Collaborating Authors

Prince George's County

The IMPACT of Summer Interns


This summer's group of interns -- Anisha Kabir, Bethany Kuo, and Tony Park -- are an excellent example of the contributions interns make to project teams over the course of 10 weeks and the valuable career-related skills they gain from working closely with experienced mentors and scientists in the fields of Earth science and computer science. IMPACT's machine learning group researches how to apply natural language processing (NLP) and knowledge graph technologies to improve the discovery of knowledge within Earth sciences. These three interns fit naturally into this effort. Bethany Kuo is a computer science and linguistics double major at the University of Maryland College Park. In collaboration with IMPACT team members, Ms. Kuo explored the effectiveness of combining a knowledge graph with BERT (bidirectional encoder representations from transformers) sentence embeddings and graph convolutions to surface related information in order to provide answers to natural language queries.

Orbit Logic Explores Machine Learning for Lunar Gateway Fault Management


Orbit Logic has been awarded a Phase I Small Business Technology Transfer (STTR) contract by NASA to develop its proof of concept for Lunar Fault Learning Agent for Prediction, Protection and Early Response (Lunar FLAPPER) – an onboard software solution that would automate routine tasks and perform rapid and intelligent responses to degradation or failures of spacecraft systems, resulting in improved mission results and safer crew environments. The solution could be relevant to systems such as NASA's planned Lunar Gateway, a multi-purpose outpost orbiting the Moon, which will be uninhabited for periods of up to nine months. When the spacecraft is not occupied by crew, robust autonomy would significantly ease (or even eliminate) mission control operator workload and safely maintain systems until astronauts return; Lunar FLAPPER is being developed in collaboration with the University of Maryland, College Park (UMD). Traditionally, spacecraft have implemented hard-coded, rules-based fault trees and sometimes require operators to be in-the-loop. These types of approaches are rigid and are not adaptive to evolving conditions or emerging fault types.

