SPACE/COSMOS
SwRI findings reconsider the existence of Europa’s vapor plumes
Reanalysis of 14 years of data shifts beliefs about Jupiter’s moon
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A new SwRI study has raised doubts about the existence of water vapor plumes on Jupiter’s moon Europa (shown above), initially reported based on Hubble Space Telescope observations from 2012. A reanalysis of the data reduced the certainty of that initial finding, but scientists are still hopeful that such plumes will be observed at some point in the future.
view moreCredit: NASA
SAN ANTONIO — May 18, 2026 — Looking back at 14 years of Hubble telescope data for Jupiter’s moon Europa has given Southwest Research Institute (SwRI) scientists a better understanding of its tenuous atmosphere. The findings have cast doubt on previous evidence suggesting that the icy moon intermittently discharges faint water plumes from a presumed subsurface ocean.
“The evidence for water vapor plumes on Europa isn’t as strong as we first understood it,” said SwRI’s Dr. Kurt Retherford, one of the authors of a 2014 paper initially making that assertion. Retherford and his colleagues have recently published a new paper reanalyzing the data.
The new paper looks at the last 14 years of data from the Hubble Space Telescope’s Space Telescope Imaging Spectrograph (HST/STIS) focused on Europa’s Lyman-alpha emissions. Lyman-alpha is a specific wavelength of ultraviolet light emitted and scattered by hydrogen atoms. From 2012-2014, the team was pushing the limits of the Hubble telescope’s capabilities.
“One of the difficulties in interpreting the data back then was determining where to place Europa within its context,” Retherford said. “The way Hubble works left some uncertainty in terms of placement relative to the center of the image. If Europa’s placement was off even just by a pixel or two, it could affect how the data gets interpreted.”
As a result, what they thought could be evidence of a water vapor plume could also just be statistical noise.
“Our reanalysis took our original 99.9% confidence in the plumes’ existence and reduced it to less than 90% confidence,” said Dr. Lorenz Roth (Royal Technical Institute, Sweden), the paper’s lead author. “That’s simply not enough evidence to support the certainty of claims we made at the time."
Retherford said the current dataset does not rule out the possibility of the water vapor plumes described in the 2014 paper, but it no longer provides concrete evidence of them.
“The description of the phenomena just doesn't hold up the same way anymore,” said Retherford. “The new data has made us reconsider the strength of the previous paper’s conclusion regarding water vapor plumes. The recent analysis also provides improved information about the neutral hydrogen atom component of Europa’s escaping atmosphere, originating from its water ice surface.”
SwRI scientists still hope to find water vapor plumes escaping from Europa. Similar water vapor plumes have been confirmed on Saturn’s moon Enceladus, and Europa’s neighbor Io, another moon of Jupiter, has plumes of sulfur dioxide expanding out into space.
Scientists are particularly interested in Europa because its icy surface is thought to obscure a vast saltwater ocean beneath. Cracks in Europa’s icy shell could provide potential pathways for liquid water to rise to the surface and shoot out into space. This remains a distinct possibility that NASA’s Europa Clipper mission will investigate when it arrives in the Jupiter system in 2030.
To read the Astronomy & Astrophysics paper titled “Europa’s Lyman-alpha emissions from HST/STIS observations,” go to https://doi.org/10.1051/0004-6361/202659406.
For more information, visit https://www.swri.org/markets/earth-space/space-research-technology/space-science/planetary-science.
Journal
Astronomy and Astrophysics
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Europa’s Lyman-alpha emissions from HST/STIS observations
Article Publication Date
15-May-2026
Georgia Tech researchers discover new form of NAND flash data storage for deep space missions
The new data storage technology is up to 30 times more radiation-resilient than current data storage.
Georgia Institute of Technology
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Asif Khan and Lance Fernandes built the ferroelectric NAND memory chips in Georgia Tech’s cleanroom, then sent the chips for radiation testing to collaborators at Pennsylvania State University. Those tests revealed just how extreme the technology’s tolerance could be.
view moreCredit: Georgia Tech
As space missions travel farther from Earth, spacecraft must increasingly be able to process and store their own data. Soon, artificial intelligence (AI) could be the primary tool for handling this growing volume of information. NAND flash memory is the current state-of-the-art technology used to store these massive amounts of data, offering storage capacities in the terabit range. It’s the same technology used in laptops, smartphones, and data centers. Ensuring NAND’s reliability in space is critical as these systems increasingly rely on high-density, low-power storage.
But the radiation in harsh space environments can significantly degrade data stored in NAND flash memory. To counteract this, Georgia Tech researchers have developed a new form of NAND flash memory that can both handle AI and withstand extreme radiation.
