By AFP
April 20, 2025
It was the fourth spaceflight for US astronaut Don Pettit, who has logged more than 18 months in orbit throughout his career - Copyright NASA/AFP Bill INGALLS
Cake, gifts and a low-key family celebration may be how many senior citizens picture their 70th birthday.
But NASA’s oldest serving astronaut Don Pettit became a septuagenarian while hurtling towards the Earth in a spacecraft to wrap up a seven-month mission aboard the International Space Station (ISS).
A Soyuz capsule carrying the American and two Russian cosmonauts landed in Kazakhstan on Sunday, the day of Pettit’s milestone birthday.
Spending 220 days in space, Pettit and his crewmates Alexei Ovchinin and Ivan Vagner orbited the Earth 3,520 times and completed a journey of 93.3 million miles over the course of their mission.
It was the fourth spaceflight for Pettit, who has logged more than 18 months in orbit throughout his 29-year career.
The trio touched down in a remote area southeast of Dzhezkazgan in Kazakhstan at 6:20 am (0120 GMT) after undocking from the space station just over three hours earlier.
NASA images of the landing showed the small capsule parachuting down to Earth with the sunrise as a backdrop.
The astronauts gave thumbs-up gestures as rescuers carried them from the spacecraft to an inflatable medical tent.
Despite looking a little worse for wear as he was pulled from the vessel, Pettit was “doing well and in the range of what is expected for him following return to Earth,” NASA said in a statement.
He was then set to fly to the Kazakh city of Karaganda before boarding a NASA plane to the agency’s Johnson Space Center in Texas.
The astronauts spent their time on the ISS researching areas such as water sanitization technology, plant growth in various conditions and fire behavior in microgravity, NASA said.
The trio’s seven-month trip was just short of the nine months that NASA astronauts Butch Wilmore and Suni Williams unexpectedly spent stuck on the orbital lab after the spacecraft they were testing suffered technical issues and was deemed unfit to fly them back to Earth.
Scientists probe the mystery of Titan’s missing deltas
image:
Earth, as seen by Cassini's radar. In order to understand what landforms on Titan could be seen by Cassini's radar, researchers looked at well-known Earth landforms through Cassini's perspective. The bottom image is how the U.S. Gulf Coast would have looked to Cassini.
view moreCredit: Birch Lab / Brown University
PROVIDENCE, R.I. [Brown University] — For scientists who want to learn about the geological history of a planet, river deltas are a great place to start. Deltas gather sediment from a large area into one place, which can be studied to reveal climate and tectonic histories or signs of past life. That’s why NASA sent its most recent Mars rover to Jezero Crater, home to a prominent and well-preserved delta.
And that’s why planetary scientists are also interested in finding deltas on Saturn’s moon Titan. Titan is the only planetary body in the solar system besides Earth that has liquid currently flowing across its surface, so its deltas could be a scientific treasure trove.
One problem: Titan appears to be largely devoid of deltas, a new study finds, despite its large rivers of liquid methane and ethane.
“It’s kind of disappointing as a geomorphologist because deltas should preserve so much of Titan’s history,” said Sam Birch, an assistant professor in Brown University’s Department of Earth, Environmental and Planetary Sciences who led the work.
But the absence of deltas raises a host of new questions.
“We take it for granted that if you have rivers and sediments, you get deltas,” Birch said. “But Titan is weird. It’s a playground for studying processes we thought we understood.”
Titan is the largest of Saturn’s 274 confirmed moons. Its thick nitrogen and methane atmosphere gives rise to a host of Earth-like climate and weather features. Titan has clouds, wind and rain as well as rivers, lakes and seas. But instead of water, Titan’s fluid bodies contain methane and ethane, which are liquid at Titan’s chilly surface temperatures.
Scientists learned of Titan’s liquid bodies when the Cassini spacecraft flew by in 2006. Peering through Titan’s thick atmosphere with Cassini’s synthetic aperture radar (SAR), the spacecraft revealed spidering channels and large flat areas consistent with large bodies of liquid.
Largely missing from Cassini’s SAR images, however, were deltas — even at the mouths of large rivers. It wasn’t clear, however, whether the deltas were truly absent, or whether they just didn’t show up in Cassini’s SAR data. That’s the question Birch and his colleagues tried to answer with this new study, published in the Journal of Geophysical Research: Planets.
The problem with Cassini’s SAR data is that shallow liquid methane is largely transparent in any images. So while the SAR images could see the broad seas and river channels, it’s harder to confidently make out coastal features because it’s difficult to see where the coast ends and where the sea floor begins.
For the study, Birch developed a numerical model to simulate what Cassini’s SAR would see if it looked at a landscape scientists understand well: Earth. In the model, the water in Earth’s rivers and oceans was replaced by Titan’s methane liquid, which has different radar absorption properties compared to water.
