For icebergs, breaking up can be easy to do

Much of the ice that blankets Antarctica is tied up in glaciers that slide slowly toward the sea. Fed by these glaciers, ice shelves form along the Antarctic coast, floating as thick, frozen plates on the sea surface. Every so often, these ice shelves calve large icebergs.

In March 2000, a colossal iceberg calved off the Ross ice shelf, Antarctica’s largest.  The iceberg — named B-15 – was 183 miles long and 23 miles wide, or nearly the size of Connecticut. Over the past decade, B-15 has broken into many pieces, and one of them, B-15J, eventually drifted north. By early December 2011, B-15J was floating in the Pacific Ocean roughly 2,400 kilometers (1,500 miles) east-southeast of New Zealand. Having migrated to warmer waters, B-15J began to break apart.

The breakup and melting are exactly what you’d expect under these conditions, but the details of the process still interest glaciologists because the melt and breakup of icebergs may shed light on what will happen to Antarctic ice shelves as climate warming continues. Besides the normal phenomenon of iceberg calving, ice shelves that drift to warm climates can mimic one of the most dramatic things ice shelves can do: rapidly disintegrate.

The Larsen Ice Shelf lies on the eastern side of the northernmost tip of the Antarctic Peninsula. In January 1995, 1,500 square kilometers of this shelf suddenly disintegrated. Seven years later, the Larsen Ice Shelf lost another 3,250 square kilometers of ice. Parts of the Wilkins Ice Shelf also disintegrated, in 1998 and in 2008.

The recent northward journey of Iceberg B-15J has provided the perfect opportunity to study the break-up process in detail.

Because the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua and Terra satellites sees every place on Earth at least once a day, MODIS proved crucial in tracking the iceberg’s movements in the vast southern ocean. After locating the iceberg fragments via MODIS imagery, staff at the National Snow and Ice Data Center (NSIDC) provided coordinates to a group of collaborators on the Formosat-2 team in Taiwan. Formosat-2 is in a special orbit, and has a highly manuverable satellite platform, enabling it to acquire a one-meter resolution image of anywhere on Earth, once each day. High-resolution imagery from Formosat-2 enables researchers to observe the details of breakup, as if a microscope had been aimed at the icebergs from space.

Warm ocean water doesn’t simply melt icebergs; the water exerts physical force on the ice, reshaping it in complicated ways. Ted Scambos of NSIDC, Douglas MacAyeal of the University of Chicago, and Cheng-Chien Liu of the National Cheng-Kung University in Taiwan have observed in the Formosat imagery evidence of three general processes of iceberg disintegration.

The first process can be described as ice waterline erosion. Heated by the Sun, warm water at the ocean surface preferentially melts away ice near the waterline, and waves lapping against the iceberg accelerate ice removal. Once significant amounts of ice have been removed from the iceberg at the waterline, the buoyant force of the water pushes parts of the iceberg up from below. As the water undercuts the iceberg edge, the upper parts of the berg fall into the sea. This eventually causes the iceberg to split from below, and break off at the edge. The process begins again on the freshly exposed vertical face.

The newly calved portion of the iceberg can present a strange appearance to the satellite sensor, with part of the ice looking like a deep trough.

Another process (which may occur at the same time as edge erosion) involves melting and surface cracking. This cracking can arise from stresses that come from floating and flexing that occurs from waves in the open ocean. In a floating iceberg, the buoyant force of the water squeezes the sides of iceberg, causing the ice to arch up a little on top, potentially causing fractures on the ice surface. The cracks usually don’t penetrate deep into the berg, but if the iceberg has migrated into warm conditions, melt water can flow into those fractures, deepening them, and eventually slicing off pieces of ice. Several of the icebergs calved from B-15J showed meltwater flooding their surfaces. This is thought to be a key step in the disintegration process.

Cracks are evident in this iceberg remnant of B-15J.

Although tiny compared to the original, Connecticut-sized iceberg from 12 years earlier, the iceberg fragments observed in December 2011 and January 2012 were still sizable, and when pieces of them calve off, they can make big waves. If those waves slam into nearby icebergs, those icebergs might also calve big pieces, making more big waves. The tendency to calve is enhanced by meltwater-filled fractures. Thus, the initial calving can lead to a runaway process where calving leads to waves that create more calvings on other icebergs (or, in the case of a warming ice sheet, other parts of the ice shelf). Dr. MacAyeal has likened this runaway situation to a mosh pit at a rock concert.

