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Atomic rockets last used during the Cold War could be NASA’s best option for landing humans on Mars.

Atomic Rockets Could Be NASA’s Best Bet for Getting Humans to Mars

<p>After axing its research on nuclear-powered rockets in the 1970s, NASA spent $18.8 million last year on a deal with BWXT Nuclear Energy Inc. to develop fuel and a reactor to power a nuclear-thermal propulsion engine. The decades-old technology is NASA’s most viable option for landing humans on Mars. Its revival has also renewed a Cold War-era competition among the United States, Russia, and China to reach the next landmark in space—this time, the red planet.</p>
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<p>The engine works by heating fuel, which expands and gets channeled through a nozzle to create thrust. Compared to standard rockets, which create thrust by burning fuel, the nuclear-powered system has huge payoffs.</p><p>Here’s Stephen Stapczynski, writing for Bloomberg:</p>
<blockquote>
<p>That doubles the efficiency at which the rocket uses fuel, allowing for a “drastically smaller” craft and shorter transit time, said Stephen Heister, a professor at Purdue University’s School of Aeronautics and Astronautics. “This factor is absolutely huge, especially for very difficult missions that necessitate a lot of propellant such as a Mars flight.”</p>
</blockquote>
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<p>In fact, this factor would nearly halve the travel time compared to recent Mars missions.</p><p>Other countries have already begun working on the same technology. Russia has the lead, having already deployed dozens of nuclear-powered rockets in space, and China has announced plans to use atomic power to fuel its space exploration. In this reincarnation of the space race, NASA also faces domestic competition from private companies like Elon Musk’s <a href="http://www.spacex.com/">SpaceX</a> and Jeff Bezos’ <a href="https://www.blueorigin.com/be4">Blue Origin</a> , which are developing their own fission engines.</p><p>Despite the technology’s promise, the cost of development and testing—the reason the original effort was canceled in the 1970s—continues to be a challenge. Yet building on prior research may give NASA an advantage.</p><p>If it succeeds, the same technology could even be the basis of energy production for future colonies on the red planet.</p>
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<p>The atomic revival has renewed a Cold War-era competition among the United States, Russia, and China to reach the next landmark in space—this time, the red planet.</p>

Archaeologists found these 115,000-year-old shell beads—the oldest personal ornaments known in the world.

Neanderthals Could Be the World's Oldest Artists

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<p>
</p>
<p>
 For a long time, it seemed like art has separated humans from our less cultured relatives. But the recent discovery of cave art predating human settlement has challenged that story.
</p>
<p>
 In southeastern Spain, archaeologists discovered more than a dozen paintings dating back to more than 65,000 years ago—before the first humans arrived in Europe. The artists, most likely Neanderthals, mixed pigments, made seashell beads, and painted symbols of their lives on the walls of caves. These discoveries suggest that our reputedly boorish cousins were just as sophisticated as humans.
</p>
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<p>
 In the same caves, archaeologists also found 115,000-year-old shell beads—the oldest personal ornaments known in the world. The wide range of dates—all of which predate
 <i>
  Homo sapiens
 </i>
 —make it unlikely that an isolated group of precocious Neanderthals were responsible. More likely, it suggests the species as a whole was innately creative.
</p>
<p>
 Here’s Michael Greshko, reporting for National Geographic:
</p>
<blockquote>
<p>
 The [discoverers] argue that, despite their oafish reputations in pop culture, Neanderthals were the cognitive equals of Homo sapiens. If their results hold, the finds imply that the smarts underpinning symbolic art may date back to the common ancestor of
 <i>
  Homo sapiens
 </i>
 and Neanderthals, some 500,000 years ago.
</p>
<p>
 “Neanderthals appear to have had a cultural competence that was shared by modern humans,” says John Hawks, a paleoanthropologist at the University of Wisconsin-Madison who wasn’t involved with the study. “They were not dumb brutes, they were recognizably human.”
</p>
</blockquote>
<p>
 The find clarifies a murky narrative that has taken shape over recent decades, which depicts Neanderthals as more sophisticated than their stereotype. During this time, archaeologists at various sites in Europe found paintings and crafts from around 40,000 years ago, when Neanderthals lived alongside early humans. Yet it was hard to prove that any of this art had been made by Neanderthals, and few archaeologists humored the idea.
</p>
<p>
 While that question now appears to be settled, the debate over what it implies about human evolution is just beginning.
</p>
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<p>
 Photo credit: J. Zilhão
</p>

