Scientists think they see evidence of two huge tsunamis having once swept across the surface of Mars.
They point to satellite data suggesting a major redistribution of sediments over a large region at the edge of the Red Planet’s northern lowlands.
The US-led team argues that asteroid or comet strikes into an ocean of water could have triggered the giant waves.
Such events could only have occurred more than three billion years ago when the planet was wetter and warmer.
Today, Mars is dry and very cold, and any impact would merely dig out a dusty hole.
But researchers have long speculated that the low, flat terrain in Mars’ northern hemisphere could have hosted an ocean if the climate conditions were just right.
The nagging doubt with this theory has been the absence of an identifiable shoreline – something the new study could now help explain.
Left: A colour-coded digital elevation model of the study area showing the two proposed shoreline levels of an early Mars ocean that existed approximately 3.4 billion years ago. Right: Areas covered by the documented tsunami events extending from these shorelines.
If tsunamis regularly inundated the “land”, dumping sediments and scouring new flow channels, they could over time have disguised what otherwise would have been an obvious “coast”.
“Clearly, it’s one of the implications of this work: to have tsunamis, you must have an ocean,” said Alexis Palmero Rodriguez from the Planetary Science Institute in Tuscon, Arizona.
“So, we think this is going to remove a lot of the uncertainty that surrounds the ocean hypothesis. Features that have in the past been interpreted as relating to an ocean have been controversial; they can be explained by several, alternative processes. But the features we are describing – such as up-slope flows including large boulders – can only be explained in terms of tsunami waves,” he told BBC News.
Dr Rodriguez and colleagues’ tsunami findings appeared on Thursday in the journal Scientific Reports. Their work centres on two connected regions of Mars, known as Chryse Planitia and Arabia Terra.
The team claims that the sediments observed by satellite betray the action of two ancient mega-tsunamis.
The older event is perhaps easier to understand in an Earth context, where energetic waves can pick up sediments, including massive boulders, and dump them at a higher elevation. The water, as it turns back to run downhill, then cuts new channels – such as the ones identified on Mars by Dr Rodriguez’s group.
But the scientists go on to describe the traces of a second, younger event. This is calculated to have occurred a few million years later, when the climate had cooled significantly. In this instance, the tsunami wave likely froze as it propagated across the land surface. This is suggested by the observation of “lobes” of sediment without the backwash channels.
On Earth, the frozen floes capping a sea or a lake can sometimes be pushed ashore by a storm surge. It is an unusual phenomenon but would be analogous to what is being suggested – albeit on a much larger scale – for Mars.
The team has estimated the energetics of the impacts and their ensuing tsunamis, based on the scale of the sediment distributions.
The craters that were produced were probably about 30km across, they say. The waves could have been 50m in height, or even 120m at some locations.
The areas affected by the tsunamis cover some 800,000 sq km for the older event and 1,000,000 sq km for the younger one.
“On Earth, the K-T boundary impact (that wiped out the dinosaurs) produced an enormous tsunami wave that hit the continental United States, equivalent to the area we see flooded in our study region on Mars,” Dr Rodriguez added.
Wet Red Planet?
Having lost some currency, the idea of an ocean on Mars is gaining popularity again.
Investigations by Nasa’s Curiosity rover at Gale Crater have revealed that the deep bowl likely contained persistent lakes in the past.
Such water, it is argued, could only have been maintained if there was a robust hydrological system on Mars, cycling moisture between a large sea somewhere on the planet, its atmosphere and its land surface.
A view (right) of a boulder-rich surface (yellow bars are 10m) deposited by the older tsunami, and then eroded (left) by channels produced as the tsunami water returned to the ocean elevation level
“[The] large expanse of currently documented tsunami inundation is but a portion of what occurred along the margin of the Martian northern plains-filling ocean,” said co-author Kenneth Tanaka of the US Geological Survey.
“Tsunami-related features along other parts of the ocean margin, and potentially other smaller former bodies of water, remain to be identified, mapped and studied in detail.”
Peter Grindrod from University College London was not involved in the study. He commented: “The idea of a northern ocean on Mars has been floating around for decades. But the evidence hasn’t been able to push this idea forward as the consensus view.
“However, this possible evidence of tsunami deposits is interesting and, along with other recent studies of widespread deltas, could perhaps mark the beginning of a reinvigoration of the ocean hypothesis.”
