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By NASA
NASA’s Dawn spacecraft captured this image of Vesta as it left the giant asteroid’s orbit in 2012. The framing camera was looking down at the north pole, which is in the middle of the image.NASA/JPL-Caltech/UCLA/MPS/DLR/IDA Known as flow formations, these channels could be etched on bodies that would seem inhospitable to liquid because they are exposed to the extreme vacuum conditions of space.
Pocked with craters, the surfaces of many celestial bodies in our solar system provide clear evidence of a 4.6-billion-year battering by meteoroids and other space debris. But on some worlds, including the giant asteroid Vesta that NASA’s Dawn mission explored, the surfaces also contain deep channels, or gullies, whose origins are not fully understood.
A prime hypothesis holds that they formed from dry debris flows driven by geophysical processes, such as meteoroid impacts, and changes in temperature due to Sun exposure. A recent NASA-funded study, however, provides some evidence that impacts on Vesta may have triggered a less-obvious geologic process: sudden and brief flows of water that carved gullies and deposited fans of sediment. By using lab equipment to mimic conditions on Vesta, the study, which appeared in Planetary Science Journal, detailed for the first time what the liquid could be made of and how long it would flow before freezing.
Although the existence of frozen brine deposits on Vesta is unconfirmed, scientists have previously hypothesized that meteoroid impacts could have exposed and melted ice that lay under the surface of worlds like Vesta. In that scenario, flows resulting from this process could have etched gullies and other surface features that resemble those on Earth.
To explore potential explanations for deep channels, or gullies, seen on Vesta, scientists used JPL’s Dirty Under-vacuum Simulation Testbed for Icy Environments, or DUSTIE, to simulate conditions on the giant asteroid that would occur after meteoroids strike the surface.NASA/JPL-Caltech But how could airless worlds — celestial bodies without atmospheres and exposed to the intense vacuum of space — host liquids on the surface long enough for them to flow? Such a process would run contrary to the understanding that liquids quickly destabilize in a vacuum, changing to a gas when the pressure drops.
“Not only do impacts trigger a flow of liquid on the surface, the liquids are active long enough to create specific surface features,” said project leader and planetary scientist Jennifer Scully of NASA’s Jet Propulsion Laboratory in Southern California, where the experiments were conducted. “But for how long? Most liquids become unstable quickly on these airless bodies, where the vacuum of space is unyielding.”
The critical component turns out to be sodium chloride — table salt. The experiments found that in conditions like those on Vesta, pure water froze almost instantly, while briny liquids stayed fluid for at least an hour. “That’s long enough to form the flow-associated features identified on Vesta, which were estimated to require up to a half-hour,” said lead author Michael J. Poston of the Southwest Research Institute in San Antonio.
Launched in 2007, the Dawn spacecraft traveled to the main asteroid belt between Mars and Jupiter to orbit Vesta for 14 months and Ceres for almost four years. Before ending in 2018, the mission uncovered evidence that Ceres had been home to a subsurface reservoir of brine and may still be transferring brines from its interior to the surface. The recent research offers insights into processes on Ceres but focuses on Vesta, where ice and salts may produce briny liquid when heated by an impact, scientists said.
Re-creating Vesta
To re-create Vesta-like conditions that would occur after a meteoroid impact, the scientists relied on a test chamber at JPL called the Dirty Under-vacuum Simulation Testbed for Icy Environments, or DUSTIE. By rapidly reducing the air pressure surrounding samples of liquid, they mimicked the environment around fluid that comes to the surface. Exposed to vacuum conditions, pure water froze instantly. But salty fluids hung around longer, continuing to flow before freezing.
The brines they experimented with were a little over an inch (a few centimeters) deep; scientists concluded the flows on Vesta that are yards to tens of yards deep would take even longer to refreeze.
The researchers were also able to re-create the “lids” of frozen material thought to form on brines. Essentially a frozen top layer, the lids stabilize the liquid beneath them, protecting it from being exposed to the vacuum of space — or, in this case the vacuum of the DUSTIE chamber — and helping the liquid flow longer before freezing again.
This phenomenon is similar to how on Earth lava flows farther in lava tubes than when exposed to cool surface temperatures. It also matches up with modeling research conducted around potential mud volcanoes on Mars and volcanoes that may have spewed icy material from volcanoes on Jupiter’s moon Europa.
“Our results contribute to a growing body of work that uses lab experiments to understand how long liquids last on a variety of worlds,” Scully said.
Find more information about NASA’s Dawn mission here:
https://science.nasa.gov/mission/dawn/
News Media Contacts
Gretchen McCartney
Jet Propulsion Laboratory, Pasadena, Calif.
