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By NASA
Figure 1. An artist’s concept of the Van Allen belts with a cutaway section of the giant donuts of radiation that surround Earth. Image Credit: NASA Goddard Space Flight Center/Scientific Visualization Studio A new instrument is using advanced detection techniques and leveraging an orbit with specific characteristics to increase our understanding of the Van Allen belts—regions surrounding Earth that contain energetic particles that can endanger both robotic and human space missions. Recently, the instrument provided a unique view of changes to this region that were brought on by an intense magnetic storm in May 2024.
The discovery of the Van Allen radiation belts by the U.S. Explorer 1 mission in 1958 marked a prominent milestone in space physics and demonstrated that Earth’s magnetosphere efficiently accelerates and traps energetic particles. The inner belt contains protons in the MeV (million electric volt) to GeV (109 electric volt) range, and even higher concentrations of energetic electrons of 100s of keV (1000 electric volt) to MeV are found in both the inner belt and the outer belt.
The energetic electrons in these belts—also referred to as “killer electrons”—can have detrimental effects on spacecraft subsystems and are harmful to astronauts performing extravehicular activities. Understanding the source, loss, and varying concentrations of these electrons has been a longstanding research objective. High-energy resolution and clean measurements of these energetic electrons in space are required to further our understanding of their properties and enable more reliable prediction of their intensity.
Overcoming the challenges of measuring relativistic electrons in the inner belt
Measuring energetic electrons cleanly and accurately has been a challenge, especially in the inner belt, where MeV to GeV energy protons also exist. NASA’s Van Allen Probes, which operated from 2012 to 2019 in low inclination, geo-transfer-like orbits, showed that instruments traversing the heart of the inner radiation belt are subject to penetration by the highly energetic protons located in that region. The Relativistic Electron Proton Telescope (REPT) and the Magnetic Electron and Ion Spectrometer (MagEIS) instruments onboard the Van Allen Probes were heavily shielded but were still subject to inner-belt proton contamination.
To attempt to minimize these negative effects, a University of Colorado Boulder team led by Dr. Xinlin Li, designed the Relativistic Electron Proton Telescope integrated little experiment (REPTile)—a simplified and miniaturized version of REPT—to fly onboard the Colorado Student Space Weather Experiment (CSSWE). An effort supported by the National Science Foundation, the 3-Unit CSSWE CubeSat operated in a highly inclined low Earth orbit (LEO) from 2012 to 2014. In this highly inclined orbit, the spacecraft and the instruments it carried were only exposed to the inner-belt protons in the South Atlantic Anomaly (SAA) region where the Earth’s magnetic field is weaker, which greatly reduced the time that protons impacted the measurement of electrons.
REPTile’s success motivated a team, also led by Dr. Xinlin Li, to design REPTile-2—an advanced version of REPTile—to be hosted on the Colorado Inner Radiation Belt Experiment (CIRBE) mission. Like CSSWE, CIRBE operates in a highly inclined low-Earth orbit to ensure the exposure to damaging inner-belt protons is minimized. The team based the REPTile-2 design on REPTile but incorporated two additional technologies—guard rings and Pulse Height Analysis—to enable clean, high-energy-resolution measurements of energetic electrons, especially in the inner belt.
Figure 2: PI observing two engineers testing the interface between the CIRBE bus and REPTile-2 on September 29, 2021. Image Credit: Xinlin Li, University of Colorado Boulder As shown on the left in Figure 3, the field of view (FOV) of REPTile-2 is 51o. Electrons and protons enter the FOV and are measured when they reach a stack of silicon detectors where they deposit their energies. However, very energetic protons (energy greater than 60 MeV) could penetrate through the instrument’s tungsten and aluminum shielding and masquerade as valid particles, thus contaminating the intended measurements. To mitigate this contamination, the team designed guard rings that surround each detector. These guard rings are electronically separated from the inner active area of each detector and are connected by a separate electric channel. When the guard rings are triggered (i.e., hit by particles coming outside of the FOV), the coincident measurements are considered invalid and are discarded. This anti-coincidence technique enables cleaner measurements of particles coming through the FOV.
Figure 3. Left (adapted from Figure 1 of Khoo et al., 2022): Illustration of REPTile-2 front end with key features labeled; Right: REPTile-2 front end integrated with electronic boards and structures, a computer-aided design (CAD) model, and a photo of integrated REPTile-2. Image Credit: Xinlin Li, University of Colorado Boulder To achieve high energy resolution, the team also applied full Pulse Height Analysis (PHA) on REPTile-2. In PHA, the magnitude of measured charge in the detector is directly proportional to the energy deposited from the incident electrons. Unlike REPTile, which employed a simpler energy threshold discrimination method yielding three channels for the electrons, REPTile-2 offers enhanced precision with 60 energy channels for electron energies ranging from 0.25 – 6 MeV. The REPT instrument onboard the Van Allen Probes also employed PHA but while REPT worked very well in the outer belt, yielding fine energy resolution, it did not function as well in the inner belt since the instrument was fully exposed to penetrating energetic protons because it did not have the guard rings implemented.