The air investigator


For Joseph Allen, the pandemic has made the connection between indoor air quality and human health clearer than ever. Joseph Allen runs a major public health research project at Harvard University, probing how indoor air quality affects human health and cognition. He consults with companies on ventilation and air filtration, and during the pandemic he became a prominent voice on public health, writing dozens of op-eds criticizing early guidance from health authorities and debunking misconceptions about how the virus spreads. But none of it would have happened if he hadn't washed out as an FBI recruit. The son of a New York City homicide detective who opened his own investigative agency, Allen spent his teens and 20s helping with the family business. He did surveillance, undercover work, computer forensics, and skiptrace—tracking down people who left town to avoid alimony. Eventually he took over the agency, leading investigations and supervising eight agents. “I enjoyed the work and thought it was challenging,” Allen recalls. But part of him always wanted to be a scientist. He majored in environmental science at Boston College, and in his late 20s, still torn, he began to apply to graduate school even as he started the process to become an FBI agent. After 2 years of interviews and testing, the last step was a routine polygraph test. He failed the first round—the trick questions he was asked were so obvious that he could not take them seriously. So FBI flew in one of its toughest examiners from Iraq—a hulking, jackbooted guy who got right in Allen's face, screaming that he knew he was lying. But Allen kept cool, and after a while, the interrogator stormed out and slammed the door. “I thought he would come back in the room and say, ‘Congratulations,’ cause I'm thinking I'm crushing it,” Allen recalls. “But they failed me because they said I employed countermeasures.” FBI apparently didn't want an agent who couldn't be unnerved by a polygraph test. And that solved Allen's career dilemma. “I guarantee I'm the only public health student ever to fail an FBI lie detector polygraph in the morning and start graduate school a few hours later,” Allen says. But his investigative instincts never left him. A tall, athletic-looking man with a bald head and stylish stubble, Allen directs the Healthy Buildings Program at Harvard's T.H. Chan School of Public Health, where he studies the effects of toxic gases emitted from furniture, carpets, and paints; stale air; and high levels of carbon dioxide. Years of studies by Allen and others have shown poorly circulated air in buildings impairs our ability to think clearly and creatively. Considering that we spend more than 90% of our lifetimes indoors, those findings have implications for personal well-being—and for businesses concerned about their bottom line. “Joe has always had a unique understanding of this range of domains—from how buildings work, to environmental exposure assessment, to making connections with health outcomes,” says Brent Stephens, chair of the Department of Civil, Architectural, and Environmental Engineering at the Illinois Institute of Technology. “There's not a tremendous number of people in this world that have worked on that whole spectrum.” When the COVID-19 pandemic arrived, the previously esoteric field of indoor air quality suddenly became the focus of widespread concern. Like many of his colleagues, Allen jumped into the fray, advising school systems, police departments, entertainment companies, the Boston Symphony, and a host of other entities on how to make their indoor air healthier, during the pandemic and afterward. “COVID really changed the conversation,” says Matt Murray, vice president of leasing at Boston Properties, the largest publicly traded developer in the United States and one of Allen's consulting clients. Before the pandemic, the company would have to explain to bored executives why they should pay attention to indoor air. “Now, the CEOs are all saying, ‘What filters do you use? How you process the air you bring into the workspace?’” Murray says. “And we're ready for those conversations because we've been working with Joe.” AFTER HE FAILED his FBI exam, Allen became a different kind of sleuth. For his doctoral thesis at the Boston University School of Public Health, he investigated toxic flame-retardant chemicals released into the air by furniture, and found they were nearly ubiquitous. (The chemicals were later banned.) After graduation he got a job with a consulting firm, where he investigated problems such as toxic emissions from drywall and outbreaks of Legionnaires' disease, which is caused by bacteria that grow in plumbing and become aerosolized by ventilation systems, showers, or even flushed toilets. Those investigations introduced him to “sick building syndrome,” a problem first identified in the 1970s in which the occupants experience fatigue, itchy eyes, headaches, and other symptoms. Exactly what causes these ailments isn't clear, but exposure to contaminated air is a likely culprit. Allen became convinced that the building you work in can have more impact on your health than your doctor. In 2014, Allen accepted a position at Harvard, where he soon turned his attention to how the indoor environment can affect people's cognitive abilities. Many of us have struggled to pay attention during a long staff meeting in a stuffy conference room. Research by Allen and others suggests that lassitude may not be due solely to boredom, but also to the carbon dioxide (CO2)-rich conference room air. Ever since the energy shocks of the 1970s, buildings in the United States have been made as airtight and energy-efficient as possible. The result was a buildup of toxic volatile organic compounds (VOCs) and exhaled CO2. “Green building standards” introduced in the late '90s focused on reducing toxic materials and making buildings