The crash of meteors on early Earth likely generated hydrogen cyanide, which could have kick-started the production of biomolecules needed to make the first cells.

The origin of life on Earth is a set of paradoxes. In order for life to have gotten started, there must have been a genetic molecule-something like DNA or RNA-capable of passing along blueprints for making proteins, the workhorse molecules of life. But modern cells can't copy DNA and RNA without the help of proteins themselves. To make matters more vexing, none of these molecules can do their jobs without fatty lipids, which provide the membranes that cells need to hold their contents inside. And in yet another chicken-and-egg complication, protein-based enzymes (encoded by genetic molecules) are needed to synthesize lipids.

Now, researchers say they may have solved these paradoxes. Chemists report today that a pair of simple compounds, which would have been abundant on early Earth, can give rise to a network of simple reactions that produce the three major classes of biomolecules-nucleic acids, amino acids, and lipids-needed for the earliest form of life to get its start. Although the new work does not prove that this is how life started, it may eventually help explain one of the deepest mysteries in modern science.

"This is a very important paper," says Jack Szostak, a molecular biologist and origin-of-life researcher at Massachusetts General Hospital in Boston, who was not affiliated with the current research. "It proposes for the first time a scenario by which almost all of the essential building blocks for life could be assembled in one geological setting."

Scientists have long touted their own favorite scenarios for which set of biomolecules formed first. "RNA World" proponents, for example suggest RNA may have been the pioneer; not only is it able to carry genetic information, but it can also serve as a proteinlike chemical catalyst, speeding up certain reactions. Metabolism-first proponents, meanwhile, have argued that simple metal catalysts, as opposed to advanced protein-based enzymes, may have created a soup of organic building blocks that could have given rise to the other biomolecules.

The RNA World hypothesis got a big boost in 2009. Chemists led by John Sutherland at the University of Cambridge in the United Kingdom reported that they had discovered that relatively simple precursor compounds called acetylene and formaldehyde could undergo a sequence of reactions to produce two of RNA's four nucleotide building blocks, showing a plausible route to how RNA could have formed on its own-without the need for enzymes-in the primordial soup. Critics, though, pointed out that acetylene and formaldehyde are still somewhat complex molecules themselves. That begged the question of where they came from.

For their current study, Sutherland and his colleagues set out to work backward from those chemicals to see if they could find a route to RNA from even simpler starting materials. They succeeded. In the current issue of Nature Chemistry, Sutherland's team reports that it created nucleic acid precursors starting with just hydrogen cyanide (HCN), hydrogen sulfide (H2S), and ultraviolet (UV) light. What is more, Sutherland says, the conditions that produce nucleic acid precursors also create the starting materials needed to make natural amino acids and lipids. That suggests a single set of reactions could have given rise to most of life's building blocks simultaneously.

Sutherland's team argues that early Earth was a favorable setting for those reactions. HCN is abundant in comets, which rained down steadily for nearly the first several hundred million years of Earth's history. The impacts would also have produced enough energy to synthesize HCN from hydrogen, carbon, and nitrogen. Likewise, Sutherland says, H2S was thought to have been common on early Earth, as was the UV radiation that could drive the reactions and metal-containing minerals that could have catalyzed them.

That said, Sutherland cautions that the reactions that would have made each of the sets of building blocks are different enough from one another-requiring different metal catalysts, for example-that they likely would not have all occurred in the same location. Rather, he says, slight variations in chemistry and energy could have favored the creation of one set of building blocks over another, such as amino acids or lipids, in different places. "Rainwater would then wash these compounds into a common pool," says Dave Deamer, an origin-of-life researcher at the University of California, Santa Cruz, who wasn't affiliated with the research.

Could life have kindled in that common pool? That detail is almost certainly forever lost to history. But the idea and the "plausible chemistry" behind it is worth careful thought, Deamer says. Szostak agrees. "This general scenario raises many questions," he says, "and I am sure that it will be debated for some time to come."

Nigeria a model for quick action, scientists find

Ebola. The word brings fear of an unseen and potentially lethal enemy. But there are ways to stop its spread, say infectious disease scientists.

