SPACE
Can astronomers use radar to spot a cataclysmic asteroid?
Scientists share their latest findings and the future of radar in planetary science and defense
How can humans protect the Earth from “devastating asteroid and comet impacts?” According to the National Academies and their 2023-2032 Planetary Science and Astrobiology Decadal Survey, ground based astronomical radar systems will have a “unique role” to play in planetary defense.
There is currently only one system in the world concentrating on these efforts, NASA’s Goldstone Solar System Radar, part of the Deep Space Network (DSN). However, a new instrument concept from the National Radio Astronomy Observatory (NRAO) called the next generation RADAR (ngRADAR) system will use the National Science Foundation’s Green Bank Telescope (GBT) and other current and future facilities to expand on these capabilities.
“There are many applications for the future of radar, from substantially advancing our knowledge of the Solar System, to informing future robotic and crewed spaceflight, and characterizing hazardous objects that stray too close to Earth,” shares Tony Beasley, NRAO’s director.
On Saturday, February 17th, scientists will showcase recent results obtained with ground-based radar systems at the American Association for the Advancement of Science’s annual conference in Denver, Colorado.
“NRAO, with the support of the National Science Foundation and oversight by Associated Universities, Inc., has a long history of using radar to further our understanding of the Universe. Most recently the GBT helped confirm the success of NASA’s DART mission, the first test to see if humans could successfully alter the trajectory of an asteroid, “ shares NRAO scientist and ngRADAR project director Patrick Taylor.
The GBT is the world’s largest fully steerable radio telescope. The maneuverability of its 100-meter dish enables it to observe 85 percent of the celestial sphere, allowing it to quickly track objects across its field of view. Adds Taylor, “With the support of Raytheon Technologies, ngRADAR pilot tests on the GBT—using a low-power transmitter with less output than a standard microwave oven—have produced the highest-resolution images of the Moon ever taken from Earth. Imagine what we could do with a more powerful transmitter.”
Scientists sharing their results at AAAS include Edgard G. Rivera-Valentín of Johns Hopkins Applied Physics Laboratory and Marina Brozović of NASA’s Jet Propulsion Laboratory, which manages Goldstone and the DSN. Adds Brozović, “The public might be surprised to learn that the technology we use in our current radar at Goldstone hasn’t changed much since World War II. For 99% of our observations, we transmit and receive from this one antenna. New radar transmitter designs, like ngRADAR on the GBT, have the potential to significantly increase the output power and waveform bandwidth, allowing for even higher resolution imaging. It will also produce a scalable and more robust system by using telescope arrays to increase the collecting area.”
“NRAO is an ideal organization to lead these efforts because of the instruments we have available to receive radar signals, like the Very Long Baseline Array has done in our pilot ngRADAR project,” explains Brian Kent, NRAO scientist and director of science communications, who coordinated the presentation at AAAS, “Future facilities like the next generation Very Large Array, as a receiver, will create a powerful combination for planetary science.”
How does ground-based astronomical radar expand our understanding of the Universe? By allowing us to study our nearby Solar System, and everything in it, in unprecedented detail. Radar can reveal the surface and ancient geology of planets and their moons, letting us trace their evolution. It can also determine the location, size, and speed of potentially hazardous Near Earth Objects, like comets or asteroids. Advances in astronomical radar are opening new avenues, renewed investment, and interest in joint industry and scientific community collaborations as a multidisciplinary venture.
About NRAO & GBO
The National Radio Astronomy Observatory (NRAO) is a facility of the National Science Foundation, operated under cooperative agreement by Associated Universities, Inc.
The Green Bank Observatory is a facility of the National Science Foundation and is operated by Associated Universities, Inc.
