Evidence of ancient tsunamis on Mars

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.

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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

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"[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.

Nasa's Valkyrie Robots Set the Table for Human Life on Mars

Four sister robots built by Nasa could be pioneers in the colonization of Mars, part of an advance construction team that sets up a habitat for more fragile human explorers. But first they're finding new homes on Earth and engineers to hone their skills.

The space agency has kept one Valkyrie robot at its birthplace, the Johnson Space Center in Houston. It has loaned three others to universities in Massachusetts and Scotland so professors and students can tinker with the 6-foot-tall, 300-pound humanoids and make them more autonomous.

One of the robots, nicknamed Val, still hasn't quite harmonized its 28 torque-controlled joints and nearly 200 sensors after arriving at a robotics center at the University of Massachusetts-Lowell.

Engineering students let the electricity-powered robot down from a harness and tried to let it walk, only to watch as Val's legs awkwardly lurched and locked into a ballet pose.

"That doesn't look good," said Taskin Padir, a professor at Northeastern University, noting Val's $2 million price tag. Northeastern and UMass-Lowell are partnering on a two-year project to improve the robot's software and test its ability to manipulate tools, climb a ladder and perform high-level tasks.

Nasa originally designed Valkyrie several years ago to compete in the disaster-relief robotics contest hosted by the US military's Defense Advanced Research Projects Agency, but now it's looking for outside expertise to craft her into a kind of space mechanic. Nasa shipped two other Valkyries to the Massachusetts Institute of Technology and the University of Edinburgh in Scotland.

This is not yet the stuff of "The Martian," the Hollywood blockbuster about surviving on the Red Planet. For one thing, the tiny holes that prevent Val from overheating could get clogged up by spiraling Martian dust. But a sturdier exterior will come later.

There are still another two decades before Nasa aims to land humans on Mars in the mid-2030s, said Johnson Space Center spokesman Jay Bolden. Now is the time, he said, to build the computer code that will make the robots useful in hostile environments. If not the Valkyries, it will be their descendants serving as the android vanguard that could make human life possible on Mars.

"It needs to be able to communicate back to Earth, very clearly and concisely, what's going on," said Holly Yanco, a computer science professor who directs UMass-Lowell's robotics center and is an expert on human-robot interactions.

A time delay between communications from Earth to Mars means humans won't be able to remotely control robots that will need to build structures and do emergency repair work.

There's a huge step between Nasa's robotic rover Curiosity, which landed on Mars in 2012, and the capabilities of a robot such as Valkyrie, said Robert Platt, an assistant professor at Northeastern University who is part of the research team.

"The rovers get their instructions uploaded at the beginning of the day," Platt said. "Those instructions amount to, 'Go over there,' or, 'Check out that rock.' It's a completely different ballgame when the job for the day is to assemble a couple of habitats."

A number of technological advancements, from faster computers to better machine-learning algorithms, will soon make it possible for a robot such as Valkyrie to perform such tasks, Platt said.

"Robotics has been making tremendous strides in the past five years. Drones, autonomous vehicles," he said. "It's one of those situations where you work on the same problem for decades and decades, and something finally starts to happen. Maybe this is that time."

Agricultural emissions 'reality check'

A new report says that global agricultural emissions must be slashed to prevent the planet warming by more than 2C over the next century.

The current focus is on reducing emissions from transport and energy.

But an international team of scientists argues that if farm-related emissions aren't tackled then the Paris climate targets will be breached.

An estimated one-third of our greenhouse gas emissions come from agriculture.

The report by researchers from the universities of Vermont and Sheffield and the CGIAR Research Program on Climate Change examines non-CO2 emissions, such as methane and nitrous oxide.

Cattle produce methane as part of their digestion and emit it mostly through belching. The addition of natural or synthetic fertilisers to soils releases large amounts of nitrous oxide.

The researchers have calculated for the first time that these emissions must be reduced by one gigatonne per year in 2030.

They estimate that the mitigation plans currently in place would only cut emissions by 21-40%.

'Reality check'

Co-author Lini Wollenberg from the University of Vermont said: "This research is a reality check. Countries want to take action on agriculture, but the options currently on offer won't make the dent in emissions needed to meet the global targets agreed to in Paris.

