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“The models were right”: astronomers find ‘missing’ matter
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By NASA
A funky effect Einstein predicted, known as gravitational lensing — when a foreground galaxy magnifies more distant galaxies behind it — will soon become common when NASA’s Nancy Grace Roman Space Telescope begins science operations in 2027 and produces vast surveys of the cosmos.
This image shows a simulated observation from NASA’s Nancy Grace Roman Space Telescope with an overlay of its Wide Field Instrument’s field of view. More than 20 gravitational lenses, with examples shown at left and right, are expected to pop out in every one of Roman’s vast observations. A journal paper led by Bryce Wedig, a graduate student at Washington University in St. Louis, Missouri, estimates that of those Roman detects, about 500 from the telescope’s High-Latitude Wide-Area Survey will be suitable for dark matter studies. By examining such a large population of gravitational lenses, the researchers hope to learn a lot more about the mysterious nature of dark matter.Credit: NASA, Bryce Wedig (Washington University), Tansu Daylan (Washington University), Joseph DePasquale (STScI) A particular subset of gravitational lenses, known as strong lenses, is the focus of a new paper published in the Astrophysical Journal led by Bryce Wedig, a graduate student at Washington University in St. Louis. The research team has calculated that over 160,000 gravitational lenses, including hundreds suitable for this study, are expected to pop up in Roman’s vast images. Each Roman image will be 200 times larger than infrared snapshots from NASA’s Hubble Space Telescope, and its upcoming “wealth” of lenses will vastly outpace the hundreds studied by Hubble to date.
Roman will conduct three core surveys, providing expansive views of the universe. This science team’s work is based on a previous version of Roman’s now fully defined High-Latitude Wide-Area Survey. The researchers are working on a follow-up paper that will align with the final survey’s specifications to fully support the research community.
“The current sample size of these objects from other telescopes is fairly small because we’re relying on two galaxies to be lined up nearly perfectly along our line of sight,” Wedig said. “Other telescopes are either limited to a smaller field of view or less precise observations, making gravitational lenses harder to detect.”
Gravitational lenses are made up of at least two cosmic objects. In some cases, a single foreground galaxy has enough mass to act like a lens, magnifying a galaxy that is almost perfectly behind it. Light from the background galaxy curves around the foreground galaxy along more than one path, appearing in observations as warped arcs and crescents. Of the 160,000 lensed galaxies Roman may identify, the team expects to narrow that down to about 500 that are suitable for studying the structure of dark matter at scales smaller than those galaxies.
“Roman will not only significantly increase our sample size — its sharp, high-resolution images will also allow us to discover gravitational lenses that appear smaller on the sky,” said Tansu Daylan, the principal investigator of the science team conducting this research program. Daylan is an assistant professor and a faculty fellow at the McDonnell Center for the Space Sciences at Washington University in St. Louis. “Ultimately, both the alignment and the brightness of the background galaxies need to meet a certain threshold so we can characterize the dark matter within the foreground galaxies.”
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This video shows how a background galaxy’s light is lensed or magnified by a massive foreground galaxy, seen at center, before reaching NASA’s Roman Space Telescope. Light from the background galaxy is distorted, curving around the foreground galaxy and appearing more than once as warped arcs and crescents. Researchers studying these objects, known as gravitational lenses, can better characterize the mass of the foreground galaxy, which offers clues about the particle nature of dark matter.Credit: NASA, Joseph Olmsted (STScI) What Is Dark Matter?
Not all mass in galaxies is made up of objects we can see, like star clusters. A significant fraction of a galaxy’s mass is made up of dark matter, so called because it doesn’t emit, reflect, or absorb light. Dark matter does, however, possess mass, and like anything else with mass, it can cause gravitational lensing.
When the gravity of a foreground galaxy bends the path of a background galaxy’s light, its light is routed onto multiple paths. “This effect produces multiple images of the background galaxy that are magnified and distorted differently,” Daylan said. These “duplicates” are a huge advantage for researchers — they allow multiple measurements of the lensing galaxy’s mass distribution, ensuring that the resulting measurement is far more precise.
