Smithsonian.com

Image via NASA/NOAA/GSFC/Suomi NPP/VIIRS/Norman Kuring

Last year, to celebrate the 42nd Earth Day, we took a look at 10 of the most surprising, disheartening, and exciting things we’d learned about our home planet in the previous year—a list that included discoveries about the role pesticides play in bee colony collapses, the various environmental stresses faced by the world’s oceans and the millions of unknown species are still out in the environment, waiting to be found.

This year, in time for Earth Day on Monday, we’ve done it again, putting together another list of 10 notable discoveries made by scientists since Earth Day 2012—a list that ranges from specific topics (a species of plant, a group of catfish) to broad (the core of planet Earth), and from the alarming (the consequences of climate change) to the awe-inspiring (Earth’s place in the universe).

Even the supposedly pristine Antarctic landscape is marred by trash heaps. Image via Germany Federal Environment Agency Report (PDF)

1. Trash is accumulating everywhere, even in Antarctica. As we’ve explored the most remote stretches of the planet, we’ve consistently left behind a trail of one supply in particular: garbage. Even in Antarctica, a February study found (PDF), abandoned field huts and piles of trash are mounting. Meanwhile, in the fall, a new research expedition went to study the Great Pacific Garbage Patch, counting nearly 70,000 pieces of garbage over the course of a month at sea.

2. Climate change could erode the ozone layer. Until recently, atmospheric scientists viewed climate change and the disintegration of the ozone layer as entirely distinct problems. Then, in July, Harvard researcher Jim Anderson (who won a Smithsonian Ingenuity Award for his work) led a team that published the troubling finding that the two might be linked. Some warm summer storms, they discovered, can pull moisture up into the stratosphere, an atmospheric layer 6 miles up. Through a chain of chemical reactions, this moisture can lead to the disintegration of ozone, which is crucial for protecting us from ultraviolet (UV) radiation. Climate change, unfortunately,  is projected to cause more of these sorts of storms.

3. This flower lives on exactly two cliffs in Spain. In September, Spanish scientists told us about one of the most astounding survival stories in the plant kingdom: Borderea chouardii, an extremely rare flowering plant that is found on only two adjacent cliffs in the Pyrenees. The species is believed to be a relic of the Tertiary Period, which ended more than 2 million years ago, and relies on several different local ant species to spread pollen between its two local populations.

4. Some catfish have learned to kill pigeons. In December, a group of French scientists revealed a phenomenon they’d carefully been observing over the previous year: a group of catfish in Southwestern France had learned how to leap onto shore, briefly strand themselves, and swim back into the water to consume their prey. With more than 2,000,000 Youtube views so far, this is clearly one of the year’s most widely enjoyed scientific discoveries.

5. Fracking for natural gas can trigger moderate earthquakes. Scientists have known for a while that whenever oil and gas are extracted from the ground at a large scale, seismic activity can be induced. Over the past few years, evidence has mounted that injecting water, sand and chemicals into bedrock to cause gas and oil to flow upward—a practice commonly known as fracking—can cause earthquakes by lubricating pre-existing faults in the ground. Initially, scientists found correlations between fracking sites and the number of small earthquakes in particular areas. Then, in March, other researchers found evidence that a medium-sized 2011 earthquake in Oklahoma(which registered a 5.7 on the moment magnitude scale) was likely caused by injecting wastewater into wells to extract oil.

6. Our planet’s inner core is more complicated than we thought. Despite decades of research, new data on the iron and nickel ball 3,100 miles beneath our feet continue to upset our assumptions about just how the earth’s core operates. A paper published last May showed that iron in the outer parts of the inner core is losing heat much more quickly than previously estimated, suggesting that it might hold more radioactive energy than we’d assumed, or that novel and unknown chemical interactions are occurring. Ideas for directly probing the core are widely regarded as pipe dreams, so our only options remains studying it from afar, largely by monitoring seismic waves.