The lobe deposits from the younger event would be an excellent location for future exploration by surface robots or astronauts, the team believes. They are relatively undisturbed and so probably retain important information about the nature of the ocean, and possibly even some bio-signatures if the body of water happened to support life.
This satellite image taken using a thermal (temperature) sensor shows ice-rich lobes thought to be the remnants of tsunami waves that transitioned into slurry ice-rich flows as they propagated under extremely cold climatic conditions. The up-slope direction of flow is indicated by the white arrows. The lobe length is about 250km.
New Study Solves Mystery of Salt Buildup on Bottom of Dead Sea
New research explains why salt crystals are piling up on the deepest parts of the Dead Sea’s floor, a finding that could help scientists understand how large salt deposits formed in Earth’s geologic past.
The Dead Sea, a salt lake bordered by Jordan, Israel and the West Bank, is nearly 10 times as salty as the ocean. Humans have visited the Dead Sea for thousands of years to experience its purported healing properties and to float in its extremely dense, buoyant waters, and mention of the sea goes back to biblical times.
Much of the freshwater feeding the Dead Sea has been diverted in recent decades, lowering the sea’s water levels and making it saltier than before. Scientists first noticed in 1979, after this process had started, that salt crystals were precipitating out of the top layer of water, “snowing” down and piling up on the lakebed. The salt layer on the lake floor has been growing about 10 centimeters (4 inches) thicker every year.
The process driving this salt crystal “snow” and buildup of salt layers on the lakebed has puzzled scientists because it doesn’t make sense according to the laws of physics. Now, a new study in AGU’s journal Water Resources Research proposes that tiny disturbances in the lake, caused by waves or other motion, create “salt fingers” that slowly funnel salt down to the lakebed. Watch a video about this research here.
“Initially you form these tiny fingers that are too small to observe… but quickly they interact with each other as they move down, and form larger and larger structures,” said Raphael Ouillon, a mechanical engineer at the University of California Santa Barbara and lead author of the new study.
“The initial fingers might only be a few millimeters or a couple of centimeters thick, but they’re everywhere across the entire surface of the lake,” said Eckart Meiburg, also a mechanical engineer at UC Santa Barbara and co-author of the new study. “Together these small fingers generate a tremendous amount of salt flux.”
The new finding helps researchers better understand the physics of the Dead Sea but also helps explain the formation of massive salt deposits found within Earth’s crust.
The Dead Sea is only hypersaline water body on Earth today where this salt fingering process is happening, so it represents a unique laboratory for researchers to study the mechanisms by which these thick salt deposits have formed, according to the authors.
“Altogether this makes the Dead Sea a unique system,” said Nadav Lensky, a geologist with the Geological Survey of Israel and co-author of the new study. “Basically, we have here a new finding that we think is very relevant to the understanding of the arrangement of these basins that were so common in Earth’s history.”
A salty mystery
As the Dead Sea has become saltier in recent decades, much of that salt has become concentrated near its surface. During the summer, extra heat from the Sun warms the surface of the Dead Sea and divides it into two distinct layers: A warm top layer sitting atop a colder lower layer. As water evaporates from the top layer in the summer heat, it becomes saltier than the cooler layer below.
Researchers realized the salt snow they observed was originating in this top salty layer, but this warm water doesn’t mix with the cooler water below because it’s so much warmer and less dense. So they were puzzled as to how salt from the surface was entering the cooler layer and plummeting to the bottom of the lake.
Lensky and his colleagues proposed an explanation in 2016, and the new research tests this theory for the first time.
They propose that when the top layer of the lake is disturbed by waves or other motion, tiny parcels of warm water enter the cooler pool of water below. Heat diffuses more rapidly than salt, so this warm water parcel rapidly cools. But as it cools it holds less salt, so the salt precipitates out and forms crystals that sink to the bottom. Watch an animation of the salt fingers here.
In the new study, researchers created a computer simulation of how water and salt would flow in the Dead Sea if the salt fingers theory was correct. They found the salt fingers theory correctly predicted the downward flow of salt snow and buildup of salt layers in the middle of the lake’s floor. Because the level of the lake is declining, due to pumping of freshwater from the nearby Jordan River, the salt layers are concentrated in the central part of the lake, according to the authors.
Understanding salt deposits elsewhere
The new finding also helps explain the formation of massive salt deposits found within Earth’s crust.
