Ars Technica - The Scientific Method

Researchers find a chemical that makes locusts swarm

Wed, 12 Aug 2020 21:39:47 GMT

The year 2020 may be one for the record books in terms of apocalyptic tidings. In addition to the usual background of fires, floods, and earthquakes, the plague is still around. And you might have heard something about a pandemic. But what really nails down the apocalyptic vibe is the fact that the year has seen swarms of locusts causing the sorts of problems they're famous for.

In a tiny bit of good news, the same sort of research that may bail us out with therapies and a vaccine for SARS-CoV-2 could potentially help us out against future locust swarms. That's because a team of biologists based in China has now identified the chemical that calls locusts to swarm and shown that genetic engineering can eliminate the response.

A lot of evidence

There's nothing especially exciting about any single aspect of the research here. Instead, the researchers simply put together techniques from a variety of specializations and then applied them to the topic of locust swarms. Locusts are normally solitary animals, but they become immensely destructive when conditions induce them to form massive swarms that are big enough to be picked up by radar. In addition to the altered behavior, swarming locusts actually look physically different, indicating that the decision to swarm involves widespread changes to a locust's biology.

Read 9 remaining paragraphs | Comments

Adding a dash of alcohol suppresses coffee ring effect in 2D printing inks

Wed, 12 Aug 2020 18:00:06 GMT

Enlarge / The coffee ring effect happens because evaporation occurs faster at the edge than at the center. (credit: MirageC/Getty Images)

Inkjet printing of two-dimensional crystals will be crucial for ushering in the next generation of printed electronics. While the technology has made a lot of progress in recent years, a major challenge to industrial-scale printed electronic components is achieving uniform distribution of the crystals; uneven distribution can result in faulty devices. The culprit is a phenomenon known as the "coffee ring effect." Now scientists have created a new family of inks that can suppress the effect, according to a new paper in the journal Science Advances.

Coffee rings are the pattern you get when a liquid evaporates and leaves behind a ring of previously dissolved solids—coffee grounds in the case of your morning cup of joe, 2D crystals in the case of inkjet printing of electrical components. (You can also see the effect with single-malt scotch. A related phenomena is wine tears.) The coffee ring effect occurs when a single liquid evaporates and the solids that had been dissolved in the liquid (like coffee grounds or 2D crystals) form a telltale ring. It happens because the evaporation occurs faster at the edge than at the center. Any remaining liquid flows outward to the edge to fill in the gaps, dragging those solids with it. Mixing in solvents (water or alcohol) reduces the effect, as long as the drops are very small. Large drops produce more uniform stains.

Similarly, when a drop of watercolor paint dries, the pigment particles of color break outward, toward the rim of the drop. So artists who work with watercolors also have to deal with the coffee ring effect if they don't want that accumulation of pigment at the edges to happen. As we reported in 2018, adding alcohol to the watercolor paint can prevent it. Alternatively, an artist may wet the paper before applying the paint. Instead of the drop remaining pinned to the paper, the ink runs off. This allows the artist to play with various effects, such as generating unusual color gradients.

Read 7 remaining paragraphs | Comments

Will any new smallsat rockets make it to orbit this year?

Wed, 12 Aug 2020 16:57:19 GMT

Enlarge / After being released from Cosmic Girl, LauncherOne ignited its engine successfully at the end of May. (credit: VirginOrbit)

In case you hadn't noticed, we're approaching mid-August. As of Wednesday, there are a mere 142 days left in the year. So as the calendar churns toward the end of the year, this is a good time to ask whether any new commercial rockets that launch small satellites will make it to orbit this year.

Back at the optimistic, pre-pandemic beginning of 2020, we had high hopes for the debut of new rockets from Astra, Firefly, and Virgin Orbit. We also expected to see the first flight of Europe's Vega C rocket, which is now confirmed to slip into 2021.

Since then, a few companies have made launch attempts and failed to reach orbit. Others have been slowed by the COVID-19 pandemic. Here's a rundown of the companies that could still make orbit this calendar year.