healthier as well as more sustainable, but they didn't prioritize indoor air quality and ultimately did little to improve it. In a multiyear series of experiments, Allen and his team have investigated the consequences. In the first study, published in 2015, they had 24 white-collar volunteers spend six working days in environmentally controlled office spaces at Syracuse University's Total Indoor Environmental Quality Laboratory. On various days the experimenters would alter ventilation rates and levels of CO2 and VOCs. Each afternoon the volunteers were tested on their ability to think analytically and react to a crisis. (One test, for example put the volunteer in the role of a small-town mayor trying to react to an emergency.) All tests were double-blind: Neither the volunteers nor the study personnel knew that day's environmental conditions. The results were dramatic. When volunteers worked in well-ventilated conditions (which lowered the levels of CO2 and VOCs), they scored 61% higher than when they worked in typical office building conditions. When they worked in the cleanest conditions, with even lower CO2 levels and higher ventilation rates, their scores climbed 101%. To find out whether the results held up in the real world, Allen and his team recruited 109 volunteers from 10 office buildings across the United States. Six had been renovated to create better heat and humidity control, improve ventilation, and lower the use of toxic materials. Four had not. Allen's team gave each office worker a Fitbit-like bracelet to record heart rate, skin temperature, sleep patterns, and other physiological signs of well-being. Workers also completed a survey each day about how comfortable they felt and whether they experienced symptoms such as drowsiness or headaches. At the end of the week, they took the cognitive tests. Workers in the buildings with good ventilation and lower levels of indoor pollution scored 26.4% higher than those in the unimproved buildings. They also reported sleeping better and experiencing fewer “sick building” symptoms. “This is really important, interesting work,” says Elliott Gall, an indoor air scientist at Portland State University. “It's a great example of the kind of interdisciplinary work [that explores] the complexity of indoor air and how it affects us.” Over time, Allen came to see businesspeople as natural allies who could act on his public health findings faster than government officials. He teamed up with John Macomber, a Harvard Business School lecturer and former CEO of one of the largest construction companies in New England. Macomber was impressed with Allen's research suggesting a tiny sacrifice in energy efficiency through improved ventilation could increase a business's bottom line by as much as 10% by decreasing absenteeism and boosting worker productivity. “I realized we've been missing the boat,” Macomber says. “We're chasing pennies on energy when there's thousands of dollars in productivity issues.” Allen and Macomber consulted with companies and spoke at corporate conferences, making the economic case for improving ventilation and filtration as well as adjusting lighting, temperature, and humidity. “The idea of a healthy building has been made too complicated,” they wrote in a book they co-authored, Healthy Buildings: How Indoor Spaces Drive Performance and Productivity . “There are just a handful of things we need to do to make a building healthier.” Allen's group continued to investigate how the indoor environment affects our mental state. They found that airline pilots exposed to CO2 levels common in cockpits did worse on Federal Aviation Administration–mandated emergency response tests than when they breathed better air. They showed that during a heat wave, students who lived in non–air-conditioned dorms had slower reaction times and poorer problem-solving skills than those with air conditioning. They showed that bringing plants and views of nature into the workplace can lower office workers' heart rate, blood pressure, and other physiological indicators of stress. In 2019, Allen's team embarked on an ambitious international project to examine the long-term impacts of indoor air quality by tracking the physical and cognitive health of more than 300 office workers in 43 buildings in six countries over the course of 1 year. They mailed each worker a wristband to monitor their physiology and a small sensor to continuously measure levels of fine particulates and CO2 in their workspace. At predetermined times and levels of CO2 and particulates, the program pinged each worker's smartphone with a quiz to test reaction time and cognitive function. The studies showed that in offices across the world, poor ventilation, CO2, and particulates (which carry VOCs) conspire to significantly impair cognitive function. WHEN THE first reports of the new coronavirus emerged from Wuhan, China, in January 2020, Allen realized his years researching air quality and disease transmission in indoor environments had new relevance. “Even though the virus was novel, there are elements in all this that feel quite familiar,” he says. “It doesn't matter if it's a radiological hazard, biological hazard, or chemical hazard. We know how to assess the risk and put in appropriate controls.” Early in the pandemic, experts at the World Health Organization (WHO) and the U.S. Centers for Disease Control and Prevention (CDC) latched onto the idea that the virus was spread by large, exhaled droplets that float for a short time and then settle on surfaces. But scientists specializing in aerosols knew airborne viruses are more likely to ride on tinier particles exhaled when people breathe, sneeze, cough, or talk. Smaller than 5 microns, these particles can travel across a room and linger in indoor air for hours. Aerosol experts such as Lidia Morawska of Australia's Queensland University of Technology, Gardens Point; Donald