In observing the fragments of Iceberg B-15J, Formosat did not capture icebergs close enough to each other to create a mosh-pit phenomenon. But the sensor did capture calving icebergs and tsunami-like waves.

Graphics by Michon Scott and Ted Scambos, NSIDC. Formosat-2 images provided by Dr. Cheng-Chien Liu, National Cheng-Kung University, and Dr. An-Ming Wu, National Space Organization, of Taiwan. Formosat-2 images acquired December 18, 2011 through January 5, 2012.

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News Roundup: A Less Hardy Hardiness Map, Arctic Freshening, and More

A Less Hardy Hardiness Map

The USDA has unveiled a new version of its plant hardiness map, which gardeners use to gauge which plants will survive in which climate zone. (Check your nearest seed packet.)  In the newest iteration, many zones have shifted northward because winters aren’t as cold as they were 22 years ago when the agency last updated the map — good news if you’re trying to grow, say, figs in Boston. On the new map, most parts of the United States are a half-zone warmer — about 5 degrees Fahrenheit (2.7 Celsius). Global warming surely underlies much of the change, but the USDA points out that more sophisticated mapping techniques, plus the inclusion of data from additional weather stations, has also affected the distribution of the zones.

Why the Arctic Ocean Isn’t Freshening
Rapid freshening on the North American side of the Arctic Ocean in recent decades has prompted speculation that rapid melting of sea ice might be causing a slowing of the “conveyor belt” that keeps water circulating through the world’s oceans. New research led by scientists at the University of Washington helps allay such fears. The researchers conclude that freshwater from the Eurasian part of the Arctic Ocean, which comes originally from rivers in Russia, has simply found a new route that brings more of it toward Canada. The cause for the new freshwater route: changes in winds associated with a weather pattern known as the Arctic Oscillation. In fact, the analysis of satellite and oceanographic data shows that overall salinity in the Arctic Ocean remained constant between 2005 and 2008; as the Canadian portion became fresher, the Eurasian portion grew saltier. The shifting path of the fresh water is shown in red in the animation below.

Temperature Ranking-palooza
There’s always a flurry of media activity in January when scientists at NASA, NOAA, and the UK Met Office tally up the year’s temperature measurements and rank how warm the past year was. This January was no exception. In NASA’s analysis, 2011 came in as the 9^th warmest year on the modern meteorological record. However, the longer-term trends are what really matter. Look at the whole record – and here are a few interactive charts that are useful for doing that – and it’s clear that the last decade has been the hottest on record. Another remarkable stat: 9 of the 10 hottest years have occurred since 2000. For more details, the science team that manages NASA’s analysis has published a thorough temperature update here.

Image Gallery: Top Climate and Weather Events of 2011
As part of an annual review of Earth’s climate, scientists from NOAA and other institutions have compiled lists of the ten most significant climate and weather events of the past year.In making their recommendations, judges considered the scope, how unusual the event was, and how much human and economic damage it caused. For the United States, the spring rash of tornadoes in the Southeast, extreme drought in the South, a tornado in Missouri, and spring flooding of the Ohio and Mississippi Rivers topped the list. For Earth as a whole, extreme drought in East Africa, flooding in Thailand and Eastern Australia, the persistence of La Nina, and Tropical Storm Washi all made the list.

A Climate Stopgap (That’s Good for Your Health)
Scanning the coverage of a study published recently in Science could leave you thinking scientists have come across a miracle cure for global warming, while simultaneously saving lives and boosting agricultural yields. The good news is that researchers have demonstrated how a set of simple control strategies for methane and black carbon – such as patching up gas pipelines or using existing technology to reduce vehicle emissions – could markedly slow the pace of climate change AND produce health and agricultural benefits. But the flip side is that such actions would provide only a short-term benefit. In the longer term, societies still have to tackle carbon dioxide emissions to get the climate back to a state of equilibrium.

