'Blood Rain' on Spanish Village Remains a Mystery

Red raindrops turn out to be a microalgae--but where it came from, nobody is sure Continue reading →

Here's one that sounds like a plot line from the upcoming reboot of "The X-Files" - or for a more arcane reference - the files of Charles Fort, the early 20th Century author who collected accounts of bizarre occurrences.

Last year, residents of the Spanish village of Zamora were startled when what looked like raindrops of blood fell from the sky. As the red fluid filled outdoor basins, some people reportedly feared that it was some sort of hazardous chemical that had been dropped from airplanes. Others remembered the Old Testament plagues afflicted upon Egypt.

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As news of the strange event got around, a man from a nearby town came to see the blood-colored water for himself, and gathered a sample of it. Over the fall and winter, he kept the blood-colored water and observed it. He noticed that the small particles in the water were staining the containers red. Finally, he sent some of the water to scientists at the University of Salamanca.

When the scientists analyzed the water under a microscope, they quickly deduced what was causing the red liquid. In a newly-published study in Spanish Royal Society of Natural History Journal, they reveal that the culprit is Haematococcus pluvialis, a freshwater green microalgae that's capable of synthesizing a red carotene pigment called astaxanthin.

But that only solves part of the mystery. Haematococcus pluvialis isn't usually found in the Mediterranean region, so the scientists aren't sure how it got into the rainfall over Zamora. Meteorological data analyzed by the scientists suggests that it could have been blown across the ocean by westerly winds, possibly from as far away as North America.

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The blood rain is rare, but isn't unprecedented. According to an article in the Hindu, an Indian newspaper, since the 1890s there have been sporadic reports of similar rainfall in the south Indian state of Kerala and the neighboring island nation of Sri Lanka, most recently in 2013.

A study published earlier this year in the journal Phylogenetics and Evolutionary Biology pointed to a different microalgae, Trentepohlia annulata, as the source. That species had previously been reported only in Austria. Scientists theorize that it somehow spreads through exchanges between ocean clouds, and that the rain is part of its very weird reproductive process.

Haematococcus pluvialis,

As we head toward 2015, look back at some of the strangest mysteries of this past year, as well as some of the mysteries that remain as we enter the new year. Keeping in mind that science is a process of continually refining a body of scientific knowledge -- that what we believe is true today may be changed by some amazing new discovery tomorrow -- here are 10 strange mysteries, both unexplained and recently explained.

Unexplained Mysteries of 2013

For almost a century one of America's strangest mysteries has been found in remote Death Valley, California. It's there -- actually at a specific dry lakebed called Racetrack Playa -- that stones are claimed to mysteriously move on their own, when no one is looking. The phenomenon occurs in a handful of other places as well, though none are as well known as those in Death Valley. They moved very slowly, in some cases only a few inches over months or years, but their trails can clearly be seen in the dried mud behind them. Over the years

many explanations

have been offered, ranging from hoaxing to aliens to some sort of localized, unknown magnetic effect. Others have suggested that the area's strong winds might move the stones, but that doesn't explain why they'd move at different rates and sometimes in different directions. For many years the best scientific explanation was that the rocks moved due to a specific combination of wind, temperature, and water. Racetrack Playa is in a desert, but sometimes collects water from rain and melting snow, providing a slick surface over which the stones might move. The mystery was


solved in 2014 when a team of researchers set up cameras over the area and measured the rocks' movement patterns. They concluded that the stones moved under just the right conditions when ice formed under the rocks and moved them, usually only a little bit at a time: "moving sheets of ice tens of meters in extent but only a few millimeters thick are clearly effective at moving rocks in their path."

The study,

"Sliding Rocks on Racetrack Playa, Death Valley National Park: First Observation of Rocks in Motion" was published on Aug. 27, 2014 in the open-access journal PLoS ONE.

Volcanoes are known around the world, though most of them can be found in the so-called Pacific Ring of Fire. It's where the world's most active volcanoes are located, covering the western edge of the Americas, Hawaii, Japan and into Oceania. The volcanoes there result from the subduction of oceanic tectonic plates moving beneath lighter continental plates. Most of Australia, however, is spared -- except for an unusual 300-mile stretch in the southeastern part of the country roughly north of Tasmania. It is the continent's only active volcanic region, but for many years no one was quite sure why. Since Australia lies well inside its own tectonic plate (called the Indo-Australian plate), it could not be caused by the same geological processes that spawned others in the nearby Ring of Fire. A team from the Research School of Earth Sciences

finally solved the mystery

earlier this year. According to lead researcher Dr. Rhodri Davies, "Volcanoes in this region of Australia are generated by a very different process to most of Earth's volcanoes.... We have determined that the volcanism arises from a unique interaction between local variations in the continent's thickness, which we were able to map for the first time, and its movement...towards New Guinea and Indonesia." The continent's drift northward creates an isolated region in its southern end which spawned the volcano. But don't stand on Australia's northern shore expecting to reach Indonesia any time soon: the continent is moving northward at about two and three-quarter inches a year. The study was published in the journal "Geology" on Sept. 24.