<p>The recent discovery of cave art predating human settlement is challenging the age-old narrative that symbolism makes us human.</p>

Artist's rendering of how the first stars in the universe may have looked.

Signals From the First Stars Could Show Hints of Dark Matter

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<p>
 Astronomers studying the dawn of the universe may have made a new detection of dark matter interacting with ordinary matter.
</p>
<p>
 In the four decades since its discovery, dark matter has eluded every attempt to directly detect it. It doesn’t interact with light or regular matter, so the only way astronomers have been able to infer its presence is in how its gravity tugs on regular matter.
</p>
<p>
 But when the universe first went from dark to light, 180 million years after the Big Bang, the particles in the cold gas throughout the universe seem to have bumped up against their dark-matter cousins, according to
 <a href="https://www.nature.com/articles/nature25791">
  new research
 </a>
 published in
 <i>
  Nature
 </i>
 on Wednesday. It’s the first sign that dark matter interacts with regular matter through anything other than gravity.
</p>
<p>
 “Finding this minuscule signal has opened a new window on the early universe,” lead author Judd Bowman of Arizona State University told The Guardian.
</p>
<p>
 The discoverers, led by Bowman, originally set out to find what’s known as “cosmic dawn”: the moment in time when the first stars flicked on. Any light these stars emitted is too faint for ordinary telescopes to pick up, but in theory, the moment should be detectable in a radio signal released when light from these stars excited the cold gas around it.
</p>
<p>
 For a long time, there was little hope. The signal seemed impossible to disentangle from other radio signals reaching Earth. But the milestone discovery published on Wednesday, radio astronomers using a small, table-shaped antenna in remote western Australia detected this blip in history.
</p>
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<p>
 As if that weren’t momentous enough, it came with a surprise: The signal was more than twice as strong as they predicted.
</p>
<p>
 Their predictions were based on the temperature of the gas pervading the early universe. They knew this was the coldest point in the universe’s history: Heat from the Big Bang had faded, and the first stars had yet to heat up the gas around them. But in order for the signal to be as strong as it was, the gas must have been even colder than they predicted.
</p>
<p>
 Something has to have cooled down the gas—and the most likely contender is cold dark matter. If this interpretation is correct, it reveals more than ever about what these mysterious particles may be like.
</p>
<p>
 Scientists currently know little about the nature of dark matter. “We have no other positive statement about it, really, other than it exists and it’s 25% of the universe,” said Matt Buckley, a professor of astrophysics at Rutgers University who studies the particle nature of dark matter.
</p>
<p>
 Buckley emphasizes the need for caution in interpreting these new results, which are based on a single observation. But if the findings are confirmed, he said, the result would be tremendously exciting. “It wouldn’t tell us what it is, but it would tell us where to start looking.”
</p>
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<p>
 Image credit: N.R.Fuller/National Science Foundation/Nature
</p>

<p>When the universe first went from dark to light, 180 million years after the Big Bang, the particles in the cold gas throughout the universe seem to have bumped up against their dark-matter cousins.</p>

The 5,000-year-old tattoos on two Ancient Egyptians suggest that the practice of tattooing has a longer history than we thought.

