سایت انفجار : Why Haven’t We Found Alien Life Yet? Blame Our Closed Minds


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This story originally appeared in the December issue of Discover magazine as “Looking for Signs.” Support our science journalism by becoming a subscriber.


Limits don’t sit well with Avi Loeb.

Loeb quickly reels some off to me over the phone (hands-free) during a drive home from work: About 25 billion stars, roughly one-quarter of those that reside in the Milky Way, lie in a habitable zone. He rounds that down to an even 10 billion to keep the calculations simple. “And then there are about a trillion galaxies like the Milky Way,” he says, “which means there are about 1022 [10 billion trillion] planets in the observable universe that could potentially host life as we know it.” In other words, searches for extraterrestrial life have barely scratched the surface. “As in other areas of exploratory science,” Loeb says, “we should investigate thoroughly before making sweeping pronouncements.”

Most of the searching so far, he adds, has been in the radio range, where scientists have examined a tiny fraction of the possible frequencies in an equally tiny fraction of the possible search space. Surveys in optical wavelengths have been much less extensive. For any new technology we develop, Loeb says, we should consider whether, somewhere, an alien civilization might have developed it, too, possibly leaving behind some detectable traces. “As our technology improves, that can help us imagine things we haven’t imagined before and explore things we haven’t searched for before.”

verarubin observatory

The Vera C. Rubin Observatory is expected to start searching the skies in 2022. (Credit: Rubin Obs/NSF/AURA)

When it comes to imagination, Loeb — cited in The New York Times “for his creative and prolific attempts to understand the … universe” — appears to have no shortage. Nor, would it seem, is he lacking in productivity. For over two decades, he has turned out an average of two academic papers each month, in addition to regular essays. He’s director of Harvard’s Institute of Theory and Computation, a member of the President’s Council of Advisors on Science and Technology, founding director of Harvard’s Black Hole Initiative and chair of the Breakthrough Starshot Advisory Committee — an endeavor aimed, among other things, at sending miniature spacecraft to other stars.

Florida Tech physicist Manasvi Lingam described his collaboration with Loeb during a postdoctoral fellowship as “exhilarating.” From 2017 to 2019, Lingam and Loeb wrote 25 research papers and a forthcoming book, Extraterrestrial Life: From Biosignatures to Technosignatures, that provides a wide-ranging discussion of SETI techniques. “With Avi, there’s always a fast turnaround time,” Lingam says. “We always try to look for left-field ideas that are nonetheless testable.”

Loeb is fearless because some of his out-there ideas have been publicly rebuked by other astronomers, says Penn State astronomer Jason Wright.

But Loeb is rarely deterred by disapproving remarks, saying skepticism “can be a self-fulfilling prophecy.” It’s far better to look, he says, than to assume there’s nothing to be seen. That attitude is apparently shared by NASA. It recently gave Loeb and others the first SETI-related grant in over 30 years that specifically supports innovative search strategies. Here are some of the unconventional notions he and his colleagues have advanced for enlarging the scope of SETI, and perhaps catching a glimpse of E.T. in the process.

Far From the City Lights

Loeb and Princeton University astronomer Edwin Turner are kindred spirits who enjoy batting around speculative ideas. “The conservative impulse that serves science well in some ways doesn’t serve us well when it comes to generating hypotheses,” says Turner. While touring Abu Dhabi a decade ago, and learning that Dubai is so bright it can be seen from outer space, Loeb and Turner started to wonder whether our telescopes could pick up light from an alien city. After some quick calculations, they determined that the Hubble Space Telescope (HST) would be able to detect light pollution from a city on the outer edges of the solar system, well beyond Pluto, and new, more advanced telescopes could extend that range considerably farther.

trappist - nasa

An artist’s concept shows the TRAPPIST-1 planetary system, with its seven Earth-sized, temperate exoplanets orbiting an ultra-cool dwarf star. It’s unusual to have so many planets in the habitable zone. (Credit: NASA/JPL/Caltech)

Although there aren’t any known planets lying in the solar system’s periphery, Loeb and Turner have come up with a method for determining whether a newly discovered light source is natural or artificial. Their technique is based on the principle that light drops off in intensity according to the square of the distance traveled.

Suppose we measure the brightness of a radiant object and repeat that measurement after the object has moved twice as far away from us, heading away from the sun. If the object was natural, such as a previously unknown planet or asteroid, and merely reflecting light from the sun, its brightness would decrease by a factor of 16: Its brightness (as measured from Earth) would have dropped off fourfold during the light’s journey from the sun to the object (since two squared equals four) and another fourfold during its journey back to us. If, on the other hand, the object was a luminous spacecraft, its brightness would drop off only by a factor of four since it produces its own light rather than reflecting it from the sun.

If our measurements of a distant light source indicate a fourfold drop in intensity, we should not immediately start worrying about an alien invasion, says Turner. “But we will want to point other telescopes there and … try to figure out what’s going on.”

Pollution As the Solution to Dilution

In 1990, as the Galileo spacecraft flew past a planet in our solar system, its instruments found evidence of an atmosphere rich in oxygen and methane — signs that the scientific team, led by Carl Sagan, deemed “strongly suggestive of life.” The planet in this case was Earth, and the exercise was mainly a proof of concept. But the HST has already started examining the atmospheres of planets around other stars, called exoplanets. And its successor, the James Webb Space Telescope, which is scheduled for launch in 2021, will soon probe atmospheres of even more distant planets, looking for biological signatures of life.