Laboratory study on conditions for spontaneous excitation of "chorus emission," wave of space plasma
Exploring common plasma phenomena in laboratory and space through experiments in the RT-1 artificial magnetosphere
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WHEN THE PLASMA CONFINED IN THE DIPOLE MAGNETIC FIELD OF RT-1 CONTAINS A SIGNIFICANT RATIO OF HIGH-TEMPERATURE ELECTRONS (RED PARTICLES), THE SPONTANEOUS FORMATION OF A CHORUS EMISSION (WHITE EMISSION LINES) IS CHARACTERIZED BY A VARIABLE FREQUENCY (SOUND HEIGHT) LIKE BIRDSONG.
view moreCREDIT: NATIONAL INSTITUTE FOR FUSION SCIENCE
A dipole magnetic field, created by a ring current, is the most fundamental type of magnetic field that is found both in laboratories and in space. Planetary magnetospheres, such as Jupiter's, effectively confine plasma. The RT-1 project aims to learn from nature and create a magnetosphere-type high-performance plasma to realize advanced fusion energy. Simultaneously, the artificial magnetosphere offers a means to experimentally understand the mechanisms of natural phenomena in a simplified and controlled environment.
The whistler mode chorus emission, observed in the space surrounding the Earth, known as "Geospace", is an important phenomenon which is related to the aurorae and space weather. The chorus emission has been actively investigated primarily through spacecraft observations, theoretical studies, and numerical simulations. While spacecraft are powerful tools for studying the actual space environment, the planetary magnetosphere is a huge and complex system that is difficult to understand in its entirety. Also, it is not easy for human beings to manipulate the space environment. On the contrary, laboratory settings allow us to create a simplified research object that is extracted from the complex properties of nature in a controlled environment. Therefore, experimental studies are expected to play a complementary role in the observation and theory of understanding chorus emissions. However, it is not straightforward to create a magnetospheric environment in the laboratory. Laboratory experiments on chorus emissions in a magnetospheric dipole magnetic field have never so far been conducted.
A research team from the National Institute for Fusion Science in Toki, Japan, and the Graduate School of Frontier Sciences at the University of Tokyo in Kashiwa, Japan, has successfully conducted laboratory studies on the whistler mode chorus emission using the RT-1 device. This "artificial magnetosphere" has a magnetically levitated superconducting coil to create a planetary magnetosphere-type dipole magnetic field in the laboratory. Using high-temperature superconducting technology, a 110 kg coil is magnetically levitated in a vacuum vessel, and the generated magnetic field confines the plasma. This unique setup allows operation without any mechanical support structures to the coil, making it possible to generate plasma in an environment akin to that of a planetary magnetosphere, even within a ground-based facility. In this study, the research team filled the vacuum vessel of the RT-1 with hydrogen gas and injected microwaves to create high-performance hydrogen plasma, primarily by heating electrons.
In the experiments plasmas were generated in various states and investigations into the generation of waves were made. Consequently, a spontaneous production of the whistler wave chorus emission was observed when the plasma contained a considerable ratio of high-temperature electrons. Measurements were also taken of the strength and frequency of the chorus emission from the plasma, focusing on its density and the state of the high-temperature electrons. The findings revealed that the generation of a chorus emission is driven by an increase in high-temperature electrons, responsible for plasma pressure. Additionally, increasing the overall plasma density had the effect of suppressing the generation of the chorus emission. Through this study, it was clarified that the chorus emission is a universal phenomenon occurring in plasma with high-temperature electrons in a simple dipole magnetic field. Properties revealed in the experiment, including appearance conditions and wave propagation, may enhance our understanding of the chorus emission and related phenomena observed in geospace.
These results have been published in a journal of the Nature publishing group, Nature Communications.
Electromagnetic waves of a chorus emission have the potential to further accelerate hot electrons to higher energy states, leading to the formation of aurorae and satellite failures. These electromagnetic waves, along with energetic particles, play a crucial role in space weather phenomena. In geospace, when explosive events (flares) occur on the solar surface, they give rise to magnetic storms, causing large fluctuations in the electromagnetic field and the generating large amounts of energetic particles. This not only causes satellite failures and impacts the ozone layer but is also known to disrupt power and communication networks on the ground. With the expansion of human activity today, understanding space weather phenomena has become increasingly important. However, numerous mechanisms and phenomena in this area remain unresolved. The outcome of this study is expected to contribute to a better understanding of the mechanisms behind the diverse space weather phenomena.
In the field of fusion plasma, which aims to ultimately solve energy problems, the loss of particles and structure formation due to interaction with waves is one of the central research issues. A precise understanding of the complex interactions between spontaneously excited waves and plasma is essential for achieving fusion. Wave phenomena with frequency variations have been widely observed in high-temperature plasmas for fusion, indicating the existence of a shared physical mechanism with the chorus emission. The findings from this study represent a step forward in comprehending the common physical phenomena found in both fusion and space plasmas. It is anticipated that future research will advance further with increased cooperation between these two fields.