Read 14 remaining paragraphs | Comments

How to turn regular bricks into electricity-storing supercapacitors

Wed, 12 Aug 2020 14:26:19 GMT

Enlarge

Usually the phrase “power brick” refers affectionately to the AC adapter of something like a laptop. But what if that term was quite literal, involving an actual brick?

A team led by Hongmin Wang at Washington University in St. Louis set out to make a genuine power brick. More specifically, they wanted to see if they could use a vapor coating technique to turn ordinary red bricks into part of a supercapacitor. That actually isn’t quite as weird as it sounds, given that the red of a brick is an iron mineral, and iron is a common component of some battery chemistries. Bricks are often porous as well, meaning there is plenty of surface area where a thin coating could interact with that iron.

The process (something they had developed previously) involves heating the brick in an enclosure along with hydrochloric acid and an organic compound that mercifully shortens to “EDOT.” The two liquid substances evaporate and condense on the brick’s convoluted surface. The acid dissolves some of the iron mineral, freeing up iron atoms that help the organic molecules link up to form polymer chains (graduating to “PEDOT”) that coat the surface. The polymer makes microscopic, entangled fibers that form a continuous and electrically conductive layer on each face of the brick, which otherwise remains. (This does have the effect of turning the brick black, though.)

Read 4 remaining paragraphs | Comments

US childhood SARS-CoV-2 infections surging with the current peak

Tue, 11 Aug 2020 19:34:18 GMT

Enlarge / NEW YORK CITY - AUGUST 08: A kid wears a face mask while riding a bicycle in Madison Square Park. (credit: Noam Galai / Getty Images)

The US is currently debating if and how schools can be reopened safely during the COVID-19 pandemic while dealing with a cloud of presidential misinformation. The debate is made difficult by a mix of ambiguous data about how much children contribute to the spread of the virus and some dramatic instances of the pandemic spreading within schools. Given the confusing and sometimes anecdotal evidence, it can be difficult to get a decent picture of how children are affected by SARS-CoV-2 and COVID-19.

Fortunately, the American Academy of Pediatrics and the Children’s Hospital Association have decided to provide some perspective. The two groups have been gathering state-level data on a number of stats in children and compiling it to produce a national picture. While there are definitely limitations to the data, the picture it paints is one in which the national surge in infections is being paralleled by a surge in cases in children, with nearly 100,000 new cases in the last two weeks of July.

Data and its limitations

The American Academy of Pediatrics and the Children’s Hospital Association have been analyzing childhood infections at weekly intervals, allowing researchers to track the pandemic's progression in the United States. Their most recent report covers up to July 30, and they have data going back to mid-April.

Read 10 remaining paragraphs | Comments

Russia skips COVID-19 vaccine trial, says millions to be vaccinated this month

Tue, 11 Aug 2020 17:07:51 GMT

Enlarge / The unproven vaccine candidate has been dubbed "Sputnik V" (credit: Aurich Lawson / Getty Images)

Russian President Vladimir Putin announced Tuesday that Russia is the first country in the world to grant regulatory approval for a COVID-19 vaccine—dubbed “Sputnik V.”

Putin claimed that one of his own daughters has already received a dose of the vaccine, according to reports from Moscow—though he didn’t note which daughter. Russian officials pledged to vaccinate millions within the month, starting with healthcare workers and teachers.

Little is known about Sputnik V, which was developed by researchers at the Gamaleya Institute in Moscow. There is no public data on the vaccine, let alone any published, peer-reviewed scientific studies. Public registration of two small clinical trials notes that Sputnik V uses a viral-vector-based design, but they suggest that it has only been tested in a small number of people. The trials, which began less than two months ago, each enrolled 38 healthy volunteers and have an estimated study completion date of August 15.