James webb telescope

(Credit: NASA/Chris Gunn)

In 2014, Loeb and two collaborators, Henry Lin and Gonzalo Gonzalez Abad, decided to flip the switch: Instead of looking for signs of life, they suggested looking for signs of death, or at least serious contamination. “Anthropogenic pollution could be used as a novel biosignature for intelligent life,” wrote the Harvard team, which proposed looking for two chlorofluorocarbon (CFC) gases, tetrafluoromethane and trichlorofluoromethane, that can survive tens of thousands of years and cannot be synthesized by known natural processes.

The James Webb telescope could spot the presence of these molecules in an exoplanet’s atmosphere, the researchers concluded, if concentrations were 10 times current terrestrial levels. Observing high levels of these long-lived pollutants and no signs of life-sustaining molecules like oxygen, Loeb and his coauthors said, “might serve as an additional warning to the ‘intelligent’ life here on Earth about the risks of industrial pollution.”

The Edge Effect

A 2005 paper in the journal Astrobiology by MIT astronomer Sara Seager and three other researchers identified a distinct feature of an Earthlike planet covered with large stretches of vegetation. Plants appear green because they reflect light in the green part of the spectrum, but at higher wavelengths, between the red and infrared range, reflectance shoots up dramatically. A graph of reflectance versus wavelength shows a steep rise at a wavelength of 700 nanometers that creates a pronounced “red edge” — a feature, though not evident to the human eye, that’s readily observable by telescopes with spectral sensitivity.

In 2017, Lingam and Loeb got to wondering: What if an exoplanet was covered by vast tracts of photovoltaic arrays instead of boundless greenery? Massive structures like this, Lingam and Loeb reasoned, would produce an artificial spectral edge analogous to the red edge caused by vegetation, though occurring at different wavelengths (depending, of course, on the materials making up the arrays). They calculated where the spectral edge would lie for silicon-based solar cells — a reasonable choice given silicon’s abundance in the universe — and those composed of other widely used photovoltaic ingredients, including gallium arsenide and perovskite. Future telescopes, such as WFIRST, set to launch in the mid-2020s, would be capable of detecting a “silicon edge,” should it exist.

Lingam and Loeb believe that such an analysis would be particularly powerful when applied to exoplanets that are “tidally locked,” meaning they keep the same orientation with respect to the parent star and therefore have permanently light and dark sides. An inhabited planet equipped with large-scale solar-electric generation could illuminate the dark side, and other installations might release significant amounts of waste heat on the cooler, darker side — developments that could be visible from afar and might remain visible after an alien civilization has gone extinct or migrated to another home.

Although these photovoltaic arrays would undergo wear and tear, Lingam and Loeb wrote in the Monthly Notices of the Royal Astronomical Society, “they can remain functional for a duration of time that is not insignificant by astrophysical standards and would thus represent genuine extraterrestrial artifacts.” If artifacts are someday spotted, they write, it could be an early, if not the first, example of a new field: “interstellar archaeology.”

The Mystery of FRBs

The first fast radio burst (FRB), an intense blast of radio waves emanating from outside our galaxy and lasting just a few milliseconds, was spotted in 2007. Astronomers have since seen more than 100 others. “The popular view is that these bursts come from young neutron stars with very strong magnetic fields,” says Loeb. But that supposition has not been confirmed. And there may not be a single source, he adds, because there are at least two types of bursts — a small minority that repeat and most that do not.

EMS-Dispersion

(Credit: Roen Kelly/Discover)

Lingam and Loeb offered a provocative solution to the puzzle: Maybe some of the FRBs are artificial. If that were the case, what would be the purpose of such incredibly powerful bursts? In a 2017 paper in Astrophysical Journal Letters, Lingam and Loeb raise two possibilities: It could be a beacon to broadcast the presence of an alien civilization, which they deem “rather implausible.” Or, it could power large spaceships tugged by even larger (in area, not in mass) light sails. “The optimal frequency for powering the light sail is shown to be similar to the detected FRB frequencies,” they write — a fact that, when combined with other technical arguments, could “lend some credence to the possibility that FRBs might be artificial in origin.”

Naysayers might dismiss this, insisting that “extraordinary claims require extraordinary evidence,” Loeb notes. “I say that they require evidence, but why should they be held to a higher plane? We should not automatically dismiss explanations just because they seem exotic to some people.”

Searching for Artifacts 

“When exploring habitable worlds around other stars, we might … find planets with burnt-up surfaces, abandoned mega-structures or planetary atmospheres rich with poisonous gases and no sign of life,” Loeb has written. One might also see an extensive network of unnatural platforms or satellites orbiting another star — perhaps part of a hypothetical energy-gathering enclosure called a Dyson sphere.

Something like this, if sufficiently large, could be spotted by NASA’s Transiting Exoplanet Survey Satellite (TESS), which looks for dips in the brightness of a star caused by a planet passing in front of it. TESS could also detect dips caused by the passage of giant artificial mega-structures. Officials announced in October 2019 that TESS would collaborate with Breakthrough Listen — a $100 million SETI initiative, the largest and most generously funded in the field’s history.