Explore Ignite@AGU

If you get a kick out of TED talks — those rapid-fire, information-packed lectures that have turned many little-known academics into YouTube stars — it’s time you also check out Ignite. Whereas TED talks can be up to 18 minutes, Ignite allows speakers just five minutes and a maximum of 20 slides. Above, watch NASA Goddard’s Richard Kleidman use his five minutes at an Ignite event to explain why the world needs a more robust network of ground sensors for monitoring air pollution.

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Parade of Volcanoes

It’s been a really active time for the Earth Observatory and volcanoes. In the past three weeks, we’ve posted images of a night-time eruption of Shiveluch, ongoing activity at Puyehue–Cordón Caulle, daytime activity at the Kizimen Volcano, and my own favorite, a brand new island in the Red Sea. And those are just the images we published!

In recent weeks, we had a good shot of activity at Kilauea, but we skipped it since it only had Halema’uma’u activity — which is much like previous images and not the new ocean entry point, which we’ve yet to glimpse in cloud-free satellite imagery. We received an excellent ALI scene of the submarine El Hierro volcano (which we published) and then the next day we received an image of the same volcano from Landsat 7  (which effectively got scooped by ALI).

Another of the moderately recent and interesting images of volcanoes we didn’t use is a very nice ALI shot of the Cerro Hudson volcano in Chile.

We do have a good reason for not using the image. Notice the volcanic activity? Yeah, we didn’t see anything either. What makes this image interesting (to me anyway) is that just two weeks earlier, it looked like this:

We did publish that one. There’s actually not much in the way of activity in that one either, but in the published image, you can see a lot of ash that’s fallen on the ground from activity in October at the volcano.

Just two weeks later, with no new activity, almost all the ashfall seems to have “disappeared.” Fresh snow fell and covered much of it. Also, we got a much better shot with ALI of the volcano, getting a very nice view of the entire caldera, the glacier draining it out of the northeast, and forests in the alpine valleys. The ashfall was nowhere near as extensive and damaging as the Puyehue eruption, which at one point spewed out ash that circled the globe.

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How forest height affected 18th-century science

The new feature story, Seeing Forests for the Trees and the Carbon, discusses the need to form a three-dimensional picture of the world’s forests. Such a three-dimensional picture includes tree canopy height (below). Although canopy height in the Amazon Rainforest doesn’t match those of the Pacific Northwest or Southeast Asia, it still far exceeds the canopy height of Western Europe.

The height differences call to mind the adventures of a European naturalist who set out from Amsterdam in 1699 and spent two years exploring the jungles of Suriname. Bugs were the main attraction; namely, bugs that transformed from caterpillars into moths and butterflies. The scientist became one of the foremost experts on insect metamorphosis, braving tropical fevers, poisonous flora, slave rebellions, and a near shipwreck. What people found most audacious about the expedition was the age (52) and gender of the person who undertook it.

Maria Sibylla Merian was born in 1647 in Frankfurt, Germany, to a family of printers. Besides helping with the family business, she nurtured her interest in bugs from an early age. By the late 1690s, she was living in the bustling metropolis of Amsterdam. Among her many contacts were missionaries who were converting “heathens” half a world away. Merian was invited to visit, giving her the chance to study insects and plants that few other naturalists had ever seen. Teenage daughter in tow, she crossed the Atlantic.

Once she arrived in Suriname, however, Merian faced a challenge she probably hadn’t anticipated. In Germany and the Netherlands, she collected caterpillars from gardens designed for human enjoyment. That meant that her prized bugs could be found on plants that were waist high at most. The tropical jungle was different—not just different from the well-manicured gardens, but from any forests she might have known.

Long before Merian’s time, Europeans had cleared the land on much of their continent, making way for farming and pasture. Suriname, however, was covered in dense forest, with trees soaring 150 feet skyward. Bugs lived high over Merian’s head, completely out of reach most of the time. And in the vertical yards of tree trunk overhead, different insect communities thrived at different levels: The bugs living 30 feet above ground might be completely different from bugs living 60 feet above ground.

She made the most of the situation, collecting and drawing the insects that were within reach, and studying detritus that fell from the forest canopy. In one instance, she even had a mighty tree chopped down to collect its caterpillars and cocoons. Illness forced Merian to cut short her trip, originally planned for five years. She did, however, return to Europe with enough samples, drawings, and notes to assemble Metamorphosis Insectorum Surinamensium (Insects of Surinam), published in 1705.

