When you look at Earth from above as often as we do, you become intimately familiar with the shapes and patterns that can emerge across the planet. Some are made by people and others by nature. Some are ephemeral and others more permanent.
Today we took a light-hearted approach to the Image of the Day, explaining the science behind one such shape—what appears to be a Valentine in the Sky. The image prompted us to look and see where other heart-shaped features have turned up.
On February 12, 1809, Charles Robert Darwin was born in England in the town of Shrewsbury. The famed naturalist, geologist, and biologist is best known for his 19th century expedition to the Galápagos Islands, which inspired revolutionary insights about evolution and natural selection. Lesser known is that the expedition to the Galápagos was just one part of a much longer journey. The Second Voyage of the HMS Beagle brought Darwin and his fellow travelers to South America, Australia, Africa, and several islands in between. Here are a few interesting places where the HMSBeagle stopped that we have covered in earlier stories.
January 1832: The Dusty Canary Islands, Tenerife
The crew of the Beagle was denied landing on Tenerife because of fears they might be carrying cholera. The Operational Land Imager (OLI) on Landsat 8 acquired this image of the island on January 25, 2016.
Darwin was struck by the intensity of the dust in this area. “The atmosphere is generally very hazy, chiefly due to an impalpable dust, which is constantly falling, even on vessels far out at sea,” he wrote. “It is produced, as I believe, from the wear and tear of volcanic rocks, and must come from the coast of Africa.”
Christmas 1832: Cape Horn, South America
Southwest of Cape Horn at the southern tip of South America, the ocean floor rises sharply. Along with the potent westerly winds that swirl around the Furious Fifties, this pushes up massive waves with frightening regularity. Add in frigid water temperatures, rocky coastal shoals, and stray icebergs—which drift north from Antarctica across the Drake Passage—and it is easy to see why the area is known as a graveyard for ships. In his journal, Darwin described the harrowing journey as the explorers tried to round the Horn just before Christmas.
September 1835: The Galapagos
The Galapagos archipelago includes more than 125 islands, islets, and rocks populated by a diversity of wildlife. Charles Darwin’s book, The Voyage of the Beagle, cast a spotlight on the Galapagos, which he called “a little world within itself, or rather a satellite attached to America, whence it has derived a few stray colonists.” It was this little world that would revolutionize scientific understanding of biology and lead to Darwin’s On the Origin of Species, which would come to be known as the foundation of evolution.
November 1835: The Coral Reefs of Tahiti
On this stopover, Darwin had a chance to explore coral reef.
“We paddled for some time about the reef admiring the pretty branching Corals,” he wrote. “It is my opinion, that besides the avowed ignorance concerning the tiny architects of each individual species, little is yet known, in spite of the much which has been written, of the structure and origin of the Coral Islands and reefs.”
The Enhanced Thematic Mapper Plus on the Landsat 7 satellite captured this natural-color image of Tahiti on July 11, 2001. This island is part of a volcanic chain formed by the northwestward movement of the Pacific Plate over a fixed hotspot.
1836: Pondering Phytoplankton Near Australia
All the sea travel offered plenty of time to observe and ponder the intricacies of phytoplankton.
“My attention was called to a reddish-brown appearance in the sea. The whole surface of the water, as it appeared under a weak lens, seemed as if covered by chopped bits of hay, with their ends jagged,” he wrote. “These are minute cylindrical, in bundles or rafts of from twenty to sixty in each…Their numbers must be infinite: the ship passed through several bands of them, one of which was about ten yards wide, and, judging from the mud-like color of the water, at least two and a half miles.”
On August 9, 2011, the Moderate Resolution Imaging Spectroradiometer (MODIS) on the Aqua satellite captured this image of a similar band of brown between the Great Barrier Reef and the Queensland shore. Though it’s impossible to identify the species from satellite imagery, such red-brown streamers are usually trichodesmium. Sailors have long called these brown streamers “sea sawdust.”
A few days after we published a Landsat 8 image of a deadly dam collapse and flood in Brazil, astronauts photographed the scene from the International Space Station on February 2, 2019.
The tailings pond label points to the source of the mine waste. When an earthen dam on the southwestern edge of that pond collapsed on January 25, it sent a torrent of sludge pouring down a valley toward the Paraopeba River. Over a distance of roughly 8 kilometers (5 miles), the mine sludge overran the mine’s headquarters, a hotel, and a residential area. Videos published by news agencies and AGU’s Landslide Blog offer a remarkable view of the dam collapsing and sludge rushing forward at roughly 120 kilometers (75 miles) per hour.