Milton of the University of Maryland, College Park; and Linsey Marr of Virginia Polytechnic Institute and State University argued that the focus on larger droplets had led to wrong-headed guidance about washing packages with bleach, staying 2 meters apart—even outdoors—and other forms of what some researchers called “hygiene theater.” They urged policies that emphasized indoor mask wearing and less draconian regulations for people outdoors, where the virus would quickly disperse. Allen signed on to that fight, collaborating with aerosol experts and public health researchers on scientific papers and bringing their case to the public. “He's a really good public communicator,” says Marr, who credits Allen with helping her work get the attention it deserves. “One of our biggest frustrations over the past year is that we knew enough to act early on,” Allen says. “Even by late January 2020 we knew that airborne transmission of aerosols was not only likely, but probable.” Waiting for proof made no sense. “This was a pandemic, an all-in moment, so why wouldn't we have immediately deployed every strategy that could have helped?” Those strategies, Allen knew from his research, include bringing more outside air into chronically underventilated buildings and using higher efficiency filters in ventilation units. He started waking up at 4 a.m. to write opinion pieces. His first two, in the Financial Times and The New York Times , argued that buildings, if properly ventilated, could be formidable weapons in the fight against the virus. He and his team had measured air flow in schoolrooms under various conditions, and Allen explained that schools could easily be made safe by opening windows and buying the kind of high-efficiency particulate air purifiers sold at local home stores. So much of his writing involved correcting misimpressions that he felt he was playing editorial whack-a-mole. No, he argued, you do not have to wipe your groceries with bleach. No, you do not have to avoid exercising outside. No, schools do not need to install costly air-purifying systems. In July 2020, Morawska and Milton wrote an open letter to WHO—a full-throated appeal to recognize the importance of aerosol transmission. Allen was among 237 other scientists in 32 countries who signed on to the letter, which urged greater emphasis on indoor air quality. But WHO continued to downplay the importance of aerosol transmission. “I think some of the reluctance was that if [health authorities] say a disease is airborne, we'd have to provide N95 masks for every health worker and have negative pressure rooms in every hospital, which wasn't possible,” Marr says. Later that month, Allen and his Harvard colleague Parham Azimi published a study in the Proceedings of the National Academy of Sciences that used computer modeling to reconstruct the spread of the COVID-19 outbreak on the Diamond Princess cruise ship. By mapping the ship's ventilation system and the locations of people who came down with the disease, they showed that only aerosols, not larger droplets, could have traveled the necessary distances through the ducts. Similar findings emerged from studies by Marr, Morawska, and others. Finally, in early May, after a series of persuasive papers in major journals, WHO and CDC acknowledged that the virus was transmitted primarily by fine aerosols. (Even then, the agencies issued no major announcements but simply changed the wording on their websites.) Since then, CDC has gone further, issuing recommendations for reopening schools that stress the importance of good ventilation in addition to vaccinations. ![Figure][1] Something in the airGRAPHIC: C. BICKEL/ SCIENCE Meanwhile, Allen and his colleagues at the Harvard Healthy Buildings Program created a website with a comprehensive guide to maintaining proper ventilation in schools, homes, and businesses. The website advises building managers to bring in as much outside air as possible—a room air exchange rate of four to six times per hour, more than double the rate in a typical office or school building. In buildings that recirculate interior air, managers should upgrade to hospital-grade MERV 13 filters, which remove up to 90% of particles 2.5 microns or smaller, rather than the typical MERV 8, which can remove as little as 20%. The new focus on indoor air quality could help hasten the end of the current pandemic and perhaps even help forestall the next one. It may bring broader changes as well. Businesspeople are recognizing the value of improving indoor air to create better working conditions and add value to their properties. “What we're seeing with some parts of the market—notably the higher end, real estate investment trusts, owners of multiple office buildings or apartments—is they're thinking really hard about competing” in the post pandemic market, Macomber says. “And one way to compete is to have healthier buildings.” Allen predicts that the new availability of cheap personal air quality monitors will quicken that competition and heighten people's awareness of the indoor environment. Previously, the only way to assess indoor air quality was to hire an expensive consultant. Now, with monitors available online for less than a couple of hundred dollars, any office worker or hotel guest can quickly monitor CO2; some devices even detect VOCs. If consumers post results on websites like Yelp, businesses would be forced to pay attention. (Indeed, some building owners already boast about air quality in advertisements.) “I think there's going to be a fundamental rebalancing in terms of how we think about indoor spaces,” Allen says. “I think that people won't tolerate sick buildings, where you feel tired, your eyes itch, you have a headache, or you're stuffed into a closetlike office with no windows.” It's one lasting positive from the pandemic. “That era is over,” Allen says. “Rightly so, and good riddance.” [1]: pending:yes