Read 12 remaining paragraphs | Comments

Greed may be good when it comes to solar power

Mon, 10 Aug 2020 22:56:33 GMT

Enlarge (credit: Jeff Martin/DOE)

Based purely on economics, there should be a lot more solar panels on roofs in the United States. With the dramatic plunge in the price of panels, solar systems have become competitive with the cost of electricity in a growing number of states, leaving the question of sun exposure to be the primary driver of whether adoption makes sense. Yet photovoltaic-equipped houses remain a rarity in the US, despite many states pushing for the adoption of renewable energy.

So why isn't that push working? To try to find out, a small team of researchers worked with a non-profit that promotes solar installs, helping test out two different message. One message focused on self-interest and emphasized the economic benefits of installing panels. The other was what's termed "pro-social," meaning it emphasized that installation of solar would bring benefits to the community. As the researchers found, self-interest was king—even after the promotion was over. But self-interest did have a side benefit in that the systems that were installed tended to get the most energy out of their panels.

Scripting Solarize

The work relies on a program called Solarize. Solarize runs town-level programs that include a single installer that provides the entire town with a group rate. Program ambassadors also run pro-solar programs within the town, encouraging adoption. These programs were the ones targeted by the researchers, who arranged an experiment based on the message delivered by these ambassadors. Some towns received messages that focused on self-interest, like “save thousands by installing solar.” Others were more community-focused—“Our community is doing something together to have more clean energy,” for example. The researchers worked with the program in Connecticut (one of the researchers is at Yale), which has expensive electricity.

Read 8 remaining paragraphs | Comments

Lest we forget: Mark 75 years of the atomic bomb with the Ars watch list

Mon, 10 Aug 2020 21:40:36 GMT

Enlarge / Ars marks the 75th anniversary of the nuclear bomb with a look at how the complicated legacy of this world-altering event has been reflected in film and television. (credit: Film collage by Aurich Lawson)

This year marks the 75th anniversary of the first atomic bomb. Just before sunrise on July 16, 1945, in a secluded spot in a central New Mexican desert, a prototype bomb nicknamed "Gadget" was hoisted to the top of a 100-foot tower and detonated. The blast vaporized the steel tower and produced a mushroom cloud rising to more than 38,000 feet. The heat from the explosion melted the sandy soil around the tower into a mildly radioactive glassy crust now known as "trinitite." And the shock wave broke windows as far as 120 miles away.

After the Trinity test, Richard Feynman recalled finding his colleague, Robert Wilson, sitting despondently amid the celebration. "It's a terrible thing that we made," Feynman remembered him saying. Hans Bethe famously observed, "The physicists have known sin. And this is a knowledge which they cannot lose." It's often said that physicists became so intent on the intellectual challenge of building an atomic bomb that they lost sight of the profound implications of what they were creating.

Those implications became all too clear on August 6, 1945, when a gun-triggered fission bomb dubbed "Little Boy" fell on Hiroshima, killing an estimated 70,000 to 130,000 people. Three days later, the implosion-triggered "Fat Man" was dropped on Nagasaki, adding another 45,000 human casualties. The United States won the war but at a horrific cost. The world has been haunted by the prospect of a devastating nuclear apocalypse ever since—and so has TV and the movies. So to mark this somber occasion, we've compiled a watch list of films and shows that we feel best reflect the complicated legacy of the atomic bomb.

Read 55 remaining paragraphs | Comments

Massive Salmonella outbreak sweeps US, Canada. Nearly 900 sickened so far

Mon, 10 Aug 2020 18:21:27 GMT

Enlarge / Red onions have been fingered as the likely culprit. (credit: Getty | Thomas Trutschel)

An outbreak of Salmonella infections linked to tainted onions has mushroomed in North America. So far, the outbreak has sickened 879 people, hospitalizing 114 across 43 US states and seven Canadian provinces.

The US Food and Drug Administration traced the outbreak back to red onions produced by Thomson International Inc. of Bakersfield, California. Thomson issued a recall of all of its onions August 1, covering red, yellow, white, and sweet bulbs that were shipped any time after May 1. But the outbreak numbers will likely continue to climb, given the potentially week-long period between eating a bad onion and developing symptoms, plus a typical two-to-four-week lag in case reporting.