NASA was mostly shut down for January 2019, but Earth wasn’t. In case you missed it, here are some of the big stories we didn’t cover during the impasse.
Scientists Find Evidence of An Ancient Earth Rock on the Moon Four billion years ago, the Moon was about three times closer to Earth than it is now. So if a large asteroid or comet slammed into Earth and jettisoned material into space, it was more likely that rock fragments might end up landing on the Moon. That’s how an international team of scientists working with the Center for Lunar Science and Exploration (CLSE) think that a small fragment composed of quartz, feldspar, and zircon—a combination of minerals commonly found on Earth—ended up embedded within a larger Moon rock collected by Apollo astronauts. The team recently revealed evidence from the ancient rock fragment, suggesting that it is one of the oldest Earth rocks ever found.
A Rare Typhoon Hits Thailand It is rare for powerful tropical storms to strike Thailand. Before January 2019, the last time it happened was 1962. So meteorologists took notice when Tropical Storm Pabuk slammed into southern Thailand on January 4, 2019, packing sustained winds of 95 kilometers per hour (60 mph) and delivering torrential rains to some of Thailand’s most popular tourist destinations. The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Aqua satellite captured this image of the storm on January 4, 2019.
Snow Falls in Algeria (Yes, the Sahara) In another unusual weather event, fresh snow created surreal scenery in Algeria when it coated Saharan desert dunes in mid-January. This is just the third time snow has fallen in Ain Sefra, the gateway to the Sahara Desert, in the past 37 years. (The last time was 2018.) The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite captured an image of the snow on January 14, 2019. It is composed with false color, using a combination of infraed and visible light (MODIS bands 7-2-1). Snow appears blue with this band combination.
China’s War on Particulates May Be Making Ozone Pollution Worse For the past few years, China has advanced an ambitious plan to reduce emissions of fine particulate (PM2.5), a harmful type of air pollution. Authorities have restricted the number of vehicles on the roads, capped how much coal industries can burn, and shuttered many polluting factories and power plants. The result has been impressive: over five years, concentrations of PM2.5 in eastern China have fallen nearly 40 percent. But, there is another wrinkle. Particulates also sponge up substances that make it harder for ground-level ozone to form. So even as concentrations of PM2.5 decline, ozone concentrations are rising, new research shows.
Can Satellites SensePoverty? Increasingly, yes, at least in rural areas. By analyzing observations of villages in Kenya, one team of researchers recently showed that land use and land cover data from satellites contains some useful clues for identifying the poorest households in rural areas. Key indicators included: the size of buildings within a homestead, the amount of bare agricultural land adjacent to a homestead, and the length of the growing season. The researchers think this type of information could make it easier to monitor the progress of efforts designed to reduce poverty in rural areas, such as the U.N. Sustainable Development Goals.
A meteor exploded over western Cuba on February 1, 2019, and it delivered an impressive light show. The event was captured by numerous ground-based cameras. It was also spotted from space.
Researchers from the Cooperative Institute for Meteorological Satellite Studies wrote a blog post showing a series of images and data from the event, including the animation above. It was composed from false-color images gathered by NOAA’s GOES-16 satellite. (NASA builds GOES satellites for NOAA.) The dark blue pixels moving toward the northeast appear to be the signature of a debris cloud drifting in the atmosphere after the meteor exploded. A close look at visible imagery from GOES-16 reveals a shadow apparently cast by the debris cloud.
Meanwhile, scientists at NASA’s Short-term Prediction Research and Transition Center (SPoRT) reported signs of the meteor flash in an image acquired by the Geostationary Lightning Mapper (GLM). The meteor flash appears in this image as blue pixels over Cuba. (The blue in the top-left corner is lightning activity over the ocean.)
Last year, we published a story explaining how scientists had used satellite images of rocks stained pink with guano to discover several unexpectedly large colonies of Adélie penguins on the Danger Islands. Now the researchers are back with a new announcement: Using Landsat data, they have analyzed how the size of that penguin population has changed since 1982. They also used Landsat’s deep archive of satellite imagery to analyze what the penguins eat and whether their diets have changed over the past three decades.
“While the Adélie population [on the Danger Islands] is massive, it was even larger in the past,” said Heather Lynch of Stony Brook University. “We believe the population peaked in the late 1990s and has been on a slow steady decline ever since.” The scientists are still working out what may have caused the 10 to 15 percent decline in the population, but they think it is probably related to changing environmental conditions.