818-287-4115
gretchen.p.mccartney@jpl.nasa.gov
Karen Fox / Molly Wasser
NASA Headquarters, Washington
202-358-1600
karen.c.fox@nasa.gov / molly.l.wasser@nasa.gov
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Last Updated Dec 20, 2024 Related Terms
Dawn Asteroids Ceres Jet Propulsion Laboratory Vesta Explore More
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By NASA
Download PDF: Statistical Analysis Using Random Forest Algorithm Provides Key Insights into Parachute Energy Modulator System
Energy modulators (EM), also known as energy absorbers, are safety-critical components that are used to control shocks and impulses in a load path. EMs are textile devices typically manufactured out of nylon, Kevlar® and other materials, and control loads by breaking rows of stitches that bind a strong base webbing together as shown in Figure 1. A familiar EM application is a fall-protection harness used by workers to prevent injury from shock loads when the harness arrests a fall. EMs are also widely used in parachute systems to control shock loads experienced during the various stages of parachute system deployment.
Random forest is an innovative algorithm for data classification used in statistics and machine learning. It is an easy to use and highly flexible ensemble learning method. The random forest algorithm is capable of modeling both categorical and continuous data and can handle large datasets, making it applicable in many situations. It also makes it easy to evaluate the relative importance of variables and maintains accuracy even when a dataset has missing values.
Random forests model the relationship between a response variable and a set of predictor or independent variables by creating a collection of decision trees. Each decision tree is built from a random sample of the data. The individual trees are then combined through methods such as averaging or voting to determine the final prediction (Figure 2). A decision tree is a non-parametric supervised learning algorithm that partitions the data using a series of branching binary decisions. Decision trees inherently identify key features of the data and provide a ranking of the contribution of each feature based on when it becomes relevant. This capability can be used to determine the relative importance of the input variables (Figure 3). Decision trees are useful for exploring relationships but can have poor accuracy unless they are combined into random forests or other tree-based models.
The performance of a random forest can be evaluated using out-of-bag error and cross-validation techniques. Random forests often use random sampling with replacement from the original dataset to create each decision tree. This is also known as bootstrap sampling and forms a bootstrap forest. The data included in the bootstrap sample are referred to as in-the-bag, while the data not selected are out-of-bag. Since the out-of-bag data were not used to generate the decision tree, they can be used as an internal measure of the accuracy of the model. Cross-validation can be used to assess how well the results of a random forest model will generalize to an independent dataset. In this approach, the data are split into a training dataset used to generate the decision trees and build the model and a validation dataset used to evaluate the model’s performance. Evaluating the model on the independent validation dataset provides an estimate of how accurately the model will perform in practice and helps avoid problems such as overfitting or sampling bias. A good model performs well on
both the training data and the validation data.
The complex nature of the EM system made it difficult for the team to identify how various parameters influenced EM behavior. A bootstrap forest analysis was applied to the test dataset and was able to identify five key variables associated with higher probability of damage and/or anomalous behavior. The identified key variables provided a basis for further testing and redesign of the EM system. These results also provided essential insight to the investigation and aided in development of flight rationale for future use cases.
For information, contact Dr. Sara R. Wilson. sara.r.wilson@nasa.gov
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By NASA
NASA’s Glenn Research Center leaders stand with Evening With the Stars presenters. Left to right: Tim Smith, Nikki Welch, Center Director Dr. Jimmy Kenyon, Acting Deputy Director Dr. Wanda Peters, and Carlos Garcia-Galan. Credit: NASA/Jef Janis NASA Glenn Research Center’s “An Evening With the Stars” showcased research and technology innovations that addressed this year’s theme, NASA Glenn’s Spotlight on the Stars: 10 Years and Counting. The event featured presentations from Glenn subject matter experts and a networking reception.
Held at Windows on the River near Cleveland’s historic waterfront on Nov. 20, the event attracted sponsors and guests from more than 50 companies, universities, and organizations eager to learn more about the center’s recent accomplishments.
Special guests Dennis Andersh, CEO and president of Parallax Advanced Research/Ohio Aerospace Institute; Terrence Slaybaugh, vice president of Sites and Infrastructure for JobsOhio; and Dr. Wanda Peters, NASA Glenn’s acting deputy director, provided remarks.
Center Director Dr. Jimmy Kenyon took the stage to welcome visitors and share some accomplishments from an exciting year at NASA Glenn. Kenyon then introduced the presenters – NASA’s stars of the evening – and their topics.
