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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/
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Karen Fox / Molly Wasser
NASA Headquarters, Washington
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Last Updated Dec 20, 2024 Related Terms
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By NASA
NASA has taken a big step forward in how engineers will assemble and stack future SLS (Space Launch System) rockets for Artemis Moon missions inside the Vehicle Assembly Building (VAB) at the agency’s Kennedy Space Center in Florida.
The VAB’s High Bay 2 has been outfitted with new tooling to facilitate the vertical integration of the SLS core stage. That progress was on full display in mid-December when teams suspended the fully assembled core stage 225 feet in the air inside the high bay to complete vertical work before it is stacked on mobile launcher 1, allowing teams to continue solid rocket booster stacking simultaneously inside High Bay 3 for Artemis II.
The fully assembled SLS (Space Launch System) core stage for the Artemis II test flight is suspended 225 feet in the air inside the newly renovated High Bay 2 at Kennedy’s Vehicle Assembly Building. The core stage was lifted to enable engineers to complete work before it is stacked on mobile launcher 1 with other rocket elements. With the move to High Bay 2, technicians now have 360-degree tip to tail access to the core stage, both internally and externally.NASA With the move to High Bay 2, technicians with NASA and Boeing now have 360-degree tip to tail access to the core stage, both internally and externally. Michigan-based supplier Futuramic Tool and Engineering led the design and build of the Core Stage Vertical Integration Center tool that will hold the core stage in a vertical position.
“High Bay 2 tooling was originally scheduled to be complete for Artemis III. We had an opportunity to get it done earlier and that will put us in a good posture to complete work earlier than planned prior to moving the core stage for Artemis II into the full integrated stack over into in High Bay 3,” said Chad Bryant, deputy manager of the NASA SLS Stages Office. “This gives us an opportunity to go in and learn how to rotate, lift, and move the core stage into the high bay.”
This move also doubles the footprint of useable space within the VAB, giving engineers access to both High Bay 2 and High Bay 3 simultaneously, while also freeing up space at NASA’s Michoud Assembly Facility in New Orleans to continue work on the individual elements for future SLS core stages.
High Bay 2 has a long history of supporting NASA exploration programs: during Apollo, High Bay 2, one of four high bays inside the VAB, was used to stack the Saturn V rocket. During the Space Shuttle Program, the high bay was used for external tank checkout and storage and as an extra storage area for the shuttle.
Under the new assembly model beginning with Artemis III, all the major structures for the SLS core stage will continue to be fully produced and manufactured at NASA Michoud. Upon completion of manufacturing and thermal protection system application, the engine section will be shipped to Kennedy for final outfitting.
The 212-foot-tall SLS (Space Launch System) core stage for NASA Artemis II is seen being moved from a horizontal position to a vertical position in High Bay 2 at the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida. With the move to High Bay 2, NASA and Boeing technicians now have 360-degree access to the core stage both internally and externally. (NASA) “Core stage 3 marks a significant change in the way we build core stages,” said Steve Wofford, manager of the SLS Stages Office. “The vertical capability in High Bay 2 allows us to perform parallel processing from the top to bottom of the stage. It’s a much more efficient way to build core stages. This new capability will streamline final production efforts, allowing our team to have 360-degree access to the stage, both internally and externally.”
The fully assembled core stage for Artemis II arrived July 23, 2024, at Kennedy, where it remained horizontal inside the VAB transfer aisle until its recent lift into the newly outfitted high bay.
Teams at NASA Michoud are outfitting the remaining core stage elements for Artemis III and preparing to horizontally join them. The four RS-25 engines for the Artemis III mission are complete at NASA’s Stennis Space Center in Bay St. Louis, Mississippi, and will be transported to NASA Kennedy in 2025. Major core stage and exploration upper stage structures are in work at NASA Michoud for Artemis IV and beyond.
NASA is working to land the first woman, first person of color, and its first international partner astronaut on the Moon under Artemis. SLS is part of NASA’s backbone for deep space exploration, along with the Orion spacecraft, supporting ground systems, advanced spacesuits and rovers, the Gateway in orbit around the Moon, and commercial human landing systems. SLS is the only rocket that can send Orion, astronauts, and supplies to the Moon in a single launch.
News Media Contact
Jonathan Deal
Marshall Space Flight Center
Huntsville, Ala.
256-544-0034
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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/Kim Shiflett In this image from Dec. 11, 2024, the 212-foot-tall SLS (Space Launch System) core stage is lowered into High Bay 2 at the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida. With the move to High Bay 2, NASA and Boeing technicians now have 360-degree access to the core stage both internally and externally.
The Artemis II test flight, targeted for launch in 2026, will be NASA’s first mission with crew under the Artemis campaign. NASA astronauts Victor Glover, Christina Koch, and Reid Wiseman, as well as CSA (Canadian Space Agency) astronaut Jeremy Hansen, will go on a 10-day journey around the Moon and back.
Image credit: NASA/Kim Shiflett
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By NASA
Teams with NASA’s Exploration Ground Systems Program lift the agency’s SLS (Space Launch System) core stage for the Artemis II mission from horizonal to vertical inside the transfer aisle at the Vehicle Assembly building at NASA’s Kennedy Space Center in Florida on Tuesday, Dec. 10, 2024. The one-of-a kind lifting beam is designed to move the core stage from the transfer aisle to High Bay 2 where it will remain while teams stack the two solid rocket boosters for the SLS core stage. NASA/Adeline Morgan NASA’s SLS (Space Launch System) Moon rocket core stage is vertical in High Bay 2 on Tuesday, Dec. 10, 2024, inside the Vehicle Assembly Building at NASA’s Kennedy Space Center in Florida.
The core stage arrived on July 23 to NASA Kennedy, where it remained horizontal inside the facility’s transfer aisle. With the move to High Bay 2, technicians with NASA and Boeing now have 360-degree access to the core stage both internally and externally. The move also frees up more space in the transfer aisle to allow technicians to continue transporting and integrating two solid rocket boosters onto mobile launcher 1 in High Bay 3 for the Artemis II mission. Boeing and their sub-contractor Futuramic refurbished High Bay 2 to increase efficiencies while processing core stages for Artemis II and beyond.
During Apollo, technicians stacked the Saturn V rocket in High Bay 2. During the Space Shuttle Program, the high bay was used for external tank checkout and storage and as a contingency storage area for the shuttle. The Artemis II test flight will be NASA’s first mission with crew under the Artemis campaign, sending NASA astronauts Victor Glover, Christina Koch, and Reid Wiseman, as well as CSA (Canadian Space Agency) astronaut Jeremy Hansen, on a 10-day journey around the Moon and back.
Image credit: NASA/Adeline Morgan
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