Listen’s ground-based telescopes would focus on potentially habitable planets identified by TESS. Loeb cites the example of Tabby’s Star: Discovered in 2016, two years before the TESS launch, it exhibited a peculiar dimming pattern, prompting some to speculate that it was surrounded by some kind of alien structure. It turns out that our view was blocked by an oddly shaped disk of dust, Loeb says, but that’s the kind of irregularity TESS scientists would be looking for.

Searching for Interstellar Visitors

On Oct. 19, 2017, an astronomer using Hawaii’s Pan-STARRS telescope discovered an object moving past the sun at 196,000 miles per hour, so fast that it almost surely originated from outside the solar system. The object, dubbed ‘Oumuamua — Hawaiian for “first scout from a distant place” — was initially classified as an asteroid and then a comet and more recently as a chunk of hydrogen ice. 

oumumaua

Interstellar visitor ‘Oumuamua has defied easy classification — Loeb has suggested it’s an artificial lightsail — but a team of astronomers concluded in 2019 that it’s a natural object. (Credit: Auntspray/Shutterstock)

But Loeb has analyzed all of these ideas and finds that they still leave some questions unanswered. He doesn’t see a plausible way that a “large hydrogen iceberg” could form. And even if it did, he says, an object like that could not survive its interstellar journey to the solar system because hydrogen evaporates so readily. Furthermore, ‘Oumuamua has unusual features that don’t match those of asteroids or comets: For one thing, it’s extremely elongated, about 10 times longer than it is wide. The object’s acceleration is also unexplained, as there’s no sign of outgassing, propulsion caused by the release of gas that’s normally seen in comets. Loeb and Shmuel Bialy of Harvard suggested that ‘Oumuamua was being pushed and sped up by solar radiation, in which case it must be shaped more like a thin pancake than a cigar as was commonly assumed. That raised the possibility that ‘Oumuamua “might be a lightsail of artificial origin” — a case they made in a November 2018 paper in Astrophysical Journal Letters.

In a July 2019 article in Nature Astronomy, an international team of 14 astronomers reached a different conclusion, contending that ‘Oumuamua is a natural object, despite its peculiar properties.

In the meantime, a second interstellar visitor, Comet Borisov, was discovered in 2019, whipping around the sun at 110,000 mph. This object is “clearly not artificial,” Loeb says, “because it looks like any other comet we’ve seen before.” But there soon should be many more interlopers to look at. The Pan-STARRS observatory has given us the capacity to survey the entire sky, and the Vera C. Rubin Observatory, expected to begin an even broader survey in 2022, “will be much more sensitive,” Loeb says, “a bigger and better telescope that could potentially detect an ‘Oumuamua-type object every month.”

When it comes to SETI, evidence ultimately carries the day, Loeb insists. “We should collect evidence without prejudice, without assuming we know the truth in advance, and see what we learn.” On the other hand, he says, we should be open-minded and allow for some risk-taking in our pursuit of that evidence. As the physicists Giuseppe Cocconi and Philip Morrison wrote in 1959, one year before SETI began: “The probability of success is difficult to estimate, but if we never search, the chance of success is zero.”


Steve Nadis is a contributing editor to Discover.

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سایت انفجار : تئوری بازی شکار تمدن های بیگانه را فقط روی یک ستاره متمرکز می کند


بازی بوم شرطی:بازی انفجار

این س ofال که آیا باید به ستاره ها پیام ارسال شود ، با مشکل روبرو است. ترس بزرگ ، تمدن پیشرفته تری را با نیت شیطانی جذب می کند. چرا باید ریسک کرد؟

در حقیقت ، مفسران مختلف اظهار داشته اند كه این ترس ممكن است پارادیوكس معروف فرمی را توضیح دهد كه می پرسد چرا از تمدنهای دیگر چیزی نشنیده ایم. پاسخ این است که یا افراد دیگری وجود ندارد یا بهترین استراتژی برای بقا سکوت است که مبادا تمدن پیشرفته تری شما را پیدا کند و نابود کند.

اما یک سوال جالب این است که آیا پارادوکس را می توان به روش دیگری حل کرد؟ اکنون ایمون کرینز در دانشگاه منچستر انگلیس می گوید با استفاده از تئوری بازی برای تعیین بهترین روش جستجو و برقراری ارتباط با تمدن های فرازمینی از پارادوکس جلوگیری می شود.

همین استراتژی همچنین زمینه نامزدهای سیاره فراخورشیدی را که ارزش بررسی دقیق برای تماس احتمالی را دارند به طرز چشمگیری محدود می کند. در حقیقت ، كرینز می گوید این روند جستجو برای سیارات فراخورشیدی قابل سكونت را كاهش می دهد كه باید فقط برای تماس با یكی در نظر گرفته شود.

نظریه بازی

ایده اصلی در رویکرد کرینز قابلیت شناسایی متقابل است. این تصور این است که بارورترین راه برای جستجوی زندگی بیگانه جستجوی مکان هایی است که یک مشاهده گر شانس دیدن آنها را داشته باشد. او می گوید: "قابلیت شناسایی متقابل یک رویکرد نظری بازی است که هدف آن افزایش احتمال برقراری ارتباط بین دو تمدن دارای توانایی SETI است."

البته هر دو طرف به اطلاعات مختلفی دسترسی خواهند داشت. این امر توسط عواملی مانند درخشندگی ستاره مادر تعیین می شود که می تواند سیگنال را از سیاره ، مدار سیاره خارج و غیره باتلاق یا پنهان کند. بنابراین قابلیت شناسایی متقابل همیشه متقارن نیست.