“I relish this evening each year because it spotlights what is most important to our success at NASA: our people,” Kenyon said.
Nikki Welch is the digital manager in the Office of Communications. In this role, she helps to tell the NASA Glenn story in engaging ways for Glenn’s hundreds of thousands of followers on social media. Welch shared details about her efforts and the importance of “Connecting People to the Mission.”
NASA Glenn Research Center’s Nikki Welch talks about connecting people to the NASA mission through storytelling. Credit: NASA/Jef Janis Tim Smith leads high-temperature alloy development at NASA Glenn and has led research that resulted in over a dozen research licenses and four commercial licenses. As one of the inventors of the metal alloy GRX-810, Smith shared information about Glenn’s “Super Alloy Achievements.”
NASA Glenn Research Center’s Tim Smith talks about NASA’s superalloy achievements. Credit: NASA/Jef Janis Carlos Garcia-Galan is the manager of the Orion program’s European Service Module Integration Office. This module, being provided by ESA (European Space Agency), is Orion’s powerhouse. Garcia-Galan shared information on the topic “Dreaming of Going to the Moon.”
NASA Glenn Research Center’s Carlos Garcia-Galan talks about the spacecraft that will bring humanity back to the Moon. Credit: NASA/Jef Janis Return to Newsletter Explore More
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By NASA
The NASA Ames Science Directorate recognizes the outstanding contributions of (pictured left to right) Maurice Valdez, Niki Parenteau, Dori Myer, and Judy Alfter. Their commitment to the NASA mission represents the entrepreneurial spirit, technical expertise, and collaborative disposition needed to explore this world and beyond.
Space Science and Astrobiology Star: Maurice Valdez
Maurice Valdez is a system administrator, supporting desktop systems and website development for the Space Science and Astrobiology Division. Maurice is recognized for his focus and commitment to supporting the division’s scientific productivity by keeping systems compliant and functioning. His can-do attitude makes him instrumental in the success of the team, whether he is finding new solutions for hybrid meetings, fixing equipment, patching systems, or troubleshooting issues.
Photo credit: Pacific Science Center Space Science and Astrobiology Star: Niki Parenteau
Niki Parenteau, a research scientist for the Exobiology Branch, embodies the true spirit of an interdisciplinary astrobiologist. She has applied her expertise to identify potential biosignatures of life on exoplanets and has taken a leading role in the project office for the development of the Habitable Worlds Observatory (HWO), where she facilitates collaborative efforts of Ames scientists across the division and shepherds the larger scientific community to enable observations of biosignatures with HWO.
Space Biosciences Star: Dori Myer
Archivist Dori Myer has made an outstanding contribution in the Flight Systems Implementation Branch’s multi-year effort to digitize and preserve institutional knowledge. Under her guidance, the records management team digitized tens of thousands of historical records, preserving the branch’s institutional knowledge for years to come. Her exceptional initiative and dedication have transformed our record management processes, ensuring the accessibility of NASA’s rich institutional knowledge while streamlining its access in the modern age.
Earth Science Star: Judy Alfter
Judy Alfter, a Deputy Project Manager in the Earth Science Project Office (ESPO), has excelled in her multi-faceted role during the field campaign for the Plankton, Aerosol, Cloud, ocean Ecosystem Post-launch Airborne eXperiment (PACE-PAX). Judy launched the deployment phase of PACE-PAX, leading the effort to set up Twin Otter flight operations at Marina Municipal Airport in California. Following this phase, she transitioned to Santa Barbara in California to support the mobilization of PACE-PAX ship operations and concluded deployment activities at NASA Armstrong Flight Research Center’s main campus as ESPO site manager for ER-2 flight operations.
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By NASA
ESA/Webb, NASA & CSA, P. Zeidler This new image of star cluster NGC 602, released on Dec. 17, 2024, combines data from NASA’s Chandra X-ray Observatory with a previously released image from the agency’s James Webb Space Telescope. Webb data provide the ring-like outline of the “wreath,” while X-rays from Chandra (red) show young, massive stars that are illuminating the wreath, sending high-energy light into interstellar space.
NGC 602 lies on the outskirts of the Small Magellanic Cloud, which is one of the closest galaxies to the Milky Way, about 200,000 light-years from Earth.
See another new, festive image: the “Christmas tree cluster.”
Image credit: X-ray: NASA/CXC; Infrared: ESA/Webb, NASA & CSA, P. Zeilder, E.Sabbi, A. Nota, M. Zamani; Image Processing: NASA/CXC/SAO/L. Frattare and K. Arcand
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