The tainted onions were shipped to wholesalers, restaurants, and grocery stores across Canada as well as in all 50 US states and the District of Columbia. Affected stores include Walmart, Kroger, Fred Meyer, Publix, Giant Eagle, Food Lion, and H-E-B. The onions were sold under brand names: Thomson Premium, TLC Thomson International, Tender Loving Care, El Competitor, Hartley’s Best, Onions 52, Majestic, Imperial Fresh, Kroger, Utah Onions, and Food Lion.

Read 6 remaining paragraphs | Comments

Russia’s space leader blusters about Mars in the face of stiff budget cuts

Mon, 10 Aug 2020 16:16:00 GMT

Enlarge / Dmitry Rogozin, director of the Roscosmos State Corporation, gives an open lecture titled "Transformation of Roscosmos" at Moscow State University on May 23, 2019. (credit: Vladimir GerdoTASS via Getty Images)

The leader of Russia's civil space program appears to be increasingly disengaged from reality. In recent months Dmitry Rogozin, the chief of Roscosmos, has given a series of interviews in which he has made all manner of big promises about the supposedly bright future of Russia's space program.

For example, in an interview published just today, Rogozin made the fantastical claim that his country's space program has the technical means to reach Mars and land cosmonauts there within eight to 10 years. If Russia is ready to finance such a plan, Rogozin guaranteed that Roscosmos stands ready to deliver.

Russia, Rogozin also recently said, is ready to do reuse better than SpaceX and the United States. SpaceX's Falcon 9 rocket, he said, is only "semi-reusable," and Russia aspires to build a 21st-century rocket capable of 100 flights. He then reiterated that Russia would like to develop a version of its Soyuz rocket that has a methane-fueled engine.

Read 5 remaining paragraphs | Comments

Real Genius turns 35—celebrating this cult classic is a moral imperative

Sun, 09 Aug 2020 13:30:03 GMT

Enlarge / Mitch (Gabriel Jarret) and Chris (Val Kilmer) play young science whizzes trying to build a 5-kilowatt laser in the 1985 film Real Genius. (credit: TriStar Pictures)

Back to the Future justly dominated the summer box office in 1985, but it's too bad its massive success overshadowed another nerd-friendly gem, Real Genius, which debuted one month later, on August 9. Now celebrating its 35th anniversary, the film remains one of the most charming, winsome depictions of super-smart science whizzes idealistically hoping to change the world for the better with their work. It also boasts a lot of reasonably accurate science—a rare occurrence at the time.

Real Genius came out the same year as the similarly themed films Weird Science—which spawned a 1990s TV sitcom—and My Science Project, because 1980s Hollywood tended to do things in threes. But I'd argue that Real Genius has better stood the test of time, despite being so quintessentially an '80s film—right down to the many montages set to electronic/synth-pop chart-toppers. The film only grossed $12.9 million domestically against its $8 million budget, compared to $23.8 million domestically for its fellow cult classic, Weird Science. (My Science Project bombed with a paltry $4.1 million.) Reviews were mostly positive, however, and over time it became a sleeper hit via VHS, and later, DVD and streaming platforms.

(Spoilers for the 35-year-old film below.)

Read 11 remaining paragraphs | Comments

COVID-19 won’t impact climate much, but economic recovery could

Sat, 08 Aug 2020 12:30:35 GMT

Enlarge / India saw a notable decline in aerosol pollution in April. (credit: NASA EO)

Given the radical changes people have undertaken to limit the spread of COVID-19 (hello month six of quarantine-except-for-groceries), many have naturally wondered what impact this has had on pollution, including greenhouse gases and climate change. Some short-lived pollutants dropped noticeably during the strong lockdowns of April, as businesses shuttered and travel was reduced. But CO₂levels don't fluctuate based on short-term events like that, so the long-term effect on climate change was expected to be trivially small—assuming economies rebounded fairly quickly.