The berries of Pollia condensata were found to produce the most intense color in the natural world. Image via PNAS

7. The world’s most intense natural color comes from an African fruit. When a team of researchers looked closely at the blue berries of Pollia condensata, a wild plant that grows in East Africa, they found something unexpected: it uses an uncommon structural coloration method to produce the most intense natural color ever measured. Instead of pigments, the fruit’s brilliant blue results from nanoscale-size cellulose strands layered in twisting shapes, which which interact with each other to scatter light in all directions.

8. Climate change will let ships cruise across the North Pole. Climate change is sure to create countless problems for many people around the world, but one specific group is likely to see a significant benefit from it: international shipping companies. A study published last month found that rising temperatures make it probable that during summertime, reinforced ice-breaking ships will be able to sail directly across the North Pole—an area currently covered by up to 65 feet of ice—by the year 2040. This dramatic shift will shorten shipping routes from North America and Europe to Asia.

9. One bacteria species conducts electricity. In October, a group of Danish researchers revealed that the seafloor mud of Aarhus’ harbor was coursing with electricity due to an unlikely source: mutlicellular bacteria that behave like tiny electrical cables. The organisms, the team found, built structures that traveled several centimeters down into the sediment and conduct measurable levels of electricity. The researchers speculate that this seemingly strange behavior is a byproduct of the way of the bacteria harvests energy from the nutrients buried in the soil.

Kepler 62f, discovered yesterday, is the most promising exoplanet candidate yet in terms of its potential to harbor life. Image via NASA/Ames/JPL-Caltech

10. Our Earth isn’t alone. Okay, this one might not technically be a discovery about Earth, but over the past year we have learned a tremendous amount about what our Earth isn’t: the only habitable planet in the visible universe. The pace of exoplanet detection has accelerated rapidly, with a total of 866 planets in other solar systems discovered so far. As our methods have become more refined, we’ve been able to detect smaller and smaller planets, and just yesterday, scientists finally discovered a pair of distant planets in the habitable zone of their stars that are relatively close in size to Earth, making it more likely than ever that we might have spied an alien planet that actually supports life.

Lashed to a spear made in the Gilbert Islands, researchers found a tooth from a dusky shark, a species previously unknown in the area. Image via PLOS ONE/Drew et. al.

For decades, a total of 124 swords, tridents and spears taken from the Pacific Ocean’s Gilbert Islands in the mid-1800s sat untouched in vaults in Chicago’s Field Museum. The weapons—each made up of dozens of individual shark teeth that islanders lashed to a wooden core with coconut fibers—were primarily considered artifacts of anthropological value.

Then, Joshua Drew, a marine conservation biologist at the museum, had an unusual idea: that the shark teeth lining the serrated blades could also serve as an ecological snapshot of the reefs that lined the islands more than a century ago. Sharks can be clearly identified solely by their teeth, so the teeth that islanders had harvested and used for their weapons might reflect historical biodiversity in the reefs that’s since been lost due to environmental degradation.

When Drew and others closely examined the hundreds of teeth on the weapons, they found that they came from eight different shark species, six of which were known to commonly swim in the Gilbert Islands’ waters. Two species, though—the dusky shark (Carcharhinus obscurus) and the spottail shark (Carcharhinus sorrah)—were something of a surprise. When the researchers looked at the scientific literature and various museum holdings of fish collected in the area, they found that these two species had never been documented within thousands of miles of the islands.

A trident lined with shark teeth, used in the study. Image via PLOS ONE/Drew et. al.

Drew calls this “shadow biodiversity”—a reflection of the life that lived in an ecosystem before we even started studying what was there. “[These are] hints and whispers of what these reefs used to be like,” he said in a press statement accompanying the paper documenting his team’s find, published today in PLOS ONE. “It’s our hope that by understanding how reefs used to look we’ll be able to come up with conservation strategies to return them to their former vivid splendor.”

Working with Mark Westneat, the museum’s curator of fishes, and Christopher Philipp, who manages the anthropology collections, Drew classified each tooth on every weapon by shark species, primarily using field guides and photos. In cases where the tooth’s identity was ambiguous, he made use of the Museum’s own ichthyological holdings, comparing it to preserved specimens from each shark species.