Ancient Egyptians May Have Worn the World’s First Tattoos

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<p>
 The practice of tattooing appears to be 1,000 years older than anyone knew.
</p>
<p>
 Since his discovery about 100 years ago, an Egyptian mummy housed in the British Museum appeared to have nothing more special than a dark smudge on his right arm. But recent infrared imaging revealed the outlines of two animals in the skin: a bull and a Barbary sheep. The discovery makes these the oldest figurative tattoos ever found.
</p>
<p>
 Soon after, anthropologists found symbols inked into the shoulder of a second mummy, a female from the same time and region. She wore a more abstract tattoo, a series of four tilde-shaped lines.
</p>
<p>
 The mummies had been unearthed from shallow graves, naturally preserved by the desert climate. In both cases, the tattoos were likely made of soot and probably served as a status symbol. Anthropologists speculate that the man’s tattoos represented strength and virility, like the bull in ancient Egyptian legends, while the woman’s tattoos signified bravery and knowledge of magic.
</p>
<p>
 For the people studying these tattooed mummies, the symbols in the ink hold meaning as well.
</p>
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<p>
 Here’s Pallab Ghosh,
 <a href="http://www.bbc.com/news/science-environment-43230202">
  writing
 </a>
 for BBC News:
</p>
<blockquote>
<p>
 Daniel Antoine, one of the lead authors of the research paper and the British Museum’s Curator of Physical Anthropology, said that the discovery had “transformed” our understanding of how people lived in this era.
</p>
<p>
 “Only now are we gaining new insights into the lives of these remarkably preserved individuals. Incredibly, at over 5,000 years of age, they push back the evidence for tattooing in Africa by a millennium,” he told BBC News.
</p>
</blockquote>
<p>
 Until now, the oldest known tattoo belonged to a mummy found in the Alps, nicknamed Ötzi, who lived earlier than 3100 B.C. and whose skin was marked with a series of lines. The discovery of these more ornately tattooed ancient Egyptians suggests that tattooing was likely widespread across the ancient world, much like it is today.
</p>
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<p>
 Photo credit:
 <a href="https://phys.org/news/2018-03-egyptian-mummies-oldest-figurative-tattoos.html">
  British Museum / phys.org
 </a>
</p>

<p>At over 5,000 years of age, these soot-based tattoos push back the evidence for tattooing in Africa by a millennium.</p>

Surgeon Takes On Organ Shortage With Twice-Owned Kidneys

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<p>
<span style="font-weight: 400;">
   Tired of seeing patients dying of kidney failure, a California surgeon has made an unprecedented move: He has begun reusing kidneys that have already been in two bodies.
  </span>
</p>
<p>
<span style="font-weight: 400;">
   A second recycling of organs is rare, but the surgeon, Jeffrey Veale of the Ronald Reagan UCLA Medical Center, estimates that a quarter of people who die after kidney transplants die with perfectly re-usable kidneys. Now, with three such surgeries behind him, he is pushing for other transplant centers to follow his lead—in the hopes that keeping healthy kidneys in circulation will help pull desperate patients off years-long waitlists.
  </span>
</p>
<figure class="richtext-image full-width">
<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/surgery.width-990_cFmy5Tr.png"/>
<figcaption>Keeping healthy kidneys in circulation could help pull desperate patients off years-long waitlists.
        
