air stratospheric ozone
The birth—and possible death—of the Sage III atmospheric satellite.
These are exactly the types of space missions that could be in jeopardy in the coming years, as the Trump administration continues active hostility toward climate research.
On the upcoming SpaceX CRS-10 mission, a rocket will launch carrying the next batch of cargo to the International Space Station. Inside its Dragon capsule’s unpressurized trunk will be a critical Earth-facing instrument—one that maps ozone molecules and other compounds in the atmosphere. Its name is the Stratospheric Aerosol and Gas Experiment III, or SAGE III.
When the Dragon arrives at the ISS, a robot arm will reach into the trunk, pull out the experiment’s parts, put them together, and install them on the outside of the habitat. Scientists at NASA’s Langley Research Center will watch streaming video of their baby being assembled, breaths held till everything is in place.
Then, for at least three years, SAGE III will stare down at Earth, measuring and mapping the atmospheric ingredients that help scientists understand, among other things, how and why the planet warms and cools. Those are exactly the types of space missions that could be in jeopardy in the coming years, as the Trump administration continues active hostility toward climate research. SAGE III, launching so soon, is hopefully safe. Its observations will speak to how good a job we’ve done of repairing our planet—and what will happen to the atmosphere in the future.
A Three-Generation Experiment
SAGE III builds on the legacy of its grandparent and parent missions. SAGE I went to space in 1979, and its look at Earth gave a baseline knowledge of how ozone, aerosolized particles, and nitrogen dioxide are distributed in the stratosphere. In 1984, SAGE II rocketed upward and made the same measurements for 21 years. Together, the missions provide the kind of long-term dataset scientists need to understand how the down-low parts of the planet respond to the up-above changes, and vice versa.
In the 1980s and ’90s, the ozone above our heads was diminishing—globally, but especially in the infamous “ozone hole” above Antarctica. Joe Zawodny, the current program’s project scientist, says the SAGE data was vital in demonstrating that decline. Seeing such concrete effects on our atmosphere, international leaders enacted the 1989 Montreal Protocol, an international treaty in which countries agreed to gradually stop making the stuff that eats through ozone, like Freon. After the Protocol went into effect, SAGE datasets also showed it was working: The ozone levels looked better and better.
“The science community came together with their evidence, presented their cause and effect, and legislators worldwide took action,” says project manager Mike Cisewski.
The scientists now anticipate pointing to SAGE III’s data, which they hope to begin collecting in March, for further positive evidence. “We expect ozone to have recovered halfway from its decline in the ’97 time period,” says Zawodny.
SAGE III will also measure aerosols—little particles of whatever. Most of them come pouring out of volcanoes, but they also come from blow-up desert dust, fires, and human-made pollutants. Aerosols mess with ozone, cloud formation, and climate. They actually—wait for it—cool Earth’s surface temporarily. “[That] puts noise in the temperature records,” says Zawodny. “So if you want to understand changes in global temperature, you have to account for aerosols.”
Without missions like SAGE, in other words, climate scientists would be missing edge pieces of their puzzle.
NASA in the New Era
But in a political era when the House Committee on Science, Space, and Technology wantonly tweets Breitbart articles denying climate change, scientists are worried about the future of Earth studies at NASA. Will there be budget cuts? Slashed projects? Or transferred ones? Trump science policy advisor Bob Walker, for instance, suggested moving home-planet research from NASA to the National Oceanic and Atmospheric Administration.
Dave Young, the head of the science directorate at NASA’s Langley Research Center—SAGE’s home institution—says this is not the first time someone has suggested consolidating Earth-science programs. It makes philosophical sense (kind of). But it doesn’t make physical sense: NOAA is not a space agency. They don’t build space stuff. In fact, NASA currently builds the satellites that NOAA uses to do things like weather prediction; NOAA just operates them. “Quite frankly, they don’t have the capability we have at NASA,” says Young. “We are the civilian space agency. Right now, without transferring a lot of assets to them—people, facilities, everything—they could not do it.”
And besides, he continues, it’s all speculation. No one knows what will happen (just try to predict 2017—I dare you).
What we do know is that the new administration has limited public communications from the likes of the Environmental Protection Agency and the Department of the Interior (what’s up, @BadlandsNPS). But Joseph Atkinson, NASA-Langley’s Earth Science public affairs specialist, says (at least his part of) the space agency has received “no guidance or instructions on any of our public affairs efforts.”