"We need a much bigger menu of technical and policy solutions, with major investment to bring them to scale."

However, the authors warn that efforts to cut emissions levels must be balanced with the need to produce food.

"We need to help farmers play their part in reaching global climate goals while still feeding the world," says Prof Pete Smith from the University of Aberdeen and co-author of the paper.

"Reducing emissions in agriculture without compromising food security is something we know how to do. A lot can already be done with existing best management practices in agriculture."

"The tough part is how to reduce emissions by a further two to five times and support large numbers of farmers to change their practices in the next 10 to 20 years."

The scientists say that "more transformative technical and policy options" will be needed.

They highlight methane inhibitors that reduce dairy cow emissions by 30% without affecting milk yields. Also, breeds of cattle that produce lower methane, and varieties of cereal crops that release less nitrous oxide.

At the Paris climate summit, 119 nations pledged to reduce agricultural emissions. However, there was no indication how they would do this.

The scientists looked at current agricultural methods that could help, such as ensuring the efficient use of water to irrigate crops, improving the use of fertilisers such as nitrogen and manure and by managing livestock in a more efficient and sustainable way.

However they argue that merely improving current systems would "require massive investment, information sharing and technical support to enable a global-scale transition."

Commenting on the report, Professor Duncan Cameron, chair of plant and soil biology at Sheffield University, said: "This study is really important because it highlights the huge contribution of agriculture makes to the amounts of greenhouse gasses released as a result of human activity every year and that much of this comes from the production of and use of nitrogen fertiliser."

"Reducing emissions by gigatonne, which is roughly equivalent to the weight of all of the major skyscrapers in the world combined, sounds like a tall order, but if we act now and take onboard the combination of approaches suggested in this study, it is potentially achievable while maintaining the security of the world's food supply."

Life forms 'went large' a billion years ago

Life was already organising itself into large communities of cells more than a billion years ago, according to evidence from China.

The centimetre-scale life forms were preserved in mudstones from the Yanshan area in the country's north and are dated to 1.56 billion years ago.

Fossils big enough to be seen by the naked eye became common between 635 and 541 million years ago.

But the latest specimens are more than twice that age.

The findings by a Chinese-American team of researchers appear in the journal Nature Communications.

The mysterious organisms from the Gaoyuzhuang rock formation appear to belong to the branch of life known as the eukaryotes, which today includes everything from single-celled amoebae to plants, fungi and animals.

The sea-dwelling life forms probably lived on the shelf areas of ancient oceans and bear a superficial resemblance to algae. They also appear to have used photosynthesis, the process by which plants, some bacteria and other simple organisms convert sunlight into chemical energy.

Prof Andrew Knoll, from Harvard University, a co-author of the paper, said the organism represented by the Chinese fossils was "large but I doubt that it was complicated - an important distinction".

He told me: "You're a good example of a complex multi-cellular organism because you have 250 cell types, dozens of tissues, different organ systems.

"On the other hand if you go to the beach you will find seaweeds that consist of a sheet of cells that are almost all identical. Most of them can either photosynthesise or be used for reproduction."

The team, including Prof Knoll and Shixing Zhu from the China Geological Survey in Tianjin, found that life in this ancient period had already developed a variety of forms.

Of 53 separate specimens, 26 (49%) were linear in shape, 16 (30%) were wedge-shaped, eight (15%) were tongue-shaped and three (6%) were oblong-shaped.

The marine organisms measured up to 30cm in length and up to 8cm wide. Some of the specimens revealed fine structure: a closely-packed arrangement of individual cells measuring about 10 micrometres long - which is the same as the width of cotton fibre.

Go big or go home

Examples of multi-cellular life dating back more than a billion-and-a-half years have been described before. They include Horodyskia, which was shaped like a strings of beads, and Grypania, a coiled, ribbon-like organism.

But the diversity of forms and the size of the fossils from Yanshan mark them out.

The researchers say the fossils are unlikely to be of agglomerations of bacteria known as microbial mats, and instead are probably early examples of eukaryotic organisms.

If so, the organisms suggest multi-cellularity was a feature of marine life a billion years before the so-called Cambrian explosion, a rapid evolutionary event that began 542 million years ago and resulted in the divergence of major animal groups.