Glossary
Whistler mode chorus emission
Whistler waves are one of the fundamental waves propagating in plasma. In chorus emissions observed around geospace and Jupiter, fluctuation events with frequency variations similar to birdsong occur repeatedly. They are thought to be closely related to aurorae and space weather phenomena, such as the production and transport of high-energy electrons.
Ring Trap 1 device (RT-1)
The RT-1 is an experimental apparatus located at the University of Tokyo. Utilizing high-temperature superconducting technology, a dipole field coil is magnetically levitated, enabling plasma experiments to be conducted in an environment close to that of the planetary magnetosphere.
Dipole magnetic field
The dipole field is the configuration of a magnetic field produced by a ring current. The shape of planetary magnetospheres, such as Earth and Jupiter, closely resembles a dipole magnetic field which is characterized by a highly non-uniform strength, rapidly weakening as it expands away. This unique characteristic enables the stable confinement of high-performance plasma.
Geospace
Geospace is the space around the Earth that is particularly closely linked to human activities. In this region, plasma confined by the Earth's magnetic field gives rise to various phenomena. With the expansion of human activities into space, the study of magnetospheric disturbances, capable of causing aurora phenomena, as well as power and communication failures, has emerged as an active research field known as "space weather”.
Exploring Chorus Emission of Space Plasma in Laboratory: Experiments in Artificial Magnetosphere RT-1 to Understand Nature and Advance Fusion Research
In the "artificial magnetosphere" RT-1, originally designed for an advanced fusion concept by drawing inspiration from nature, this study has conducted experiments to understand the natural phenomena and elucidate the conditions for the appearance of a "chorus emission" in space plasma.
CREDIT
National Institute for Fusion Science
Nature Communications
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Experimental study on chorus emission in an artificial magnetosphere
ARTICLE PUBLICATION DATE
15-Feb-2024
SwRI scientists find evidence of geothermal activity within icy dwarf planets
Webb telescope observes potentially young methane deposits on surfaces of Eris, Makemake
Peer-Reviewed PublicationIMAGE:
SWRI SCIENTISTS USED DATA FROM THE JAMES WEBB SPACE TELESCOPE TO MODEL THE SUBSURFACE GEOTHERMAL PROCESSES THAT COULD EXPLAIN HOW METHANE ENDED UP ON THE SURFACES OF ERIS AND MAKEMAKE, TWO DWARF PLANETS IN THE DISTANT KUIPER BELT. THE ILLUSTRATION POINTS TO THREE POSSIBILITIES, INCLUDING THE POTENTIAL THAT LIQUID WATER EXISTS WITHIN THESE ICY BODIES AT THE EDGE OF THE SOLAR SYSTEM, FAR FROM THE HEAT OF THE SUN.
view moreCREDIT: SOUTHWEST RESEARCH INSTITUTE
SAN ANTONIO — February 15, 2024 —A team co-led by Southwest Research Institute found evidence for hydrothermal or metamorphic activity within the icy dwarf planets Eris and Makemake, located in the Kuiper Belt. Methane detected on their surfaces has the tell-tale signs of warm or even hot geochemistry in their rocky cores, which is markedly different than the signature of methane from a comet.
“We see some interesting signs of hot times in cool places,” said SwRI’s Dr. Christopher Glein, an expert in planetary geochemistry and lead author of a paper about this discovery. “I came into this project thinking that large Kuiper Belt objects (KBOs) should have ancient surfaces populated by materials inherited from the primordial solar nebula, as their cold surfaces can preserve volatiles like methane. Instead, the James Webb Space Telescope (JWST) gave us a surprise! We found evidence pointing to thermal processes producing methane from within Eris and Makemake.
The Kuiper Belt is a vast donut-shaped region of icy bodies beyond the orbit of Neptune at the edge of the solar system. Eris and Makemake are comparable in size to Pluto and its moon Charon. These bodies likely formed early in the history of our solar system, about 4.5 billion years ago. Far from the heat of our Sun, KBOs were believed to be cold, dead objects. Newly published work from JWST studies made the first observations of isotopic molecules on the surfaces of Eris and Makemake. These so-called isotopologues are molecules that contain atoms having a different number of neutrons. They provide data that are useful in understanding planetary evolution.