“We basically made synthetic SAR images of Earth that assume properties of Titan’s liquid instead of Earth’s,” Birch said. “Once we see SAR images of a landscape we know very well, we can go back to Titan and understand a bit better what we’re looking at.”
The research found that the synthetic SAR images of Earth clearly resolved large deltas and many other large coastal landscapes.
“If there are deltas the size of the one at the mouth of the Mississippi River, we should be able to see it,” Birch said. “If there are large barrier islands and similar coastal landscapes like those we see all along the U.S. Gulf Coast, we should be able to see those.”
But when Birch and his colleagues combed over the Titan images in light of their new analysis, they came up mostly empty. Aside from two probable deltas near Titan’s south pole, the rest of the moon’s rivers were entirely delta-free. The researchers found that only about 1.3% of Titan’s large rivers that terminate at coastlines have deltas. On Earth, in contrast, nearly every river of similar size has a delta.
It's not entirely clear why Titan generally lacks deltas, Birch says. The fluid properties of Titan’s rivers should make them perfectly capable of carrying and depositing sediment. It could be, the researchers say, that sea levels on Titan rise and fall so rapidly that deltas are smeared across the landscape more quickly than they can be built up in a single spot. Winds and tidal currents along Titan’s coasts may also play an equally large role in preventing delta formation.
And missing deltas aren’t the only mystery raised by the new research. The new analysis of Cassini SAR data of Titan’s coasts revealed pits of unknown origin deep within lakes and seas. The study also found deep channels on the floors of the seas that seem to have been carved by river flows, but it’s not clear how they got there.
All of these surprises will require more research to fully understand, Birch says.
“This is really not what we expected,” Birch said. “But Titan does this to us a lot. I think that’s what makes it such an engaging place to study.”
Journal
Journal of Geophysical Research Planets
Article Title
Detectability of Coastal Landforms on Titan With the Cassini RADAR
New study unveils volcanic history and clues to ancient life on Mars
The proof may be in the pudding, but according to a Texas A&M University geologist, when it comes to ancient life on the Red Planet, the proof is in the rocks.
Texas A&M University
image:
A mosaic of two pictures showing the rover arm after scanning and sampling one of the rocks discussed in the paper. The rock itself is in the lower right and clearly shows the hole where the sample was collected. The rock was given the informal name "Rochette" by the Perseverance science team.
view moreCredit: NASA/JPL-Caltech/ASU
In a groundbreaking study co-authored by a Texas A&M University scientist, researchers have revealed new insights into the geological history of Mars' Jezero Crater, the landing site of NASA’s Perseverance rover. Their findings suggest that the crater's floor is composed of a diverse array of iron-rich volcanic rocks, providing a window into the planet’s distant past and the closest chance yet to uncover signs of ancient life.
Research scientist Dr. Michael Tice, who studies geobiology and sedimentary geology in the Texas A&M College of Arts and Sciences, is part of an international team exploring the surface of Mars. He and his co-authors published their findings in Science Advances.
“By analyzing these diverse volcanic rocks, we’ve gained valuable insights into the processes that shaped this region of Mars,” Tice said. “This enhances our understanding of the planet’s geological history and its potential to have supported life.”
Unlocking Mars’ Secrets With Unrivaled Technology
Perseverance, NASA’s most advanced robotic explorer, landed in the Jezero Crater on Feb. 18, 2021, as part of the Mars 2020 mission’s search for signs of ancient microbial life on the Red Planet. The rover is collecting core samples of Martian rock and regolith (broken rock and soil) for possible future analysis on Earth.
Meanwhile, scientists like Tice are using the rover’s high-tech tools to analyze Martian rocks to determine their chemical composition and detect compounds that could be signs of past life. The rover also has a high-resolution camera system that provides detailed images of rock texture and structures. But Tice said the technology is so advanced compared to that of past NASA rovers that they are gathering new information at unprecedented levels.
"We’re not just looking at pictures — we’re getting detailed chemical data, mineral compositions and even microscopic textures,” Tice said. “It’s like having a mobile lab on another planet."
Tice and his co-authors analyzed the rock formations within the crater to better understand Mars' volcanic and hydrological history. The team used the Planetary Instrument for X-ray Lithochemistry (PIXL), an advanced spectrometer, to analyze the chemical composition and textures of rocks in the Máaz formation, a key geological area within Jezero Crater. PIXL’s high-resolution X-ray capabilities allow for unprecedented detail in studying the elements in the rocks.
Tice noted the importance of the technology in revolutionizing Martian exploration. “Every rover that has ever gone to Mars has been a technological marvel, but this is the first time we’ve been able to analyze rocks in such high resolution using X-ray fluorescence. It has completely changed the way we think about the history of rocks on Mars,” he said.
