Dr. Sarah Moran Named UArizona Sursum Fellow
Dr. Moran was selected for her proposal on Haze Evolution in sub-Neptune Exoplanets through UV Laboratory Experiments.
Dr. Sukrit Ranjan Joins LPL Faculty Starting Fall 2022
Sukrit's work is focused on the origin of life on Earth, the search for life on other worlds, and the atmospheres of rocky exoplanets. He applies photochemistry to questions related to the origin of life on Earth and the search for life on other worlds.
Dr. Sukrit Ranjan will join LPL as an assistant professor. Sukrit completed his Ph.D. in Astronomy and Astrophysics at Harvard University, where he was the first student to earn a certificate in Origin of Life studies. Sukrit completed his undergraduate work at MIT, majoring in physics and minoring in astronomy and history. In addition to research, Dr. Ranjan values outreach and education.
Sukrit works to constrain the palette of environmental conditions from which life arose on Earth to constrain and guide experimental studies of the origin of life. To search for life elsewhere, he works to determine observational tests by which life on other worlds may be remotely discriminated. In collaboration with experimental colleagues, Sukrit seeks to obtain the critical measurements of fundamental photochemical parameters required to build robust models in support of both goals.
Dr. Kathryn Volk, Vera Rubin Early Career Prize Winner
LPL Research Scientist Dr. Kathryn Volk has been named the recipient of the Vera Rubin Early Career Prize, which recognizes an early career dynamicist who demonstrates excellence in scientific research in dynamical astronomy. Dr. Volk received her Ph.D. from LPL in 2013.
The American Astronomical Society’s Division on Dynamical Astronomy (DDA) is pleased to announce that the 2022 recipient of the Vera Rubin Early Career Award is Dr. Kathryn Volk of the University of Arizona, for her work on both the dynamics of small bodies beyond Neptune, and the long-term dynamics and stability of tightly packed exoplanetary systems.
Dr. Volk earned her Ph.D. from the University of Arizona in 2013 under the direction of Prof. Renu Malhotra, then held a postdoctoral fellowship at the University of British Columbia before returning to the University of Arizona, first as a postdoctoral associate and later as an Associate Staff Scientist. Her numerous contributions span both Solar System and exoplanetary science, powerfully bringing together theory, numerics and observation.
Orbital migration of the giant planets early in the Solar System’s history can explain various small-body populations in the outer Solar System. In particular, groups of trans-Neptunian objects (TNOs) captured into different mean motion resonances with Neptune are natural consequences of the latter migrating outward, and close encounters with Neptune are thought to be responsible for the dynamically excited scattered disk. Dr. Volk has made fundamental contributions both to the observational characterization of these small-body populations through her core role in the Outer Solar System Origins Survey, as well as to rigorously confronting this theoretical picture of the early Solar System against observations through her extensive numerical investigations. Her work has been influential in quantifying the rates at which Jupiter-family comets are generated from their hypothesized source in the scattered disk beyond Neptune, and in characterizing the underlying resonant TNO populations as observational anchors for theories of the early Solar System.
Dr. Volk has also significantly shaped the field of exoplanetary science. Her proposal that most planetary systems begin in compact configurations, which continually destabilize and rearrange throughout their lifetimes, has been highly influential, and she has made fundamental contributions to our understanding of the long-term dynamical stability of exoplanetary systems. In particular, her work demonstrates that the future lifetimes of mature exoplanet systems are set by slow chaotic diffusion induced by the overlap of secular (rather than mean-motion) resonances.
Finally, Dr. Volk has made central and persistent contributions to the division itself. Her leadership as Vice-Chair and then Chair of the DDA was instrumental through the COVID-19 pandemic. She was the principal force behind the restructuring and organization of the highly successful 2020 and 2021 meetings in a virtual format, not only maintaining the operations of the division, but also managing to grow and diversify the membership in the process.
Dr. Volk will be invited to give a lecture at the 54th annual DDA meeting in the spring of 2023.
NASA Gives Green Light for OSIRIS-REx Spacecraft to Visit Another Asteroid
The extended mission, dubbed OSIRIS-APEX, will study the near-Earth asteroid Apophis, which will have a close encounter with Earth in 2029.