This technology uses ferroelectricity, which is when certain materials can hold a permanent, spontaneous electric charge, called polarization. In a recent Nano Letters paper, the researchers show that NAND flash memory made with ferroelectric materials can withstand radiation levels up to 30 times higher than more conventional NAND flash memory.
“If you send traditional flash memory to space, the radiation interacting with flash memory’s trapped electric charge can easily corrupt the data,” said Asif Khan, an associate professor in the School of Electrical and Computer Engineering (ECE). “In contrast, ferroelectric NAND flash storage does not store data as trapped electrical charge, but rather stores it as polarization in the material. And polarization is very resilient to radiation effects.”
Radiation Revelation
The insight that NAND flash-compatible ferroelectric memory could withstand high amounts of radiation surprised the researchers. Ferroelectricity in hafnium oxide — the silicon-compatible material that makes this memory possible — was discovered just 15 years ago, and Khan’s lab has been determining its capabilities for the past decade. The team knew ferroelectricity was radiation-tolerant, but not exactly how tolerant when implemented in NAND flash architectures.
Lance Fernandes, an ECE Ph.D. student and the paper’s first author, built the ferroelectric NAND memory chips in Georgia Tech’s cleanroom, then sent the chips for radiation testing to collaborators at Pennsylvania State University. Those tests revealed just how extreme the technology’s tolerance could be.
The Penn State researchers’ testing showed that ferroelectric flash technology can sustain radiation as high as 1 million rads (radiation absorbed doses) — the equivalent of 100 million X-rays — making it 30 times more durable than traditional memory. This is well within the radiation-tolerance threshold for most spacecraft: Low-Earth orbit satellites require a tolerance of 5 – 30 kilorads, geostationary orbits need 100 – 300 kilorads, and deep space missions top out at 1 million rads.
“For data storage in space, it’s not enough for memory to work. It has to remain reliable under extreme radiation,” said Fernandes.
“And what makes our storage especially exciting," added Khan, “is that ferroelectric NAND flash isn't just radiation-tolerant; it also stays reliable even in extremely harsh radiation environments. That's exactly what we need for space.”
From orbiting satellites to future missions surveying Jupiter’s moons, successful space exploration requires electronics that can process abundant AI data and will not fail when communication is delayed. Ferroelectric memory offers a way to keep critical data intact, no matter how harsh the environment.
The work was supported in part by SUPREME, one of seven centers in JUMP 2.0, a Semiconductor Research Corporation (SRC) program sponsored by DARPA. The work was performed as part of the Interaction of Ionizing Radiation With Matter University Research Alliance, sponsored by the Department of Defense, Defense Threat Reduction Agency, under grant HDTRA1-20-2-0002.
Enabling Radiation Hardness in Solid-State NAND Storage Utilizing a Laminated Ferroelectric Stack Lance Fernandes, Stuart Wodzro, Prasanna Venkatesan, Priyankka Ravikumar, Ming-Yen Lee, Minji Shon, Dyutimoy Chakraborty, Taeyoung Song, Sanghyun Kang, Salma Soliman, Mengkun Tian, Jason Yeager, Jackson Adler, Jiayi Chen, Zekai Wang, Douglas Wolfe, Shimeng Yu, Andrea Padovani, Suman Datta, Biswajit Ray, and Asif Khan. Nano Letters 2026 26 (10), 3390-3397
DOI: 10.1021/acs.nanolett.5c05947
Journal
Nano Letters
DOI
Shooting for the moon: Ultrastable lasers in dark craters could enable lunar navigation, precision timekeeping, new science
National Institute of Standards and Technology (NIST)
They rank among the darkest and coldest places in the solar system: Hundreds of lunar craters, many of them at the Moon’s south pole, never receive direct sunlight and lie in permanent shadow. That’s exactly why physicist Jun Ye and his colleagues suggest that these craters are the perfect place to build a critical component for an ultrastable laser.
On the Moon, a highly stable laser — a source of coherent light that has a nearly unwavering frequency, or color — could provide a master time signal and offer GPS-like lunar navigation, said Ye, who is affiliated with both the National Institute of Standards and Technology (NIST) and JILA, a joint institute of NIST and the University of Colorado Boulder. Multiple copies of these lunar lasers could precisely measure the distances between objects and potentially detect exotic physics phenomena such as ripples in space-time.
To construct a lunar laser, astronauts would first install a key component known as an optical silicon cavity — a block of silicon that permits only certain frequencies of light to bounce back and forth between mirrors on each end of the block. The distance between the two mirrors determines the frequencies that are allowed to resonate; for a highly stable optical cavity, that distance, and therefore those frequencies, does not vary.