Figure 4: The CIRBE team after a successful “plugs-out” test of the CIRBE spacecraft on July 21, 2022. During this test the CIRBE spacecraft successfully received commands from ground stations and completed various performance tests, including data transmission back to ground stations at LASP. Image Credit: Xinlin Li, University of Colorado Boulder CIRBE and REPTile-2 Results
CIRBE’s launch, secured through the NASA CubeSat Launch Initiative (CSLI), took place aboard SpaceX’s Falcon 9 rocket as part of the Transporter-7 mission on April 15, 2023. REPTile-2, activated on April 19, 2023, has been performing well, delivering valuable data about Earth’s radiation belt electrons. Many features of the energetic electrons in the Van Allen belts have been revealed for the first time, thanks to the high-resolution energy and time measurements REPTile-2 has provided.
Figure 5 shows a sample of CIRBE/REPTile-2 measurements from April 2024, and illustrates the intricate drift echoes or “zebra stripes” of energetic electrons, swirling around Earth in distinct bunches. These observations span a vast range across the inner and outer belts, encompassing a wide spectrum of energies and electron fluxes extending over six orders of magnitude. By leveraging advanced guard rings, Pulse Height Analysis (PHA), and a highly inclined LEO orbit, REPTile-2 is delivering unprecedented observations of radiation belt electrons.
Figure 5: Color-coded electron fluxes detrended between REPTile-2 measurements for a pass over the South Atlantic Anomaly region on April 24, 2023, and their average, i.e., the smoothed electron fluxes using a moving average window of ±19% in energy; Black curves plotted on top of the color-coded electron fluxes are contours of electron drift period in hr. The second horizontal-axis, L, represents the magnetic field line, which CIRBE crosses. The two radiation belts and a slot region in between are indicated by the red lines and arrow, respectively. Image Credit: Xinlin Li, University of Colorado Boulder In fact, the team recently announced that measurements from CIRBE/REPTile-2 have revealed a new temporary third radiation belt composed of electrons and sandwiched between the two permanent belts. This belt formed during the magnetic storm in May 2024, which was the largest in two decades. While such temporary belts have been seen after big storms previously, the data from CIRBE/REPTile-2 are providing a new viewpoint with higher energy resolution data than before. Scientists are currently studying the data to better understand the belt and how long it might stick around — which could be many months.
PROJECT LEAD
Dr. Xinlin Li, University of Colorado Laboratory for Atmospheric and Space Physics and Department of Aerospace Engineering Sciences.
SPONSORING ORGANIZATIONS
Heliophysics Flight Opportunities for Research & Technology (H-FORT) program, National Science Foundation
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Last Updated Sep 17, 2024 Related Terms
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By European Space Agency
Mars once hosted a lake larger than any on Earth. The broken-down and dried-up remnants of this ancient lakebed are shown here in amazing detail by ESA’s Mars Express.
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By NASA
6 min read
Preparations for Next Moonwalk Simulations Underway (and Underwater)
On Christmas Day in 1968, the three-man Apollo 8 crew of Frank Borman, Jim Lovell, and Bill Anders found a surprise in their food locker: a specially packed Christmas dinner wrapped in foil and decorated with red and green ribbons. Something as simple as a “home-cooked meal,” or as close as NASA could get for a spaceflight at the time, greatly improved the crew’s morale and appetite. More importantly, the meal marked a turning point in space food history.
The prime crew of the Apollo 8 lunar orbit mission pose for a portrait next to the Apollo Mission Simulator at the Kennedy Space Center (KSC). Left to right, they are James A. Lovell Jr., command module pilot; William A. Anders, lunar module pilot; and Frank Borman, commander.NASA On their way to the Moon, the Apollo 8 crew was not very hungry. Food scientist Malcolm Smith later documented just how little the crew ate. Borman ate the least of the three, eating only 881 calories on day two, which concerned flight surgeon Chuck Berry. Most of the food, Borman later explained, was “unappetizing.” The crew ate few of the compressed, bite-sized items, and when they rehydrated their meals, the food took on the flavor of their wrappings instead of the actual food in the container. “If that doesn’t sound like a rousing endorsement, it isn’t,” he told viewers watching the Apollo 8 crew in space ahead of their surprise meal. As Anders demonstrated to the television audience how the astronauts prepared a meal and ate in space, Borman announced his wish, that folks back on Earth would “have better Christmas dinners” than the one the flight crew would be consuming that day.1
If that doesn’t sound like a rousing endorsement, it isn’t.