Roman’s 300-megapixel camera, known as its Wide Field Instrument, will allow researchers to accurately determine the bending of the background galaxies’ light by as little as 50 milliarcseconds, which is like measuring the diameter of a human hair from the distance of more than two and a half American football fields or soccer pitches.
The amount of gravitational lensing that the background light experiences depends on the intervening mass. Less massive clumps of dark matter cause smaller distortions. As a result, if researchers are able to measure tinier amounts of bending, they can detect and characterize smaller, less massive dark matter structures — the types of structures that gradually merged over time to build up the galaxies we see today.
With Roman, the team will accumulate overwhelming statistics about the size and structures of early galaxies. “Finding gravitational lenses and being able to detect clumps of dark matter in them is a game of tiny odds. With Roman, we can cast a wide net and expect to get lucky often,” Wedig said. “We won’t see dark matter in the images — it’s invisible — but we can measure its effects.”
“Ultimately, the question we’re trying to address is: What particle or particles constitute dark matter?” Daylan added. “While some properties of dark matter are known, we essentially have no idea what makes up dark matter. Roman will help us to distinguish how dark matter is distributed on small scales and, hence, its particle nature.”
Preparations Continue
Before Roman launches, the team will also search for more candidates in observations from ESA’s (the European Space Agency’s) Euclid mission and the upcoming ground-based Vera C. Rubin Observatory in Chile, which will begin its full-scale operations in a few weeks. Once Roman’s infrared images are in hand, the researchers will combine them with complementary visible light images from Euclid, Rubin, and Hubble to maximize what’s known about these galaxies.
“We will push the limits of what we can observe, and use every gravitational lens we detect with Roman to pin down the particle nature of dark matter,” Daylan said.
The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory in Southern California; Caltech/IPAC in Pasadena, California; the Space Telescope Science Institute in Baltimore; and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
By Claire Blome
Space Telescope Science Institute, Baltimore, Md.
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Last Updated Jun 12, 2025 EditorAshley BalzerContactAshley Balzerashley.m.balzer@nasa.govLocationNASA Goddard Space Flight Center Related Terms
Nancy Grace Roman Space Telescope Astrophysics Dark Matter Galaxies Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research The Universe Explore More
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By NASA
5 min read
Percolating Clues: NASA Models New Way to Build Planetary Cores
NASA’s Perseverance rover was traveling in the channel of an ancient river, Neretva Vallis, when it captured this view of an area of scientific interest nicknamed “Bright Angel” – the light-toned area in the distance at right. The area features light-toned rocky outcrops that may represent either ancient sediment that later filled the channel or possibly much older rock that was subsequently exposed by river erosion. NASA/JPL-Caltech A new NASA study reveals a surprising way planetary cores may have formed—one that could reshape how scientists understand the early evolution of rocky planets like Mars.
Conducted by a team of early-career scientists and long-time researchers across the Astromaterials Research and Exploration Science (ARES) Division at NASA’s Johnson Space Center in Houston, the study offers the first direct experimental and geochemical evidence that molten sulfide, rather than metal, could percolate through solid rock and form a core—even before a planet’s silicate mantle begins to melt.
For decades, scientists believed that forming a core required large-scale melting of a planetary body, followed by heavy metallic elements sinking to the center. This study introduces a new scenario—especially relevant for planets forming farther from the Sun, where sulfur and oxygen are more abundant than iron. In these volatile-rich environments, sulfur behaves like road salt on an icy street—it lowers the melting point by reacting with metallic iron to form iron-sulfide so that it may migrate and combine into a core. Until now, scientists didn’t know if sulfide could travel through solid rock under realistic planet formation conditions.
Working on this project pushed us to be creative. It was exciting to see both data streams converge on the same story.