Adélie penguins are particularly sensitive to changes in climate because they require ice-free land areas to breed and access to open water. They also need enough sea ice to support populations of key food sources. The researchers thought that changing diets would accompany the decline in population, but by analyzing the spectral signatures of all the guano stains found in cloud-free Landsat image of the islands since 1982, they were surprised to discover the penguins’ diets have stayed the same.
Penguin guano ranges from white to pink to dark red. White guano is from eating mostly fish; pink and red is from mostly eating krill. The University of Connecticut’s Casey Youngflesh, however, noticed some intriguing regional patterns in what Adélie penguins eat. Colonies in West Antarctica tend to eat more krill, while colonies in East Antarctic consume more fish. The reasons for the difference are not clear, though Youngflesh is looking into the possibility that differences in the Antarctic silverfish population may be a factor.
Discovering the big colonies on the Danger Islands has also opened up a new pathway for figuring out when penguins first arrived. By digging through layers of guano-stained pebbles during a recent field expedition and dirt and dating them with radiocarbon techniques, Michael Polito of Louisiana State University worked out that penguins must have arrived on the Danger Islands about 2,900 ago, thousands of years earlier than previous evidence suggested.
Credits: Heather Lynch, Stony Brook University.
Expect to hear even more guano-stained discoveries in the future. “We are only just scratching the surface of what we can do in terms of tracking seabirds from space,” said Lynch. “We should be able to extend the technique to snow petrel, boobies, and cormorants.”
Lynch put the total number of penguins on the Danger Islands at roughly 1.5 million — more than live on all the rest of the Antarctic Peninsula combined.
Read more about the Danger Island Adélie penguins from NASA and MAPPPD.
Lately, it feels like we’re hearing about wildfires erupting in the western United States more often. But how have wildfire occurrences changed over the decades?
Researchers with the NASA-funded Rehabilitation Capability Convergence for Ecosystem Recovery (RECOVER) have analyzed more than 40,000 fires from Colorado to California between 1950 to 2017 to learn how wildfire frequency, size, location, and a few other traits have changed.
Here are six trends they have observed in the western United States:
1. There are more fires.
Over the past six decades, there has been a steady increase in the number of fires in the western U.S. In fact, the majority of western fires—61 percent—have occurred since 2000 (shown in the graph below).
Those fires are also burning more acres of land. The average annual amount of acres burned has been steadily increasing since 1950. The number of megafires—fires that burn more than 100,000 acres (156 square miles)—has increased in the past two decades. In fact, no documented megafires occurred before 1970.
Source: NASA RECOVER / Keith Weber
The recent increase in fire frequency and size is likely related to a few reasons, including the rise of global temperatures since the start of the new millennia. Seventeen of the 18 warmest years on record have occurred since 2001.
Global temperatures can affect local fire conditions. Amber Soja, a wildfire expert at NASA’s Langley Research Center, said fire-weather conditions—high temperatures, low relative humidity, high wind speed, and low precipitation—can increase dryness and make vegetation in the west easier to burn. “Those fire conditions all fall under weather and climate,” said Soja. “The weather will change as Earth warms, and we’re seeing that happen.”
3. A small percentage of the West has burned.
Even though fire frequency and size has increased, only a small percentage of western lands— 11 percent—has burned since 1950. In this map, wildfires are shown in orange. Private lands are shown in purple while public lands are clear (no color). The location of wildfires was random; that is, there was no bias toward fires affecting private or public land.
Keith Weber, a professor at Idaho State University who led the analysis, was surprised at the 11 percent figure. There’s no clear reason yet for why more of the region hasn’t burned. “Some of the 89% may not burn because it has low susceptibility—not dry enough or it has low fuel (vegetation),” said Weber. “Some areas may be really ripe for a fire, but they have not had an ignition source yet.”
4. The same areas keep burning.
How has only 11 percent of the west burned, yet the annual number of acres burned and the frequency of fire increased? It turns out that many fires are occurring in areas that have already experienced fires, known as burn-on-burn effects. About 3 percent—almost a third of the burned land—has seen repeated fire activity.
The map here shows the locations of repeated fire activity. While you can’t see it at this map’s resolution, some areas have experienced as many as 11 fires since 1950. In those areas, fires occurred about every seven years, said Weber, which is about the amount of time it takes for an ecosystem to build up enough vegetation to burn again.
5. Recent fires are burning more coniferous forests than other types of landscape.
Since 2000, wildfires have shifted from burning shrub-lands to burning conifers. The Southern Rocky Mountains Ponderosa Pine Woodland landscape has experienced the most acres burned—more than 3 million.