Image credit: UF Digital Collections. Some rights reserved.

The same tall tropical trees that occasionally hampered Merian’s research continue to provide homes and food for insects, birds, and mammals today. While Merian could only gaze at the trees from the ground, modern satellite sensors can monitor the trees from above, gauging their height, and helping scientists understand how much carbon they hold.

Further reading: Todd, Kim. (2007). Chrysalis: Maria Sibylla Merian and the Secrets of Metamorphosis. Harcourt, Inc., Orlando.

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Happy birthday, Steno

On January 11, 2012, Google celebrated the 374th birthday of geology pioneer, Nicolaus Steno, with a special Google Doodle.

Steno was a 17th-century anatomist and pioneering geologist. After dissecting a shark head, he realized that “tongue stones” — believed to belong to snakes turned to stone — were actually shark teeth.

In Steno’s era, many people believed fossils were just weird objects created by rocks. But he realized that fossils were the remains of ancient organisms.

Besides studying fossils, Steno examined rocks around Tuscany. He found that they were deposited in layers, with older rocks underlying newer rock layers. This basic principle of geology helped later scientists piece together the history of life on Earth.

You can learn more about Steno’s life and work in this Earth Observatory feature story published in 2004.

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Coming Soon to a Theater or Billboard Near You

For a month in the fall of 2011, NASA staff conducted an experiment of a different kind. They shared satellite images and maps with Chicagoans, but not in a classroom or a museum. The images of Earth were posted at malls, at bus and train stations, in O’Hare Airport, and on roadside billboards. The experimental question was: would compelling images of the city and planet provoke people to learn more about earth science?

“We wanted to try and grab the attention and interest of an ‘on-the-go’ audience, one that might not seek out NASA information unless they had a primer,” said Brian Campbell, a NASA Earth science education specialist who led the effort. “The health of our planet is in jeopardy, and we want the public to know why and how we are trying to understand what is happening.”

The idea was to meet Americans where they live; that is, to bring science to the people, instead of waiting for the people to find science. Twelve NASA missions collaborated on images, messages, and strategic development of the Know Your Earth public awareness campaign. (Click on the link to see all of the images.)

A secondary goal was to make the public aware that NASA does Earth science. So many Americans think the agency is just human spaceflight, big astronomy, and planetary probes. But in fact NASA is one of the world’s largest funders and employers of earth scientists.

Know Your Earth first launched in 2010 with the premiere of video segments shown in 291 movie theaters across the United States. The full-length video is available here on YouTube. Below is the shorter teaser that also hit theaters in July 2010.

Results and evaluations of the fall 2011 awareness campaign are still being compiled, but early reactions are positive. So what do you think of the Know Your Earth campaign?  Does it make you want to learn more?  Where should they take this project next?  See www.nasa.gov/KnowYourEarth

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The rising costs of natural hazards

Some of the world’s largest companies suffered multimillion-dollar losses from flooding or drought in the past year, according to a November 16 report from The Guardian. Citing a study from the Carbon Disclosure Project, The Guardian stated that although too much or too little water can affect the profits of large companies, many of those companies remain unprepared for problems likely to arise in the future.

Natural hazards cause widespread losses in dollars and lives, but Mother Nature does not deserve all the blame. Growing human populations and increasingly expensive infrastructure have also contributed to the losses. In short, more people have more stuff for Nature to damage or destroy. For more background, see the Earth Observatory feature The Rising Cost of Natural Hazards.

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News Roundup: When Music and Climate Change Meet; A Hair Below a Sea Ice Record, and More

When Music and Climate Change Meet
During a recent event that highlighted the intersection of art and science, NASA climatologist Gavin Schmidt offered an intriguing pitch (see 5:15 in the video above) for a climate change symphony that would use music to tell the story of Earth’s long and varied geologic history. “There are trends in the tides of the planet that come from the changes in the continents, the wobbles in the Earth’s orbit,” he said, emphasizing Earth’s many rhythms, crescendos, and cataclysms that lend themselves to music. Schmidt’s comment came during a panel discussion that included former New York Times reporter Andy Revkin and EPA climatologist Irene Nielson, and followed a unique  Antarctica-inspired performance from a string quartet arranged by Paul Miller (aka DJ Spooky). Schmidt isn’t alone in thinking along these lines. NPR recently interviewed composer Andre Gribou about creating musical scores for films shown on spherical visualization system called Science on a Sphere. A new SOS film – called Loop – came out this week.