Dr. Jake Setera
ARES Scientist with Amentum
The study results gave researchers a way to directly observe this process using high-resolution 3D imagery—confirming long-standing models about how core formation can occur through percolation, in which dense liquid sulfide travels through microscopic cracks in solid rock.
“We could actually see in full 3D renderings how the sulfide melts were moving through the experimental sample, percolating in cracks between other minerals,” said Dr. Sam Crossley of the University of Arizona in Tucson, who led the project while a postdoctoral fellow with NASA Johnson’s ARES Division. “It confirmed our hypothesis—that in a planetary setting, these dense melts would migrate to the center of a body and form a core, even before the surrounding rock began to melt.”
Recreating planetary formation conditions in the lab required not only experimental precision but also close collaboration among early-career scientists across ARES to develop new ways of observing and analyzing the results. The high-temperature experiments were first conducted in the experimental petrology lab, after which the resulting samples—or “run products”—were brought to NASA Johnson’s X-ray computed tomography (XCT) lab for imaging.
A molten sulfide network (colored gold) percolates between silicate mineral grains in this cut-out of an XCT rendering—rendered are unmelted silicates in gray and sulfides in white. Credit: Crossley et al. 2025, Nature Communications X-ray scientist and study co-author Dr. Scott Eckley of Amentum at NASA Johnson used XCT to produce high-resolution 3D renderings—revealing melt pockets and flow pathways within the samples in microscopic detail. These visualizations offered insight into the physical behavior of materials during early core formation without destroying the sample.
The 3D XCT visualizations initially confirmed that sulfide melts could percolate through solid rock under experimental conditions, but that alone could not confirm whether percolative core formation occurred over 4.5 billion years ago. For that, researchers turned to meteorites.
“We took the next step and searched for forensic chemical evidence of sulfide percolation in meteorites,” Crossley said. “By partially melting synthetic sulfides infused with trace platinum-group metals, we were able to reproduce the same unusual chemical patterns found in oxygen-rich meteorites—providing strong evidence that sulfide percolation occurred under those conditions in the early solar system.”
To understand the distribution of trace elements, study co-author Dr. Jake Setera, also of Amentum, developed a novel laser ablation technique to accurately measure platinum-group metals, which concentrate in sulfides and metals.
“Working on this project pushed us to be creative,” Setera said. “To confirm what the 3D visualizations were showing us, we needed to develop an appropriate laser ablation method that could trace the platinum group-elements in these complex experimental samples. It was exciting to see both data streams converge on the same story.”
When paired with Setera’s geochemical analysis, the data provided powerful, independent lines of evidence that molten sulfide had migrated and coalesced within a solid planetary interior. This dual confirmation marked the first direct demonstration of the process in a laboratory setting.
Dr. Sam Crossley welds shut the glass tube of the experimental assembly. To prevent reaction with the atmosphere and precisely control oxygen and sulfur content, experiments needed to be sealed in a closed system under vacuum. Credit: Amentum/Dr. Brendan Anzures The study offers a new lens through which to interpret planetary geochemistry. Mars in particular shows signs of early core formation—but the timeline has puzzled scientists for years. The new results suggest that Mars’ core may have formed at an earlier stage, thanks to its sulfur-rich composition—potentially without requiring the full-scale melting that Earth experienced. This could help explain longstanding puzzles in Mars’ geochemical timeline and early differentiation.
The results also raise new questions about how scientists date core formation events using radiogenic isotopes, such as hafnium and tungsten. If sulfur and oxygen are more abundant during a planet’s formation, certain elements may behave differently than expected—remaining in the mantle instead of the core and affecting the geochemical “clocks” used to estimate planetary timelines.
This research advances our understanding of how planetary interiors can form under different chemical conditions—offering new possibilities for interpreting the evolution of rocky bodies like Mars. By combining experimental petrology, geochemical analysis, and 3D imaging, the team demonstrated how collaborative, multi-method approaches can uncover processes that were once only theoretical.