Autonomous excavators ready for around the clock real-world deployment


Researchers from Baidu Research Robotics and Auto-Driving Lab (RAL) and the University of Maryland, College Park, have introduced an autonomous excavator system (AES) that can perform material loading tasks for a long duration without any human intervention while offering performance closely equivalent to that of an experienced human operator. AES is among the world's first uncrewed excavation systems to have been deployed in real-world scenarios and continuously operating for over 24 hours, bringing about industry-leading benefits in terms of enhanced safety and productivity. The researchers described their methodology in a research paper published on June 30, 2021, in Science Robotics. "This work presents an efficient, robust, and general autonomous system architecture that enables excavators of various sizes to perform material loading tasks in the real world autonomously," said Dr. Liangjun Zhang, corresponding author and the Head of Baidu Research Robotics and Auto-Driving Lab. Excavators are vital for infrastructure construction, mining, and rescue applications.

Careers - Airgility, Inc.


Aspen Avionics is aligning their graphical user interface development with Airgility and we will in turn/time begin to align our algorithms and AI development into their avionics products. Since the vision is to cross-align each other's company capabilities, while the position can be held remotely, it is highly preferable to have the new hires that are able to physically be present at Airgility in College Park (MD) or in Albuquerque (NM). The physical presence of the Software Engineer(s) will allow the new hire access to learn about the robotics work performed at Airgility. Therefore, future development that inlays Airgility's work into Aspen's Avionics products will likely create a smoother workflow since a portion of Aspen's engineering team is deployed within Airgility. If the hire is located at Airgility, travel to Albuquerque (NM) is required.

Responsible Computing During COVID-19 and Beyond

Communications of the ACM

The COVID-19 pandemic has both created and exacerbated a series of cascading and interrelated crises whose impacts continue to reverberate. From the immediate effects on people's health to the pressures on healthcare systems and mass unemployment, millions of people are suffering. For many of us who work in the digital technology industry, our first impulse may be to devise technological solutions to what we perceive as the most urgent problems when faced by crises such as these. Although the desire to put our expertise to good use is laudable, technological solutions that fail to consider broader social, political, and economic contexts can have unintended consequences, undermining their efficacy and even harming the very communities that they are intended to help.10 To ensure our contributions achieve their intended results without causing inadvertent harm, we must think carefully about which projects we work on, how we should go about working on them, and with whom such work should be done.

The 10th IEEE International Workshop on the Analysis and Modeling of Faces and Gestures


"What I cannot create, I do not understand," said the famous writing on Dr. Feynman's blackboard. The ability to create or to change objects requires us to understand their structure and factors of variation. For example, to draw a face an artist is required to know its composition and have a good command of drawing skills (the latter is particularly challenging for the presenter). The animation additionally requires the knowledge of rigid and non-rigid motion patterns of the object. This talk shows that generation, manipulation, and animation skills of deep generative models substantially benefit from such understanding.

Collaborative Team to Advance Artificial Intelligence and Autonomy


An interdisciplinary research team led by the University of Maryland, College Park (UMD) and in partnership with the University of Maryland, Baltimore County (UMBC) has entered into a cooperative agreement with the U.S. Army Research Laboratory(ARL) worth up to $68 million. The agreement brings together a large, diverse collaborative of researchers--leveraging the University System of Maryland's national leadership in engineering, robotics, computer science, operations research, modeling and simulation, and cybersecurity--to drive transformational advances in artificial intelligence (AI) and autonomy. The five-year agreement will accelerate the development and deployment of safe, effective, and resilient capabilities and technologies, from wearable devices to unmanned aircraft, that work intelligently and in cooperation with each other and with human actors across multiple environments. The robust effort encompasses three areas of research thrusts, each supported by a team of faculty, staff, and students. The new collaboration builds on a more than 25-year research partnership between UMD and ARL in AI, autonomy, and modeling and simulation to spur the development of technologies that reduce human workload and risk in complex environments such as the battlefield and search-and-rescue operations.