The reason might lie within the tree species. Ponderosa Pine is a fire-adapted species. With its thick and flaky bark, the tree can withstand low-intensity surface fires. It also drops branches lower as they age, which deters fire from climbing up the tree and burning their green needles. “The fire will remove forest undergrowth, but will be just fine for the pines,” said Weber. “We are starting to see Ponderosa Pines thrive in those areas.”
Source: National Park Service
6. Wildfires are going to have a big impact on our future.
Research suggests that global warming is predicted to increase the number of very large fires (more than 50,000 acres) in the western United States by the middle of the century (2041-2070).
The map below shows the projected increase in the number of “very large fire weeks”—periods where conditions will be conducive to very large fires—by mid-century (2041-2070) compared to the recent past (1971-2000). The projections are based on scenarios where carbon dioxide emissions continue to increase.
Wildfires are expected to further stress our nation’s “aging and deteriorating infrastructure.”
Smoke from wildfires is expected to impair outdoor recreational activities.
Wildfires on rangelands are expected to disrupt the U.S.’s agricultural productivity, creating challenges to livestock health, declining crop yields and quality, and affecting sustainable food security and price stability.
Increased wildfire activity is “expected to decrease the ability of U.S. forests to support economic activity, recreation, and subsistence activities.”
More about the source data:
Unless otherwise stated in the article, these data come from NASA’s Rehabilitation Capability Convergence for Ecosystem Recovery. RECOVER is an online mapping tool that pulls together data on 26 different variables useful for fires managers, such as burn severity, land slope, vegetation, soil type, and historical wildfires. In the past, fire managers might need several days or weeks to assemble and present such a large amount of information. RECOVER does so in five minutes, with the help of sophisticated server technologies that gather data from a multitude of sources. Funded by NASA’s Applied Science Program, RECOVER provides these data on specific fires to help fire managers to start rehabilitation plans earlier and implement recovery efforts quickly.
Every month on Earth Matters, we offer a puzzling satellite image. The November 2018 puzzler is above. Your challenge is to use the comments section to tell us what we are looking at and why it is interesting.
How to answer. You can use a few words or several paragraphs. You might simply tell us the location. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure feature in the image. If you think something is interesting or noteworthy, tell us about it.
The prize. We can’t offer prize money or a trip to Mars, but we can promise you credit and glory. Well, maybe just credit. Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. After we post the answer, we will acknowledge the first person to correctly identify the image at the bottom of this blog post. We also may recognize readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have shaped the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you would like to recognize, please mention that as well.
Recent winners. If you’ve won the puzzler in the past few months or if you work in geospatial imaging, please hold your answer for at least a day to give less experienced readers a chance to play.
Releasing Comments. Savvy readers have solved some puzzlers after a few minutes. To give more people a chance to play, we may wait between 24 to 48 hours before posting comments.
November 22nd, 2018 by Adam Voiland & Michael Carlowicz
Editor’s Note: We have highlighted the story of the Pilgrims and Thanksgiving several times over the years. Here are some of those pieces in one convenient place.
First stop, Holland. Image credit: NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey.
Most school children in America learn about the Pilgrims—the group of English settlers who endured a harrowing journey to the New World in 1620 on the Mayflower. It is sometimes overlooked, however, that Plymouth was not the first stop—nor the intended destination—for this congregation of religious separatists from the town of Scrooby in the English county of Nottinghamshire.
Before ever setting foot in North America, the Pilgrims spent several years living in Leiden, a city in the Netherlands. Most of the hundred or so people in the congregation lived in one-room cottages near Leiden University, in the shadow of the Pieterskerk, the oldest church in the city.
About a decade after they arrived, the congregation decided it was time to move. Tough economic conditions in Leiden meant few new recruits from England were willing to join them; Dutch culture was thought to be a bad influence on the children; and there was a looming possibility that Holland would go to war with Spain, a leading Catholic power.
Leaving Leiden University. NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey.
Leiden was a city of many waterways, so when the Pilgrims were ready to leave in July 1620, they boarded several small boats on the Rapenburg Canal (near the university). This narrow canal fed into the larger Vliet Canal, which flows from Leiden toward Delft.
From there, they made their way back to England, where they struggled for a few months trying to repair a leaking ship. After abandoning that ship, they finally set sail for the New World on September 6, 1620, knowing they had to cross nearly 3,000 miles of open ocean.