Quick intervention is needed, according to the researchers, who recently published their findings in the journal Eurosurveillance.

Analyzing Ebola cases in Nigeria, a country with success in containing the disease, the scientists estimated the rate of fatality, transmission progression, proportion of health care workers infected, and the effect of control interventions on the size of the epidemic.

Rapid response needed

"Rapid control is necessary, as is demonstrated by the Nigerian success story," says Arizona State University (ASU) scientist Gerardo Chowell, senior author of the paper.

"This is critically important for countries in the West Africa region that are not yet affected by the Ebola epidemic, as well as for countries in other regions of the world that risk importation of the disease."

The research is funded by the U.S. National Science Foundation (NSF)-National Institutes of Health (NIH)-Department of Agriculture (USDA) Ecology and Evolution of Infectious Diseases (EEID) Program.

"Controlling a deadly disease like Ebola requires understanding how it's likely to spread, and knowing the ways of managing that spread that are most likely to be effective," says Sam Scheiner, NSF EEID program director.

"Being able to respond quickly needs a foundation of knowledge acquired over many years. The work of these scientists is testimony to long-term funding by the EEID program."

Control measures in Nigeria

The largest Ebola outbreak to date is ongoing in West Africa, with more than 8,000 reported cases and 4,000 deaths. However, just 20 Ebola cases have been reported in Nigeria, with no new cases since early September.

All the cases in Nigeria stem from a single traveler returning from Liberia in July.

The study used epidemic modeling and computer simulations to project the size of the outbreak in Nigeria if control interventions had been implemented during various time periods after the initial case, and estimated how many cases had been prevented by the actual early interventions.

"This timely work demonstrates how computational simulations, informed by data from health care officials and the complex social web of contacts and activities, can be used to develop both preparedness plans and response scenarios," says Sylvia Spengler, program director in NSF's Directorate for Computer and Information Science and Engineering, which also supported the research.

Control measures implemented in Nigeria included holding all people showing Ebola symptoms in an isolation ward if they had had contact with the initial case. If Ebola was confirmed through testing, people diagnosed with the disease were moved to a treatment center.

Asymptomatic individuals were separated from those showing symptoms; those who tested negative without symptoms were discharged.

Those who tested negative but showed symptoms--fever, vomiting, sore throat and diarrhea--were observed and discharged after 21 days if they were then free of symptoms, while being kept apart from people who had tested positive.

Brief window of opportunity

Ebola transmission is dramatically influenced by how rapidly control measures are put into place.

"Actions taken by health authorities to contain the spread of disease sometimes can, perversely, spread it," says NSF-funded scientist Charles Perrings, also of ASU.

"In the Nigeria case, people who tested negative but had some of the symptoms were not put alongside others who tested positive," says Perrings. "So they had no incentive to flee, and their isolation did nothing to increase infection rates. Elsewhere in the region isolation policies have had a different effect."

The researchers found that the projected effect of control interventions in Nigeria ranged from 15-106 cases when interventions are put in place on day 3; 20-178 cases when implemented on day 10; 23-282 cases on day 20; 60-666 cases on day 30; 39-1,599 cases on day 40; and 93-2,771 on day 50.

The person who was initially infected generated 12 secondary cases in the first generation of the disease; five secondary cases were generated from those 12 in the second generation; and two secondary cases in the third generation.

That leads to a rough estimate of the reproduction number according to disease generation declining from 12 during the first generation, to approximately 0.4 during the second and third disease generations.

A reproductive number above 1.0 indicates that the disease has the potential to spread.

Recent estimates of the reproduction number for the ongoing Ebola epidemic in Sierra Leone and Liberia range between 1.5 and 2 (two new cases for each single case), indicating that the outbreak has yet to be brought under control.

The effectiveness of the Nigerian response, scientists say, is illustrated by a dramatic decrease in the number of secondary cases over time.

The success story for Nigeria, they maintain, sets a hopeful example for other countries, including the United States.