By Mikayla Mace Kelley, University Communications - April 25, 2022
NASA's OSIRIS-REx spacecraft will swing by Earth to deliver a sample from asteroid Bennu on Sept. 24, 2023. But it won't clock out after that.
NASA has extended the University of Arizona-led mission, which will be renamed OSIRIS-APEX, to study near-Earth asteroid Apophis for 18 months. Apophis will make a close approach to Earth in 2029.
The University of Arizona will lead the mission, which will make its first maneuver toward Apophis 30 days after the OSIRIS-REx spacecraft delivers the sample it collected from Bennu back in October 2020. At that point, the original mission team will split – the sample analysis team will analyze the Bennu sample, while the spacecraft and instrument team transitions to OSIRIS-APEX, which is short for OSIRIS-Apophis Explorer.
Regents Professor of Planetary Sciences Dante Lauretta will remain principal investigator of OSIRIS-REx through the remaining two-year sample return phase of the mission. Planetary sciences assistant professor and OSIRIS-REx deputy principal investigator Dani DellaGiustina will then become principal investigator of OSIRIS-APEX. The extension adds another $200 million to the mission cost cap.
The mission team did an exhaustive search for potential asteroid targets. The OSIRIS-REx spacecraft was built for what's called a rendezvous mission, meaning instead of making a single flyby of an object and quickly snapping images and collecting data, it was designed to "get up close and personal with the object." DellaGiustina said. "Our spacecraft is really phenomenal at that."
"Apophis is one of the most infamous asteroids," DellaGiustina said. "When it was first discovered in 2004, there was concern that it would impact the Earth in 2029 during its close approach. That risk was retired after subsequent observations, but it will be the closest an asteroid of this size has gotten in the 50 or so years asteroids have been closely tracked, or for the next 100 years of asteroids we have discovered so far. It gets within one-tenth the distance between the Earth and moon during the 2029 encounter. People in Europe and Africa will be able to see it with the naked eye, that's how close it will get. We were stoked to find out the mission was extended."
OSIRIS-REx was launched in 2016 to collect a sample from Bennu that will help scientists learn about the formation of the solar system and Earth as a habitable planet. OSIRIS-REx is the first NASA mission to collect and return a sample from a near-Earth asteroid.
OSIRIS-APEX will not collect a sample, but when it reaches Apophis, it will study the asteroid for 18 months and collect data along the way. It also will make a maneuver similar to the one it made during sample collection at Bennu, by approaching the surface and firing its thrusters. This event will expose the asteroid's subsurface, to allow mission scientists to learn more about the asteroid's material properties.
The scientists also want to study how the asteroid will be physically affected by the gravitational pull of Earth as it makes its close approach in 2029.
They also want to learn more about the composition of the asteroid. Apophis is about the same size as Bennu – nearly 1000 feet at its longest point – but it differs in what's called its spectral type. Bennu is a B-type asteroid linked to carbonaceous chondrite meteorites, whereas Apophis is an S-type asteroid linked to ordinary chondrite meteorites.
"The OSIRIS-REx mission has already achieved so many firsts and I am proud it will continue to teach us about the origins of our solar system," said University of Arizona President Robert C. Robbins. "The OSIRIS-APEX mission extension keeps the University of Arizona in the lead as one of the premier institutions in the world to study small bodies with spacecraft and demonstrates again our incredible capacity in space sciences."
DellaGiustina is also excited that the mission provides an excellent opportunity for early career scientists to gain professional development. OSIRIS-REx veterans will work closely with these early career scientists as mentors in the early mission phases. By the time the spacecraft arrives at Apophis, the next generation will step into leadership roles on OSIRIS-APEX.
"OSIRIS-APEX is a manifestation of a core objective of our mission to enable the next generation of leadership in space exploration. I couldn't be prouder of Dani and the APEX team," Lauretta said. "Dani first started working with us in 2005 as an undergraduate student. To see her take on the leadership of the mission to asteroid Apophis demonstrates the outstanding educational opportunities at the University of Arizona."