Crossley led the research during his time as a McKay Postdoctoral Fellow—a program that recognizes outstanding early-career scientists within five years of earning their doctorate. Jointly offered by NASA’s ARES Division and the Lunar and Planetary Institute in Houston, the fellowship supports innovative research in astromaterials science, including the origin and evolution of planetary bodies across the solar system.
As NASA prepares for future missions to the Moon, Mars, and beyond, understanding how planetary interiors form is more important than ever. Studies like this one help scientists interpret remote data from spacecraft, analyze returned samples, and build better models of how our solar system came to be.
For more information on NASA’s ARES division, visit: https://ares.jsc.nasa.gov/
Victoria Segovia
NASA’s Johnson Space Center
281-483-5111
victoria.segovia@nasa.gov
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Last Updated May 22, 2025 Related Terms
Astromaterials Planetary Science Planetary Science Division The Solar System Explore More
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Quantum Sensing via Matter-Wave Interferometry Aboard the International Space Station
Future space missions could use quantum technologies to help us understand the physical laws that govern the universe, explore the composition of other planets and their moons, gain insights into unexplained cosmological phenomena, or monitor ice sheet thickness and the amount of water in underground aquafers on Earth.
Upgraded hardware being prepared at Jet Propulsion Lab for launch and install into the Cold Atom Lab on the International Space Station. The Science Module in the background enables CAL researchers to conduct atom interferometry research in Earth’s orbit. Credit: NASA/JPL-Caltech NASA’s Cold Atom Lab (CAL), a first-of-its-kind facility aboard the International Space Station, has performed a series of trailblazing experiments based on the quantum properties of ultracold atoms. The tool used to perform these experiments is called an atom interferometer, and it can precisely measure gravity, magnetic fields, and other forces.
Atom interferometers are currently being used on Earth to study the fundamental nature of gravity and are also being developed to aid aircraft and ship navigation, but use of an atom interferometer in space will enable innovative science capabilities.
Physicists have been eager to apply atom interferometry in space, both to enable new measurements for space science and to capitalize on the extended free-fall conditions found in space. This could enable researchers to achieve unprecedented performance from these quantum sensors.
These interferometers, however, require exquisitely sensitive equipment, and they were previously considered too fragile to function for extended periods without hands-on attention. The Cold Atom Lab, which is operated remotely from Earth, has now demonstrated that it is possible to conduct atom interferometry in space. The CAL Science Team has published two papers so far documenting these experimental milestones.
Depiction of the atom interferometer (AI) setup onboard the ISS in CAL (on the right), showing the interior components of the instrument, and the path of a retro-reflected laser beam (red) inside the vacuum system. The expanded image on the left shows the beam entering the vacuum chamber through a window and between pairs of traces on the atom chip, which are used to confine and cool the atoms to ultracold temperatures. Credit: NASA/JPL-Caltech The results of the first study, published in the November 2023 issue of Nature, described the demonstration of simultaneous atom interferometry with both rubidium and potassium quantum gases for the first time in space. The dual-species atom interferometer not only exhibited robust and repeatable operation of atom interferometry in Earth orbit, but it also served as a pathfinder for future experiments that aim to use quantum gases to test the universality of free fall, a key tenet of Einstein’s theory of general relativity.
In the second study, the results of which were featured in the August 2024 issue of Nature Communications, members of the science team used the CAL atom interferometer to measure subtle vibrations of the space station and to remotely measure the frequency of the atom interferometer laser— the first time ultra-cold atoms have been used to detect changes in the surrounding environment in space. This paper also reported on the demonstration of the wave-like nature of matter persisting for the longest ever freefall time (over a tenth of a second) in space.
“Reaching these milestones was incredibly challenging, and our success was not always a given,” said Jason Williams, the Cold Atom Lab project scientist at NASA’s Jet Propulsion Laboratory in Southern California. “It took dedication and a sense of adventure by the team to make this happen.”
Space-based sensors that can measure gravity with high precision have a wide range of potential applications. They could reveal the composition of planets and moons in our solar system, because different materials have different densities that create subtle variations in gravity.