Because dusky and spottail shark teeth were found on the weapons—crafted sometime between the 1840s and 1860s, shortly before they were collected—the researchers believe these two species were once part of the ecosystem and have since been eradicated. There is the possibility that the teeth were harvested elsewhere and came to the Gilbert Islands via trade, but the team says it’s unlikely.

For one, sharks figure largely in the islanders’ traditional culture, and it’s well-known that they had effective shark-fishing techniques, making it unlikely that they’d go to the trouble of exporting teeth from afar. The two species’ teeth were among the most common found on the weapons, so it also stands to reason that they were fairly abundant nearby. Secondly, there is no historical or archaeological evidence that trade occurred between the extremely remote Gilbert Islands and either the Solomon Islands (the closest known location of spottail sharks) or Fiji (for dusky sharks).

It’s impossible to know for sure, but given the environmental degradation that’s occurred over the past century in the Pacific’s coral reefs, the researchers suspect that humans played a role in these sharks’ local eradication. Because sharks mature slowly and have a small number of offspring per individual, they can be wiped out quickly by moderate levels of fishing, and the commercial shark fishing industry started up in the area as early as 1910.

Rigorous fish surveys of the Pacific didn’t begin for a few more decades, so these weapons—and perhaps other human artifacts that incorporate biological specimens—serve as a valuable time capsule of the ecosystems that predated scientific study. Drew thinks that the “shadow diversity” we’ve since lost should inspire people in the marine conservation field to recreate the biodiversity that predates the Industrial Age.

“When we set up modern conservation plans, we shouldn’t sell ourselves short,” he told Nature last year, when he revealed his preliminary results at a conference. “We might not recapture the vivid splendor of those super-rich levels, but this information argues for setting up management plans to protect what sharks are there.”

Beneath the seafloor, there is an ecosystem of microbes living in the oceanic crust, independent of sunlight. Here, the seafloor of McMurdo Sound in Antarctica. NSF/USAP photo by Steve Clabuesch

If you were to hit the seafloor and continue to travel down, you’d run into an ecosystem unlike any other on earth. Beneath several hundred meters of seafloor sediment is the Earth’s crust: thick layers of lava rock running with cracks that cover around 70% of the planet’s surface. Seawater flows through the cracks, and this system of rock-bound rivulets is enormous: it’s the largest aquifer on earth, containing 4% of global ocean volume, says Mark Lever, an ecologist who studies anaerobic (no-oxygen) carbon cycling at Aarhus University in Denmark.

The sub-seafloor crust may also be the largest ecosystem on earth, according to a new study by Lever, published this month in Science. For seven years, he incubated 3.5 million-year old basalt rock collected from 565 meters below the ocean floor–the depth of nearly two stacked Eiffel towers–and found living microbes. These microbes live far away from the thriving bacterial communities at mid-ocean ridges, and survive by slowly churning sulfur and other minerals into energy.

But just how big is this chemically-fueled ecosystem that survives entirely without oxygen? If the results from his sample, collected from below the seafloor off the coast of Washington state, are similar to those found across the planet, then diverse microbial communities could survive throughout the ocean’s crust, covering two-thirds of the earth’s surface and potentially going miles deep.

The sub-seafloor crust has plenty of space and energy-rich minerals–a welcoming potential habitat for a large microbial community–“but we have no idea what the ecosystem looks like,” says Julie Huber, a microbial oceanographer at the Marine Biological Laboratory in Woods Hole, Massachusetts. “Mark’s evidence would point to it being a very different world.”

Microbes that get their energy from minerals, rather than from sunlight, are far from rare. The most well known of these so-called chemoautotrophic or chemosynthetic bacteria are those found at hydrothermal vents in the deep sea. Some of these bacteria live symbiotically with giant tubeworms, mussels and clams, providing chemically-produced energy to these larger organisms as they “breathe” the sulfur-rich water erupting from the vent–not unlike how plants convert sunlight into energy at the surface. Chemosynthetic microbes are also found in the rotting and oxygen-poor muck of salt marshes, mangroves and seagrass beds—“any place you’ve got stinky black mud, you can have chemoautotrophy,” says Chuck Fisher, a deep-sea biologist at Pennsylvania State University in College Park.