The JWST team measured the composition of the dwarf planets’ surfaces, particularly the deuterium (heavy hydrogen, D) to hydrogen (H) ratio in methane. Deuterium is believed to have formed in the Big Bang, and hydrogen is the most abundant nucleus in the universe. The D/H ratio on a planetary body yields information about the origin, geologic history and formation pathways of compounds containing hydrogen.
“The moderate D/H ratio we observed with JWST belies the presence of primordial methane on an ancient surface. Primordial methane would have a much higher D/H ratio,” Glein said. “Instead, the D/H ratio points to geochemical origins for methane produced in the deep interior. The D/H ratio is like a window. We can use it in a sense to peer into the subsurface. Our data suggest elevated temperatures in the rocky cores of these worlds so that methane can be cooked up. Molecular nitrogen (N2) could be produced as well, and we see it on Eris. Hot cores could also point to potential sources of liquid water beneath their icy surfaces.”
Over the past two decades, scientists have learned that icy worlds can be much more internally evolved than once believed. Evidence for subsurface oceans has been found at several icy moons such as Saturn’s moon Enceladus and Jupiter’s moon Europa. Liquid water is one of the key ingredients in determining potential planetary habitability. The possibility of water oceans inside Eris and Makemake is something that scientists are going to study in the years ahead. If either of them is habitable, then it would become the most distant world in the solar system that could possibly support life. Finding chemical indicators of internally driven processes takes them a step in this direction.
“If Eris and Makemake hosted, or perhaps could still host warm, or even hot, geochemistry in their rocky cores, cryovolcanic processes could then deliver methane to the surfaces of these planets, perhaps in geologically recent times,” said Dr. Will Grundy, an astronomer at Lowell Observatory, one of Glein's co-authors and lead author of a companion paper. “We found a carbon isotope ratio (13C/12C) that suggests relatively recent resurfacing.”
This work is part of a paradigm shift in planetary science. It is increasingly being recognized that cold, icy worlds may be warm at heart. Models developed for this study additionally point to the formation of geothermal gases on Saturn’s moon Titan, which also has abundant methane. Furthermore, the inference of unexpected activity on Eris and Makemake underscores the importance of internal processes in shaping what we see on large KBOs and is consistent with findings at Pluto.
“After the New Horizons flyby of the Pluto system, and with this discovery, the Kuiper Belt is turning out to be much more alive in terms of hosting dynamic worlds than we would have imagined,” said Glein. “It’s not too early to start thinking about sending a spacecraft to fly by another one of these bodies to place the JWST data into a geologic context. I believe that we will be stunned by the wonders that await!”
Access Glein’s Icarus paper, “Moderate D/H ratios in methane ice on Eris and Makemake as evidence of hydrothermal or metamorphic processes in their interiors: Geochemical analysis,” at: https://doi.org/10.1016/j.icarus.2024.115999 or https://arxiv.org/abs/2309.05549.
For more information, visit https://www.swri.org/planetary-science.
A team co-led by Southwest Research Institute found evidence for hydrothermal or metamorphic activity deep within the icy dwarf planets Eris and Makemake (artistic illustration). Located in the Kuiper Belt, a vast donut-shaped region of icy bodies beyond the orbit of Neptune at the edge of the solar system, Eris and Makemake are comparable in size to Pluto and its moon Charon.
CREDIT
Southwest Research Institute
JOURNAL
Icarus
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE PUBLICATION DATE
15-Feb-2024
A star like a Matryoshka doll: New theory for gravastars
Physicists at Goethe University Frankfurt find new solution to Einstein's general theory of relativity
Peer-Reviewed PublicationIMAGE:
ACCORDING TO FINDINGS BY PHYSICISTS AT GOETHE UNIVERSITY FRANKFURT, A GRAVASTAR COULD LOOK LIKE A MATRYOSHKA DOLL.