Small but Mighty: How UArizona Professors are Harnessing the Power of Algae to Capture Carbon
An astrobiologist, an engineer and an ecologist have teamed up to mitigate the worst effects of climate change.
By Mikayla Mace Kelley, University Communications - April 20, 2022
As a University of Arizona professor of astronomy and planetary sciences who studies planets orbiting other stars, Daniel Apai spends much of his time thinking about what makes worlds habitable.
On Earth, the carbon cycle plays a key role in maintaining conditions for life. Earth releases carbon into the atmosphere and reabsorbs it through geological and biological processes. But humans have released more carbon dioxide into the atmosphere than the carbon cycle naturally would, causing global temperatures to rise.
Apai has assembled a team that plans to harness the principles of the carbon cycle to trap massive amounts of carbon dioxide and curb the worst impacts of climate change.
They call themselves Atmospherica. In addition to Apai, the team includes Joel Cuello, a professor of agricultural and biosystems engineering and BIO5 Institute member; Régis Ferrière, an associate professor of ecology and evolutionary biology; Martin Schlecker, an astrophysicist and postdoctoral research associate; and Jack Welchert, a biosystems engineering doctoral student.
Reports from the Intergovernmental Panel on Climate Change and future climate projections find that preventing the worst effects of climate change will require carbon removal from the atmosphere at gigaton-per-year levels.
"Yet, no existing technology is thought to be scalable enough to succeed in this," Apai said. "What we need to do as a civilization is to reduce our emissions as much as possible, because extracting from the air is much more difficult than not emitting it. No one has come up with a solution that extracts carbon dioxide so efficiently as to allow the continued burning of fossil fuels."
The Atmospherica team team hopes to be a part of the solution, by harnessing the power of algae.
It's all in the algae
"Climate change is one of the great challenges we are facing as a species and civilization," Apai said.
He began the search for potential climate change solutions as a hobby seven years ago. He found that most existing carbon removal solutions could not be scaled up to the levels required, were prohibitively expensive or were harmful to the environment.
As an astrobiologist, he decided to pursue solutions inspired by nature. That's when he learned about coccolithophores – single-celled marine algae. What makes these algae special is the fact that they use atmospheric carbon dioxide and calcium from saltwater to create intricate shells made of calcium carbonate – a very stable, chalk-like mineral. These shells evolved to protect the algae and regulate the algae's buoyancy and light exposure.
Coccolithophores naturally extract carbon dioxide from the ocean as part of their life cycle. While most of them are consumed by predators, a very small fraction decompose, uneaten, while their carbon-containing shells sink to the ocean floor, where they remain indefinitely. The White Cliffs of Dover on the English coastline are huge 90-million-year-old deposits of these shells and demonstrate their incredible stability.
Apai wondered if it would be possible to grow coccolithophores on a large enough scale to change Earth's atmospheric composition. To do this would require a safe and controlled environment for the algae to grow.
Enter the air accordion
Cuello and his Biosystems Engineering Lab have developed a portfolio of patented low-cost novel photobioreactors in which to grow algae and other types of cell cultures in an efficient and productive way. One of the designs is the air accordion photobioreactor. Photobioreactor
The air accordion photobioreactor consists of a rectangular metal frame with horizontal bars – like steps on a ladder – spaced closer together at the bottom and farther apart at the top. A polyethylene bag full of nutrient-rich saltwater is woven throughout this ladder-like frame. Air is pumped in from the bottom and circulated through the saltwater mixture. The design maximizes the liquid-mixing capacity of air bubbles pumped in from the bottom and allows for even distribution of light and dissolved nutrients.
The photobioreactor make it possible to efficiently grow large amounts of algae. And because the algae is grown in a controlled environment, within the polyethylene bag, it is protected from predators. The researchers say their air accordion photobioreactor is also easy to scale up.
Cuello and Apai patented the use of coccolithophore algae for carbon dioxide removal in this kind of photobioreactor, and they hope to continue to optimize the design for even more efficient coccolithophore growth and carbon uptake.
"Our goal is to reach a gigaton-per-year level of carbon dioxide extraction capacity, while remaining affordable and with very limited environmental impact," Apai said.