But what makes Lever’s sub-seafloor microbes different is that they don’t use any oxygen at all. The symbiotic bacteria at hydrothermal vents are often described as “life without sunlight,” but they still rely on sunlight indirectly by using sun-produced oxygen in the chemical reaction to generate energy. Chemosynthetic microbes in salt marshes feed on decomposing plants and animals, which got their energy from sunlight. Even deep-sea sediment is accumulated from an assortment of dead animals, plants, microbes and fecal pellets that relies on light energy.

The oceanic crust microbes, on the other hand, rely entirely on non-oxygen-containing molecules derived from rock and completely removed from photosynthesis, such as sulfate, carbon dioxide and hydrogen. “In that sense it’s a parallel universe, in that it runs on a different type of energy,” says Lever. These molecules provide a lot less energy than oxygen, creating a sort of microbial slow food movement. So instead of dividing and growing quickly like many oxygen-based bacteria, Fisher suspects that microbes in the Earth’s crust may divide once every hundred or thousand years.

A hydrothermal vent, covered with tube worms, spews black sulfur smoke on the Juan de Fuca Ridge. The oceanic crust microbes were collected hundreds of meters under the seafloor beneath this same ridge. Photo via University of Washington; NOAA/OAR/OER

But just because they’re slow doesn’t mean they’re uncommon. “There are lots of data that there is a large, very productive biosphere under the surface,” says Fisher.

In addition, microbial population sizes in different areas of the crust may vary greatly, Huber notes. Through her studies on the fluid found between the cracks in the crust,  she says that in some areas the fluid contains about the same number of microbes as standard deep-sea water collected at ocean depths of 4,000 meters (2.5 miles): around 10,000 microbial cells per milliliter. In other regions, such as at the Juan de Fuca Ridge in the Pacific Ocean where Lever found his microbes, there are fewer cells, around 8,000 microbes per milliliter. And in other regions, such as in non-oxygenated fluid deep in hydrothermal vents, there can be around 10 times more.

It’s not just the number of microbes that vary depending on location–it’s possible that different microbial species are found in different types of crust. “Different types of rock and different types of chemistry should result in different types of microbes,” says Andreas Teske, a deep-sea microbial ecologist at the University of North Carolina at Chapel Hill and co-author on Lever’s paper. The Juan de Fuca Ridge is a relatively hot area bursting with new rock, which tends to be made of more reactive minerals and thus able to provide more energy. Other parts of the crust are older, composed of different minerals, and cooler. And, in some regions, oxygenated water reaches down to the cracks.

It’s this infiltrating seawater that keeps this sub-seafloor ecosystem from existing on a completely separate plane from our oxygenated one. “The crust plays a significant role in influencing the chemical composition of the ocean and the atmosphere, ultimately influencing [nutrient] cycles on earth,” says Lever. Some of the compounds created by oceanic crust microbes from rock are water soluble, and will eventually enter the ocean. Sulfur, for example, is present in magma—but after the microbes use it for energy, it’s converted to sulfate. Then it dissolves and becomes an important nutrient in the ocean food chain.

Lever’s find of a microbial community in the crust could catalyze the scientific community to answer these questions. For example, what kinds of microbes are found where, do they interact through interconnected cracks in the rock, and what role do they play in mineral and nutrient cycling? In some ways, it’s very basic exploratory work. “A lot of what we do on the seafloor is similar to what we’re doing on Mars right now,” says Huber. “Controlling [NASA’s Mars Rover] Curiosity is very similar to operating an ROV under the ocean.”

  Learn more about the deep sea from the Smithsonian’s Ocean Portal.

An island of ice breaking away from Greenland’s Petermann Glacier (in the center of the photo)  in the summer of 2010. By NASA

On the morning of July 16, 2010, a hunk of ice four times the size of Manhattan cracked away from the tongue of Greenland’s Petermann Glacier and drifted to sea as the largest iceberg since 1962. Just two years later, another massive section of ice calved from the same glacier. Icebergs like these don’t stay put in the Arctic–they get picked up by currents and ushered to warmer climates, melting along the way.