view moreCREDIT: DANIEL JAMPOLSKI AND LUCIANO REZZOLLA, GOETHE UNIVERSITY FRANKFURT
FRANKFURT. The interior of black holes remains a conundrum for science. In 1916, German physicist Karl Schwarzschild outlined a solution to Albert Einstein's equations of general relativity, according to which the center of a black hole consists of a so-called singularity, a point at which space and time no longer exist. Here, the theory goes, all physical laws, including Einstein's general theory of relativity, no longer apply; the principle of causality is suspended. This constitutes a great nuisance for science: after all, it means that no information can escape from a black hole beyond the so-called event horizon. This could be a reason why Schwarzschild's solution did not attract much attention outside the theoretical realm for a long time – that is, until the first candidate for a black hole was discovered in 1971, followed by the discovery of the black hole in the center of our Milky Way in the 2000s, and finally the first image of a black hole, captured by the Event Horizon Telescope Collaboration in 2019.
In 2001, Pawel Mazur and Emil Mottola proposed a different solution to Einstein's field equations that led to objects which they called gravitational condensate stars, or gravastars. Contrary to black holes, gravastars have several advantages from a theoretical astrophysics perspective. On the one hand, they are almost as compact as black holes and also exhibit a gravity at their surface that is essentially as strong as that of a black hole, hence resembling a black hole for all practical purposes. On the other hand, gravastars do not have an event horizon, that is, a boundary from within which no information can be sent out, and their core does not contain a singularity. Instead, the center of gravastars is made up of an exotic – dark – energy that exerts a negative pressure to the enormous gravitational force compressing the star. The surface of gravastars is represented by a wafer-thin skin of ordinary matter, the thickness of which approaches zero.
Theoretical physicists Daniel Jampolski and Prof. Luciano Rezzolla of Goethe University Frankfurt have now presented a solution to the field equations of general relativity that describes the existence of a gravastar inside another gravastar. They have given this hypothetical celestial object the name "nestar" (from the English “nested”).
Daniel Jampolski, who discovered the solution as part of his Bachelor’s thesis supervised by Luciano Rezzolla, says: “The nestar is like a matryoshka doll”, adding that, “our solution to the field equations allows for a whole series of nested gravastars.” Whereas Mazur and Mottola posit that the gravastar has a near infinite thin skin consisting of normal matter, the nestar’s matter-composed shell is somewhat thicker: “It’s a little easier to imagine that something like this could exist.”
Luciano Rezzolla, Professor of Theoretical Astrophysics at Goethe University, explains: “It’s great that even 100 years after Schwarzschild presented his first solution to Einstein’s field equations from the general theory of relativity, it’s still possible to find new solutions. It’s a bit like finding a gold coin along a path that has been explored by many others before. Unfortunately, we still have no idea how such a gravastar could be created. But even if nestars don't exist, exploring the mathematical properties of these solutions ultimately helps us to better understand black holes”.
JOURNAL
Classical and Quantum Gravity
METHOD OF RESEARCH
Computational simulation/modeling
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Nested solutions of gravitational condensate stars
ARTICLE PUBLICATION DATE
15-Feb-2024
Diverse ancient volcanoes on Mars discovered by HKU planetary scientist may hold clues to pre-plate tectonic activity on Earth
IMAGE:
FIGURE 1. TOPOGRAPHIC DATA ARE DRAPED OVER INFRARED IMAGE DATA SHOWING COMPLEX TECTONIC STRUCTURES AND VOLCANIC DEPOSITS IN THE ERIDANIA REGION OF MARS. WARM COLOURS ARE HIGHER ELEVATION.
view moreCREDIT: NASA/MARS ODYSSEY/HRSC
Volcanoes are a common feature on the surfaces of solid planets within the solar system, resulting from magmatic activity occurring within the planetary crust. On Earth, volcanism is driven primarily by heat and crustal recycling associated with plate tectonics, but Mars lacks plate tectonics and the driver of volcanism is not well understood.
Recent research by Professor Joseph MICHALSKI, a geologist in the Department of Earth Sciences at The University of Hong Kong (HKU), has revealed intriguing insights into the volcanic activity on Mars. He proposes that Mars has significantly more diverse volcanism than previously realised, driven by an early form of crust recycling called vertical tectonics. The findings, recently published in Nature Astronomy, shed light on the ancient crust of Mars and its potential implications for understanding early crustal recycling on both Mars and Earth.