Frank Borman
Apollo 8 Astronaut
Over the 1960s, there were many complaints about the food from astronauts and others working at the Manned Spacecraft Center (now NASA’s Johnson Space Center). After evaluating the food that the Apollo 8 crew would be consuming onboard their upcoming flight, Apollo 9 astronaut Jim McDivitt penciled a note to the food lab about his in-flight preferences. Using the back of the Apollo 8 crew menu, he directed them to decrease the number of compressed bite-sized items “to a bare minimum” and to include more meat and potato items. “I get awfully hungry,” he wrote, “and I’m afraid I’m going to starve to death on that menu.”2
In 1969, Rita Rapp, a physiologist who led the Apollo Food System team, asked Donald Arabian, head of the Mission Evaluation Room, to evaluate a four-day food supply used for the Apollo missions. Arabian identified himself as someone who “would eat almost anything. … you might say [I am] somewhat of a human garbage can.” But even he found the food lacked the flavor, aroma, appearance, texture, and taste he was accustomed to. At the end of his four-day assessment he concluded that “the pleasures of eating were lost to the point where interest in eating was essentially curtailed.”3
Food used on the Gemini-Titan IV flight. Packages include beef sandwich cubes, strawberry cereal cubes, dehydrated peaches, and dehydrated beef and gravy. A water gun on the Gemini spacecraft is used to reconstitute the dehydrated food and scissors are used to open the packaging.NASA Apollo 8 commander Frank Borman concurred with Arabian’s assessment of the Apollo food. The one item Borman enjoyed? It was the contents of the Christmas meal wrapped in ribbons: turkey and gravy. The Christmas dinner was so delicious that the crew contacted Houston to inform them of their good fortune. “It appears that we did a great injustice to the food people,” Lovell told capsule communicator (CAPCOM) Mike Collins. “Just after our TV show, Santa Claus brought us a TV dinner each; it was delicious. Turkey and gravy, cranberry sauce, grape punch; [it was] outstanding.” In response, Collins expressed delight in hearing the good news but shared that the flight control team was not as lucky. Instead, they were “eating cold coffee and baloney sandwiches.”4
The Apollo 8 Christmas menu included dehydrated grape drink, cranberry-applesauce, and coffee, as well as a wetpack containing turkey and gravy.U.S. Natick Soldier Systems Center Photographic Collection The Apollo 8 meal was a “breakthrough.” Until that mission, the food choices for Apollo crews were limited to freeze dried foods that required water to be added before they could be consumed, and ready-to-eat compressed foods formed into cubes. Most space food was highly processed. On this mission NASA introduced the “wetpack”: a thermostabilized package of turkey and gravy that retained its normal water content and could be eaten with a spoon. Astronauts had consumed thermostabilized pureed food on the Project Mercury missions in the early 1960s, but never chunks of meat like turkey. For the Project Gemini and Apollo 7 spaceflights, astronauts used their fingers to pop bite-sized cubes of food into their mouths and zero-G feeder tubes to consume rehydrated food. The inclusion of the wetpack for the Apollo 8 crew was years in the making. The U.S. Army Natick Labs in Massachusetts developed the packaging, and the U.S. Air Force conducted numerous parabolic flights to test eating from the package with a spoon.5
Smith called the meal a real “morale booster.” He noted several reasons for its appeal: the new packaging allowed the astronauts to see and smell the turkey and gravy; the meat’s texture and flavor were not altered by adding water from the spacecraft or the rehydration process; and finally, the crew did not have to go through the process of adding water, kneading the package, and then waiting to consume their meal. Smith concluded that the Christmas dinner demonstrated “the importance of the methods of presentation and serving of food.” Eating from a spoon instead of the zero-G feeder improved the inflight feeding experience, mimicking the way people eat on Earth: using utensils, not squirting pureed food out of a pouch into their mouths. Using a spoon also simplified eating and meal preparation. NASA added more wetpacks onboard Apollo 9, and the crew experimented eating other foods, including a rehydrated meal item, with the spoon.6
Malcolm Smith demonstrates eating space food.NASA Food was one of the few creature comforts the crew had on the Apollo 8 flight, and this meal demonstrated the psychological importance of being able to smell, taste, and see the turkey prior to consuming their meal, something that was lacking in the first four days of the flight. Seeing appetizing food triggers hunger and encourages eating. In other words, if food looks and smells good, then it must taste good. Little things like this improvement to the Apollo Food System made a huge difference to the crews who simply wanted some of the same eating experiences in orbit and on the Moon that they enjoyed on Earth.