According to a new study published in the journal Geophysical Research Letters, Greenland’s melting glaciers and ice caps sent 50 gigatons of water gushing into the oceans from 2003 to 2008. This comprises about 10 percent of the water flowing from all ice caps and glaciers on Earth. The research comes on the heels of a study last year that showed the ice sheets of Greenland and Antarctica are disappearing three times faster than in the 1990s, and that Greenland’s is melting at an especially accelerated rate. In the new study, scientists were able to put an even finer point to the ice-melt situation by separating out the glaciers and ice caps from the ice sheet, which blankets 80 percent of the island. What they discovered is that Greenland’s glaciers are actually melting more quickly than the ice sheet.

Studies such as these demonstrate the impacts of a warming climate on Greenland’s glaciers. But, as they say, a picture is worth a thousand words. Visual evidence of this liquefaction is captured by NASA satellites, which are able to take snapshots of calving glaciers and document longer-term ice melt. NASA displays photos of the glaciers in its State of Flux photo gallery, along with a rotating collection of satellite images that illustrate other changes to the environment, including wildfires, deforestation and urban development.

The photos, with their “now-you-see-it, now-you-don’t” quality, illustrate how glaciers are fast becoming ephemeral. Here are a few stark examples:

Greenland’s Helheim Glacier can be seen retreating and thinning from 2001 (left) to 2003 (center) to 2005 (right). By NASA 

The set of images above shows the edge of Greenland’s Helheim Glacier, located on the fringe of the Greenland Ice Sheet, as captured by a satellite in 2001, 2003 and 2005. The calving front is marked by the curved line through the valley, while bare ground appears brown or tan and vegetation is red.

According to NASA, when warmer temperatures initially cause a glacier to melt, it can spark a chain reaction that accelerates the thinning of the ice. As the edge of the glacier begins to liquefy, it crumbles, creates icebergs and eventually disintegrates. The loss of mass throws the glacier off balance, and further thinning and calving occurs, a process that stretches the glacier through its valley. Total ice volume decreases then shrinks the glacier as calving carries ice away. Helheim’s calving front stayed put from the 1970s until 2001, at which point the glacier began hasty cycles of thin, advance, and dramatic retreat, ultimately moving 4.7 miles toward land by 2005.

Greenland’s Petermann Glacier on June 26, 2010 (left) , before a massive iceberg broke away, and on August 13, 2010, after the break. By NASA

The massive calving event at Petermann Glacier in 2010 is pictured in these two images. The glacier is the white ribbon on the right side of each photo, and its tongue extends into the Nares Strait, which appears as a bluish-black stripe across the center of the right image and is heavily flecked with white chunks in the photo on the left. In the first image, the tongue of the glacier is intact; in the second, a huge chunk of ice has broken off and can be seen floating away through the fjord. This iceberg was 97 square miles in size–four times bigger than the island of Manhattan.

Greenland’s Petermann Glacier on July 16, 2012 (left and center), before a major calving event, and July 17, 2012, after an iceberg broke off. By NASA

In the summer of 2012, a second massive iceberg crumbled away from the Petermann Glacier. In these images, the glacier is the white ribbon snaking up from the bottom right. If you follow the tongue up, you’ll see that it appears intact in the photos at left and center (though the center image has an ominous crack spanning its width), which were taken the day before the calving occurred. The photo on the right shows that it crumbled as the glacier calved.

Given that Greenland experienced an exceptionally warm summer in 2012 and temperatures were higher than average this winter, 2013 is primed for more melting and massive icebergs. Last year’s ice-melt season lasted two months longer than the average since 1979, and this year’s is already off to an inauspicious start. It kicked off on March 13 with the sixth-smallest sea-ice area on record for Greenland, according to the National Snow and Ice Data Center. What will the new summer calving season bring?

Polar bear-brown bear hybrids like this pair at Germany’s Osnabrück Zoo are becoming more common as melting sea ice forces the two species to cross paths. Photo by Corradox/Wikimedia Commons

Scientists and science writers have created catchy monikers for hybrid species, much the way tabloid writers merge the names of celebrity couples (Kimye, Brangelina, anyone?). Lions and tigers make ligers. Narwhals meet beluga whales in the form of narlugas. And pizzlies and grolar bears are a cross between polar bears and grizzlies. In coming years, their creativity may get maxed out to meet an expected spike in the number of hybrids. A driving force? Climate change. 