همچنین ممکن است تمدن دیگری به دنبال همان نوع سیگنالی نباشد که ما بدنبال آن هستیم. در واقع ، می تواند اطلاعاتی وجود داشته باشد که وجود ما را آشکار می کند و ما از آنها بی خبریم. اگر تمدن دیگری به دنبال این باشد ، بعید است که با آنها ارتباط برقرار کنیم.

بنابراین بهترین استراتژی محدود کردن جستجوهای ما به سیارات فراخورشیدی است که به شما اجازه می دهد تمدن به همان روشی که ما به دنبال آنها هستیم ، به دنبال ما باشد. در این صورت ، هر دو اطلاعات مشترکی دارند. کرینز این "اطلاعات مخرج مشترک" را می نامد.

با پیدا کردن چنین سیاره فراخوانی ، این سوال پیش می آید که چه کسی باید با چه کسی تماس بگیرد. هر دو طرف ممکن است تصمیم بگیرند که اختیار قسمت بهتری از شجاعت است و سکوت اختیار کنند. اما در غیر این صورت ، پس تئوری بازی پیشنهاد می کند که طرفی که بیشترین اطلاعات مخرج را دارد ابتدا باید صحبت کند. "مسئولیت انتقال به عهده حزب با برتری است [common denominator information] درباره طرف دیگر ، "می گوید Kerins.

این حداقل تئوری است. Kerins ادامه می دهد تا آن را در بایگانی سیارات فراخورشیدی ناسا اعمال کند که در حال حاضر شامل 74 سیاره فراخورشیدی در مناطق قابل سکونت ستاره های اصلی آنها است.

طبق قانون قابلیت شناسایی متقابل ، بهترین مکان برای جستجوی سایر تمدن ها در زیرمجموعه سیارات فراخورشیدی است که می توانند زمین را با همان روش مشاهده کنند. محبوب ترین راه برای لکه بینی سیارات فراخورشیدی جستجوی کم نور شدن ستاره اصلی هنگام عبور یک سیاره از مقابل آن است.

واضح است که فقط کسری از سیارات فراخورشیدی دیگر با منظومه شمسی همسو می شوند تا زمین را از مقابل خورشید ببینند. ستاره شناسان این منطقه را منطقه ترانزیت زمین می نامند. و معلوم شد که ما فقط سیاره فراخورشیدی قابل سکونت را در این منطقه می شناسیم.

این K2-155d است. این یک ابر زمین است که در منطقه قابل سکونت ستاره ای به نام K2-155 در صورت فلکی گاو می چرخد. با استفاده از تلسکوپ فضایی کپلر در سال 2018 به همراه دو سیاره خواهر که در منطقه قابل سکونت نیستند کشف شد.

اولین تماس

اما آیا باید با آنها تماس بگیریم یا برعکس؟ رویکرد نظری بازی کرینز پاسخ می دهد. از آنجا که K2-155d یک ابر زمین در اطراف یک ستاره نسبتاً درخشان است ، برای ما بیشتر از زمین برای آنها قابل مشاهده است. او می گوید: "در این حالت ، مسئولیت نظریه بازی به عهده ما است تا به K2-155d منتقل شود."

بنابراین اگر تمدنی در K2-155d از حساب مشابهی استفاده می کند ، باید منتظر تماس ما باشد. اینکه آیا ما آن تماس را برقرار می کنیم یا خیر هنوز یک سوال دشوار است.

این رویکرد نظری بازی هنوز کاندیدایی را که مسئولیت تماس با ما را دارد مشخص نمی کند. اما کرینز می گوید این به این دلیل است که ستاره های درخشندگی کمتری که به احتمال زیاد میزبان این نامزدها هستند هنوز به خوبی بررسی نشده اند.

البته این با گذشت زمان تغییر خواهد کرد. در واقع ، او محاسبه می کند که کهکشان راه شیری هزاران سیاره فراخورشیدی را هم در منطقه قابل سکونت و هم در منطقه ترانزیتی زمین که می توانند معیارهای تئوری بازی را برای تماس بالقوه داشته باشند ، در خود جای دهد.

البته ، هیچ یک از اینها به معنای وجود تمدن در هر یک از این سیارات فراخورشیدی نیست. فقط اگر این کار را انجام دهند ، بهترین فرصت تماس را دارند.

در حال حاضر ، فقط یک مسئله زمان است که ما یک سیاره فراخورشیدی را پیدا می کنیم که مسئولیت آن با ما است و می توانند با ما تماس بگیرند. تنها کاری که باید انجام دهیم تماشا و انتظار است. البته مگر اینکه آنها همین کار را انجام دهند.


مرجع: قابلیت شناسایی متقابل: یک استراتژی هدفمند SETI که از پارادوکس SETI جلوگیری می کند arxiv.org/abs/2010.04089

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سایت انفجار : Cropland vs Climate Change: A Conversation with Wolfgang Busch


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For billions of years, plants and their ancestors, the cyanobacteria, have been powerful agents of change on Earth. They pumped out oxygen and squirreled away carbon dioxide, transforming the chemistry of the biosphere. They colonized land and allowed animal life to follow, changing the course of evolution.