The researchers hope the photobioreactors can be made even more sustainable in the future. They envision a world in which solar-powered bioreactors would be located by the ocean, allowing for easy access to the seawater required to help the coccolithophores grow. Even better, the researchers say, would be to establish the photobioreactors near desalination plants, which produce calcium as a waste product. Calcium is an important nutrient for coccolithophores and is used in the saltwater mixture.
The team hopes the design offers a viable solution for carbon removal that overcomes some of the limitations of existing technologies, such as chemical filtration techniques, which are difficult to scale up because they are energy intensive and often require rare minerals. They also can produce environmentally harmful waste products.
To ensure that their method is scalable and confirm how much net carbon dioxide it pulls from the atmosphere, members of the Atmospherica team plan to build a demonstration facility in a greenhouse atop the university's Sixth Street Garage and a larger facility at the university's Biosphere 2 research facility.
They also plan to "do a full accounting of its carbon footprint, from cradle to grave," Apai said.
"We have completed a promising exploratory analysis and plan to publish a paper on the subject this summer," Apai said.
The team is also aiming to keep the cost of carbon removal to less than $100 per ton extracted.
"Anything more expensive is not viable," Apai said.
The urgency
Apai stressed that even if we can transition most industries efficiently toward zero emissions, for a few decades we will still end up producing about 15% of our current emissions, or about 6 billion tons of carbon dioxide annually. That's partly because things like large airplanes and cargo ships rely on fossil fuels that pack a lot of energy in a small volume. They physically cannot be battery powered.
That remaining 6 billion tons of carbon dioxide is what Atmospherica hopes the coccolithophores can successfully absorb.
"Our governments have delayed action so much that we now need to be successful on both counts: building a sustainable future and fixing the damage we keep doing in the meantime," Ferrière said. "With its emphasis on resilience science, our university and its international partners are committed to advance the interdisciplinary research that will solve this grand challenge."
Dr. Tyler Robinson Joins LPL Faculty Starting Fall 2022
Ty conducts theoretical studies of the atmospheres of extrasolar planets and brown dwarfs and has made major contributions to the planning for the next NASA great observatories. He has had great success in building diverse research groups.
Dr. Tyler Robinson will join LPL as an associate professor. He is an alumnus of the University of Arizona, earning a B.S. in Physics and Mathematics in 2006. He completed a Ph.D. in Astronomy and Astrobiology from the University of Washington in 2012. Ty held prestigious postdoctoral positions as a NASA Postdoctoral Program Fellow at NASA Ames Research Center and as a Sagan Fellow at the University of California, Santa Cruz, and is a Cottrell Scholar (Research Corporation for Science and Advancement).
Dr. Robinson uses sophisticated radiative transfer and climate tools to study the atmospheres of Solar System worlds, exoplanets, and brown dwarfs. He also develops instrument models for exoplanet direct imaging. He combines these areas of expertise in his work on the Habitable Exoplanet Observatory (HabEx) Science and Technology Definition Team, and in his contributions to the LUVOIR, WFIRST/Rendezvous, and Origins Space Telescope mission concept studies.
UArizona to Help NASA Understand Solar Wind and Plasma With HelioSwarm Mission
Most visible matter in the universe exists as plasma, and NASA has funded a new mission to study this state of matter that's rarely found on Earth.
By Mikayla Mace Kelley, University Communications - March 2, 2022
Plasma is rare on Earth, but it fills the sky. From stars and nebulas to auroras at the poles and solar wind, plasma is the most common visible state of matter – the more familiar ones being liquid, gas and solid.
To more deeply understand this state of matter that makes up 99% of the visible universe, NASA has selected the HelioSwarm mission, an array – or "swarm" – of nine spacecraft, which is tentatively scheduled to launch in 2028 and collect data for at least one year. Kristopher Klein, University of Arizona assistant professor of planetary sciences in the Lunar and Planetary Laboratory, will serve as the mission's deputy principal investigator.
Plasma is matter so incredibly hot that atoms are stripped of their electrons to create what's called ionized gas.
"This mission is leveraging the fact that we have a powerful source of plasma nearby – the sun – that we can use like a natural laboratory to understand this universal process," Klein said.
