Members Can Post Anonymously On This Site
Comet Fragment Slams into Jupiter
-
Similar Topics
-
By NASA
NASA, ESA, and M. Wong (University of California – Berkeley); Processing: Gladys Kober (NASA/Catholic University of America) This NASA Hubble Space Telescope image shows the planet Jupiter in a color composite of ultraviolet wavelengths. Released on Nov. 3, 2023, in honor of Jupiter reaching opposition, which occurs when the planet and the Sun are in opposite sides of the sky, this view of the gas giant planet includes the iconic, massive storm called the “Great Red Spot.” Though the storm appears red to the human eye, in this ultraviolet image it appears darker because high altitude haze particles absorb light at these wavelengths. The reddish, wavy polar hazes are absorbing slightly less of this light due to differences in either particle size, composition, or altitude.
Learn more about Hubble and how this type of data can help us learn more about our universe.
Image credit: NASA, ESA, and M. Wong (University of California – Berkeley); Processing: Gladys Kober (NASA/Catholic University of America)
View the full article
-
By NASA
On Jan. 7, 1610, Italian astronomer Galileo Galilei peered through his newly improved 20-power homemade telescope at the planet Jupiter. He noticed three other points of light near the planet, at first believing them to be distant stars. Observing them over several nights, he noted that they appeared to move in the wrong direction with regard to the background stars and they remained in Jupiter’s proximity but changed their positions relative to one another. Four days later, he observed a fourth point of light near the planet with the same unusual behavior. By Jan. 15, Galileo correctly concluded that he had discovered four moons orbiting around Jupiter, providing strong evidence for the Copernican theory that most celestial objects did not revolve around the Earth.
Two of Galileo’s telescopes.National Geographic. Painting by Giuseppe Bertini (1858) of Galileo demonstrating his telescope to the Doge of Venice.gabrielevanin.it Page from Galileo’s notebook about his observations of Jupiter’s satellites.University of Michigan Special Collections Library. In March 1610, Galileo published his discoveries of Jupiter’s satellites and other celestial observations in a book titled Siderius Nuncius (The Starry Messenger). As their discoverer, Galileo had naming rights to Jupiter’s satellites. He proposed to name them after his patrons the Medicis and astronomers called them the Medicean Stars through much of the seventeenth century, although in his own notes Galileo referred to them by the Roman numerals I, II, III, and IV, in order of their distance from Jupiter. Astronomers still refer to the four moons as the Galilean satellites in honor of their discoverer.
In 1614, the German astronomer Johannes Kepler suggested naming the satellites after mythological figures associated with Jupiter, namely Io, Europa, Ganymede, and Callisto, but his idea didn’t catch on for more than 200 years. Scientists didn’t discover any more satellites around Jupiter until 1892 when American astronomer E.E. Barnard found Jupiter’s fifth moon Amalthea, much smaller than the Galilean moons and orbiting closer to the planet than Io. It was the last satellite in the solar system found by visual observation – all subsequent discoveries occurred via photography or digital imaging. As of today, astronomers have identified 95 moons orbiting Jupiter.
Image of Jupiter and three of its four Galilean satellites through an amateur telescope, similar to what Galileo might have seen. Hubble Space Telescope image of Jupiter and three of its four Galilean satellites during a rare triple transit. Although each of the Galilean satellites has unique features, such as the volcanoes of Io, the heavily cratered surface of Callisto, and the magnetic field of Ganymede, scientists have focused more attention on Europa due to the tantalizing possibility that it might be hospitable to life. In the 1970s, NASA’s Pioneer 10 and 11 and Voyager 1 and 2 spacecraft took ever increasingly detailed images of the large satellites including Europa during their flybys of Jupiter. The photographs revealed Europa to have the smoothest surface of any object in the solar system, indicating a relatively young crust, and also one of the brightest of any satellite indicating a highly reflective surface. These features led scientists to hypothesize that Europa is covered by an icy crust floating on a subsurface salty ocean. They further postulated that tidal heating caused by Jupiter’s gravity reforms the surface ice layer in cycles of melting and freezing.
Image of Europa taken by Pioneer 10 during its flyby of Jupiter in 1973. Image of Europa taken by Voyager 1 during its 1979 flyby of Jupiter. Image of Europa taken by Voyager 2 during its 1979 flyby of Jupiter. More detailed observations from NASA’s Galileo spacecraft that orbited Jupiter between 1995 and 2003 and completed 11 close encounters with Europa revealed that long linear features on its surface may indicate tidal or tectonic activity. Reddish-brown material along the fissures and in splotches elsewhere on the surface may contain salts and sulfur compounds transported from below the crust and modified by radiation. Observations from the Hubble Space Telescope and re-analysis of images from Galileo revealed possible plumes emanating from beneath Europa’s crust, lending credence to that hypothesis. While the exact composition of this material is not known, it likely holds clues to whether Europa may be hospitable to life.
Global view of Europa from the Galileo spacecraft. More detailed views of varied terrain on Europa from Galileo. Cutaway illustration of Europa’s icy crust, subsurface ocean and possible vents that transport material to the surface. Future robotic explorers of Europa may answer some of the outstanding questions about this unique satellite of Jupiter. NASA’s Europa Clipper set off in October 2024 on a 5.5-year journey to Jupiter. After its arrival in 2030, the spacecraft will enter orbit around the giant planet and conduct 49 flybys of Europa during its four-year mission. Managed by the Jet Propulsion Laboratory in Pasadena, California, and the Applied Physics Laboratory at Johns Hopkins University in Baltimore, Maryland, Europa Clipper will carry nine instruments including imaging systems and a radar to better understand the structure of the icy crust. Data from Europa Clipper will complement information returned by the European Space Agency’s JUICE (Jupiter Icy Moon Explorer) spacecraft. Launched in April 2023, JUICE will first enter orbit around Jupiter in 2031 and then enter orbit around Ganymede in 2034. The spacecraft also plans to conduct studies of Europa complementary with Europa Clipper’s. The two spacecraft should greatly increase our understanding of Europa and perhaps uncover new mysteries.
Illustration of the Europa Clipper spacecraft investigating Europa. Illustration of the JUICE spacecraft exploring Europa.European Space Agency. View the full article
-
By Amazing Space
Winter Sky Guide: Orion, Pleiades & Jupiter Alignment | Meteor Shower Captured! Stargazing
-
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
2024-178
Share
Details
Last Updated Dec 20, 2024 Related Terms
Dawn Asteroids Ceres Jet Propulsion Laboratory Vesta Explore More
5 min read Avalanches, Icy Explosions, and Dunes: NASA Is Tracking New Year on Mars
Article 1 hour ago 5 min read Cutting-Edge Satellite Tracks Lake Water Levels in Ohio River Basin
Article 3 days ago 5 min read NASA Mars Orbiter Spots Retired InSight Lander to Study Dust Movement
Article 4 days ago Keep Exploring Discover More Topics From NASA
Missions
Humans in Space
Climate Change
Solar System
View the full article
-
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
View the full article
-
-
Check out these Videos
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.