What The Rocks Reveal
The team’s analysis revealed two distinct types of volcanic rocks. The first type, dark-toned and rich in iron and magnesium, contains intergrown minerals such as pyroxene and plagioclase feldspar, with evidence of altered olivine. The second type, a lighter-toned rock classified as trachy-andesite, includes plagioclase crystals within a potassium-rich groundmass. These findings indicate a complex volcanic history involving multiple lava flows with varying compositions.
To determine how these rocks formed, researchers conducted thermodynamic modeling — a method that simulates the conditions under which the minerals solidified. Their results suggest that the unique compositions resulted from high-degree fractional crystallization, a process where different minerals separate from molten rock as it cools. They also found signs that the lava may have mixed with iron-rich material from Mars' crust, changing the rocks' composition even more.
“The processes we see here — fractional crystallization and crustal assimilation — happen in active volcanic systems on Earth,” said Tice. “It suggests that this part of Mars may have had prolonged volcanic activity, which in turn could have provided a sustained source for different compounds used by life.”
This discovery is crucial for understanding Mars' potential habitability. If Mars had an active volcanic system for an extended period, it might have also maintained conditions suitable for life for long portions of Mars’ early history.
“We’ve carefully selected these rocks because they contain clues to Mars’ past environments,” Tice said. “When we get them back to Earth and can analyze them with laboratory instruments, we’ll be able to ask much more detailed questions about their history and potential biological signatures.”
The Mars Sample Return mission, a collaborative effort between NASA and the European Space Agency, aims to bring the samples back within the next decade. Once on Earth, scientists will have access to more advanced laboratory techniques to analyze them in greater detail.
Tice said that given the astounding level of technology on Perseverance, more discoveries are ahead. “Some of the most exciting work is still ahead of us. This study is just the beginning. We're seeing things that we never expected, and I think in the next few years, we’ll be able to refine our understanding of Mars’ geological history in ways we never imagined.”
Read more about the Perseverance rover and learn about the Texas A&M Department of Geology and Geophysics.
Tice’s co-authors on the study are:
- Mariek E. Schmidt and Tanya V. Kizovski, Brock University
- Yang Liu, Abigail C. Allwood, Morgan L. Cable, and Christopher M. Heirwegh, NASA Jet Propulsion Laboratory
- Juan D. Hernandez-Montenegro, California Institute of Technology
- Anastasia Yanchilina, Impossible Sensing, Inc.
- Joel A. Hurowitz, Stony Brook University
- Allan H. Treiman, Lunar and Planetary Institute
- David A. Klevang and Jesper Henneke, Danish Technical University
- Nicholas J. Tosca, University of Cambridge
- Scott J. VanBommel, Washington University in St. Louis
- Richard V. Morris and Justin I. Simon, NASA Johnson Space Center
By Lesley Henton, Texas A&M University Division of Marketing and Communications
###
Journal
Science Advances
Article Title
Diverse and highly differentiated lava suite in Jezero crater, Mars: Constraints on intracrustal magmatism revealed by Mars 2020 PIXL
Article Publication Date
16-Apr-2025
Turning down starlight to spot new exoplanets
New coronagraph could reveal hidden planets beyond our solar system
Peer-Reviewed Publicationimage:
To capture an image of the exoplanet without the star, the new coronagraph design uses a mode sorter to isolate and eliminate light from the star and an inverse mode sorter to recompose the optical field after the starlight is rejected.
view moreCredit: Nico Deshler, University of Arizona
WASHINGTON — Researchers have developed a new coronagraph — an optical device that blocks out light from a bright source — that could make it possible to see distant exoplanets obscured by light from their parent stars. The new device could reveal exoplanets beyond our solar system that today's telescopes cannot resolve, providing insights into the possibility of life beyond Earth.
“Earth-like planets in the habitable zone — the region around a star where temperatures could allow liquid water to exist — can easily be up to a billion times dimmer than their host star,” said research team leader Nico Deshler from the University of Arizona. “This makes them difficult to detect because their faint light is overwhelmed by the star's brightness. Our new coronagraph design siphons away starlight that might obscure exoplanet light before capturing an image.”
In Optica, Optica Publishing Group’s journal for high-impact research, the researchers show that the new coronagraph can theoretically achieve the fundamental limits of exoplanet detection and localization set by quantum optics. They also used it to capture images that allowed them to estimate the position of artificial exoplanets with distances from their host star up to 50 times smaller than what the telescope's resolution limit would normally allow.
“Compared to other coronagraph designs, ours promises to supply more information about so-called sub-diffraction exoplanets – those which lie below the resolution limits of the telescope,” said Deshler. “This could allow us to potentially detect biosignatures and discover the presence of life among the stars.”