Footnotes
[1] Apollo 8 Mission Commentary, Dec. 25, 1968, p. 543, https://historycollection.jsc.nasa.gov/JSCHistoryPortal/history/mission_trans/AS08_PAO.PDF; Apollo 8 Technical Debriefing, Jan. 2, 1969, 078-15, Apollo Series, University of Houston-Clear Lake, Houston, Texas (hereafter UHCL); Malcolm C. Smith to Director of Medical Research and Operations, “Nutrient consumption on Apollo VII and VIII,” Jan. 13, 1969, Rita Rapp Papers, Box 1, UHCL.
[2] Jim McDivitt food evaluation form, n.d., Box 17, Rapp Papers, UHCL.
[3] Donald Arabian to Rapp, “Evaluation of four-day food supply,” May 8, 1969, Box 17, Rapp Papers, UHCL.
[4] Apollo 8 Mission Commentary, Dec. 25, 1968, p. 545.
[5] Malcolm Smith, “The Apollo Food Program,” in Aerospace Food Technology, NASA SP-202 (Washington, DC: 1970), pp. 5–8; Whirlpool Corporation, “Space Food Systems: Mercury through Apollo,” Dec. 1970, Box 9, Rapp Papers, UHCL.
[6] Smith, “The Apollo Food Program,” pp. 7–8; Smith to the Record, “Christmas Dinner for Apollo VIII,” Jan. 10, 1969, Box 1, Rapp Papers, UHCL; Smith et al, “Apollo Food Technology,” in Biomedical Results of Apollo, NASA SP-368 (Washington, DC: NASA, 1975), p. 456.
About the Author
Jennifer Ross-Nazzal
NASA Human Spaceflight HistorianJennifer Ross-Nazzal is the NASA Human Spaceflight Historian. She is the author of Winning the West for Women: The Life of Suffragist Emma Smith DeVoe and Making Space for Women: Stories from Trailblazing Women of NASA's Johnson Space Center.
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Last Updated Dec 21, 2023 EditorMichele Ostovar Related Terms
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By NASA
This 360-degree mosaic from the “Airey Hill” location inside Jezero Crater was generated using 993 individual images taken by the Perseverance Mars rover’s Mastcam-Z from Nov. 3-6. The rover remained parked at Airey Hill for several weeks during solar conjunction.NASA/JPL-Caltech/ASU/MSSS Now at 1,000 days on Mars, the mission has traversed an ancient river and lake system, collecting valuable samples along the way.
Marking its 1,000th Martian day on the Red Planet, NASA’s Perseverance rover recently completed its exploration of the ancient river delta that holds evidence of a lake that filled Jezero Crater billions of years ago. The six-wheeled scientist has to date collected a total of 23 samples, revealing the geologic history of this region of Mars in the process.
One sample called “Lefroy Bay” contains a large quantity of fine-grained silica, a material known to preserve ancient fossils on Earth. Another, “Otis Peak,” holds a significant amount of phosphate, which is often associated with life as we know it. Both of these samples are also rich in carbonate, which can preserve a record of the environmental conditions from when the rock was formed.
The discoveries were shared Tuesday, Dec. 12, at the American Geophysical Union fall meeting in San Francisco.
“We picked Jezero Crater as a landing site because orbital imagery showed a delta – clear evidence that a large lake once filled the crater. A lake is a potentially habitable environment, and delta rocks are a great environment for entombing signs of ancient life as fossils in the geologic record,” said Perseverance’s project scientist, Ken Farley of Caltech. “After thorough exploration, we’ve pieced together the crater’s geologic history, charting its lake and river phase from beginning to end.”
This image of Mars’ Jezero Crater is overlaid with mineral data detected from orbit. The green color represents carbonates – minerals that form in watery environments with conditions that might be favorable for preserving signs of ancient life. NASA’s Perseverance is currently exploring the green area above Jezero’s fan (center).NASA/JPL-Caltech/MSSS/JHU-APL Jezero formed from an asteroid impact almost 4 billion years ago. After Perseverance landed in February 2021, the mission team discovered the crater floor is made of igneous rock formed from magma underground or from volcanic activity at the surface. They have since found sandstone and mudstone, signaling the arrival of the first river in the crater hundreds of millions of years later. Above these rocks are salt-rich mudstones, signaling the presence of a shallow lake experiencing evaporation. The team thinks the lake eventually grew as wide as 22 miles (35 kilometers) in diameter and as deep as 100 feet (30 meters).