The North Atlantic can be treacherous. Image credit: NASA Earth Observatory image by Jesse Allen and Robert Simmon, using VIIRS data from the Suomi National Polar-orbiting Partnership.
The original destination: the mouth of the Hudson River. NASA Earth Observatory image by Jesse Allen, using Landsat data from the U.S. Geological Survey.
The first half of the two month journey proved to be smooth and uneventful. But in October, they encountered a series of storms that turned the sea into a writhing cauldron. During one particularly bad storm, the ship nearly capsized.
Their intended destination was the northern edge of Virginia Colony, which at the time stretched from to the mouth of the Hudson River. However, the storms blew the Pilgrims off course toward Cape Cod in Massachusetts.
Provincetown, Massachusetts. NASA Earth Observatory image by Jesse Allen, using Landsat data from the U.S. Geological Survey.
When they realized this, they contemplated heading south. However, they were wary of the shallow waters and shoals east and south of Cape Cod and Nantucket—waters full of the sandy, rocky outwash from ancient glaciers. They sailed instead around the northeastern tip of the Cape and on November 21, 1620, dropped anchor just off the shores of modern-day Provincetown. While resting in that harbor, they composed and signed the first self-governing document in American history, the Mayflower Compact.
Over the coming weeks, they made first contact with Native American people, likely the Nauset tribe. First Encounter Beach in Eastham marks the reported location of a skirmish between the colonists and the tribe. The Pilgrims eventually sailed across Cape Cod Bay and settled in Plymouth.
First Encounter Beach. NASA Earth Observatory image by Jesse Allen, using Landsat data from the U.S. Geological Survey.
It was in Plymouth where the Pilgrims celebrated the first Thanksgiving, a three-day harvest celebration that included feasting, games, and military exercises.
While there continues to be debate among historians about the circumstances and influences that led to the first Thanksgiving, there is evidence that the roots of the tradition might be traced back to Leiden. During their time in the city, the Pilgrims would have experienced a celebratory thanksgiving service and festival that was held each year on October 3 to mark the 1574 end of the Spanish siege of the city.
Crossing Cape Cod Bay brought the Pilgrims to Plymouth. This astronaut photograph was acquired on November 7, 2007.
As powerful downslope winds sent the deadly Camp Fire raging through bone-dry vegetation in northern California on November 8, 2018, sensors on the ground and in space began to detect sharp increases in air pollution downwind of the inferno.
Meanwhile on the ground, atmospheric scientists Pawan Gupta,Robert Levy, Prakash Doraiswamy, and Olga Pikelnaya have been keeping a close eye on air quality data from a network of low-cost sensors distributed throughout the region. These sensors measure the mass concentration of fine particulate matter (PM2.5). Some stations measured PM2.5 values higher than 500 micrograms per cubic meter, which is about 40 times higher than the level considered safe to breathe.
“On November 9th, due to favorable wind direction, most of the smoke was confined to a smaller region north of San Francisco, but the wind direction changed on the 10th, and smoke spread over a much larger region,” noted Gupta, who is based at NASA’s Marshall Space Flight Center and works with NASA’s SERVIR and ARSET programs. “On the 11th and 12th, the wind direction again changed, and most of the smoke blew over the ocean.”
Gupta is involved in an ongoing effort to deploy and test low-cost commercial air quality sensors to see how well their measurements compare with standard EPA measurements and NASA satellite observations. The ground-based sensors that are part of official state and federal government observing networks cost several thousand dollars each, but the new generation of sensors cost just a few hundred dollars—cheap enough that Gupta thinks they could proliferate and potentially be used to help fill in crucial gaps, particularly in countries with few air quality sensors.
Image Credit: NASA Earth Observatory/Landsat 8/OLI
“The low-cost sensors have performed as expected, though with varying accuracy for certain types of particles,” said Gupta. “Going forward, we hope to use what we learn from them to improve the techniques scientists use to derive levels of particulate matter at the surface from the entire column aerosol measurements observed by satellites.”
So far, Gupta and his colleagues have deployed about 40 low-cost sensors in California. Next summer, they plan to add hundreds of additional sensors in New Delhi, an area that regularly gets hit with dust storms and smoke from agricultural burning. They also plan to deploy sensors in North Carolina, an area with relatively clean air.
Citizen scientists interested in air quality can get involved in the project. Gupta and colleagues from RTI International, South Coast Air Quality Management District, NASA, and other institutions are recruiting volunteers to host the low-cost sensor and share the results with the experts.