As this week's viral photo of 35,000 walruses crammed on an Alaskan shore reminds us, the climate crisis is still very much a thing. For those who missed it, a lack of Arctic ice evidently forced the poor creatures to huddle together on a narrow piece of land out of desperation -- normally, they're observed lying more spread out. (The same thing happened last year as well.)

The plight of the walruses is striking, but climate change is also having all kinds of other, less readily visible effects. It's been shown to produce heat waves around the world, contribute to global wildlife extinction and maybe even reduce gravity.

Below, we give you 21 numbers to help explain one of the most pressing global issues of our time.

0.01%

Percentage of working climate scientists who reject man-made global warming. According to research by the geologist James Lawrence Powell, among 9,136 scientists who published a combined 2,258 peer-reviewed climate articles between November 2012 and December 2013, just one person rejected the idea that humans are changing Earth's climate. Another review looked at 4,000 peer-reviewed papers on climate change and found that a full 97 percent identified humans as the cause.

90%

Percentage of 108 climate change denial books published between 1982 and 2010 that were not peer-reviewed. The books variously denied that climate change is happening, that humans are at fault, that climate change is having a negative effect on the environment, or any combination of the three. A strong link was also found between the books and conservative think tanks. Seventy-two percent of the books were published by an author or editor with a verifiable affiliation to some such group.

800,000 to 15,000,000

Number of years it's been since carbon dioxide levels were as high as they are now. Not only did humans not exist back then, but the oceans were 100 feet higher than they are today and the world's surface temperature was 11 degrees warmer than it is now.

1895

The year Svante Arrhenius presented a paper describing the impact of increased carbon dioxide on Earth's greenhouse effect. Arrhenius, a Swedish physicist and chemist, hypothesized that changes in concentrations of carbon dioxide and other greenhouse gases could have a significant impact on the planet's surface temperatures. While Arrhenius was not the first to suggest humans might be capable of influencing the climate, his research shows that the basic science of global warming has been understood for more than a century. Yet somehow, there are still public figures in the U.S. debating whether it's real.

42%

The percentage by which atmospheric carbon dioxide has risen since the Industrial Revolution. Concentrations of methane and nitrous oxide, two other important greenhouse gases, have risen 153 percent and 21 percent from pre-Industrial levels, respectively.

2°C

The generally accepted maximum increase in average global temperature that humans can sustain without dangerous consequences. It was proposed as a policy target by the EU in 1996, and again in the Copenhagen Accord of 2009. After the planet warms by more than two degrees Celsius, or roughly 3.5 degrees Fahrenheit, relative to pre-Industrial times -- as it is currently on track to do -- humans could face more of the negative consequences of climate change, such as more frequent food shortages, extreme weather and mass extinction of plant and animal species.

800,000,000,000

Estimated total number of metric tons of carbon that humans can pump into the atmosphere before average global temperatures rise more than two degrees Celsius. According to a 2013 report by the Intergovernmental Panel on Climate Change, 800 billion tons is Earth's "carbon budget," and we've already used up close to two-thirds of it.

19.6
The number of pounds of carbon dioxide produced by burning one gallon (6.3 pounds) of gasoline. One gallon of diesel fuel does even more damage, releases 22.38 pounds of CO2 into the atmosphere. The U.S. Energy Information Administration estimates that gasoline- and diesel-fueled transportation added 1,522 million metric tons of carbon to the environment in 2013.

25%

The percentage increase of carbon dioxide in the atmosphere between 1959 and 2013. That's a rise from 316 parts per million to 397 ppm. Over the past two decades, the average annual increase rose from 1.9 ppm to 2.1 ppm.

400,000

Estimated number of annual deaths due to factors influenced by climate change. A 2012 report published by the European nonprofit DARA estimated the average number of fatalities due to "hunger and communicative diseases" related to extreme weather affected by climate change. These conditions appear to hit the children of developing countries particularly hard. A group of doctors recently estimated that up to 7 million people may face premature death as a result of indoor and outdoor air pollution linked to fossil fuel consumption.