U.S. law sets stage for boost to artificial intelligence research


Low-income commuters who rely on public transit face many challenges—multiple transfers, long waits, and off-hour travel—that aren't measured in the usual ridership surveys. Vanessa Frias-Martinez, a computer scientist at the University of Maryland, College Park, wants to ease their commute by harnessing two hot trends in computer science, cloud computing and artificial intelligence (AI), which Congress now hopes to scale up dramatically for U.S. scientists. With support from the National Science Foundation, including an NSF-funded effort called CloudBank that subsidizes access to commercial cloud services, Frias-Martinez plans to track the movements of thousands of Baltimore residents while protecting their privacy. And by applying AI algorithms to the large data sets, she hopes to identify ways to eliminate transit bottlenecks and improve service. Frias-Martinez predicts CloudBank “will flatten the steep learning curve” for first-time cloud users like her. Congress has now embraced a plan to ensure there are many more. The National Artificial Intelligence Initiative Act (NAIIA) of 2020, which became law last week, aims to bolster AI activities at more than a dozen agencies. Its directives include a study of how to create a national research cloud that would build on CloudBank. It also calls for an expansion of a network of research institutes launched last summer, and the creation of a White House AI office and an advisory committee to monitor those efforts. “It's the closest thing to a national strategy on AI from the United States to be formally endorsed by Congress,” says Tony Samp, a former congressional staffer turned high-tech lobbyist for DLA Piper. He and others say the new law is meant to keep the country at the forefront of global AI research in the face of growing investments by other countries. The NAIIA authorizes spending but doesn't appropriate money. If funded, however, it would significantly ramp up federal AI investments. It authorizes $4.8 billion for NSF over the next 5 years, with another $1.15 billion for the Department of Energy (DOE) and $390 million for National Institute of Standards and Technology (NIST). NSF, which funds the vast majority of federally supported AI academic research, estimates it spent $510 million on AI in 2020, so the NAIIA would roughly double that effort. The military is also upping its AI game. The NAIIA is appended to the National Defense Authorization Act, a 4500-page bill providing annual policy guidance to the Department of Defense that survived a presidential veto. This year's version of the must-pass bill raises the stature of the Pentagon's Joint Artificial Intelligence Center formed in 2018 and gives it new authority to use AI to improve combat readiness and fight wars. The NAIIA both codifies what some federal agencies are already doing and gives them an extensive to-do list. For example, it endorses NSF's network of seven AI research institutes, launched last summer with help from the U.S. Department of Agriculture and in partnership with industry, and backs similar centers at DOE and the Department of Commerce—which includes NIST and the National Oceanic and Atmospheric Administration. The NSF institutes, each funded at roughly $20 million over 5 years, will support research in applying AI to a variety of topics including weather forecasting, sustainable agriculture, drug discovery, and cosmology. NSF is already soliciting proposals for a second round of multidisciplinary institutes, and many AI advocates would like to see its growth continue. A white paper for President-elect Joe Biden, for example, calls for an initial investment of $1 billion, and a 2019 community road map envisions each institute supporting 100 faculty members, 200 AI engineers, and 500 students. Their popularity has revived a recurring debate about how to grow such an initiative without hurting the core NSF research programs that support individual investigators. “We're very proud of the institutes, which have gotten a lot of attention, and we think they can be wonderfully transformational,” says Margaret Martonosi, head of NSF's Computing and Information Science and Engineering (CISE) directorate. But Martonosi also notes that CISE spends even more on its core programs—and still rejects more good proposals than it funds. Cloud computing could also boost AI, because it enables researchers to compile and analyze the huge data sets required to train AI algorithms. It, too, gets a big shoutout in the new law, which directs the NSF director and the president's science adviser to assemble a 12-member task force to study the feasibility of a National Research Resource (NRR). Such a national cloud would scale up what CloudBank is now doing and give researchers the tools to analyze large public data sets containing, say, anonymized government health records or satellite data. “At present, only a handful of companies can afford the substantial computational resources required to develop and train the machine learning models underlying today's AI,” says Stanford University's John Etchemendy. “What's more, the large data troves required to train these algorithms are for the most part controlled by either industry or government. Academic researchers struggle to gain access to both.” Etchemendy, a former longtime provost, and computer scientist Fei-Fei Li direct Stanford's Institute for Human-Centered Artificial Intelligence and co-authored a proposal for an NRR that legislators used as a template in the NAIIA. Columbia University computer scientist Jeannette Wing, whose resume includes leading NSF's computing directorate and running Microsoft's research shop, would like to see “all universities use the cloud routinely for all research and all educational activities.” Scientists who continue to rely on their own institutional computing resources, expertise, and support staff, she believes, will find it increasingly difficult to keep pace with competitors who can address cutting-edge research questions via the cloud. Creating such a ubiquitous network, which she calls an academic cloud, won't be easy. “Current commercial cloud providers have interfaces and services that are not nontechie friendly and price points that are out of line for academics,” she explains. But she thinks those problems can be solved. How a national cloud would be structured or managed poses another challenge. Some have suggested linking it to DOE's network of national labs, or to the supercomputing centers that DOE and NSF support. Etchemendy hopes the government will decide to contract with commercial cloud services such as Amazon Web Services, Google Cloud, Microsoft Azure, and IBM Cloud rather than starting from scratch. “The commercial cloud providers are doing the innovation, and they invest massive amounts of money to keep it up-to-date,” he says. “It would be a huge mistake to build a facility like a supercomputer center because it would be obsolete within a few years.” Even if the spending levels authorized by the new law are aspirational, AI advocates say the act demonstrates the remarkable support that the field now enjoys. “There was a real sense of urgency on this issue,” Samp says. “I also think [the NAIIA] provides a foundation for years to come.”