Yet.
So far, the only order affecting NASA, along with all other federal agencies, is a hiring freeze (Jimmy Carter and Ronald Reagan also made full-on freezes; George W. Bush and Obama froze certain agencies). And one of NASA’s two new presidential liaisons actually worked as an atmospheric scientist at NASA’s Goddard Space Center (before he worked as a Trump campaign data analyst). But the agency doesn’t yet have a new administrator, a presidentially mandated plan for the future, or a muzzle on either their climate science or its communication.
And so SAGE III and its measurements move forward—toward the launch pad, toward space, toward a clearer view of our planet and its future.
Cisewski, for his part, feels excited about SAGE’s contribution not just to science and the people but also to policy. “We’ll close the loop and provide politicians and legislators with evidence that the action they took [with the Montreal Protocol] and the belief they put in us—their trust in our sound science—was founded and paid off,” he says. “It was the right action.”
And whether more sound science, from SAGE III and other Earth-watching instruments, will engender more trust and more action in this brave new world—well, that remains to be seen. But these scientists plan to put the data, and their conclusions, out there. Around six months from launch, the team will release the first batch of observations, making SAGE III’s numbers available to the public. For the good of international science community—for you and for me and for the entire human race.
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Pollution from India and China has reached the stratosphere.
Pollutants from China and India, are not only increasing in quantity, but are also being pumped to greater heights in the atmosphere, thanks to the South Asian summer monsoon system, scientists have discovered.
Monsoon storms are pumping pollution from India and China over the Himalayas and into the stratosphere, speeding up global warming.
Pollution from India and China has reached the stratosphere
Image credit: NASA
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Pollutants from China and India, are not only increasing in quantity, but are also being pumped to greater heights in the atmosphere, thanks to the South Asian summer monsoon system, scientists have discovered.
In turn, this pollution is affecting the very pattern of the South Asian monsoon. The polluting aerosols, from the burning of fossil fuels and, to a lesser extent, biomass, also absorb heat from the sun’s radiation, further increasing global warming.
A new paper published in the journal Climate Dynamics in November concludes that aerosols have strong impacts on regional monsoon rainfall and circulation. The scientists found that the complex and steep topography of the Himalayan foothills helps in the build-up of thick layers of dust aerosols transported by monsoon winds from the Arabian deserts across the Arabian Sea. This build-up of aerosols causes the monsoon to arrive early.
These findings are important not only for climate change, but also for predicting the Asian monsoon in the future.
A team of scientists headed by William Lau from the Earth Science Interdisciplinary Center, University of Maryland, studied the unusual 2008 Indian monsoon. This year saw “exceptional heavy loading of dust aerosols over the Arabian Sea and northern-central India, near normal all-India rainfall, but excessive heavy rains and disastrous floods in the Northern Indian Himalaya Foothills, and persistent drought conditions in central and southern India,” according to the paper.
Using a NASA model, the scientists showed that the movement of polluting aerosols “plays a key role in altering the large-scale monsoon circulation system”. This led to larger differences in temperatures in the northern and southern portions of the stratosphere, a northward shift of heavy monsoon rainfall and advanced monsoon onset by one to five days.
Stratospheric pollution
Meanwhile, other scientists have discovered polluting aerosols now reach up to 18 km in the stratosphere – the atmospheric layer directly above the troposphere that contains most of Earth’s ozone. Findings from CALIPSO, a joint French-US satellite launched in 2006, indicate that a strange phenomenon in the atmosphere, functioning like a heat pump, drives air laden with aerosols 15-18 km high over the Himalayas, into a zone that forms a boundary between the lower and upper atmosphere layers – or the troposphere (0-16 kms) and stratosphere (16-50 km). This zone is also called the Asian Tropopause Aerosol Layer.
The idea that hot air and pollution is pumped up over the Himalayas was first put forward in 2006 by a team also led by Lau. He proposed that in the pre-monsoon season, from March to May, soot from northern India and dust from the deserts of western China, Afghanistan and Pakistan gather at the foothills of the Himalayas in the Indo–Gangetic Basin. Since these aerosols absorb heat, they warm the surrounding air, making it rise vertically over the Himalayas to more than 10-15 km high, acting like an “elevated heat pump”.
The rising warm air, in turn, sucks in cooler air from the Indian Ocean, causing an earlier onset of the monsoon.