Some scientists partly attribute this evolutionary flowering to a rise in oxygen levels, although the causes are the matter of continuing debate.

The findings also suggest that the preceding era, characterised by lower oxygen levels and sometimes referred to as the "boring billion", may have been misjudged.

Prof Knoll told BBC News: "It looks like the leap from single cells to simple multi-cellularity is easy - in relative terms. It was done many times (over the course of evolution) and this really cements the case that it was done early in the history of eukaryotes.

"There are a couple of cases where we know the genomes of both unicellular (single-celled) organisms and their closest multi-cellular relatives. When the jump is from a single cell to simple multi-cellularity, there's very little difference in the gene content of the organism. That's a small leap forward.

"The difference when you go from simple multi-cellularity to complex multi-cellularity, however, is large. The tree of life suggests that has happened only rarely."

However, the team was not able to link the fossils with any other known group of eukaryotes - living or extinct.

Dog sex cancer's global march mapped in DNA

For the first time, researchers have traced the global spread of a baffling cancer transmitted between mating dogs.

The tumour originated in a single dog 11,000 years ago but outlived its host by transferring to another dog - and is still on the march today.

An international team led by Cambridge scientists mapped its progress based on DNA from 449 tumours in 39 countries.

Some of the cancer's more recent travel between continents, they found, aligns with maritime trade routes.

But apart from reflecting the shared migration history of dogs and humans, the tumour's genetic history includes a surprising quantity of DNA pilfered from its hosts.

The findings, reported in the open access journal eLife, are based on mitochondrial DNA - small, circular chains of genetic information parcelled up in mitochondria, the "batteries" of cells.

And the study centres on a rare but recurring event: at least five times during the tumour's poisonous coexistence with millions of dogs through the ages, it appears to have traded mitochondrial DNA with its host.

"Normally the dog is a transient host - and then the tumour gets passed on to more dogs. But what has happened occasionally is that DNA from the dog actually enters the tumour cell," explained Dr Elizabeth Murchison, a Wellcome Trust Investigator at the University of Cambridge and the paper's senior author.

"So rather than carrying the mitochondria of the original dog that lived 11,000 years ago, the tumour is now carrying the host dog's mitochondria. And it's going to pass those on to the next dog."

Those five wholesale transfer events create five major ancestral groups or "clades" for the tumours that exist today. By further analysing the gradual, piecemeal mutations that accumulate during the rest of the cancer's history, Dr Murchison and her colleagues built up a family tree and a clear picture of the disease's journey around the planet.

Known as canine transmissible venereal tumour (CTVT), the cancer can affect any breed of dog and is usually found in the animal's genitals. From there it is easily transmitted during sex, and is currently found in dogs on six continents.

It is one of just a handful of infectious cancers known to science, including the face tumour threatening Tasmanian devils with extinction.

Because all CTVT cells can be traced back to a single dog some 11 millennia in the past, it is regarded as the oldest and most prolific cancer lineage in nature.

A previous study showed that the tumour was able to steal DNA from its host dogs.

Dr Murchison, working with a large international team, conducted a thorough search for such genetic thievery.

"Every time the DNA from the host dog has been picked up, that acts as a little genetic flag for us," she told the BBC.

One such event, dated to about 500 years ago, spawned cancerous progeny in a tell-tale, transcontinental pattern.

"You can kind of imagine those dogs on boats, which must have taken that tumour around with them."

For the geneticists involved, the highlight of this large study was a cancerous specimen from Nicaragua which showed something never seen before: not only had the tumour pinched some mitochondrial DNA from its canine host, but the two sequences had been spliced together.

This "recombination" is a routine part of how the regular DNA in our chromosomes gets jostled around - but evidence of it happening in mitochondria is rare and controversial. Many researchers "still don't really believe" it is possible, Dr Murchison said.

And it has never been seen in the mitochondria of a cancer cell.

"Mitochondrial DNA recombination could be happening on a much wider scale, including in human cancers, but it may usually be very difficult to detect," said Máire Ní Leathlobhair, co-first author of the study.

"In human cancer, the tumour's mitochondrial DNA is likely to be very similar to the mitochondrial DNA in the patient's normal cells, so the result of recombination would be almost impossible to recognise."