Traditionally, Mars has been known to have large shield volcanoes similar to those in Hawaii. However, it was not known that Mars also possessed the diverse, explosive volcanoes that form on Earth due to crustal recycling.
The recent research conducted by Professor Michalski and his international team discover a vast number of diverse volcanoes in the ancient crust of Mars. ‘We have known for decades that Mars has volcanoes, but most of the recognised volcanoes correspond to large basaltic shield volcanoes similar to the ones that make up Hawaii,’ he explains. ‘In this work, we show that the ancient crust has many other types of volcanoes such as lava domes, stratovolcanoes, calderas and large shields of ash, not lava. Further, most scientists see Mars as a planet composed of basalt, which has low silica content and represents little crustal evolution, but these volcanoes have high silica content which means they formed from a complex process of magma evolution not known before.’
The paper suggests that intense volcanism occurred on ancient Mars, causing the crust to collapse into the mantle, where the rocks re-melted, resulting in magmas that have high silica. This tectonic process, called vertical tectonics, is hypothesised to have occurred on the ancient Earth, but rocks on Earth from that period (the Archean, more than 3 billion years ago) are highly modified by later geological activity, so we cannot see evidence for this process clearly on this planet. Therefore, exploring other planets like Mars, which has volcanism but no plate tectonics, can help reveal the mysteries of early crustal recycling on both the Red Planet, and by analogy, on early Earth.
Professor Michalski concluded, ‘Mars contains critical geological puzzle pieces that help us understand not only that planet, but the Earth as well. Martian volcanism is much more complex and diverse than has been previously thought.’
‘This is a significant discovery because it has revealed that crustal recycling can occur not only in plate tectonic regimes dominated by horizontal movements, but can also occur in pre-plate tectonic regimes dominated by vertical movements. This finding can help earth scientists revolve the long-term controversial issues of how and when felsic continents formed in our planet (Earth)’, said Professor Guochun ZHAO, the Chair Professor of HKU Earth Sciences.
The journal paper can be accessed here: https://www.nature.com/articles/s41550-023-02191-7
About Professor Joseph Michalski
A Professor in the Department of Earth Sciences and Deputy Director of the Laboratory for Space Research at HKU, he collaborated with colleagues from mainland China and USA on this research project. He is a Research Fellow of the Hong Kong Research Grants Council, and winner of a Tencent Xplorer Prize in 2023. The funding for this work was provided by the RGC Collaborative Research Fund.
For more information on Professor Joseph Michalski's research, please visit: http://www.clays.space; Twitter: @JoePlanets
Image and caption for download: https://www.scifac.hku.hk/press
For media enquiries, please contact Ms Casey To, External Relations Officer (tel: 39174948; email: caseyto@hku.hk / Ms Cindy Chan, Assistant Director of Communications of HKU Faculty of Science (tel: 3917 5286; email: cindycst@hku.hk).
Figure 2. Colour image data are draped onto topography to show a 3-D view of a large stratovolcano in the Eridania region of Mars.
CREDIT
NASA/ESA/HRSC
JOURNAL
Nature Astronomy
METHOD OF RESEARCH
Observational study
SUBJECT OF RESEARCH
Not applicable
ARTICLE TITLE
Diverse volcanism and crustal recycling on early Mars
ARTICLE PUBLICATION DATE
15-Feb-2024
Cathedral termite mounds inspire UArizona-designed lunar structures
Associate professor Jekan Thanga and a team of student researchers in the College of Engineering are developing smart, robot-built sandbag shelters for NASA astronauts on the moon.
Reports and ProceedingsIMAGE:
UARIZONA AEROSPACE ENGINEERING STUDENTS, FROM LEFT: MIN SEOK KANG, ATHIP THIRUPATHI RAJ, CHAD JORDAN CANTIN, SIVAPERUMAN MUNIYASAMY AND KORBIN AYDIN HANSEN DISPLAY A SMART SANDBAG STRUCTURE. CANTIN AND HANSEN ARE UNDERGRADUATES.
view moreCREDIT: COLLEGE OF ENGINEERING
NASA has big plans for its Artemis program – to return Americans to the moon for the first time since 1972 and establish a lunar base for humans by the end of the decade.
With NASA funding, a team of University of Arizona engineers is using robot networks to create termite-inspired structures that will help astronauts survive the moon's harsh environment.