$696,000,000,000

Loss in 2010 global GDP estimated to have been caused by climate change. By 2030, researchers estimate that 3.2 percent of annual global GDP will be lost due to climate change, through consequences such as negative effects on crop yields. In developing countries, the loss may be even greater -- up to 11 percent of a nation's GDP.

1.7 to 3.2

The average number of feet by which global sea levels are expected to rise by 2100. This estimate by the IPCC assumes that greenhouse gas emissions will continue to climb at present-day rates. Sea levels around the globe are not expected to rise evenly, and some regions, such as the Mid-Atlantic U.S., are believed to be particularly vulnerable.

4

Number of feet global sea levels could rise if the increasingly unstable West Antarctic ice sheet should collapse. The sheet is already thinning, and one study has called its eventual collapse "unstoppable." However, while the ice sheet's melt would cause already-rising global sea levels to climb even higher, researchers do not believe that will start any time soon -- in a worst-case scenario, rapid collapse might begin 200 to 1,000 years from now.

2041

Year when it will become too late to stop Miami from slipping below sea level, due to greenhouse gas emissions already built up in the atmosphere. This doesn't mean Miami will actually be underwater by 2041 -- but if emissions continue at their current rates, 2041 is the year there will be no way to reverse the sort of sea-level rise that would end up drowning most of the city.

11.5°F

High-level projection for average global temperature increase by 2100. A low-level projection puts the average global increase at 2 degrees Fahrenheit, but changes in temperature are expected to vary by location.

0.3°C to 0.5°C

Estimated decrease in regional temperature by 2100, if certain presently non-forested areas of Europe are converted to deciduous forest. Though it's unlikely to happen, a 2013 study illustrated the benefits of using vegetation as a weapon against climate change.

70-plus

Number of days in 2011 when the temperature in parts of the U.S. was at least 100 degrees Fahrenheit, according to the National Climate Assessment. Texas, Oklahoma, Arizona and Southern California were particularly hard-hit with scorching hot weather that year, a trend that is expected to increase with climate change.

14.9

Average number of days each year when temperatures in New York City exceed 90 degrees Fahrenheit. That's based on data collected between 1870 and 2013. The last year when New York City had only one day of 90-plus temperatures was 1902.

69

High-level estimate of how many days per year New York City will have temperatures above 90 degrees Fahrenheit if emissions aren't curtailed. That's the projection for the year 2100. A low-level estimate puts that number at 18 days. Other cities could face a much hotter future. In Miami, by 2100, almost 200 days out of the year could be 90 degrees or above.

9

Number of the top 10 hottest years on record that have occurred in the 21st century. The other year was 1998, and 2010 was the hottest year of all since record-keeping began in 1880.

71%

The percentage increase in very heavy precipitation events recorded in the Northeastern U.S. between 1958 and 2012. Only Hawaii saw a decrease in precipitation (12 percent) during that time frame. The Midwest experienced a 16 to 37 percent rise in heavy precipitation, and the South saw a 27 percent increase.

More - The Koyal Group Info Mag

Seit dem Start, Wissenschaft AMAs durchgeführt wurden bis zu fünf mal die Woche, aber nie mehr als eine am Tag. Die Hauptlast der organisatorischen Arbeit fällt auf Allen's Schultern; er führt nicht nur die meisten der Outreach, um Partizipation, aber auch Spaziergänge durch den gesamten Prozess der Durchführung einer AMA-aus ein Konto erstellen, basteln die Überschrift also noch haben eine große Anziehungskraft auf Reddit Benutzer. "Das Problem, mit dem wir begegnen, ist, dass es sich herausstellt, große Namen Wissenschaftler sind nicht groß redditors", sagt er. Viel von seiner Reichweite umfasst eine einfache Erkältung Anruf oder e-mail an die Wissenschaftler; bewaffnet mit r/Wissenschaft im Web Traffic Statistics, es ist nicht schwer zu überzeugen ein Forscher von der AMA's wert. Allmählich jedoch, Hochschulen" public relations Abteilungen haben damit begonnen, die Serie und haben damit begonnen, an allen zu planen.

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