Mars lander spies the planet's deep boundaries


Two years ago, NASA's InSight spacecraft alighted on the surface of Mars, aiming to glean clues to the planet's interior from the shaking of distant earthquakes and deep heat leaking from its soil. Mars, it turned out, had other ideas. Its sticky soil has thwarted InSight's heat probe, and in recent months howling winds have deafened its sensitive seismometers. Most mysteriously, the planet hasn't been rattled by the large marsquakes that could vividly illuminate its depths. Despite these hurdles, a precious clutch of small-but-clear quakes has enabled the InSight team to see hints of boundaries in the rock, tens and hundreds of kilometers below. They are clues to the planet's formation billions of years ago, when it was a hot ball of magma and heavier elements like iron sank to form a core, while lighter rocks rose up out of the mantle to form a capping lid of crust. The results, some debuting this month at an online meeting of the American Geophysical Union (AGU), show that the planet's crust is surprisingly thin, its mantle cooler than expected, and its large iron core still molten. The findings suggest that in its infancy, Mars efficiently shed heat—perhaps through a pattern of upwelling mantle rock and subducting crust similar to plate tectonics on Earth. “This may be evidence for a far more dynamic crust formation in Mars's early days,” says Stephen Mojzsis, a planetary scientist at the University of Colorado, Boulder, who is unaffiliated with the mission. The evidence has been hard won. Early in the mission, winds were quiet enough for InSight's seismometers, housed in a small dome placed on the surface, to hear a multitude of small quakes—nearly 500 in total. But since June, winds have shaken the surface strongly enough to smother all but a handful of new quakes. Yet frustratingly, the winds have not been strong enough to sweep away dust that is darkening the craft's solar panels and foreshadowing the mission's end sometime in the next few years. The seismometers are still running nonstop, but power constraints have forced the team to turn off a weather station when using the lander's robotic arm. “We are starting to feel the effects,” says Bruce Banerdt, InSight's principal investigator and a geophysicist at NASA's Jet Propulsion Laboratory. Meanwhile, the heat probe, about the length of a paper towel tube, is stuck in soil that compacted instead of crumbling as the rod tried to delve in. Mission engineers have used the robotic arm to push the probe down and scrape dirt on top. In the next month or two, they'll try once more to get the probe to burrow in, Banerdt says. “If that doesn't work, we'll call it a day and accept disappointment.” Perhaps the biggest disappointment is the lack of a marsquake larger than magnitude 4.5. The seismic waves of a large quake travel more deeply, reflecting off the core and mantle boundaries and even circling the planet on its surface. The multiple echoes of a large quake can enable just a single seismic station like InSight's to locate the quake's source. But above magnitude 4, Mars has been curiously silent—an apparent violation of the scaling laws that apply on Earth and the Moon, where 100 magnitude 3 events correspond to 10 magnitude 4 quakes, and so on. “That is a bit weird,” says Simon Stähler, a seismologist on the team from ETH Zurich. It could simply be that Mars's faults aren't big enough to sustain big strikes, or that its crust isn't brittle enough. But two moderate quakes, at magnitude 3.7 and 3.3, have been treasure troves for the mission. Traced to Cerberus Fossae, deep fissures in the crust 1600 kilometers east of the landing site that were suspected of being seismically active, the quakes sent a one-two punch of compressive pressure (P) waves, followed by sidewinding shear (S) waves, barreling