Now molecular biologist Wolfgang Busch wants to recast plants into agents of stability, offsetting the tremendous amount of climate-warming carbon dioxide that humans are pouring into the environment. As part of the Harnessing Plants Initiative at the Salk Institute in La Jolla, California, Busch is working on a bold scheme to modify major crop plants so that they grow deeper, bigger root systems, leaving those carbon-rich roots embedded in the soil after harvest time. While we humans get to work cutting back on our carbon emissions, the plants will be busily lending a hand.

A fundamental challenge with this idea is that the shallow roots of crops normally rot and release much of their carbon over the course of the year. The Harnessing Plants team, under the direction of Joanne Chory, has come up with a clever solution. The researchers are modifying plants so that they produce suberin (the primary ingredient in cork) in their roots. Suberin stubbornly resists decomposition, so the roots masses of these “Salk Ideal Plants” could remain in the soil for an extremely long time without sending their carbon back into the air.

Many different parts of the plan have to come together just right for the Harnessing Plants Initiative to work. The plants have to bury carbon efficiently and effectively. The modified crops have to provide all the same seed yield as before. Farmers need to embrace these crops on a global scale. And the rest of the world still needs to keep working on cutting carbon emissions, since plants alone won’t save our bacon.

On the other hand, the humongous scale of agriculture provides a unique opportunity for large-scale decarbonization. Busch and his colleagues are therefore plowing full-speed ahead (with some COVID speed bumps along the way) to see whether carbon-sequestering corn and wheat can help us turn down the heat from climate change while also recharging the planet’s carbon-depleted soils. An edited version of my conversation with Busch follows.

What drew you to the idea of using plants as a way of burying carbon dioxide in the ground?

I’ve been conducting research on the genetic and molecular basis of root growth since a long time. I started my own lab almost 10 years ago in Vienna. Then I moved three and a half years ago to the Salk Institute. My main interest has long been the factors in plant genes that determine whether roots grow deep or shallow, and how they respond to the environment.

Just around the time when I was negotiating with the institute, Elizabeth Blackburn [Salk’s president at the time] asked the faculty, “What’s the most important question that you’d like to address with your fundamental research?” The plant faculty group came up with an answer after considering: Plants are very good at catching carbon, so they thought about how to make this ability useful for addressing climate change. Which they thought, and I thought, was the world’s most pressing problem.

And that fit in with the work you were already doing?

It was a very good coincidence. The main effort at Salk [the Harnessing Plants Initiative] is related to the root system. We’re trying to put more carbon in the root system, to make it deeper with more root mass, and to produce molecules such as suberin that keep the carbon longer in the soil. It fits very well my interests. I have been worried about climate
change since I was in middle school. The Harnessing Plants Initiative gives us all the opportunity to merge our research expertise with what we consider the most pressing problem.

Lots of people talk about planting trees, but this is the first I’ve heard of using crops to fight climate change. Where did the idea come from?

We had an evolving thought process. At first, we thought about using plants to sequester carbon on marginal lands, and we focused on the things that can grow that can grow on those marginal lands. We would do a good thing for the soil there, and for carbon sequestration.

But soon we realized that it’s all about acreage. Focusing on [small amounts of] marginal land, we’d have only a small potential to increase its ability to sequester carbon. Plus, every plant species is different in its lifestyle, and if you have to work with the genetics of many different a species, it’s a lot of effort.

Then it became obvious that we should be focusing on crops, because there are only a handful of species that populate a vast area. There’s more than 600 million hectares worldwide for the four most prevalent crops. There’s also an existing distribution system. You already have people planting and updated seeds every year. You already have a system of incentives that are market-driven, but also government-driven, like crop insurance.

Each year, human activity releases 18 gigatons more carbon dioxide than the Earth can absorb. Enhanced plants could take up some of that excess. (Credit: Salk/HPI)

Human activity releases 18 gigatons more carbon dioxide than the Earth can absorb. Enhanced plants could take up some of that excess. (Credit: Salk/HPI)

With all of that acreage to work with, how much could re-engineered crops do to offset human carbon emissions?

We did a back of the envelope calculation. Taking into account published biomass data and the acreage of the planted crops, how much biomass do they yield above ground? Taking into account root to mass fractions, how much of the plant is root and how much is shoot?

We ran these numbers on five target crops that we think we can deal with: corn, soy, wheat, rice, canola. We considered that at some point in the future, 70 percent of the target crops could be enhanced for carbon-sequestration traits. Then we asked, what would happen if we could stabilize 30 percent of the biomass in the root mass?

If you run the numbers, you end up with 5.5 gigatons of CO2 [per year], which is roughly 30 percent of the annual surplus [anthropogenic emissions] that is leaked in the atmosphere. I have to say, this is just a very rough calculation, but it showed us that if we could make plants better, it would have a global impact. Even if only 10 percent of the biomass is stabilized, you have 1.8 gigatons [of CO2 sequestered].

Essentially, it looked like we could offset 10 percent to 30 percent of the surplus of CO2 that is currently emitted in the atmosphere each year. So, that was to us encouraging.

Those are huge numbers, but to get there you’d also have to make a huge change in the crops we grow. What are the steps to make that happen?

That, basically, is the question driving us. We and others have to do much more research to know how much can we actually sequester. There are so many unknowns. We need to know the residence time of carbon [how long it stays buried]. Soil chemistry and local microbiomes will play a role.