The U.S.-German GRACE-FO (Gravity Recovery and Climate Experiment Follow-on) mission is currently collecting gravity measurements using classical sensors that detect slight changes in gravity to track the movement of water and ice on Earth. A future mission using atom interferometry could provide better precision and stability, revealing even more detail about surface mass changes.
Precise measurements of gravity could also offer insights into the nature of dark matter and dark energy, two major cosmological mysteries. Dark matter is an invisible substance that makes up about 27% of the universe, while the “regular” matter that composes planets, stars, and everything else we can see makes up only 5%. Dark energy makes up the remaining 68% of the universe and is the driver of the universe’s accelerating expansion.
“Atom interferometry could also be used to test Einstein’s theory of general relativity in new ways,” said University of Virginia professor Cass Sackett, a Cold Atom Lab principal investigator. “This is the basic theory explaining the large-scale structure of our universe, and we know that there are aspects of the theory that we don’t understand correctly. This technology may help us fill in those gaps and give us a more complete picture of the reality we inhabit.”
About the size of a minifridge, the Cold Atom Lab launched to the space station in 2018 with the goal of advancing quantum science by placing a long-term facility in the microgravity environment of low Earth orbit. The lab cools atoms to almost absolute zero, or minus 459 degrees Fahrenheit (minus 273 degrees Celsius). At this temperature, some atoms can form a Bose-Einstein condensate, a state of matter in which all atoms essentially share the same quantum identity. As a result, some of the atoms’ typically microscopic quantum properties become macroscopic, making them easier to study.
Quantum properties can sometimes cause atoms to act like solid objects and sometimes like waves. Scientists don’t yet entirely understand how the building blocks of matter can transition between such different physical behaviors, but they’re using quantum technology like what’s available on the Cold Atom Lab to seek answers.
In microgravity, Bose-Einstein condensates can reach colder temperatures and can exist for longer, giving scientists more opportunities to study them. The atom interferometer is among several tools in the CAL facility enabling precision measurements by harnessing the quantum nature of atoms.
Dual-species atom interferometry in space. (Left) Normalized population for ultracold gases of potassium (blue) and rubidium (red) in one of two output states following a simultaneous dual-species atom interferometry sequence. (Right) Correlations observed in the relative population of potassium and rubidium output states. Credit: NASA/JPL-Caltech Due to its wave-like behavior, a single atom can simultaneously travel two physically separate paths. If gravity or other forces are acting on those waves, scientists can measure that influence by observing how the waves recombine and interact.
“I expect that space-based atom interferometry will lead to exciting new discoveries, fantastic quantum technologies impacting everyday life, and will transport us into a quantum future,” said Nick Bigelow, a professor at University of Rochester in New York and Cold Atom Lab principal investigator for a consortium of U.S. and German scientists who co-authored the studies cited above.
Designed and built at the NASA Jet Propulsion Laboratory, Cold Atom Lab is sponsored by the Biological and Physical Sciences (BPS) Division of NASA’s Science Mission Directorate at the Agency’s headquarters in Washington DC and the International Space Station Program at NASA’s Johnson Space Center in Houston, Texas. The work carried out at the Jet Propulsion Laboratory, California Institute of Technology, was executed under a contract with the National Aeronautics and Space Administration.