A new study led by the University of Leeds’ Piers Forster (and his daughter Harriet) takes advantage of phone location data to re-examine the first six months of the year, tracking more than just CO₂. While they ultimately find that the impact has been small, their results also highlight that the way economies choose to rebound could have a much bigger effect over the long term.

The work relies on mobility data made public by Google and Apple, covering 114 countries. Using that along with energy and emissions datasets, the researchers converted behavior changes into pollution changes. The phone data record changes in transportation use quite well, although purported changes in activity between residential, commercial, and industrial settings are harder to relate to energy. The researchers compared the changes they saw in their phone data to a May study that estimated April emissions using things like utility data. They found their phone-based estimate of home energy use probably overestimates the real change.

Read 10 remaining paragraphs | Comments

Bill Gates on Covid-19: Most tests are "completely garbage”

Sat, 08 Aug 2020 11:05:12 GMT

Enlarge / Despite trillions of dollars of economic damage, Bill Gates is optimistic that a strong pipeline of therapies and vaccines will carry the US through the pandemic. (credit: Jeff Pachoud | Getty Images)

For 20 years Bill Gates has been easing out of the roles that made him rich and famous—CEO, chief software architect, and chair of Microsoft—and devoting his brain power and passion to the Bill and Melinda Gates Foundation, abandoning earnings calls and antitrust hearings for the metrics of disease eradication and carbon reduction. This year, after he left the Microsoft board, one would have thought he would have relished shedding the spotlight directed at the four CEOs of big tech companies called before Congress.

But as with many of us, 2020 had different plans for Gates. An early Cassandra who warnedof our lack of preparedness for a global pandemic, he became one of the most credible figures as his foundation made huge investments in vaccines, treatments, and testing. He also became a target of the plague of misinformation afoot in the land, as logorrheic critics accused him of planning to inject microchips in vaccine recipients. (Fact check: false. In case you were wondering.)

My first interview with Gates was in 1983, and I’ve long lost count of how many times I’ve spoken to him since. He’s yelled at me (more in the earlier years) and made me laugh (more in the latter years). But I’ve never looked forward to speaking to him more than in our year of Covid. We connected on Wednesday, remotely of course. In discussing our country’s failed responses, his issues with his friend Mark Zuckerberg’s social networks, and the innovations that might help us out of this mess, Gates did not disappoint. The interview has been edited for length and clarity.

Read 51 remaining paragraphs | Comments

In a consequential decision, Air Force picks its rockets for mid-2020s launches

Fri, 07 Aug 2020 22:46:51 GMT

Enlarge / Artist's rendering of a Vulcan-Centaur rocket launch. (credit: United Launch Alliance)

On Friday afternoon, the US Air Force answered one of the big questions that had been hanging over the US launch industry for more than a year—which two companies will be selected to compete for national security launch contracts from 2022 to 2026?

During a video call with reporters, William Roper, Assistant Secretary of the Air Force for Acquisition, Technology and Logistics, said that United Launch Alliance will receive approximately 60 percent of the launch orders and SpaceX will receive the other 40 percent. Two other bidders, Northrop Grumman with its Omega rocket, and Blue Origin with its New Glenn vehicle, will not receive awards.

"The ability to meet our technical factors to do the mission is the most important thing," Roper said, in response to a question on the Air Force criteria. Secondary factors included past performance, the ability to work with small businesses, and total evaluated price. The military has nine reference orbits for large and complex payloads that these rockets must meet.

Read 11 remaining paragraphs | Comments

New study models ways of emerging from a pandemic lockdown

Fri, 07 Aug 2020 14:54:01 GMT

Enlarge / Testing and contact tracing may be essential for exiting pandemic lockdowns. (credit: Sean Gallup / Getty Images)

As the scale and threat of the COVID-19 pandemic became clear, researchers who trace the spread of diseases were pretty unanimous: to buy us time to develop a therapy or vaccine, countries needed to implement heavy-handed restrictions to limit the opportunities for the virus to spread. Experts painted frightening pictures of huge peaks of infections that would overwhelm local hospital systems if lockdowns weren't put in place, leading to many unnecessary deaths. For countries like Italy and Spain, which were already in the throes of an uncontrolled spread, reality bore these predictions out. Peaks rose sharply in advance of restrictions but fell nearly as sharply once they were put in place.