The sun's plasma is so superheated and energetic that it escapes the sun's gravity and rushes outward as solar wind.
The mission will provide scientists with data to study turbulence in the solar wind. As the solar wind expands to fill the heliosphere – the outermost atmosphere of the sun, which encompasses much of the solar system – it interacts with the magnetic fields of Earth and the sun, so the mission will study the interaction between these fields as well.
"Studying the interaction between the solar wind and Earth's magnetic field is important from a basic physics perspective, and it's also important to understand how energy moves through the system and evolves," Klein said. "And during periods of heightened solar activity, these processes also affect things like global positioning and communications satellites, other spacecraft and astronauts."
"As a species, we're launching more spacecrafts and are becoming more reliant on having more satellites for everyday activities, so understanding how to live with our star is important," he said.
Most of Klein's research is theoretical. He studies how energy moves through different kinds of plasma. With that background, Klein's role as mission deputy principal investigator is to ensure that the science questions can be answered with the instruments onboard the HelioSwarm spacecraft.
Klein has been involved in two other NASA missions to study the sun: the Wind Spacecraft and the Parker Solar Probe. Many other UArizona Lunar and Planetary Lab faculty will also provide support as the HelioSwarm mission progresses.
HelioSwarm is so named because rather than measuring the solar wind at a single point in space at a given time, the mission will consist of one hub spacecraft and eight co-orbiting small satellites, which will swing in large 14-day-long flower-petal-shaped orbits around Earth to allow for multiple measurements in many different configurations. At its farthest point in orbit, a satellite will reach 60 times the distance between Earth and the moon. The hub spacecraft will maintain radio contact with the other satellites, and radio contact between the swarm and Earth will be conducted through the hub spacecraft and the NASA Deep Space Network of spacecraft communication antennas.
The spacecrafts' ever-changing orbital patterns were intentionally designed to provide a more holistic picture of the solar wind as it evolves.
"Think about the solar wind like a waterfall," Klein said. "If you want to understand a waterfall, you have to measure at multiple points throughout its flow. There have been previous missions that have had a few spacecrafts providing multipoint measurement, but the dream is to have a set of spacecrafts that will be separated in such a way that some of them will be relatively close and others far. By doing that, we can measure both large- and small-scale physics at the same time and get a better understanding of how energy flows and evolves as it moves through the solar system."
The HelioSwarm mission's principal investigator is Harlan Spence from the University of New Hampshire. NASA's Alan Zide is the program executive. NASA's Ames Research Center in Silicon Valley, California, will provide project management. Funding and management oversight for the mission is provided by the Heliophysics Explorers Program, managed by the Explorers Program Office at NASA's Goddard Space Flight Center in Greenbelt, Maryland.
UArizona Students Confirm Errant Rocket's Chinese Origin, Track Lunar Collision Course
Students studying the object's composition confirmed that it is most likely a Chinese booster and not a SpaceX booster, as previously reported.
By Mikayla Mace Kelley, University Communications - February 15, 2022
The presumed SpaceX Falcon 9 rocket booster that's on a course to hit the moon March 4 is actually a Chinese booster from a rocket launch in 2014, a University of Arizona team has confirmed.
UArizona students in the university's Space Domain Awareness lab at the Lunar and Planetary Laboratory have had their eyes on the piece of space junk for weeks as they studied its rotation. They have been gathering other data as well, which they used to confirm its Chinese origin.
"We took a spectrum (which can reveal the material makeup of an object) and compared it with Chinese and SpaceX rockets of similar types, and it matches the Chinese rocket," said UArizona associate professor Vishnu Reddy, who co-leads the Space Domain Awareness lab with engineering professor Roberto Furfaro. "This is the best match, and we have the best possible evidence at this point."
Reddy and his students are providing observations to NASA's Jet Propulsion Laboratory to help pinpoint the location of the booster's upcoming impact on the moon, which could be imaged and verified by NASA's Lunar Reconnaissance Orbiter.
They estimate that it will hit somewhere in or near the Hertzsprung crater on the moon's far side. UArizona is the only public university that has a dedicated academic program for space domain awareness. UArizona's space science program was ranked No. 2 among public U.S. universities and No. 10 in the world in U.S. News & World Report's 2021 Best Global Universities rankings.