Learn more about Cold Atom Lab at https://coldatomlab.jpl.nasa.gov/
Just how cold are the atoms in Cold Atom Lab? Find out at https://www.jpl.nasa.gov/news/news.php?feature=7311
To learn more about the Cold Atom Lab’s recent upgrades visit https://www.jpl.nasa.gov/news/upgrading-the-space-stations-cold-atom-lab-with-mixed-reality and https://www.jpl.nasa.gov/news/news.php?feature=7660
Project Lead: Kamal Oudrhiri, Jet Propulsion Laboratory, California Institute of Technology
Sponsoring Organization: Biological and Physical Sciences Division (BPS)
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Last Updated May 06, 2025 Related Terms
Technology Highlights Biological & Physical Sciences Cold Atom Laboratory (CAL) GRACE-FO (Gravity Recovery and Climate Experiment Follow-on) Science-enabling Technology View the full article
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By NASA
6 min read
NASA Data Helps Map Tiny Plankton That Feed Giant Right Whales
This North Atlantic right whale, named “Bowtie,” was spotted feeding in southern Maine waters in January 2025. A new technique aims to use NASA satellite data to see the plankton these whales depend on from space. Credit: New England Aquarium, taken under NMFS permit # 25739 In the waters off New England, one of Earth’s rarest mammals swims slowly, mouth agape. The North Atlantic right whale filters clouds of tiny reddish zooplankton — called Calanus finmarchicus — from the sea. These zooplankton, no bigger than grains of rice, are the whale’s lifeline. Only about 370 of these massive creatures remain.
For decades, tracking the tiny plankton meant sending research vessels out in the ocean, towing nets and counting samples by hand. Now, scientists are looking from above instead.
Using NASA satellite data, researchers found a way to detect Calanus swarms at the ocean surface in the Gulf of Maine, picking up on the animals’ natural red pigment. This early-stage approach, described in a new study, may help researchers better estimate where the copepods gather, and where whales might follow.
Tracking the zooplankton from space could aid both the whales and maritime industries. By predicting where these mammals are likely to feed, researchers and marine resource managers hope to reduce deadly vessel strikes and fishing gear entanglements — two major threats to the species. Knowing the feeding patterns could also help shipping and fishing industries operate more efficiently.
Calanus finmarchicus, a tiny zooplankton powering North Atlantic food webs, fuels right whale populations with its energy-rich lipid reserves. Credit: Cameron Thompson “NASA invests in this kind of research because it connects space-based observation with real-world challenges,” said Cynthia Hall, a support scientist at NASA headquarters in Washington. She works with the Early Career Research Program, which partly funded the work. “It’s yet another a way to put NASA satellite data to work for science, communities, and ecosystems.”
Revealing the Ocean’s Hidden Patterns
The new approach uses data from the Moderate Resolution Imaging Spectroradiometer (MODIS) aboard NASA’s Aqua satellite. The MODIS instrument doesn’t directly see the copepods themselves. Instead, it reads how the spectrum of sunlight reflected from the ocean surface changes in response to what’s in the water.
When large numbers of the zooplankton rise to the surface, their reddish pigment — astaxanthin, the same compound that gives salmon its pink color — subtly alters how photons, or particles of light, from the sun are absorbed or scattered in the water. The fate of these photons in the ocean depends on the mix of living and non-living matter in seawater, creating a slight shift in color that MODIS can detect.
“We didn’t know to look for Calanus before in this way,” said Catherine Mitchell, a satellite oceanographer at Bigelow Laboratory for Ocean Sciences in East Boothbay, Maine. “Remote sensing has typically focused on smaller things like phytoplankton. But recent research suggested that larger, millimeter-sized organisms like zooplankton can also influence ocean color.”
A few years ago, researchers piloted a satellite method for detecting copepods in Norwegian waters. Now, some of those same scientists — along with Mitchell’s team — have refined the approach and applied it to the Gulf of Maine, a crucial feeding ground for right whales during their northern migration. By combining satellite data, a model, and field measurements, they produced enhanced images that revealed Calanus swarms at the sea surface, and were able to estimate numbers of the tiny animals.
“We know the right whales are using habitats we don’t fully understand,” said Rebekah Shunmugapandi, also a satellite oceanographer at Bigelow and the study’s lead author. “This satellite-based Calanus information could eventually help identify unknown feeding grounds or better anticipate where whales might travel.”