Associate professor Jekan Thanga and his students in the Department of Aerospace and Mechanical Engineering, in the College of Engineering, have developed prototypes of their lunar sandbag structures and the underlying concept for a network of robots that can build them. The structures contain sensors that aid in construction, then alert astronauts to changes in environmental conditions.
Tech Launch Arizona, the university’s commercialization arm, worked with Thanga to file patents on the distributed computer processing networks that the team developed to link these structures and robots together.
Sivaperuman Muniyasamy, an aerospace engineering doctoral student, and Thanga presented a paper detailing the technology on Feb. 1 at the American Astronautical Society Guidance, Navigation and Control Conference.
"By publishing the paper at the conference, we're gaining feedback from other experts that really helps us move forward," said first author Muniyasamy.
Teaming up for moon landings
Thanga estimates astronauts will first land on the moon as part of Artemis in 2026 or 2027. In a consortium called LUNAR-BRIC, his team is partnering with NASA's Jet Propulsion Laboratory at Caltech and MDA, a space robotics company, to develop technology for Artemis moon landings.
"It's no accident this team has an academic partner, a commercial partner and a government agency," Thanga said. "Given the challenges, part of the path is for us to collaborate."
The moon structures are just a start for Thanga's university team and LUNAR-BRIC in their quest to support a space economy. Within a few years of the first successful landing, he said, NASA will look to building facilities for long-term habitation and industry, such as environmentally responsible moon and asteroid mining.
Moon dwellers will need semi-permanent safe shelters while they search for optimal locations to erect permanent buildings, Thanga said, adding that he is confident the fundamentally simple sandbag structures will be employed.
Insect inspiration
Thanga was first intrigued by a YouTube video showing the work of Nader Khalili. In the 1980s, the late architect presented to NASA the idea of sandbag structures for lunar and space habitation. Then Khalili developed SuperAdobe sandbag construction for homes around the world.
Thanga layered onto Khalili's ideas the concepts of insect skyscrapers. These cathedral termite mounds common in African and Australian deserts regulate the subterranean nest environment.
"In the case of the termites, it's very relevant to our off-world challenges. The extreme desert environments the termites face are analogous to lunar conditions," Thanga said. "Importantly, this whole approach doesn't rely on water. Most of the moon is bone-dry desert."
Thanga has long been interested in applying the architecture of insect social systems – like a termite colony constructing and maintaining a large, complicated mound – to distributed robot networks, in which machines work together cooperatively without human intervention.
"Learning about that helped direct me toward distributed systems for construction," he said.
Thanga's team investigated whether sandbags filled with regolith, soil and mineral fragments from the moon's surface, could replace traditional building materials for lunar housing, warehouses, control towers, robot garages, landing pads, protective jackets for robots, and blast walls to protect assets during turbulent takeoffs and landings.
The quickly and easily robot-assembled sandbag shelters reduce the material that must be transported to the moon, provide good climate control, and protect against moonquakes and other hazards.
Robots embed sensors and electronics in the sandbags and fill them with lunar regolith before assembling the structures in place. Some sensors provide location data to help the robots place the sandbags. Others supply environmental information and communication capabilities to warn of danger. On the moon, temperatures range from -298 to 224 degrees Fahrenheit; micro-meteors bombard the surface at an average of 60,000 mph; and solar radiation and lunar dust threaten exploration.
Serving underrepresented students
NASA has granted Thanga's team $500,000 for lunar surface projects through the agency's Space Technology Artemis Research program, or M-STAR, which is part of NASA's Minority University Research and Education Project, or MUREP. Those funds extend until summer 2024. Funding from another MUREP program, MIRO, helps cover costs of the lunar projects.
MIRO, which supports STEM research and education at Minority-Serving Institutions, has provided $1 million a year for UArizona student research projects over the last five years.
"The goal is to raise the participation of underrepresented groups in aerospace," Thanga said. "And these are hands-on, student-centric projects."
Muniyasamy, who moved from India to study at the university and plans to launch a space mining company after completing his Ph.D., leads a team of eight undergraduate and master's students working on lunar surface projects.
"This lab offers me the exact environment – it's startup culture," he said. "I'm leading a team and working with multidisciplinary people. I'm glad I'm here."