But those same models also predicted that ending the restrictions would put countries at risk of a return of the virus a few months later, forcing governments to again decide between strict restrictions or an out-of-control pandemic in the next step of a cycle that would repeat until a vaccine or therapy became available. Those countries now have a somewhat different question: are there ways of controlling the virus without resorting to a cycle of on-and-off lockdowns? For countries like the US, which implemented restrictions briefly, erratically, and half heartedly, such that peaks haven't been separated by much of a trough, the same question will become relevant if we ever get the virus under control.

A new study by a large international team uses epidemiological models to explore ways of keeping things in check while allowing most of the population to resume a semi-normal life. It finds that there are ways of handling restriction easing, but they require a combination of an effective contact tracing system, extensive testing, and a willingness of households to quarantine together.

Read 15 remaining paragraphs | Comments

Rocket Report: South Korea’s SpaceX dilemma, Rocket Lab finds a quick fix

Fri, 07 Aug 2020 11:00:44 GMT

Enlarge / An overview of Astra's picturesque launch site for Rocket 3.1. (credit: John Kraus for Astra)

Welcome to Edition 3.11 of the Rocket Report! A lot of the most interesting news this week came in the world of small launch, with Electron announcing a quick return to flight as well as boosting the capacity of its Electron booster. We were also surprised to see such a robust fundraising effort by ABL Space Systems.

As always, we welcome reader submissions, and if you don't want to miss an issue, please subscribe using the box below (the form will not appear on AMP-enabled versions of the site). Each report will include information on small-, medium-, and heavy-lift rockets as well as a quick look ahead at the next three launches on the calendar.

Astra attempts launch of second orbital rocket. The launch window for launching Rocket 3.1 from the company's spaceport on Kodiak Island, Alaska, opened Sunday night. A combination of technical issues with the rocket and ground systems, as well as weather issues, precluded launches on Sunday through Wednesday.

Read 26 remaining paragraphs | Comments

Updated hurricane-season outlooks: Expect plenty more storms

Thu, 06 Aug 2020 22:03:29 GMT

Enlarge / Hurricane Isaias passed north of Haiti and the Dominican Republic on July 31 before spinning up the East Coast. (credit: NASA EO)

Hurricane season in the Atlantic has so far been quite active, with nine storms chewing through the alphabet already—two of them (Hanna and Isaias) reached hurricane strength before making landfall. Unfortunately, this pattern isn’t expected to let up, as hurricane outlooks have upgraded the odds that this highly active season is going to continue. In fact, NOAA is suggesting that we could be considering names starting with Y before things settle down for the winter.

In May, NOAA’s hurricane season outlook gave 60 percent odds of above-average activity, with something like 13 to 19 named storms, six to 10 hurricanes, and three to six major hurricanes of Category 3 or higher.

On Thursday, NOAA released an updated outlook with higher probabilities. “The season is now expected to be one of the more active in the historical record,” it notes. The outlook now calls for between 19 and 25 named storms and with seven to 11 hurricanes, though the number of major hurricanes is unchanged. Because the potential energy available for storms can produce one big storm or multiple smaller ones, the total is often calculated as “Accumulated Cyclone Energy,” or ACE. An above-normal hurricane season hits 120 percent of the median ACE, while clearing 165 percent defines an extremely active season. The new outlook sees the 2020 season hitting anywhere from 140 to 230 percent of median ACE.