Tracking Elusive Giants
Despite decades of study, North Atlantic right whales remain remarkably enigmatic to scientists. Once fairly predictable in their movements along the Eastern Seaboard of North America, these massive mammals began abandoning some traditional feeding grounds in 2010-2011. Their sudden shift to unexpected areas like the Gulf of Saint Lawrence caught people off guard, with deadly consequences.
“We’ve had whales getting hit by ships and whales getting stuck in fishing gear,” said Laura Ganley, a research scientist in the Anderson Cabot Center for Ocean Life at the New England Aquarium in Boston, which conducts aerial and boat surveys of the whales.
In 2017, the National Oceanic and Atmospheric Administration designated the situation as an “unusual mortality event” in an effort to address the whales’ decline. Since then, 80 North Atlantic right whales have been killed or sustained serious injuries, according to NOAA.
NASA satellite imagery from June 2009 was used to test a new method for detecting the copepod Calanus finmarchicus in the Gulf of Maine and estimating their numbers from space. Credit: NASA Earth Observatory image by Wanmei Liang, using data from Shunmugapandi, R., et al. (2025) In the Gulf of Maine, there’s less shipping activity, but there can be a complex patchwork of lobster fishing gear, said Sarah Leiter, a scientist with the Maine Department of Marine Resources. “Each fisherman has 800 traps or so,” Leiter explained. “If a larger number of whales shows up suddenly, like they just did in January 2025, it is challenging. Fishermen need time and good weather to adjust that gear.”
What excites Leiter the most about the satellite data is the potential to use it in a forecasting tool to help predict where the whales could go. “That would be incredibly useful in giving us that crucial lead time,” she said.
PACE: The Next Generation of Ocean Observer
For now, the Calanus-tracking method has limitations. Because MODIS detects the copepods’ red pigment, not the animals themselves, that means other small, reddish organisms can be mistaken for the zooplankton. And cloud cover, rough seas, or deeper swarms all limit what satellites can spot.
MODIS is also nearing the end of its operational life. But NASA’s next-generation PACE (Plankton, Aerosol, Cloud, ocean Ecosystem) satellite — launched in 2024 — is poised to make dramatic improvements in the detection of zooplankton and phytoplankton.
NASA’s Ocean Color Instrument on the PACE satellite captured these swirling green phytoplankton blooms in the Gulf of Maine in April 2024. Such blooms fuel zooplankton like Calanus finmarchicus. Credit: NASA “The PACE satellite will definitely be able to do this, and maybe even something better,” said Bridget Seegers, an oceanographer and mission scientist with the PACE team at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The PACE mission includes the Ocean Color Instrument, which detects more than 280 wavelengths of light. That’s a big jump from the 10 wavelengths seen by MODIS. More wavelengths mean finer detail and better insights into ocean color and the type of plankton that the satellite can spot.
Local knowledge of seasonal plankton patterns will still be essential to interpret the data correctly. But the goal isn’t perfect detection, the scientists say, but rather to provide another tool to inform decision-making, especially when time or resources are limited.
By Emily DeMarco
NASA Headquarters
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Last Updated May 05, 2025 Editor Emily DeMarco Related Terms
Earth Moderate Resolution Imaging Spectroradiometer (MODIS) Oceans PACE (Plankton, Aerosol, Cloud, Ocean Ecosystem) Explore More
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May’s Night Sky Notes: How Do We Find Exoplanets?
Astronomers have been trying to discover evidence that worlds exist around stars other than our Sun since the 19th century. By the mid-1990s, technology finally caught up with the desire for discovery and led to the first discovery of a planet orbiting another sun-like star, Pegasi 51b. Why did it take so long to discover these distant worlds, and what techniques do astronomers use to find them?
