The readings were taken from InSight, which landed on Mars in 2018. InSight is the first outer space seismometer to study in-depth the “inner space” of Mars: its crust, mantle and core.

“The seismometer aboard the InSight lander has recorded thousands of marsquakes but never one this large, and it took over three years after landing to record it,” said corresponding author Caroline Beghein, a professor of Earth, planetary and space sciences. “This quake generated different kinds of waves, including two types of waves trapped near the surface. Only one of those two has been observed on Mars before, after two impact events, never during a marsquake.”

Mapping the seismic activity, the location and frequency of impacts on Mars and the interior structure is important for future missions to the red planet as it will inform scientists and engineers where and how to build structures to ensure the safety of future human explorers.

As on Earth, studying how seismic waves travel through rocks can give scientists clues about the temperature and composition of the planet below the surface that help inform the search for underground water or magma. It also helps scientists understand the past forces that shaped the planet.

Beghein’s group combined measurements from two types of surface waves, called Love and Rayleigh waves, to infer the speed of underground shear-waves, which travel horizontally and move rocks perpendicular to the direction of wave propagation. This is the first time Love waves have been observed in conjunction with Rayleigh waves on Mars.

The measurements showed that the shear-waves move faster in the crust when rocks between 10 and 25 kilometers underground oscillate in a direction almost parallel to the planet surface than if the rocks vibrate in the vertical direction.

“This wave speed information is related to deformations inside the crust,” Beghein said. “Alternating volcanic rocks and sedimentary layers, which were deposited long ago, or a very large impact, such as a meteoroid, most likely account for the seismic wave measurements we observed.”

These data also enabled Jiaqi Li, a UCLA postdoctoral researcher in Beghein’s group, to learn that shear-waves move faster in the Martian southern highland areas than in the northern lowlands. The northern hemisphere of Mars has a lower elevation and is covered with more craters than the southern hemisphere. A large impact in the lowlands has been the prevalent theory to explain the origin of this difference.

The new data point toward the presence of thick accumulations of sedimentary rocks and relatively higher porosity in the lowlands. Larger amounts of gas, such as trapped air in these sedimentary rocks, slow the waves down.

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Materials provided by University of California – Los Angeles. Original written by Holly Ober. Note: Content may be edited for style and length.