Read 4 remaining paragraphs | Comments

With COVID-19 spreading, 49% of low-income communities have zero ICU beds

Wed, 05 Aug 2020 20:35:17 GMT

Enlarge / Medics transfer a patient on a stretcher from an ambulance outside of Emergency at Coral Gables Hospital where coronavirus patients are treated in Coral Gables near Miami, on July 30, 2020. (credit: Getty | CHANDAN KHANNA)

As the coronavirus pandemic spreads uncontrolled in much of the United States, a new study finds that almost half of low-income areas are gravely unprepared to treat severe cases of COVID-19, hinting at higher death rates to come.

Forty-nine percent of the country’s lowest-income communities—with median incomes of $35,000 or less—have zero intensive care unit beds in their area hospitals. Looking only at rural areas, the picture is even worse: 55 percent had no ICU beds. This is in stark contrast to the highest-income communities, defined by a median income of $90,000 and above. Of those, only 3 percent overall lack access to ICU beds. The study, published by researchers at the University of Pennsylvania, appeared this week in the journal Health Affairs.

The findings further heighten concern over how the pandemic is exacerbating gaping socioeconomic disparities in the US. Low-income communities are already more vulnerable to contracting COVID-19 due to unavoidable job-related exposure, reliance on mass transit, higher population densities, and less ability to quarantine upon potential exposure, the authors note.

Read 5 remaining paragraphs | Comments

What we know about the massive chemical explosion in Beirut

Wed, 05 Aug 2020 20:10:07 GMT

The red-orange cloud rising above the site of the explosion in Beirut on August 4 is due to nitrogen dioxide, a byproduct of the explosion of ammonium nitrate. [credit: ANWAR AMRO/AFP via Getty Images ]

On Tuesday, Beirut was devastated by a massive chemical explosion that occurred at the city's port a little after 6pm local time. The blast killed at least 135 people and injured thousands more, and it may have left 300,000 residents homeless after the shockwave shattered glass and damaged buildings across the Mediterranean city. Initial reports blamed improperly stored fireworks for the disaster, but the real culprit soon emerged: 2,750 tons of ammonium nitrate (NH₄NO₃) that had been seized by Lebanese officials from a freighter in 2013 and stored at a warehouse at the port ever since.

It's now believed that a fire broke out at the warehouse—possibly due to careless welding performed as an anti-theft measure—which caused the stockpile of the chemical, often used as a fertilizer, to explode catastrophically.

Ammonium nitrate has often been combined with fuel oil to create an explosive that's used in mining and construction, and it has been used as an oxidizer for rocket engines. But it's also been employed for more nefarious ends. The first recorded ammonium nitrate fuel oil (ANFO) bomb was detonated in 1970 at the University of Wisconsin-Madison as a protest against the Vietnam War. Terror groups on both sides of Northern Ireland's sectarian conflict also built bombs using ANFO from the 1970s until the 1990s, and Timothy McVeigh used a combination of ammonium nitrate and nitromethane for a terror attack in Oklahoma City in 1995.

Read 8 remaining paragraphs | Comments

Many of Mars’ stream valleys might have formed under an ice sheet

Wed, 05 Aug 2020 19:08:02 GMT

Enlarge / Examples of different types of valleys on Mars. (credit: Galofre et al./Nature Geoscience)

The further back into Earth’s history your mind wanders, the more work your imagination has to put in. That’s even more true for Mars. None of us have physically stepped foot on the present-day version of the planet, and its past was clearly very different from its present, with evidence pointing to flowing and standing water.

Among the relics of the watery past are networks of valleys incised into Mars’ surface. The Red Planet’s southern hemisphere highlands host many valleys, which have largely been interpreted as formed by rivers and groundwater springs. The source of water in rivers—whether rainfall in a warm climate or just melt from glacial ice—has been a question mark.

It’s thought that Mars’ past was generally quite cold, so a connection between the valleys and glacial ice is quite plausible. But how direct is that connection? We can identify the drainages in which water flows beneath ice sheets based on physical characteristics of the valleys left behind. So a team led by Anna Grau Galofre at Arizona State set out to analyze the valleys on Mars to see if any would better match a sub-glacial origin.

Read 7 remaining paragraphs | Comments