The Transit Method
A planet passing in front of its parent star creates a drop in the star’s apparent brightness, called a transit. Exoplanet Watch participants can look for transits in data from ground-based telescopes, helping scientists refine measurements of the length of a planet’s orbit around its star. Credit: NASA’s Ames Research Center One of the most famous exoplanet detection methods is the transit method, used by Kepler and other observatories. When a planet crosses in front of its host star, the light from the star dips slightly in brightness. Scientists can confirm a planet orbits its host star by repeatedly detecting these incredibly tiny dips in brightness using sensitive instruments. If you can imagine trying to detect the dip in light from a massive searchlight when an ant crosses in front of it, at a distance of tens of miles away, you can begin to see how difficult it can be to spot a planet from light-years away! Another drawback to the transit method is that the distant solar system must be at a favorable angle to our point of view here on Earth – if the distant system’s angle is just slightly askew, there will be no transits. Even in our solar system, a transit is very rare. For example, there were two transits of Venus visible across our Sun from Earth in this century. But the next time Venus transits the Sun as seen from Earth will be in the year 2117 – more than a century from the 2012 transit, even though Venus will have completed nearly 150 orbits around the Sun by then!
The Wobble Method
As a planet orbits a star, the star wobbles. This causes a change in the appearance of the star’s spectrum called Doppler shift. Because the change in wavelength is directly related to relative speed, astronomers can use Doppler shift to calculate exactly how fast an object is moving toward or away from us. Astronomers can also track the Doppler shift of a star over time to estimate the mass of the planet orbiting it. NASA, ESA, CSA, Leah Hustak (STScI) Spotting the Doppler shift of a star’s spectra was used to find Pegasi 51b, the first planet detected around a Sun-like star. This technique is called the radial velocity or “wobble” method. Astronomers split up the visible light emitted by a star into a rainbow. These spectra, and gaps between the normally smooth bands of light, help determine the elements that make up the star. However, if there is a planet orbiting the star, it causes the star to wobble ever so slightly back and forth. This will, in turn, cause the lines within the spectra to shift ever so slightly towards the blue and red ends of the spectrum as the star wobbles slightly away and towards us. This is caused by the blue and red shifts of the star’s light. By carefully measuring the amount of shift in the star’s spectra, astronomers can determine the size of the object pulling on the host star and if the companion is indeed a planet. By tracking the variation in this periodic shift of the spectra, they can also determine the time it takes the planet to orbit its parent star.
Direct Imaging
Finally, exoplanets can be revealed by directly imaging them, such as this image of four planets found orbiting the star HR 8799! Space telescopes use instruments called coronagraphs to block the bright light from the host star and capture the dim light from planets. The Hubble Space Telescope has captured images of giant planets orbiting a few nearby systems, and the James Webb Space Telescope has only improved on these observations by uncovering more details, such as the colors and spectra of exoplanet atmospheres, temperatures, detecting potential exomoons, and even scanning atmospheres for potential biosignatures!
NASA’s James Webb Space Telescope has provided the clearest look in the infrared yet at the iconic multi-planet system HR 8799. The closest planet to the star, HR 8799 e, orbits 1.5 billion miles from its star, which in our solar system would be located between the orbit of Saturn and Neptune. The furthest, HR 8799 b, orbits around 6.3 billion miles from the star, more than twice Neptune’s orbital distance. Colors are applied to filters from Webb’s NIRCam (Near-Infrared Camera), revealing their intrinsic differences. A star symbol marks the location of the host star HR 8799, whose light has been blocked by the coronagraph. In this image, the color blue is assigned to 4.1 micron light, green to 4.3 micron light, and red to the 4.6 micron light. NASA, ESA, CSA, STScI, W. Balmer (JHU), L. Pueyo (STScI), M. Perrin (STScI) You can find more information and activities on NASA’s Exoplanets page, such as the Eyes on Exoplanets browser-based program, The Exoplaneteers, and some of the latest exoplanet news. Lastly, you can find more resources in our News & Resources section, including a clever demo on how astronomers use the wobble method to detect planets!
The future of exoplanet discovery is only just beginning, promising rich rewards in humanity’s understanding of our place in the Universe, where we are from, and if there is life elsewhere in our cosmos.
Originally posted by Dave Prosper: July 2015
Last Updated by Kat Troche: April 2025
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