“We know that many places around the world have thick salt deposits in the Earth’s crust, and these deposits can be up to a kilometer thick,” Meiburg said. “But we’re uncertain how these salt deposits were generated throughout geological history.”
One notable example is the thick salt layer underneath the Mediterranean Sea. Researchers know that about six million years ago, the Strait of Gibraltar closed off, because of the movements of Earth’s tectonic plates. This cut off the supply of water from the Atlantic Ocean to the Mediterranean, creating a giant shallow inland sea.
After several hundred thousand years, the Mediterranean’s water levels dropped so much that the sea partly or nearly dried out, leaving behind thick deposits of salt. The new finding suggests these deposits formed during this time in a similar manner to what is happening right now in the Dead Sea. When the Strait of Gibraltar opened up again, water flooded the basin and the salt deposits were buried under new layers of sediment, where they remain today.
Using Handheld Devices May Cause Young Children’s Speech Delay, new study claims
While technology offers convenience on one’s life, it could also impose negativity on its users especially on children.
A new study presents the possible speech delay in children upon usage of handheld devices last May 6 during 2017 Pediatric Academic Societies (PAS) meeting…
While technology offers convenience on one’s life, it could also impose negativity on its users especially on children.
A new study presents the possible speech delay in children upon usage of handheld devices last May 6 during 2017 Pediatric Academic Societies (PAS) meeting.
The study was presented as an abstract entitled, “Is handheld screen time use associated with language delay in infants?” which claims that a thirty-minute daily usage of such devices increases the risk of a child’s speech delay by 49 percent.
“Handheld devices are everywhere these days,” said Dr. Catherine Birken, MD, MSc, FRCPC, the study’s principal investigator and a staff pediatrician and scientist at The Hospital for Sick Children (SickKids).
A total of 894 children from ages six to twenty-four months participated in the study, conducted from 2011 to 2015.
Dr. Birken, says in a news release, the research findings could reinforce the policy recommendation of the American Academy of Pediatrics (AAP) to limit any type of screen media in children primarily on the younger ones, 18 months and below.
However, she also added that more research is required to have a clearer understanding of how screen devices affect a child’s speech delay – like knowing what type of content children indulge with.
Lead by the author Julia Ma, HBSc, an MPH student at the University of Toronto, the study is the first to probe the correlation between handheld screen time and risk of expressive language delay.
Last year, November 2016, AAP issued their three policy statements, which detailed how children should use media and avoid unnecessary repercussions: “Media and Young Minds,” “Media Use in School-Aged Children and Adolescents,” and “Children, Adolescents and Digital Media.”
In these policy statements, AAP encourages parents to be vigilant as they play an integral role if technology would benefit their children or not.
“Families should proactively think about their children’s media use and talk with children about it, because too much media use can mean that children don’t have enough time during the day to play, study, talk, or sleep,” said Jenny Radesky, MD, FAAP, lead author of the policy statement, “Media and Young Minds.”
AAP policy statements elaborated the effects of media on children, prominently on health issues.
With different age group as subjects, the “Media and Young Minds” included infants, toddlers and pre-school children while “Media Use in School-Aged Children and Adolescents” focused from ages 5 to 18.
In addition, AAP released a Family Media Plan Tool on October 2016, which can be used to help parents in guiding their children for using media.
AAP have also laid several recommendations for avoiding overexposure of children on media. These are divided into three subgroups: pediatricians, families, and industries.
Greenland Shark may live up to 250 years
In the freezing waters of the sub-Arctic ocean lurks a mysterious and slow-moving beast known as the Greenland shark. It’s a massive animal that can grow up to six metres in length. Now, new research suggests it may have a massive lifespan as well.
According to a paper published recently in Science, the Greenland shark could live for well over 250 years, making it the longest-living known vertebrate on Earth.
“I am 95 percent certain that the oldest of these sharks is between 272 and 512 years old,” said lead author Julius Nielsen, a marine biologist at the University of Copenhagen.
“That’s a big range, but even the age estimate of at least 272 years makes it the oldest vertebrate animal in the world.”
The oldest-animal record holder is a clam called Ming that was dredged up from the ocean floor off the coast of Iceland. It was said to be 507 years old when it died in 2006.