Play Volcano Explorer

The riddle of Mars has captivated people for generations. Dozens of artists, writers, astronomers and dreamers -- from H.G. Wells to Orson Welles, Ray Bradbury to Carl Sagan -- have speculated about what life might be like on the Red Planet. In 2011, NASA's Curiosity Rover was launched into space, landing on Mars the following year. Mankind's amazing little mechanical scientist trooper has spent the past few years poking, plodding and examining the surface. A lot has been learned about Martian climate and geology, but in 2014 the biggest news was that Curiosity gathered evidence that a peak there, known as Mount Sharp,

was created by sediments

in a huge surrounding lake bed. Yes, sediments -- which if you remember high school geology, is particulate matter carried by water or wind (in this case water). And yes, lake bed: There's no water there now, at least not on the surface, but the discovery is very strong evidence that rivers and lakes have existed periodically in Martian history. Having spent a Martian year on the planet, scientists now believe that the environmental conditions on Mars may be favorable for microbial life, and the search continues.

Lake in Mars' Gale Crater Adds Twist to Climate Story

If you're lucky enough to get away from urban light pollution and into rural areas, it's astonishing how many stars you can see; they seem to litter the sky. And, of course, only a small fraction of the stars are visible to our naked eye. But even still, there should be more of them -- many more. One of the most enduring astronomical puzzles has been not why there are so many stars, but instead so few. According to computer models there should be an estimated 100 to 300 sextillion stars, or 100,000,000,000,000,000,000,000 to 300,000,000,000,000,000,000,000, give or take a few. It's a number so large that it defies comprehension and raises an interesting question: where are they? Why isn't the night sky positively lit up with stars? Surely the light from a small number of them (say, maybe a few hundred million or so) might be blocked from reaching us by planets or other celestial objects, but that still leaves some ridiculously large number of stars unaccounted for. Earlier this year astronomer James Geach and his team at the University of Hertsfordshire found that "nuclear bursts of star formation are capable of ejecting large amounts of cold gas from the central regions of galaxies, thereby strongly affecting their evolution by truncating star formation and redistributing matter." In other words, the cold gases used as the raw material for stars -- and driven out during the star formation process itself -- can inhibit the creation of new stars.

The article,

"Stellar feedback as the origin of an extended molecular outflow in a starburst galaxy," was published in the Dec 4 issue of the journal Nature.

Star Birthing in Violent Galaxy Mergers

There are several well-known mysterious sounds in the world. The most famous is New Mexico's Taos Hum, but another mysterious hum has plagued residents in Windsor, Ontario, since 2011. Not everyone hears it, and even those who do don't all describe it in the same way; some say it's like a running refrigerator or an idling big truck. For years residents heard it -- and complained about it -- but local police couldn't help and no one was sure of its origin. Several investigations were conducted including by the Canadian government. Finally in May a study confirmed for the first time that the hum is real (and not, for example, an auditory illusion), and

conclusively identified the source

of the sound: Michigan's Zug Island, across the Detroit River, the site of heavy manufacturing including a U.S. Steel plant. Though it's clear that the hum is mechanical in nature and coming from the island, scientists haven't been able to locate a specific building or piece of heavy machinery that's causing it. Though the infernal Windsor Hum remains, nearby residents can sleep a little easier knowing it's not all in their heads.

Mysterious Sounds Reported Around the World

Though a variety of old and new mysteries were solved in 2014, many more mysteries remain unexplained as we begin 2015. In what was one of the most bizarre unexplained mysteries of 2014, on March 8, Malaysia Airlines Flight 370 veered off course after it left Kuala Lumpur and soon vanished. It seems impossible that with modern technology, the cooperation of several countries, and an estimated $33 to $42 million in search costs, the plane would simply vanish, never to be found. Dozens of planes, submersibles and ships searched in vain for the Boeing 777, but as 2015 arrives not a trace has been found. Hopes for finding the flight mostly depended on locating the airplane's "black box," equipped with an electronic pinger that sends out a regular sound signature. Unfortunately, the batteries died after three months, and early pings detected by the U.S. Navy were later determined to be false alarms that wasted precious time. The search for the missing plane was

plagued by problems

from the beginning, with erroneous information sending teams from one search area to another and another. To this day many questions remain: Were the pilots on a suicide mission, and if so, why? Did a mechanical failure cause the plane to go down? The search continues and though it's likely that this mystery will be solved one day, it may take months or years longer.

Malaysia Flight MH370: 5 Likeliest Possibilities

Given that Jack the Ripper stalked and killed five prostitutes in London over 125 years ago -- and that his identity has been a classic enduring mystery -- placing the unknown serial killer on a list of unsolved mysteries would seem to be too obvious to mention. And it would be, if not for the fact that in 2014 a man named Russell Edwards made international news by claiming to have finally, really, definitively, not-joking-now, seriously and conclusively identified Jack the Ripper. The evidence was as rock-solid as genetic analysis: According to Edwards and microbiologist Dr. Jari Louhelainen, DNA evidence taken from the shawl of a Ripper victim matched that of a Ripper suspect named Aaron Kosminski. This identification, which was touted as "definitely, categorically and absolutely" a match for Kosminski, seemed credible and was widely reported. However, doubts soon emerged when the research was examined.