The Moon is an ideal location for building an optical cavity because it’s subject to relatively few vibrations compared with Earth and has a high vacuum (since its environment is devoid of air).
But the permanently shadowed craters at the lunar south pole provide an even greater advantage. Their frigid temperature of around 50 degrees above absolute zero (50 kelvins) drastically reduces the random jitter of the mirrored surfaces.
In addition, these craters have an even higher vacuum than the lunar surface, further reducing or eliminating vibrations from sound waves and stray particles that could strike the mirrors and change the distance between them.
By radiating any residual heat from the cavity system into the much colder abyss of outer space, the optical cavity could be cooled further, without the need for a cryostat or other equipment, to a temperature of 16 K. At that temperature, silicon neither expands nor contracts when exposed to tiny changes in temperature, ensuring that light entering the cavity always traverses exactly the same distance between the two mirrors.
Once the optical silicon cavity is deployed, a commercially available laser would be placed nearby — either on the rim or inside the permanently shadowed crater. A small amount of laser light directed into the optical cavity would be used to lock the laser frequency to one of the resonant frequencies allowed by the cavity, ensuring that the laser emits light of a single unchanging color.
After stabilizing the frequency of its light, the laser could act as a GPS-like signal, guiding lunar spacecraft to land safely, especially those set to touch down on dimly lit regions near the south pole. By tuning its light to the signals of atomic clocks on satellites, a high-stability lunar laser could also form the backbone of the first optical atomic clock on an extraterrestrial surface. This timekeeping signal would rival those from the most precise and accurate optical atomic clocks on Earth, which Ye and colleagues have built in Earth-bound laboratories.
A lunar laser locked to an ultrastable silicon cavity placed inside one of the Moon’s permanently shadowed craters could provide the infrastructure for a lunar time scale, Earth-Moon optical communication, satellite-based space distance measurements and imaging, and a space-based optical atomic clock.
Credit: J. Ye/NIST with lunar background image produced by NASA’s Visualization Studio
Ye and his colleagues, including researchers from JILA; NASA’s Jet Propulsion Laboratory in Pasadena, California; the Physikalisch-Technische Bundesanstalt (PTB) in Germany; and Lunetronic Inc. in San Francisco, describe their proposal in a recent issue of the Proceedings of the National Academy of Sciences.
Although the idea of building a laser inside a lunar crater may seem like pie in the sky, NASA has already designated regions near the south pole’s permanently shadowed craters as landing sites for the space agency’s Artemis mission.
Ye, an expert on lasers and precision measurements, came up with the idea for a lunar laser after talking with colleagues about the types of instruments that the Artemis mission could carry and install on the lunar surface. Some ideas seemed impractical or involved technology not fully developed on Earth.
“I thought, ‘let me throw out another crazy idea’ — except it turned out to be not so crazy after all,” Ye noted. After working with silicon resonant cavities for years, Ye and his colleagues at both JILA and the German national metrology institute “know exactly what the key ingredients are for building a silicon cavity,” he added. “As soon as I understood what the permanently shadowed regions can offer, I felt that this would be the most ideal environment for a super-stable laser.”
If astronauts were to install a network of these lunar lasers, said Ye, the instruments could measure distances between objects on the Moon with extraordinarily high precision. Such precision could enable the Moon-based lasers to act as a detector for gravitational waves, ripples in space-time that would jostle the Moon and alter ever so slightly the distance between lunar objects as they pass by.
The silicon optical cavity, small enough to fit inside an Artemis spacecraft, would be fully assembled on Earth, said study co-author Wei Zhang of NASA’s Jet Propulsion Laboratory. During deployment on the Moon, the device’s radiation panels would need to unfold. Astronauts would use a remote or mechanically controlled lunar rover to lower the cavity into the crater, Zhang added.
Because of poor illumination, it will be challenging to land on the Moon’s polar regions, noted co-author Yiqi Ni, of Lunetronic. However, permanently shadowed regions on the Moon remain central to long-term lunar exploration because they contain water-ice and other resources needed to maintain a human presence.
Ni estimates that a silicon optical cavity could be demonstrated in low-Earth orbit within two years, deployed on the lunar surface within three to five years, and eventually installed inside a dark crater through coordinated multiagency efforts.
Paper: Jun Ye, Zoey Z. Hu, Ben Lewis, Wei Zhang, Fritz Riehle, Uwe Sterr, Yiqi Ni and Julian Struck. Lunar Silicon Cavity. Proceedings of the National Academy of Sciences. Published online May 8, 2026. DOI: 10.1073/pnas.2604438123
Journal
Proceedings of the National Academy of Sciences
Method of Research
Content analysis
Subject of Research
Not applicable
Article Title
Lunar Silicon Cavity
Article Publication Date
8-May-2026
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