Shortraker rockfish off the Alaskan coast and orange roughy off Namibia are both estimated to live up to 200 years or longer. Harriet, a Galapagos tortoise from the Australia Zoo, lived to be about 170 years old.
Still, if Nielsen’s estimates are correct, the Greenland shark would be a record breaker.
Greenland sharks are among the largest sharks on the planet. They are dark brown or purple with small, beady eyes. They inhabit the Arctic and sub-Arctic waters, as well as cold, deep water in other oceans throughout the world.
Because they spend most of their time in the darkness their eyesight is thought to be very poor, but a vast network of neurons in their snouts suggests they hunt and scavenge using their powerful sense of smell.
“They are basically a giant swimming nose,” said Aaron Fisk, a professor at the University of Windsor who has studied the Greenland shark for two decades.
Scientists have long suspected that these lethargic giants have extremely long lifespans in part because previous research shows that they grow very slowly – possibly as little as a centimetre per year.
“In colder temperatures, growth slows and fish tend to get older,” said Fisk, who was not involved in the study.
“It’s not hard to imagine that they could be 200 or 400 years old.”
But determining the exact age of the Greenland shark is a tricky business. When scientists determine the age of fish such as cod, rockfish and salmon, they usually look at the otolith – a bony structure that grows in the ear of a fish.
Otoliths have seasonal growth rings, kind of like the rings in tree trunks. If researchers can figure out how long it took the animal to lay down one ring, they can easily determine the age of the fish.
Sharks and rays don’t have otoliths, so scientists have found other ways to determine their ages. For some species of sharks, it’s possible to tell how old they are by looking at growth layers deposited in calcified parts of their vertebra or fin spines. But the Greenland shark doesn’t have fin spines, and its cartilage skeleton is extremely soft with almost no calcified material, so there are no layers to count.
To overcome this hurdle, Nielsen and his collaborators turned to a more complicated technique called eye lens radiocarbon dating, which has been used to determine the age of other animals.
The eye lenses of all vertebrates continue to grow with the animal through its life, adding layers like an onion. However, the core of the eye lens is formed before the animal is born and remains metabolically stable throughout its life, Nielsen explained. That means that embedded in this small piece of tissue in the centre of a shark’s eye is a chemical signature from the environment just before it was born.
In the late 1950s, atmospheric tests of thermonuclear weapons caused a big and easily detectable spike in the amount of radiocarbon that eventually made its way into the sea. Scientists call this bump “the bomb pulse,” and it has become a handy way to verify the age of marine organisms.
If the amount of radiocarbon in a shark’s lens represents post bomb-pulse levels, that’s a pretty clear indicator that the animal was born after 1960. (It took a few years for the radiocarbon to filter down into the deep water.)
For this study, Nielsen examined the eye lenses of 28 female specimens that were caught off the coast of Greenland between 2010 and 2013.
The radiocarbon levels in the lenses of the two smallest sharks had a clear post-bomb pulse signature, suggesting that these animals were 50 or younger. The radiocarbon levels of the third-smallest shark put it right on the onset of the bomb pulse. The researchers say this means the third shark was likely born in the early 1960s.
However, the centre of the eye lenses of the 25 larger sharks all had pre-bomb-pulse radiocarbon levels, leading the authors to conclude that they were more than 60 years old.
The group’s next step was to determine how long before 1960 the other 25 sharks were born, and here’s where they had to get creative. They measured the radiocarbon levels in each of the remaining eye lens samples and then compared them to a published reference of how radiocarbon levels in the ocean have changed over time.
This chronology of much more subtle radiocarbon fluctuations goes back 50,000 years and is usually used to date corals and other organisms that are thousands of years old. When it is used to date more recent organisms, it shows a wide range of error.
To further constrain their results, the authors made the assumption that the longer a shark is, the older it is.
When they added the lengths of the specimens to their model, they found that the biggest shark in the data set – a 16-footer – would have been 392 years old, give or take 120 years.
The authors concede that the margin of error is still very large, but they say their findings demonstrate that the Greenland shark is extremely long-lived and that its population would take a long time to bounce back to normal if the animals were exploited by humans.
Aaron MacNeil, a research scientist at the Australian Institute of Marine Science who was not involved in the work, said the study represents an interesting approach to a difficult biological problem, but added that the findings are not necessarily conclusive.
“I don’t think this is the final word on Greenland shark ages,” he said.
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