Later, fast-flowing water carried in boulders from outside Jezero, distributing them atop of the delta and elsewhere in the crater.
“We were able to see a broad outline of these chapters in Jezero’s history in orbital images, but it required getting up close with Perseverance to really understand the timeline in detail,” said Libby Ives, a postdoctoral fellow at NASA’s Jet Propulsion Laboratory in Southern California, which manages the mission.
Enticing Samples
The samples Perseverance gathers are about as big as a piece of classroom chalk and are stored in special metal tubes as part of the Mars Sample Return campaign, a joint effort by NASA and ESA (European Space Agency). Bringing the tubes to Earth would enable scientists to study the samples with powerful lab equipment too large to take to Mars.
This animated artist’s concept depicts water breaking through the rim of Mars’ Jezero Crater, which NASA’s Perseverance rover is now exploring. Water entered the crater billions of years ago, forming a lake, delta, and rivers before the Red Planet dried up. NASA/JPL-Caltech To decide which samples to collect, Perseverance first uses an abrasion tool to wear away a patch of a prospective rock and then studies the rock’s chemistry using precision science instruments, including the JPL-built Planetary Instrument for X-ray Lithochemistry, or PIXL.
At a target the team calls “Bills Bay,” PIXL spotted carbonates – minerals that form in watery environments with conditions that might be favorable for preserving organic molecules. (Organic molecules form by both geological and biological processes.) These rocks were also abundant with silica, a material that’s excellent at preserving organic molecules, including those related to life.
“On Earth, this fine-grained silica is what you often find in a location that was once sandy,” said JPL’s Morgan Cable, the deputy principal investigator of PIXL. “It’s the kind of environment where, on Earth, the remains of ancient life could be preserved and found later.”
Perseverance’s instruments are capable of detecting both microscopic, fossil-like structures and chemical changes that may have been left by ancient microbes, but they have yet to see evidence for either.
PIXL, one of the instruments aboard NASA’s Perseverance Mars rover, analyzed the chemical makeup of an area of abraded rock dubbed “Ouzel Falls,” finding it rich in minerals containing phosphate, a material found in the DNA and cell membranes of all known life.NASA/JPL-Caltech/MSSS Analyzing this abraded rock patch dubbed “Bills Bay,” the PIXL instrument on NASA’s Perseverance Mars rover found it rich in carbonates (purple) and silica (green), both of which are good at preserving signs of ancient life. The image is overlaid with the instrument’s chemical data.NASA/JPL-Caltech/MSSS At another target PIXL examined, called “Ouzel Falls,” the instrument detected the presence of iron associated with phosphate. Phosphate is a component of DNA and the cell membranes of all known terrestrial life and is part of a molecule that helps cells carry energy.
After assessing PIXL’s findings on each of these abrasion patches, the team sent up commands for the rover to collect rock cores close by: Lefroy Bay was collected next to Bills Bay, and Otis Peak at Ouzel Falls.
“We have ideal conditions for finding signs of ancient life where we find carbonates and phosphates, which point to a watery, habitable environment, as well as silica, which is great at preservation,” Cable said.
Perseverance’s work is, of course, far from done. The mission’s ongoing fourth science campaign will explore Jezero Crater’s margin, near the canyon entrance where a river once flooded the crater floor. Rich carbonate deposits have been spotted along the margin, which stands out in orbital images like a ring within a bathtub.
More About the Mission
A key objective for Perseverance’s mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and cache Martian rock and regolith (broken rock and dust).
Subsequent NASA missions, in cooperation with ESA (European Space Agency), would send spacecraft to Mars to collect these sealed samples from the surface and return them to Earth for in-depth analysis.
The Mars 2020 Perseverance mission is part of NASA’s Moon to Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.
JPL, which is managed for NASA by Caltech in Pasadena, California, built and manages operations of the Perseverance rover.
For more about Perseverance:
mars.nasa.gov/mars2020/
Learn about all the samples collected by Perseverance Where is Perseverance right now? News Media Contacts
Andrew Good
Jet Propulsion Laboratory, Pasadena, Calif.
818-393-2433
andrew.c.good@jpl.nasa.gov
Karen Fox / Alana Johnson
NASA Headquarters, Washington
301-286-6284 / 202-358-1501
karen.c.fox@nasa.gov / alana.r.johnson@nasa.gov
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Last Updated Dec 12, 2023 Related Terms
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By European Space Agency
Image: The Copernicus Sentinel-2 mission takes us over Venezuela’s Lake Maracaibo, the largest natural body of water in South America. View the full article
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