A new study published in the journal PLOS Genetics showed that there’s a historic precedent for cross-breeding among polar bears and brown bears–we’ll jump on the bandwagon and call them brolar bears. The researchers also asserted that such hybridization is currently occurring at an accelerated clip. As sea ice melts, polar bears are forced ashore to an Arctic habitat that’s increasingly hospitable to brown bears. There have been recent sightings in Canada of the resulting mixed-breed animals, which have coloring anomalies such as muddy-looking snouts and dark stripes down their backs, along with the big heads and humped backs typical of brown bears.

As it turns out, climate-change-induced hybridization extends well beyond bears. A 2010 study published in the journal Nature listed 34 possible and actual climate-change-induced hybridizations (PDF) of Arctic and near-Arctic marine mammals–a group that has maintained a relatively consistent number of chromosomes over time, making them particularly primed for hybridization. Here are some highlights from this list, along with some more recent discoveries. 

In 2009, a bowhead-right-whale hybrid was spotted in the Bering Sea by the National Oceanic and Atmospheric Administration’s (NOAA) National Marine Mammal Laboratory. Right whales, which typically hail from the North Pacific and North Atlantic, will increasingly be migrating north into the Arctic Ocean, the domain of bowheads, as a result of climate change–and co-mingling their DNA. The authors of the Nature study determined that “[d]iminishing ice will encourage species overlap.”

The narluga has a very big head, according to the scientists who found one in West Greenland. Its snout and lower jaw were particularly burly, and its teeth shared some similarities with both narwhals and belugas. Both species, which form a whale family called monodontidae, live in the Arctic Ocean and hunters have reported seeing more whales of similar stature in the region.

Harbor and Dall’s porpoises have already been mixing it up off the coast of British Columbia, and given that harbor porpoises are likely to keep moving north from the temperate seas of the North Atlantic and North Pacific into the home waters of the Dall’s, the trend is expected to continue. (Click here to see rare photos of the hybrid porpoise.)

Scientists in Ontario, Canada, are investigating inter-breeding between southern and northern flying squirrels as the southern rodents push into northern habitats. The hybrid squirrels have the stature of the southern species and the belly coloring of the northern one. The video below details the research.

Hybrid species often suffer from infertility, but some of these cross-breeds are having success at procreating. For example, researchers recently discovered the offspring of a female pizzly and a male grizzly bear (a subspecies of the brown bear) in Canada’s Northwest Territories. Despite cases like these, scientists are debating whether all of this hybridization is healthy. “Is this going to be a problem for the long-term existence of parental species? Are they going to merge into one big hybrid population?” asked University of California, Berkeley evolutionary biologist Jim Patton in an interview.

In the case of inter-bred polar bears, the concern is that the changing climate will be more welcoming to brown bears, and that while inter-species mating at first might appear to be an adaptive technique for polar bears, it could end up spelling their demise in all ways except cellular structure–much the way Neanderthals were folded into the human gene pool thanks to early humans in Europe more than 47,000 years ago.

Rare and endangered species are particularly vulnerable to the pitfalls of hybridization, according to the authors of the Nature study. “As more isolated populations and species come into contact, they will mate, hybrids will form and rare species are likely to go extinct,” they wrote. “As the genomes of species become mixed, adaptive gene combinations will be lost.”

Such is likely the case with the narluga. Scientists determined the animal’s lack of a tusk is a liability because the tusk is a measure of the narwhal’s breeding prowess. And a pizzly living at a German zoo showed seal-hunting tendencies, but lacked the swimming prowess of polar bears.

As Patton pointed out, it will be many years until we know the full consequences of hybridization. “We’re only going to find out in hindsight,” he said. But that’s not a reason to be complacent, according to the Nature authors, who called for the monitoring of at-risk species. “The rapid disappearance of sea ice,” they wrote, “leaves little time to lose.”

Sign up for our free email newsletter and receive the best stories from Smithsonian.com each week.