Based on its path through the sky, the booster was initially thought to be a SpaceX Falcon 9 rocket booster from a 2015 launch, with a trajectory that put it on a path to hit the moon. The unintentional impact of space junk on the moon is uncommon. But the rocket is now believed to be a booster for the Chang'e 5-T1, launched in 2014 as part of the Chinese space agency's lunar exploration program.
Using the RAPTORS system, a telescope atop the Kuiper Space Sciences building on campus, UArizona students took observations on the nights of Jan. 21 and Feb. 7, the latter of which was the last time the rocket would be visible before it hits the moon in March.
"I am astounded that we can tell the difference between the two rocket body options – SpaceX versus Chinese – and confirm which one will impact the moon with the data we have. The differences we see are primarily due to type of paint used by SpaceX and the Chinese," said Adam Battle, a graduate student studying planetary science. Battle has worked at the Space Domain Awareness lab since 2018 and focuses on spectroscopy, which helped confirm the booster's origins. An object's spectrum can also reveal the effects of space weathering.
"We don't often get a chance to track something we know is going to hit the moon ahead of time," said Tanner Campbell, an aerospace and mechanical engineering graduate student who has worked with Reddy since 2017. "There is particular interest in seeing how impacts produce craters. It's also interesting from an orbital prediction perspective, because it's traveling between the Earth and moon unpropelled. It's just an inert rocket body tossed around by its own energy and by solar radiation pressure, so we can evaluate our models and see how good our predictions are."
Campbell focused on photometry of the object, meaning he determined how fast it spins. Rocket bodies have a distinct pattern of brightness that makes them easily identifiable.
This booster is just one of many pieces of space junk that the UArizona team and others around the world are tracking. There are roughly 3,500 active satellites orbiting Earth, and another 20,000 pieces of debris or space junk, according to Reddy. There is significantly less space debris surrounding the moon, however.
"While this isn't the most detrimental impact, the idea of so many objects in space with unknown orbits and identities is worrying," said Grace Halferty, an undergraduate student double majoring in mechanical engineering and biology. She has, since September 2018, been studying SpaceX's Starlink satellites and their effect on ground-based astronomy. "We need better space traffic management."
"There are only a handful of objects in lunar orbit," Reddy said, "but I hope this event sheds light on the growing problem of space junk. This science community is concerned about the growing pollution."
The UArizona team has also tracked and identified many other humanmade objects as they travel across the sky.
- In 2018, the UArizona team used a $1,500 optical sensor they built in four months to track the defunct Chinese space station Tiangong-1 before it fell into the sea on March 31.
- In 2020, the team tracked a piece of an Atlas rocket that launched Surveyor 2 in 1966. Using spectroscopy, the team confirmed that it was what's called the "Centaur upper stage" – the part of the rocket that provides the in-space thrust to set the spacecraft on a precise trajectory toward the moon.
- In 2021, the team tracked the 22-ton Long March 5B rocket that launched China's Tianhe space station module into Earth's orbit before the rocket fell to Earth on May 8.
$7.5M Effort Seeks to Prevent Lunar Traffic Jams
University of Arizona researchers are developing ways to detect, characterize and track objects in cislunar space, or the space between Earth and the moon.
By Emily Dieckman, College of Engineering - February 14, 2022
The moon is top of mind for many national space programs and private companies, with some planning to send humans back to the lunar surface as early as 2025.
In advance, scientists are launching satellites and other payloads to orbit the moon. But so far, no one has kept track of just how many artificial objects are already up there, or where they are at any given moment. Without a way to keep track of traffic, the orbital space surrounding the moon could quickly grow crowded.
The Air Force Research Laboratory's Space Vehicles Directorate has tasked University of Arizona researchers with getting a handle on this impending lunar traffic jam, awarding them $7.5 million in funding.
"The University of Arizona has been a world leader in space exploration for decades, and our scientists were instrumental in mapping the surface of the moon for NASA's Apollo 11 mission in 1969," said University of Arizona President Robert C. Robbins. "We are now building upon this legacy to better understand and proactively address possible traffic congestion between Earth and the moon."
