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By NASA
1 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
NASA Glenn employees donated 11 boxes of new, unwrapped gifts to the Toys for Tots program. Credit: NASA/Sara Lowthian-Hanna NASA’s Glenn Research Center continued a decades-long tradition of participating in the Marine Corps Reserve Toys for Tots program during the 2024 holiday season. On Dec. 9, members of the Marine Corps Reserve (3rd Battalion, 25th Marines) picked up 11 boxes of toys donated by employees from NASA Glenn’s facilities in Cleveland and Sandusky, Ohio.
Marine Corps representatives stand at far left and far right of NASA Glenn’s Associate Director Larry Sivic, left, Center Director Dr. Jimmy Kenyon, center, and Acting Deputy Director Dr. Wanda Peters. Credit: NASA/Sara Lowthian-Hanna The Glenn Veterans Employee Resource Group led the donation drive. The Toys for Tots campaign collects and distributes new, unwrapped toys to less fortunate children in the area for Christmas.
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By European Space Agency
A study using data from ESA’s Swarm mission suggests that faint magnetic signatures created by Earth’s tides can help us determine magma distribution under the seabed and could even give us insights into long-term trends in global ocean temperatures and salinity.
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By NASA
This artist’s concept shows interstellar object 1I/2017 U1 (‘Oumuamua) after its discovery in 2017. While itself not a dark comet, ‘Oumuamua’s motion through the solar system has helped researchers better understand the nature of the 14 dark comets discovered so far.European Southern Observatory / M. Kornmesser These celestial objects look like asteroids but act like comets now come in two flavors.
The first dark comet — a celestial object that looks like an asteroid but moves through space like a comet — was reported less than two years ago. Soon after, another six were found. In a new paper, researchers announce the discovery of seven more, doubling the number of known dark comets, and find that they fall into two distinct populations: larger ones that reside in the outer solar system and smaller ones in the inner solar system, with various other traits that set them apart.
The findings were published on Monday, Dec. 9, in the Proceedings of the National Academy of Sciences.
Scientists got their first inkling that dark comets exist when they noted in a March 2016 study that the trajectory of “asteroid” 2003 RM had moved ever so slightly from its expected orbit. That deviation couldn’t be explained by the typical accelerations of asteroids, like the small acceleration known as the Yarkovsky effect.
“When you see that kind of perturbation on a celestial object, it usually means it’s a comet, with volatile material outgassing from its surface giving it a little thrust,” said study coauthor Davide Farnocchia of NASA’s Jet Propulsion Laboratory in Southern California. “But try as we might, we couldn’t find any signs of a comet’s tail. It looked like any other asteroid — just a pinpoint of light. So, for a short while, we had this one weird celestial object that we couldn’t fully figure out.”
Weird Celestial Objects
Farnocchia and the astronomical community didn’t have to wait long for another piece of the puzzle. The next year, in 2017, a NASA-sponsored telescope discovered history’s first documented celestial object that originated outside our solar system. Not only did 1I/2017 U1 (‘Oumuamua) appear as a single point of light, like an asteroid, its trajectory changed as if it were outgassing volatile material from its surface, like a comet.
“‘Oumuamua was surprising in several ways,” said Farnocchia. “The fact that the first object we discovered from interstellar space exhibited similar behaviors to 2003 RM made 2003 RM even more intriguing.”
By 2023, researchers had identified seven solar system objects that looked like asteroids but acted like comets. That was enough for the astronomical community to bestow upon them their own celestial object category: “dark comets.” Now, with the finding of seven more of these objects, researchers could start on a new set of questions.
“We had a big enough number of dark comets that we could begin asking if there was anything that would differentiate them,” said Darryl Seligman, a postdoctoral fellow in the department of Physics at Michigan State University, East Lansing, and lead author of the new paper. “By analyzing the reflectivity,” or albedo, “and the orbits, we found that our solar system contains two different types of dark comets.”
Two Kinds of Dark Comets
The study’s authors found that one kind, which they call outer dark comets, have similar characteristics to Jupiter-family comets: They have highly eccentric (or elliptical) orbits and are on the larger side (hundreds of meters or more across).
The second group, inner dark comets, reside in the inner solar system (which includes Mercury, Venus, Earth, and Mars), travel in nearly circular orbits, and are on the smaller side (tens of meters or less).
Like so many astronomical discoveries, Seligman and Farnocchia’s research not only expands on our knowledge of dark comets, but it also raises several additional questions: Where did dark comets originate? What causes their anomalous acceleration? Could they contain ice?
“Dark comets are a new potential source for having delivered the materials to Earth that were necessary for the development of life,” said Seligman. “The more we can learn about them, the better we can understand their role in our planet’s origin.”
For more information about asteroids and comets, visit:
https://www.jpl.nasa.gov/topics/asteroids/
Small Body Research at JPL NASA Learns More About Interstellar Visitor 'Oumuamua Lesson: Comet on a Stick News Media Contacts
Ian J. O’Neill
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-2649
ian.j.oneill@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
Bethany Mauger
Michigan State University, East Lansing
maugerbe@msu.edu
2024-168
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Last Updated Dec 09, 2024 Related Terms
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By NASA
2 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
ESI24 Haghighi Quadchart
Azadeh Haghighi
University of Illinois, Chicago
In-space manufacturing and assembly are vital to NASA’s long-term exploration goals, especially for the Moon and Mars missions. Deploying welding technology in space enables the assembly and repair of structures, reducing logistical burdens and supply needs from Earth. The unique challenges and extreme conditions of space–high thermal variations, microgravity, and vacuum–require advanced welding techniques and computational tools to ensure reliability, repeatability, safety, and structural integrity in one-shot weld scenarios. For the first time, this project investigates these challenges by focusing on three key factors: (1) Very low temperatures in space degrade the weldability of high thermal conductivity materials, like aluminum alloys, making it harder to achieve strong, defect-free welds. (2) The extreme vacuum in space lowers the boiling points of alloying elements, altering the keyhole geometry during welding. This selective vaporization changes the weld’s final chemical composition, affecting its microstructure and properties. (3) Microgravity nearly eliminates buoyancy-driven flow of liquid metal inside the molten pool, preventing gas bubbles from escaping, which leads to porosity and defects in the welds. By examining these critical factors using multi-scale multi-physics models integrated with physics-informed machine learning, and forward/inverse uncertainty quantification techniques, this project provides the first-ever real-time digital twin platform to evaluate welding processes under extreme space/lunar conditions. The models are validated through Earth-based experiments, parabolic flight tests, and publicly available data from different databases and agencies worldwide. Moreover, the established models will facilitate extendibility to support in-situ resource utilization on the Moon, including construction and repair using locally sourced materials like regolith. The established fundamental scientific knowledge will minimize trial-and-error, enable high-quality one-shot welds in space, and reduce the need for reworks, significantly reducing the costs and time needed for space missions.
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