We know that the [plant root] traits that we are working on can make a difference, but we want to get to more quantitative models. We’ve started field research — collaborations
with soil scientists, soil biochemists, soil geochemists — to systematically study these questions. Time is short, so we are developing our [engineered plant] traits and coming up with a better quantification at the same time.

This month we are starting two field trials. We wanted to have more, but COVID makes it really hard. Next year we want to have 10 field sites, and then 15, maybe more, depending on whether we can get additional funding. We will be planting our first plants in a couple weeks. One of our field trials will be located in Yuma, Arizona; one will close to the Central Valley in California. Those are with commercial partner field sites. In the long term, we want to work with a couple of universities on this.

Plants absorb CO2 as they grow, then release it as they decompose. Engineered "ideal" plants would store carbon for many decades in deep roots. (Credit: Salk/HPI)

Plants absorb CO2 as they grow, then release it as they decompose. Engineered “ideal” plants would store carbon for many decades in deep roots. (Credit: Salk/HPI)

What about the central issue of how long the carbon stays buried? Can cropland hold the carbon in place long enough to be useful?

So, we know from the literature that deeper rooting leads to slow decomposition rates. And suberin or potentially other stable compounds go into long-lived carbon pools, which can have interactions with the soil minerals. These pools are considered to be stable from decades to centuries.

Centuries! I had no idea.

The root depth and the root depth distribution are important factors in how much carbon you can put into the long-lived carbon fractions in the soil, including suberin. We know it will be dependent on soil chemistry. The quantities and the residence time [of the buried carbon] will very much depend on these variables. That’s why we need to get the experiments going, to be able to quantify these things better.

Right, I was also wondering about total quantity of carbon that farmland can absorb. Can you keep burying more carbon there, year after year?

One fundamental consideration is that the soil carbon content has been reduced dramatically over the past century in industrialized, monoculture agriculture. We know there’s a huge potential, because if the soil carbon was there before, we can at least replenish it. I can’t give you a specific number until we do more modeling. But there is definitely many years of potential carbon sequestration that can happen.

How far along are you in developing and testing the engineered, deep-root plants you would need for agricultural carbon sequestration?

In the first year [of field experiments], we are not planting any genetically changed plants. We are basically taking crops that we know and quantifying different properties of rooting under field conditions. We estimate that our first [suberin-enhanced] test lines will hit the field site next year. The bulk of our studies of the potential of our changes will come in three years, say.

Have you done studies yet to make sure that suberin-enhanced crops are just as good as the ones the farmers are planting now — similar in yield, quality and so
on?

That’s a very important and interesting question. What we are currently trying to do is to have a first pass at answering these questions with the help of our collaboration partners. We are looking to see whether there are trade-offs.

A trade-off that one would be worried about would be the root mass to yield allocation [with the increase in root mass coming at the cost of the harvest]. I think there is ample evidence from the literature that it’s not a fixed trade-off. We’re going to try a lot of different strains. We’re going to evaluate the genetic recipe to store more carbon in the roots, and at the same time we will also measure the yield.

Despite COVID, we just finished the construction of a 10,000-square-foot greenhouse that will allow us to grow the crops we are interested in — corn, soy, wheat, rice, canola — in field-like conditions. Not true field condition, but field-like.

Wolfgang Busch (right) with his postdoc Takehiko Ogura, examining one of his green test subjects. (Credit: Salk Institute)

Wolfgang Busch (right) with his postdoc Takehiko Ogura, examining one of his green test subjects. (Credit: Salk Institute)

Let’s be optimistic and assume the experiments go well. How do you get farmers planting carbon-sequestering crops on the scales needed to have a meaningful impact?

We have started talking to many different agribusiness companies. We are all active scientists in the [Harnessing Plants] initiative. We get invited to talk a lot, we go to a lot of conferences. Most of the companies in this space are very aware of our activities. Some of them have expressed interest in talking more about the specific issues that are important to them.

We know we won’t get the scale we need without partnering with big seed companies and big ag [agribusiness]. Without seed companies that will allow us to distribute seeds to the farmers, and without the farmers who are interested, this project will never fly. We’re also talking to NGOs [non-governmental organizations], because some crops and some parts of the world are not dominated by the big ag companies. We’re trying to spread the word so that NGOs and companies come to us, but we are also talking to as many of them as we can, to see if we can get together.

In the future, there might be market incentives when it comes to things like carbon credits or other ways that governments might reimburse farmers to store carbon in the soil. We’re
exploring all this, because this is more than just a science project. We really want this to succeed.

What about the consumer side? I’m picturing a future in which some customers might seek out products that have a stamp that says “this was made with greenhouse-fighting crops” or something like that.

That would be wonderful if it could be a consumer choice. We are thinking about this, too.
We have this term, the “Salk ideal plant.” It would be wonderful if that would be a label that consumers at some point could say, “Okay, I’m going to make this choice.”

How does the Harnessing Planet Initiative fit in with related concepts, like using partially burned plants (biochar) to increase the carbon content of soils? Are these
potentially synergistic approaches?

Absolutely. Just before the COVID lockdown in California, we had a conference called Plant
Carbon Drawdown 2020 at Salk. We wanted to bring together scientists who think about all these different solutions for sequestering carbon, like biochar, enhanced rock weathering, forestry, and enhanced carbon absorption in the oceans and in wetlands.