Principal investigators Roberto Furfaro, professor of systems and industrial engineering, and Vishnu Reddy, an associate professor in the College of Science's Lunar and Planetary Laboratory, are developing ways to detect, characterize and track objects in cislunar space, or the space between Earth and the moon.
"With projects like the Catalina Sky Survey and Near-Earth Object Surveyor mission, LPL is at the cutting edge of detecting and characterizing natural moving space objects such as asteroids," said Carmala Garzione, dean of the College of Science. "This team is drawing on decades of expertise to do the same for humanmade objects between Earth and the moon."
Getting ahead of potential problems
According to NASA, there are more than 23,000 cataloged objects orbiting Earth, and congestion is an increasing concern. In contrast, Furfaro and Reddy estimate there are just dozens of payloads orbiting the moon.
"The orbital space around the Earth is becoming extremely congested, so the Space Force and Air Force Research Laboratory are trying to get ahead of the problem around the moon," said Furfaro, who initiated a space domain awareness program at the university in 2015. "The University of Arizona and the Air Force Research Lab have been working together for years on space domain awareness. Now, we're taking the next step and expanding this awareness all the way to the moon."
While the team's prior Air Force collaborations focused on awareness of objects in geostationary range – approximately 36,000 miles out from the center of the Earth – this project extends to 437,700 miles away from Earth's center, and beyond.
Payloads launched into cislunar orbit are mostly self-reported, and they are not monitored by a central international agency. The UArizona team will create cyberinfrastructure to characterize and identify the objects, paving the way for a well-organized path to the moon. Reddy compared it to coming in on the ground floor of a new infrastructure plan. That is, they're not trying to increase the efficiency of roads, but are studying the early sources of traffic to better inform decision making before the roads even exist.
"University collaborations like this are key to the Space Force's goal of providing a safe and sustainable space ecosystem and developing a highly capable talent pool for the U.S. Space Force now and in the future," said Benjamin Seibert, Space Control Mission Area lead for the Air Force Research Laboratory, or AFRL. "Capabilities to detect, track and catalog objects from the Earth to the moon and beyond enable freedom of navigation critical to civil and commercial use of space. We are very excited to continue our collaborations with University of Arizona."
Tracking from a distance
Reddy and his students in the Lunar and Planetary Laboratory use dedicated sensors at the university's Biosphere 2 research facility to characterize objects in space. Their suite of equipment includes several telescopes dedicated to space domain awareness, including one built by a group of UArizona engineering undergraduates.
Tracking humanmade objects in cislunar space, rather than natural objects such as asteroids, comes with a unique set of challenges. Objects in cislunar space are harder to see, not only because they're farther away than objects orbiting Earth, but because they can be lost in the moon's glare.
"It's like tracking a firefly that's flying around a searchlight," said Reddy, who has pioneered the observational techniques to track cislunar objects.
Furfaro's background is in orbital mechanics and machine learning for artificial objects in space. While Reddy is concentrating on detection and tracking, Furfaro will create methods to analyze and catalog the data. The team will also partner with future missions sending objects into cislunar orbit, so new objects can be tracked and cataloged from the start of their journeys.
"Roberto (Furfaro) has earned a lot of recognition for his work – including being named the College of Engineering's 2020 da Vinci Fellow and having an asteroid named after him," said David W. Hahn, Craig M. Berge Dean of the College of Engineering. "He and Vishnu (Reddy) have worked together on several successful, high-profile projects. I'm confident they're the perfect people to lead this effort, and to place the University of Arizona at the forefront of cislunar space domain awareness."
It Takes a Special Kind of Planet to Make a Moon
Generally thought to be the products of celestial bodies crashing into each other, moons around terrestrial planets may play important roles in shaping the conditions for life to emerge. For sizable moons to form successfully, the circumstances must be just right, according to a study published in Nature Communications.
By University Communications - February 1, 2022
Based on analyses of lunar rock samples that Apollo and other space missions brought back to Earth, scientists know more about Earth's moon than any other planetary body. However, questions continue to vex scientists regarding how a planet forms a moon, and why some planets have moons while others do not.