Blinded by the light
Optically analyzing exoplanets poses a formidable challenge because, at astronomical scales, they are often too close to their parent star for current telescopes to resolve. Exoplanets can also be orders of magnitude dimmer than their host star. Although astronomers have developed various ways to indirectly infer the presence of a planet around a prospective star, directly observing exoplanets in images would be ideal.
With NASA’s next-generation space telescope, the Habitable Worlds Observatory (HWO), being dedicated to exoplanet science, many coronagraph designs have emerged, each with different practical and theoretical performance trade-offs. At the same time, recent work has shown that traditional notions of resolution for telescopes do not reflect fundamental limits and can be circumvented with careful optical pre-processing.
Inspired by these developments, the researchers decided to use a spatial mode sorter available in their lab to develop an improved coronagraph that theoretically rejects all the light from an on-axis star while achieving maximal throughput of an off-axis exoplanet.
Much like piano notes emit different acoustic frequencies, light sources in space excite different spatial modes — unique shapes and patterns of oscillation — depending on their position. The researchers separated these different modes using a mode sorter to isolate and eliminate light from a star and an inverse mode sorter to recompose the optical field after the starlight is rejected. This made it possible to capture an image of the exoplanet without the star.
“Our coronagraph directly captures an image of the exoplanet, as opposed to measuring only the quantity of light from the exoplanet without any spatial orientation,” said Deshler. “Images can provide context and composition information that can be used to determine exoplanet orbits and identify other objects that scatter light from a star such as exozodiacal dust clouds.”
Imaging faint exoplanets
After configuring their coronagraph in the lab, the researchers constructed an artificial star-exoplanet scene in which the exoplanet was positioned close enough to the star to be unresolvable with a traditional telescope. The contrast ratio between the star and the planet was set to 1000:1.
The researchers scanned the position of the exoplanet to simulate an orbit where the planet traverses in front of the star and then tried to determine its position in each frame. The images captured with their experimental setup incorporating the new coronagraph allowed them to estimate the position of the exoplanet at sub-diffraction planet-star separations.
The researchers are working to improve the mode sorter to reduce crosstalk, a type of interference in which light leaks across different optical modes. For scenes with moderate contrast levels, crosstalk is not very problematic. However, the extreme contrasts found in exoplanet science would require a very high-fidelity spatial mode sorter to sufficiently isolate light from the star.
The researchers say that this proof-of-principle experiment could inspire further exploration of optical pre-processing with spatial mode sorters in future astronomical instrumentation. For example, the spatial mode filtering methods they used could address more complex scenarios, such as treating stars as extended objects, and may also lead to new imaging methods for quantum sensing, medical imaging and communications.
Paper: N. Deshler, I. Ozer, A. Ashok, S. Guha, “Experimental Demonstration of a Quantum-Optimal Coronagraph Using Spatial Mode Sorters,” 12, 518-529 (2025).
DOI: 10.1364/OPTICA.545414.
About Optica
Optica is an open-access journal dedicated to the rapid dissemination of high-impact peer-reviewed research across the entire spectrum of optics and photonics. Published monthly by Optica Publishing Group, the Journal provides a forum for pioneering research to be swiftly accessed by the international community, whether that research is theoretical or experimental, fundamental or applied. Optica maintains a distinguished editorial board of more than 60 associate editors from around the world and is overseen by Editor-in-Chief Prem Kumar, Northwestern University, USA. For more information, visit Optica.
About Optica Publishing Group
Optica Publishing Group is a division of the society, Optica, Advancing Optics and Photonics Worldwide. It publishes the largest collection of peer-reviewed and most-cited content in optics and photonics, including 18 prestigious journals, the society’s flagship member magazine, and papers and videos from more than 835 conferences. With over 400,000 journal articles, conference papers and videos to search, discover and access, our publications portfolio represents the full range of research in the field from around the globe.
Researchers developed a new coronagraph that could make it possible to see exoplanets that are normally obscured by light from their parent stars. The images show theoretical, experimental and simulated direct imaging measurements of an artificial exoplanet for various sub-diffraction star-planet separations along the y-axis with a 1000:1 star-planet contrast. In each image, the true location of the exoplanet is shown with the white crosshairs while the star is located at the origin.
Turning down starlight video [VIDEO] |
eo shows theoretical and experimental results from using the new method for direct imaging measurements of an artificial exoplanet (white crosshairs) passing in front of a simulated star. The new coronagraph design made it possible to estimate the position of artificial exoplanets with distances from their host star up to 50 times smaller than what the telescope's resolution limit would normally allow.
Credit
Nico Deshler, University of Arizona
Journal
Optica
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