According to "The Guardian,"

"four experts with intimate knowledge of DNA analysis -- including Professor Sir Alec Jeffreys, the inventor of genetic fingerprinting -- found that Dr. Louhelainen made a basic mistake in analyzing the DNA." In essence, instead of a specific genetic marker narrowing down the pool of suspects to a handful of people, including Kosminski, it was actually shared by about 99 percent of Europeans. It's far from the first time that amazing, "definitive" Ripper evidence evaporated upon closer inspection: In 1993 Warner Books was set to publish a recently-discovered diary of a man named James Maybrick, in which he admitted to his double life as the infamous Ripper. Yet suspicions were raised about the diary's unknown provenance, and forensic document examiners soon branded it a hoax. Over a hundred people have been suggested as Jack the Ripper, and given the exhaustive research brought to bear on the killings, it's virtually certain that Jack the Ripper has already been identified -- though which one of the dozen or so prime suspects is really the Ripper likely will never be known.

Why Each New 'Jack the Ripper' Suspect Is Compelling

With the Rosetta mission, humankind managed to land a probe on a comet in an amazing achievement celebrated around the world. The Philae lander ran out of battery power soon after arriving on the comet, ending up in a shadowy crag that prevents the sun from recharging its batteries. But before it died it sent a trove of useful data, including information that might help astronomers the answer one of the fundamental questions of how water came to Earth billions of years ago: could it have arrived on a comet? Scientists have long known that comets contain water, but they didn't know if it's the same type of water found here on Earth. The answer, so far, remains unknown. That's because when researchers compared the type of water found on Earth to the type found on the comet,

they didn't match;

the comet's water has a heavier mass. It's possible that another comet may have carried the type of water found on Earth, but so far the idea doesn't look promising. The study was published on Dec. 10 in the journal Science.

Rosetta Captures Comet Lander Philae's Big Adventure

Ball lightning, according to the American Meteorological Society's Dr. Walter Lyons in his "The Handy Weather Answer Book," is "one of nature's most mysterious phenomena. Usually seen during violent thunderstorms, the spheres of glowing light are typically the size of bowling balls or basketballs. They can last from a few seconds to many minutes. The spheres can simply vanish into thin air, but can also pass through window glass and screens, leaving burn marks behind.... They usually do not cause much damage and can even seem playful." Over the centuries, ball lightning has been attributed to various causes (including supernatural ones), though scientists have come up with a handful of

physics-based theories

. One is that ball lightning is a form of globe-shaped plasma (the fourth state of matter consisting of electrically-charged gas); another is that the lightning is composed of elements from the soil surrounding it when it strikes. Earlier this year the emission spectrum of a ball lightning strike was analyzed for the first time. As the

American Physical Society noted

, a research team led by Ping Yuan saw and recorded a ball lighting strike in northwest China in July 2012: "They were able to record a spectrum and high-speed video footage of the ball. The recorded glow was about 5 meters across -- the actual size of the ball was much smaller -- and it changed from white to reddish during the second or so that it lasted... Yuan says that this is the first time ball lightning has been seen to be created by a cloud-to-ground lightning strike. The researchers found that the spectrum contained several emission lines from silicon, iron, and calcium -- all elements expected to be abundant in soil." This suggests that the lightning may be created by some unknown interaction with the soil, and though the research offers some tantalizing clues about the origin and nature of ball lightning, the phenomenon remains elusive and largely unexplained.

From the famously frisky and polyamorous bonobo apes to swan pairs that often mate for life, sex in the animal world can be both strange and varied. But scientists are baffled by the activity they found on Marion Island, a small island near Antarctica. Fur seals there usually chase and eat the king penguins they share the land with, but on rare occasions

they mount them.

Instances of seal/penguin sex had been seen at least twice before, but researchers weren't sure if it was an aberration (such as a seal misidentifying a mate, which happens) or an unusual but natural part of their behavior. Sometimes animal behavior can be changed in the process of recording it -- what in science is called "the observer effect." If animals (whether people, penguins, or anything else) know that they're being watched or recorded, they may change their behavior. But that didn't seem to be the case. After documenting this behavior for the third time earlier this year, scientists concluded that it wasn't just one or two isolated instances, but an apparently new behavior (for obvious reasons it's not an evolutionarily adaptive behavior for the fur seals). Why exactly this behavior goes on remains unexplained, though the researchers offered two possible explanations in their study: "It may be learned behavior associated with some sort of reward or it may be an extreme case of reproductive interference that can be explained by the 'mate deprivation hypothesis,' resulting from the continued growth of the

A. gazella

population on the island." In other words, there aren't enough female fur seals to mate up with the males. The

research study,

titled "Multiple occurrences of king penguin (

Aptenodytes patagonicus

) sexual harassment by Antarctic fur seals (

Arctocephalus gazella

)," was published in the Nov. 11 journal "Polar Biology" and is recommended for mature readers only.