In a new paper published in Nature Communications, researchers from the University of Rochester, University of Arizona and Tokyo Institute of Technology have made an important discovery that helps unravel the mysteries of the moon. The new study proposes that planets have to be of a certain makeup and within a limited mass range for moons to form.
"The question we set out to answer is: Can all planets form substantial moons?" said study co-author Erik Asphaug, a professor in UArizona Lunar and Planetary Laboratory.
As scientists continue to explore the possibility of other life in the universe, the research has important implications for determining the factors that make a planet habitable. A planet may not require a large moon to be habitable, but Earth's moon is vitally important in shaping life as we know it: It controls the length of the day and ocean tides, which affect the planet's biological cycles. The moon also contributes to Earth's climate by stabilizing its spin axis, offering an ideal environment for life to develop and evolve.
"By understanding moon formations, we have a better constraint on what to look for when searching for Earthlike planets," said lead study author Miki Nakajima, an assistant professor of Earth and environmental sciences at the University of Rochester. "We expect that exomoons (moons orbiting planets outside our solar system) should be everywhere, but so far we haven't confirmed any. Our constraints will be helpful for future observations."
Earth is the only known planet to host life and has a number of features that make it unique. These include active plate tectonics, a strong magnetic field and a moon that is quite large. More than a quarter of the size of Earth, the moon raises tides in the oceans that are important to life, so researchers have conjectured that a moon may be a potentially beneficial feature for harboring life on other planets.
It is generally accepted that Earth's large moon was generated by a collision between proto-Earth and another planet about 4.5 billion years ago. The collision resulted in the formation of a disc of mostly melted, partially vaporized rock that eventually became the moon.
To find out whether other planets can form similarly large moons, the researchers conducted 3D computer simulations, starting with a number of hypothetical planets of varying masses. The fledgling planets either had an architecture similar to Earth's – namely a mantle of rock and a core of iron – or they were icy planets in which the mantle is water ice and the core is rock.
They found that if the planet is too massive, giant impacts produce discs consisting entirely of vapor. This is because impacts between more massive planets are more energetic and happen at higher velocity. Over time, the vapor disc from such an impact cools, and liquid moonlets – the building blocks of moons – are formed.
"These growing moonlets experience a strong drag force as they plow through the vapor disc, which slows them down," Asphaug said. "Before long, they succumb to the gravity of the planet and fall into it, without making a moon."
Once the disc has cooled off and its vapor has begun to dissipate, moonlets face less drag and stand a better chance of growing into moons. However, by that time, a significant portion of them have been lost to the planet. The researchers conclude that a vapor-only disc is not capable of forming large moons. The disc has to start off initially low in vapor for the moonlets to grow without experiencing strong gas drag.
"Giant impacts work great at making moons, but only to a point," Asphaug said.
The results provide important guideposts for researchers studying planets in other solar systems, according to the authors. In particular, some planets are too massive to form a sizable moon. Computer simulations showed that rocky planets more than six times the mass of Earth – so-called super-Earths – end up with vapor-only discs, meaning that a large moon could not grow. The same is true for planets with a water-rich or icy composition whose mass exceeds that of Earth; they, too, will end up with vapor-only disks and no moon.
Thousands of exoplanets have been discovered, but astronomers have yet to definitively spot a moon orbiting a planet outside our solar system.
"We're still a long way off until we learn the different kinds of moons that orbit the exoplanets that are out there," Asphaug said.
"The exoplanet search has been focused on large planets, typically larger than 1.6 Earth radii (60% larger than Earth)," Nakajima said. "We are proposing that, instead, we should look at smaller planets because they are probably better candidates to host fractionally large moons."
The research is based on computer simulations that are the result of efforts since the 1980s to understand how Earth's moon formed as the result of a giant impact at the end of Earth’s formation, Asphaug said.
"Most of the focus so far has been on how the Earth's moon came to be, but we think the moon started off as a flying magma ocean, not mostly vapor,” he said, referring to the disc of molten rock around the early Earth. "These moonlets were able to accrete into the major body that we know and love."