    </figcaption>
</figure>
<p>
<span style="font-weight: 400;">
   In general, transplant surgeons are wary of the idea. As they see it, living through the death of two bodies is traumatic for organs, and transplant surgery can cause kidneys further injury, as they get artificially flushed, cooled, and infused with drugs to keep bodies from rejecting them. But Veale argues that judging a kidney based on the lives it’s lived disqualifies some organs unnecessarily, leading to preventable loss of life.
  </span>
</p>
<p>
<span style="font-weight: 400;">
   Today, the U.S. has
  </span>
<a href="https://transplant.surgery.ucsf.edu/conditions--procedures/kidney-transplant.aspx">
<span style="font-weight: 400;">
    more than 74,000 people
   </span>
</a>
<span style="font-weight: 400;">
   on waiting lists for kidney transplants—a wait that often outlasts their ability to survive kidney failure.
  </span>
<a href="https://transplant.surgery.ucsf.edu/conditions--procedures/kidney-transplant.aspx">
<span style="font-weight: 400;">
    Hundreds of thousands
   </span>
</a>
<span style="font-weight: 400;">
   of people are currently surviving on dialysis, a several-hour treatment multiple times a week that does the kidneys’ job of flushing waste from the body. However,
  </span>
<a href="https://pharm.ucsf.edu/kidney/need/statistics">
<span style="font-weight: 400;">
    only a third of people survive
   </span>
</a>
<span style="font-weight: 400;">
   more than three years on dialysis—meaning many never live to see their turn for a transplant.
  </span>
</p>
<p>
<span style="font-weight: 400;">
   Whether it’s a literal lifesaver or an immense reprieve from time-consuming dialysis, a donor kidney can make all the difference in someone’s life. Here’s Usha Lee McFarling, reporting for STAT News:
  </span>
</p>
<blockquote>
<p>
   Vertis Boyce of Las Vegas is thrilled with the “pre-owned” kidney she received in July, which allowed her to stop the dialysis treatments she’d been on for nine years and start traveling again. She recently attended a nephew’s wedding in North Carolina.
  </p>
<p>
   “I feel free again,” she said. “I can do all those normal things you take for granted.”
  </p>
</blockquote>
<p>
<span style="font-weight: 400;">
   At the moment, it’s too soon—and there are too few cases—to tell how the performance of twice-reused kidneys compares to ordinary transplants, which typically last up to 12 years. But all three of Veale’s patients now living with twice-recycled kidneys are doing well, months after surgery.
  </span>
</p>
<p>
<span style="font-weight: 400;">
   Now, “pre-owned” kidneys are not the only kidneys being reconsidered for transplants. Around the country, surgeons are successfully transplanting kidneys from HIV- and other disease-infected donors into similarly infected patients.
  </span>
</p>
<p>
<span style="font-weight: 400;">
   In light of his preliminary success, Veale stands by his hunch—that the best way to determine a kidney’s suitability for transplant, he says, is how it performs in a lab test, not its history.
  </span>
</p>
</section>
<p>
 Photo credit:
 <a href="https://pixabay.com/en/surgery-action-hospital-doctor-1822458/">
  sasint / Pixabay (Creative Commons CC0)
 </a>
</p>

Each year, about eight million tons of plastic float out to sea.

Pacific Garbage Patch May Be 16 Times Bigger Than Once Thought

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<p>
 In the vast stretch of ocean between California and Hawaii, there’s a patch of plastic twice the size of Texas—and it’s between four and 16 times the size scientists previously thought.
</p>
<p>
 Researchers drew this surprising conclusion by analyzing 7,000 aerial photographs of the so-called Great Pacific Garbage Patch. This method, they say, is more precise than earlier estimates made based on observations from boats. But there’s likely a secondary reason that the patch is so much larger than last estimated: it’s growing.
</p>
<p>
 Laurent Lebreton, the lead researcher of the study, saw the growing patch for himself. Here are Merrit Kennedy and Christopher Joyce, reporting for NPR:
</p>
<blockquote>
<p>
 Lebreton, an oceanographer with The Ocean Cleanup Foundation, describes the experience of flying over the trash.
</p>
<p>
 “You start to see one debris, two debris, three debris and so on,” he told NPR. “Oh, there’s a crate, oh, there’s a buoy, oh, there’s a bottle. And it’s crazy because there’s nothing else around. There’s no land mass, there’s no humans, there’s nothing.”
</p>
</blockquote>
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<p>
 About eight million tons—that’s roughly 200,000 tractor trailers’ worth—of plastic garbage drifts out to sea each year. Half of what makes it to the garbage patch is fishing nets; much of the rest is debris that comes through rivers or washes off coasts. Based on the Japanese text discernible on about 30% of the debris, researchers suspect that a great deal of it was washed out to sea by the tsunami that struck Japan in 2011.
</p>
<p>
 But the patch, created by a Pacific Ocean-wide whirlpool caused by the Earth’s rotation, only accounts for about 76,000 tons of plastic. While that’s a lot, it’s less than a tenth of what gets washed to sea in a single year. No one knows exactly what happens to the rest. Researchers believe that much of the less buoyant plastic sinks to the seafloor, while some other portion of it gets consumed by sea creatures or washed back up to shore.
</p>
<p>
 As for the plastic that does make it to the patch, out of sight does not mean out of mind. As the debris breaks down into microplastics, or often-invisible particles less than five millimeters across, it’s easily ingested by marine life and begins to make its way up the food chain. Scientists are
 <a href="http://theconversation.com/how-microplastics-make-their-way-up-the-ocean-food-chain-into-fish-69148">
  still working on understanding
 </a>
 how ingesting microplastics can harm different living things.
</p>
<p>
 Before attempting a cleanup, researchers say that the first priority needs to be prevention—keeping fishing materials from getting lost at sea and stopping debris from leaving our coasts in the first place.
</p>
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<p>
 Photo credit:
 <a href="https://commons.wikimedia.org/wiki/File:Litter_on_Singapore%27s_East_Coast_Park.jpg">
  vaidehi shah / Wikimedia Commons (CC BY 2.0)
 </a>
</p>