A lot of these approaches could be important. We just come at the issue from a genetics
perspective because genetics has revolutionized agriculture multiple times. There’s a huge potential to make a global impact by changing plants in a manner that’s beneficial for humans. But then, everything else, like no-till agriculture [allowing more organic material
to stay in the ground], and supplementing soils with different materials, is also wonderful. The more approaches, the better.

Who is supporting this type of research? Do you get any state or federal funding?

Not yet. We’re reaching out to funding agencies to see if that would fit in. The [government] funding is not currently structured in a way that you could say, “Oh, we want to do carbon sequestration using plants.” We’re pretty much ahead of the curve. But we’re hoping that by providing data and evidence that we can actually do it, we make it possible for the federal government to spend money on this, and to allow other groups to work on this.

We were lucky to get Audacious funding [funded by the TED nonprofit] last year: a large grant to do what we think we have to do, and to show others that there is a potential. Part of where I see us as hopefully having a big impact is to show not only scientists, but also potential funding agencies and the government that there’s something else [for agricultural funding] beyond crop yield and stress resilience. That we should, as a society, put money into this because it’s really important, and also realistic.

Your idea to remake agricultural crops around the globe is, as you say, rather far ahead of the curve. What are the obstacles you’re most concerned about?

I think the main unknown is, if we change the crop plants, will there be a trade-off? Will there be something that a farmer will not like about it? Until we have the data, we don’t know. But we know that we don’t need to change the traits radically. Even a small improvement would help. We think that there’s not a lot of question that we can make a large impact just by making roots deeper and having more suberin in them. So, we are optimistic about that.

Another unknown is whether governments will be convinced that addressing climate change is something important. Will they take real action on changing the incentives in our systems to make a positive impact?

Personally, I hope there will be an incentive system for storing carbon in the soil, and good protocols for quantifying this. It really depends on governments all around the planet. There are already a lot of incentives given to farmers in the big agricultural regions; it’s just a shift in the type of incentives. Countries could say, “We don’t really care about providing incentives for drawing down carbon.” That’s a risk. On the other hand, I’m hopeful, because it seems that governments are more and more willing to think about this.

Clearly you wouldn’t be devoting your energy to a project like this if you weren’t fundamentally hopeful the world will step up and address climate change.

Yeah. We are all really enthusiastic and motivated here! I’m thrilled to be doing this every day.


For more science news and ideas, follow me on Twitter: @coreyspowell


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بازی انفجار : نظریه عجیب Coronavirus از فضا


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نظریه های غیرمعمول زیادی در مورد منشأ SARS-CoV-2 ، ویروس مسئول COVID-19 وجود دارد. از ادعا ها مبنی بر اینکه ویروس یک بیوجاون است ، به این عقیده که انتقال 5G در پشت همه گیر است ، هیچ کمبودی در ایده های باورنکردنی وجود ندارد.

اما یک نظریه COVID-19 چنان چشمگیر است که باعث می شود دیگران با مقایسه خسته کننده به نظر برسند: پیشنهادی که تاج ویروس از فضا آمده است.

در این پست ، من درباره این ایده شگفت انگیز و تاریخ به همان اندازه عجیب و غریب آن بحث خواهم کرد.


تئوری ویروس فضایی کار گروهی از محققان است ، به ویژه ادوارد جی استیل و ن. چاندرا ویکرامایزه. این گروه از زمان شروع همه گیری ، ده مقاله در این زمینه منتشر کرده است ، اما این مقاله از 14 ژوئیه استدلال دقیق ترین ارائه می دهد.

استیل و همکاران. پیشنهاد می کند COVID-19 در 11 اکتبر سال 2019 به شهاب سنگی رسید که به عنوان یک آتش نشانی روشن بر فراز شهر سونگیان در شمال شرقی چین مشاهده شد.

آنها پیشنهاد می کنند که شهاب سنگ ممکن بوده است "یک شهاب سنگ شکننده و سست نگهدارنده و دارای یک محموله از تریلیون ها ویروس / باکتری و سایر سلولهای منبع اصلی."

نویسندگان اعتراف می کنند که شهاب سنگیونگ در بیش از 2 هزار کیلومتری شمال شرقی ووهان واقع شده است ، جایی که اولین موارد COVID-19 گزارش شده است ، اما آنها با این فرضیه برخورد می کنند با این فرضیه که قطعه متفاوتی از شهاب وارد منطقه ووهان می شود:

یک شهاب سنگ اصلی بسیار بزرگتر به راحتی می توانست قبل از احتراق این رویداد آتشنشانی ، قطعات آن را پراکنده و پراکنده کند. یک فرض معقول این است که آتش بس که 2،000 کیلومتری شمال ووهان را لرزاند ، ممکن است بخشی از لوله گسترده ای از زباله ها باشد که بخش عمده ای از آن در استراتوسفر سپرده شده است تا بر فراز ووهان بیفتد.

نیازی به گفتن نیست ، این تئوری نیست که هیچ مدرکی برای آن وجود دارد. هیچ مدرکی مبنی بر وجود ویروس یا باکتری (یا زندگی دیگر) در فضا وجود ندارد و استیل و همکاران. هیچ مدرک مستقیمی مبنی بر ورود coronavirus از آسمانها ارائه نکنید.

اما معلوم می شود که تئوری زندگی (و بیماری) از فضا چیز جدیدی نیست. این تئوری نامیده می شود لوزالمعده و تعداد معدودی از محققان ، از جمله استیل و ویکراماشینگ ، چندین دهه است که از آن حمایت می کنند.