It’s Official: 2011 Sea Ice Second Lowest on Record
A few weeks ago, the National Snow and Ice Data Center offered an initial assessment of Arctic sea ice that showed that the minimum extent for the year was the second lowest on record. Since then, NASA scientists have dotted the i’s and crossed the t’s and confirmed the finding. Joey Comiso, a NASA sea ice expert, said the continued pattern of low sea ice extents fits into the large-scale decline that has unfolded over the past three decades. “The sea ice is not only declining, the pace of the decline is becoming more drastic,” Comiso pointed out. “The older, thicker ice is declining faster than the rest, making for a more vulnerable perennial ice cover.”

So That’s What Happened to UARS
An old stalwart of NASA’s Earth-observing fleet, the six-ton Upper Atmosphere Research Satellite (UARS), came tumbling through the atmosphere in an uncontrolled reentry in late-September that generated a slew of headlines about the risks of being struck by falling space junk. Those risks, of course, are minuscule (about 1 in 21 trillion) and the handful of satellite pieces that did survive reentry ended up falling harmlessly into a remote area of the South Pacific in the general vicinity of Christmas Island. After its launch in 1991, UARS played a critical role in parsing out how chlorofluorocarbons, chemicals that used to be used widely as refrigerants, deplete  ozone. UARS is gone, but for NASA the study of ozone goes on. Later this month, a new ozone-monitoring instrument called Ozone Mapper Profile Suite (OMPS) will launch as part of the NPOESS Preparatory Project.

Texas Drought Overstays Its Welcome
If you’re from Texas, you know this already. But for those who aren’t: the state has been embroiled in an extended heat wave and drought that has left large portions of the state on fire and caused billions of dollars in losses for farmers. If that’s not gloomy enough for you, climatologist John Nielsen-Gammon of the University of Texas warned that the situation isn’t likely to improve anytime soon. The drought could easily persist until 2012.  The problem? The establishment of a new La Niña in the central Pacific Ocean, a phenomenon characterized by cooler ocean temperatures that leads to wetter than normal conditions in the Pacific Northwest and drier conditions in the Southwest.

Dramatic Arctic Ozone Loss
In April, the World Meteorological Organization announced that scientists had observed significant thinning of the ozone layer over the Arctic. That news turned heads because it’s the ozone layer over Antarctica that’s most prone to ozone loss. Recently, a research team associated with NASA’s Jet Propulsion Laboratory offered a more comprehensive assessment of the unusual spring thinning in the Arctic  based on data collected by the Aura and CALIPSO satellites, balloon instruments, and atmospheric models. The bottom line: the upper atmosphere of the Arctic grew so cold this winter that ozone loss was severe enough that scientists say what amounts to a “hole” (five times the size of California) formed over the region and persisted for more than a month. Is climate change to blame?  Sort of, but not exactly. Manmade chlorofluorocarbons drive ozone depletion (not the greenhouse gas carbon dioxide), but scientists say that global warming has likely exacerbated ozone loss because it cools the upper part of the atmosphere even as it warms the lower part. Confused? The Capital Weather Gang has a post that delves into the details.

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What are you doing to celebrate?

It’s Earth Science Week. What are you doing to celebrate?

Our colleagues within NASA and at other institutions have organized a series of educational and outreach activities this week that showcase our science and the people behind it. Some highlights include:

+ A webcast with NASA’s chief scientist, Waleed Abdalati, from 1-2 p.m. Eastern Time on October 12. Teachers and students are invited to join Waleed Abdalati to share stories and perspectives on our ever-changing Earth. Participants can email questions during the webcast. Visit http://dln.nasa.gov/dln and scroll down to the DLiNfo Channel Webcasts to link to the webcast (no registration necessary).

+ Profiles of women making a difference in Earth science at http://women.nasa.gov/earth-science-week-special. The stars include: Cynthia Rosenzweig, who leads a group studying the impacts of climate change; Erika Podest, who studies wetlands and the global carbon and water cycles; Erica Alston, who focuses on fisheries and atmospheric science, including air quality; and Claire Parkinson, project scientist for the Aqua mission and a climatologist studying sea ice.