<p>In the vast stretch of ocean between California and Hawaii, there’s a patch of plastic twice the size of Texas—and it’s between four and 16 times the size scientists previously thought.</p>

Climate change has helped dry out African summers, feeding the growing Sahara.

Thanks to Climate Change, the Sahara is Inching South

<div class="related"></div>
<p>
 While the face of climate change often looks like dramatic natural disasters—hurricanes, massive fires, floods, or heat waves—the African continent is facing a much more subtle catastrophe: the spread of the Sahara.
</p>
<p>
 The desert, which is roughly the size of the United States, has grown by about 10% in the last century, in large part thanks to climate change. Researchers worry that this slowly unraveling disaster hasn’t gotten the attention it warrants to prepare affected populations for the consequences.
</p>
<p>
 Here’s Darryl Fears, writing for The Washington Post:
</p>
<blockquote>
<p>
 “If you have a hurricane come suddenly, it gets all the attention from the government and communities galvanize,” said Sumant Nigam, a professor of atmospheric and oceanic science at the University of Maryland and the senior author of the study. “The desert advance over a long period might capture many countries unawares. It’s not announced like a hurricane. It’s sort of creeping up on you.”
</p>
</blockquote>
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<p>
 In fact, the governments of Sudan and Chad have barely noticed, despite the fact that their rainy season has traded itself in for a dry spell that has allowed the desert to creep south.
</p>
<p>
 But what might not be clear in the day-to-day stood out in the data. Researchers studied 93 years of climate data beginning in 1920 and found that climate change is likely helping drive the southward spread, for two reasons.
</p>
<p>
 First, shifting weather patterns driven by climate change are likely widening what’s called a “Hadley cell,” a region of dry air that leads to the formation of deserts. That’s compounded by drier-than-usual stretches in the Sahara’s natural 50- to 70-year cycle of wetter and drier periods.
</p>
<p>
 Most alarming to the researchers was the discovery that the spreading is happening during the African summer, which is typically rainy in the regions just south of the Sahara. Loss of the rainy season threatens agriculture, which currently supports 80% of Sudan and Chad’s workforce. And although the African continent is least responsible for global climate change, its populations continue to suffer the brunt of its consequences on account of its geography.
</p>
<p>
 Yet, while this research focused on the Sahara, deserts around the world are also likely inching wider. The study’s senior researcher suggests that it’ll take long-term planning to protect water resources as disasters like these play out.
</p>
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<p>
 Photo credit: Public Domain
</p>

<p>The desert, which is roughly the size of the United States, has grown by about 10% in the last century, in large part thanks to climate change.</p>

Samia Bouzid

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