Panspermia ، به طور کلی ، این ایده است که زندگی از فضا به زمین رسیده است ، و همچنان ادامه دارد. این ایده به کلیه یونانیان باستان برمی گردد ، اما به شکل مدرن آن به دهه 1970 و کار دو اخترشناس ، فرد هویل (1915-2001) و چاندرا ویکرامایزینگ برمی گردد.

هویل یک ستاره شناس مشهور بود که در طول حرفه خود مشاجرات زیادی را به دنبال داشت. وی شاید بیشتر به خاطر آمدن اصطلاح "بیگ بنگ" شناخته شود - اگرچه برخلاف اکثریت قریب به اتفاق همکارانش ، وی هرگز اعتبار نظریه بیگ بنگ را نپذیرفت. Wickramasinghe دانشجوی دکترای هویل بود.

در حالی که آنها داستان را بیان می کنند ، هویل و ویکرامینشینه در حالی که سعی در توضیح چگونگی جذب غبار بین ستاره ای داشتند ، از پانسرمیا تصور کردند. آنها متوجه شدند که اگر گرد و غبار از باکتریها تشکیل شده باشد ، این الگوی مشاهده شده از جذب نور را تولید می کند.

Hoyle و Wickramasinghe سرانجام به ایده کهکشان کاملاً پر از میکروارگانیسم ها ، موجود در دنباله دارها و شهاب سنگها و همچنین ابرهای گرد و غبار رسیدند.

panspermia - http://cosmology.com/Panspermia4.html

نمودار "حلقه تقویت کننده برای میکروارگانیسم های اولیه در کهکشان". (اعتبار: Napier & Wickramasinghe 2010 مجله کیهان شناسی)

در حالی که موجودات موجود در فضا عمیق به تنهایی نمی توانند زنده باشند ، هویل و ویکرامایز معتقد بودند که میکروارگانیسم های فضایی می توانند در صورت ورود به یک سیاره مناسب ، مانند زمین - دوباره فعال شوند و احتمالاً موجودات بومی را نیز آلوده کنند.

Hoyle و Wickramasinghe در سال 1979 بازگرداندن عنوان "بیماری هایی از فضا" به عنوان عنوان یکی از کتاب های خود نوشتند. آنها در ادامه به دنبال منشا بین سیاره ای برای چندین شیوع بیماری ، از جمله SARS اصلی در سال 2003 و آنفولانزا بودند.


من فکر می کنم کهکشان کهکشانی با زندگی جذاب است. من آن را باور نمی کنم ، و panspermia توسط اکثر دانشمندان رد می شود ، اما مطمئناً یک ایده جسورانه و خلاق بود. ممکن است واقعیت نداشته باشد ، اما در بدترین حالت ، این علمی تخیلی خوب است.

با این حال ، تلاشهای اخیر برای توضیح COVID-19 به عنوان ناشی از فضا ، جالب توجه و خطرناک به نظر می رسد.

COVID از فضا یک فرضیه جالب نیست. این تئوری به وضوح فقط تلاشی برای متناسب کردن COVID-19 در مدل panspermia موجود است - هیچ چیز جدید یا خلاق در مورد آن وجود ندارد.

صادقانه بگویم، حتی اگر شما به panspermia اعتقاد دارید ، من نمی توانم ببینم چرا فکر می کنید COVID-19 از فضا آمده است. ویروس SARS-CoV-2 برخی از عوامل بیماری زای عجیب و غریب نیست. این بسیار شبیه به اولین ویروس SARS ، و با coronaviruses های مختلف پستانداران ، به ویژه ویروس های خفاش است. بنابراین حتی اگر شما به ویروس های فضایی اعتقاد دارید ، این ویروس است که به وضوح منشاء زمین دارد.

COVID- از فضا نیز یک فرضیه خطرناک است. استیل ، Wickramasinghe و همکاران. گفته اند كه COVID-19 از فرد به شخص دیگر مسری نیست (یا فقط بندرت). براساس این عقیده ، آنها (در ماه فوریه) پیشنهاد کردند كه COVID-19 عمدتاً چین را تحت تأثیر قرار دهد و هنگامی كه گرد و غبار پراکنده شود ، از بین می رود. آنها همچنین نوشتند که هیچ نکته ای برای جستجوی واکسن وجود ندارد:

بنابراین ، ایجاد واکسن به نام "COVID-19" که در زمان نوشتن اخبار بسیار زیاد است ، می تواند هدر رفته از بودجه پرداخت کننده مالیات عمومی باشد ، اگر در مقیاس پیش بینی شده توسط دولت ها و مراکز ملی کنترل بیماری انجام شود.

واضح است که اگر کسی این ایده را جدی گرفت ، برای سلامتی عمومی بسیار خطرناک خواهد بود. خوشبختانه ، فکر نمی کنم کسی چنین کند.

با این حال ، من می گویم که نظریه coronavirus-from-space هنوز قابل باورتر از برخی دیگر از تئوری های COVID-19 است. به عنوان مثال ، باور اینکه کرونا ویروس در اثر انتقال 5G ایجاد می شود ، حتی علمی کمتر از اعتقاد ورود به یک شهاب سنگ باعث می شود. یک شهاب سنگ میتوانستاز نظر تئوری ، ویروس را حمل می کنید ، اما امواج رادیویی نمی توانند.

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