+ An introduction to the next Earth-science satellite, NPP, set to launch later this month. The National Polar-orbiting Operational Environmental Satellite System Preparatory Project will play a key role in studying climate change. Learn more about NPP and its polar bear mascot NPPy at http://npp.gsfc.nasa.gov/kids.html.

+ Short videos introducing Earth Science Week and NASA’s role in studying Earth, as well as educator resources and programs. Visit http://climate.nasa.gov/esw2011

Organized by the American Geological Institute and its federal and private partners, Earth Science Week was created in 1998 to help the public gain a better appreciation for the science and stewardship of our planet. The theme this year is “Our Ever-Changing Earth,” something you can observe daily here on the Earth Observatory.

“We invite you to join us online, explore our changing planet, and share this work with your students, family, and colleagues,” says Eric Brown de Colstoun, a scientist who also coordinates Earth science education for NASA’s Goddard Space Flight Center. “You can also choose to reflect on how lucky we are to live on this beautiful and ever-changing planet, the home base from which we carry out our many explorations into the universe.”

More information about Earth Science Week can be found at http://climate.nasa.gov/esw2011/. Archived events from 2011 and years past can be found here.

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Where are the stars?

Vishnu, an Earth Observatory reader, posed a great question after viewing “The Six-Million Mile View of Earth and Moon“:

“I’ve never seen a photo like that. Was the background beyond Earth ‘photoshopped’ to remove background stars, or is that angle so narrow and the background space so coincidentally ‘empty’ that no visible stars are there to be seen?”

Our colleague D.C. Agle from the Jet Propulsion Laboratory worked with the Juno science team to provide this answer:

“The exposure time for the image — it’s actually three images: red, green and blue — was too short for any stars to be seen. Earth and the Moon were bright enough that a short-duration exposure was all that was needed. The brighter an object is, the shorter the exposure time required to capture an image of it. It’s similar to why you don’t really see stars in Apollo photos from the moon – the subjects being photographed were so much brighter than the background stars that the exposures weren’t long enough to capture the stars.

Here are two examples from the Cassini mission to Saturn showing long exposures that did capture stars. In both cases, the stars show up as streaks because of the relatively long exposures required to capture a good image of the moons.
+ Tethys in Eclipse
+ Iapetus by Saturn Shine
Cassini stays locked onto its target and actually turns very slightly during the exposures. Meanwhile the stars move slowly across the sky, and their images are smeared out as streaks.

Interestingly, the Voyager spacecraft took this remarkable image from about 7 million miles away in 1977. The difference is that Voyager was a survey and flyby mission, and its cameras were like long-range telescopes. Juno is an orbiter that will get extremely close to Jupiter every 11 days, and its camera is designed for that. It will take amazing wide-angle views from only a few thousand miles above the cloud tops. So that’s why Juno’s camera has a field of view about 130 times wider than Voyager, and thus why Eath seems so much smaller even though Voyager was a little farther away when it took its Earth-moon image.”

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Along those same lines, another reader (Norton) pointed out the lack of stars in a shot closer to Earth: ”I was curious to see stars in this image of earth, yet in most other images the stars aren’t visible.

In one of your images of the day a week or two later, there are no stars visible. Is this solely due to how much light is captured by the camera and the stars are a weaker source; or is something else occurring that the stars aren’t visible?”

Our colleague Will Stefanov of the ISS Crew Earth Observations Team at NASA’s Johnson Space Center offered this explanation:

“It’s dependant on the camera settings, and to some degree the camera itself. The Nikon D3 cameras the astronauts often use are designed to be more sensitive in low-light situations, so you are more likely to capture some bright stars in the imagery. Images taken with long exposures and/or wide apertures will also record more starlight due to the greater amount of light on the camera sensor. Shorter exposure imagery of the Earth — the majority of daytime images — typically do not record stars as they are too dim compared to the brightness of the planet.

The astronauts generally follow a set procedure, with defined camera settings, for Crew Earth Observations imagery. But occasionally they will change those settings for a specific purpose or for personal experimentation. This can lead to images in which the stars are more visible for the reasons described above.

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