toward the lander. Some of the waves were confined to the crust; others reflected off the top of the mantle. Offsets in the travel times of the P and S waves hint at the thickness of the crust and suggest distinct layers within it, Brigitte Knapmeyer-Endrun, a seismologist at the University of Cologne, said in an AGU presentation. The top layer may reflect material ground up in the planet's first billion years, a period of intense asteroid bombardment, says Steven Hauck, a planetary scientist at Case Western Reserve University. At 20 or 37 kilometers thick, depending on whether the reflections accurately trace the top of the mantle, the martian crust appears to be thinner than Earth's continental crust—a surprise. Researchers had thought that Mars, a smaller planet with less internal heat, would have built up a thicker crust, with heat escaping through limited conduction and bouts of volcanism. (Though Mars is volcanically dead today, giant volcanoes dot its surface.) A thin crust, however, might mean Mars was losing heat efficiently, recycling its early crust, rather than just building it up, perhaps through a rudimentary form of plate tectonics, Mojzsis says. A handful of distant quakes, originating some 4000 kilometers away, provided a further clue. Those waves traveled deep through the mantle and interacted with the mantle transition zone, a layer where pressure transforms the mineral olivine into wadsleyite. By analyzing the travel time of waves that passed above, below, and through the transition zone, the team located its depth—and found it shallower than expected, an indication of a cooler mantle. For the mantle to be this cool today suggests that convection—the swirling motions that, on Earth, drive tectonic plates and carry heat from the mantle to the surface—might have operated early on, says Quancheng Huang, a Ph.D. student at the University of Maryland, College Park, who presented some of the results at the AGU meeting. “Plate tectonics is a very effective way of cooling a planet.” A third science experiment aboard InSight probes deeper still, using tiny Doppler shifts in radio broadcasts sent from Earth to receivers on the probe to detect slight wobbles in the planet's spin. The size and consistency of the planet's iron core affect the wobbles, much as raw eggs spin differently from cooked ones. “We've had something like 350 hours of tracking,” says Véronique Dehant, a geophysicist at the Royal Observatory of Belgium. The preliminary results confirm that the core is liquid, with a radius compatible with previous estimates made by spacecraft measuring tiny variations in the planet's gravity, Dehant reports in her AGU poster. Those gravity estimates have found a core with a radius of about 1800 kilometers—taking up more than half the planet's diameter. Rebecca Fischer, a mineral physicist and modeler at Harvard University, isn't surprised at the signs of a liquid core. “It would be a pretty big surprise if it weren't,” she says. Sulfur and other elements mixed with the iron should help it to remain molten while cool, much as salt prevents icing. On Earth, convective motions in the molten outer core drive the magnetic dynamo. But on Mars, those motions seem to have stopped long ago—and without a magnetic field, the planet's atmosphere was vulnerable to the Sun's cosmic rays and leached water to space. Banerdt hopes to sharpen this fuzzy picture of the planet's interior, and he thinks calmer winds will soon make that possible. After two Earth years, the probe's first martian year is ending, and the quiet of the mission's first months is returning. “We're looking forward to another whole pile of event detections,” Banerdt says. And though the planet has not cooperated so far, perhaps the Big One is poised to strike Mars like a gong—a reverberation that would at last make all clear.