In a parallel effort, in 2009, a team led by Jean-Paul Vernier, from the NASA Langley Research Center, Virginia, also found a thick layer of aerosols between 13 and 18 kilometers high, spanning the eastern Mediterranean Sea, northern India and western China.
In 2015, Vernier’s team found that the amount of aerosols in this layer had increased by three times since 1996, the earliest time when they appeared in satellite observations. His team, made up of Chinese, Swiss and Swedish scientists published their findings in the Journal of Geophysical Research.
The NASA team, in collaboration with Indian scientists at the National Aeronautical Research Laboratory, Tirupati, has verified satellite data using data gathered from 30 balloons launched in India and Saudi Arabia over the last three years.
The results confirm a sharp increase of aerosols 15-18 km in the atmosphere across the Asian region in the past few years, said physicist Abhay Singh from Benaras Hindu University, who was involved in the study. “This confirms that the ATAL is likely resulting from heavy pollution over North India and Western China, for example, sulfur dioxide, from power plants, and can make its way to the lower stratosphere and form aerosols.”
Describing the preliminary findings, Vernier said: “Large storms during the monsoon vent and lift up air from the ground to the upper atmosphere and provide a vehicle also for pollution to reach higher altitude.”
“To me, monsoon storms are the main vehicle for the transport of polluted air into the upper atmosphere, and not only over the Tibetan plateau but also over North India and Western China,” he adds.
Global impacts
Meanwhile, Lau’s more recent studies, presented at an international workshop on land-surface interactions in the Tibetan Plateau, held in China in August 2016, show the wider implications of the findings.
“Aerosols from surface pollutants not only have local effects on health and environment; and surface climate change in monsoon region, (but) may (also) have even stronger impacts on global climate change through radiation feedback processes, which are most strong and efficient in the upper troposphere and lower stratosphere,” Lau explained.
These new findings show that pollution will not only continue to change the pattern of the monsoon within and between seasons and exacerbate global warming.
Once that high, pollutants can spread globally and destroy the ozone layer that protects us from ultraviolet radiation. This, in turn, is likely to lead to skin cancers, cataracts and a suppressed immune system in humans, as well as reduced yields of crops.
And scientists are still trying to unravel the impacts of aerosols at higher levels, which they believe will impact cloud formation and weather patterns.
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Good news: The hole in the ozone layer is finally starting to heal.
Sometimes the world really can get together and avert a major environmental catastrophe before it's too late.
lized that we were rapidly depleting Earth's stratospheric ozone layer, which protects us from the sun's harmful ultraviolet rays.
The culprit? Chlorofluorocarbons (CFCs), a chemical widely used in refrigerators and air conditioners. These chemicals had already chewed a massive "hole" in the ozone layer above Antarctica, and the damage was poised to spread further north.
Without the ozone layer's protection, more and more people would be exposed to UV rays. Skin-cancer rates would have soared in many regions, as they already have in Puentas Arenas, Chile, which lies under the existing ozone hole. Those UV rays would also harm crops and the marine food chain.
Fortunately, this apocalyptic scenario never came to pass. Scientists uncovered the problem in time. And, under the 1987 Montreal Protocol, world leaders agreed to phase out CFCs, despite industry warnings that abolishing the chemicals would impose steep costs. The hole in the ozone layer stopped expanding. The global economy kept chugging along.
Now comes further good news. The latest study, conducted by scientists at MIT and elsewhere, identifies several "fingerprints" suggesting that the ozone layer is on its way toward actually healing. They note that the annual ozone hole that appears above Antarctica in September has shrunk by some 4 million square kilometers since 2000, although there are ups and downs each year due to volcanic eruptions.
This 2014 video from NASA illustrates the healing process, showing the minimum concentration of ozone in the southern hemisphere each year from 1979 to 2013. The process is sluggish: The ozone layer kept thinning in the 1980s and 1990s, even after the big agreement to phase out CFCs. In 2006, another major hole appeared. But recently, the hole has started shrinking and ozone concentrations have started rebounding:
Back in 2014, a UN assessment projected that the ozone layer would fully recover by 2050. "There are positive indications that the ozone layer is on track to recovery towards the middle of the century," said UN Under-Secretary-General Achim Steiner. "The Montreal Protocol — one of the world's most successful environmental treaties — has protected the stratospheric ozone layer and avoided enhanced UV radiation reaching the earth's surface."
Granted, just because the world banded together and saved the ozone layer doesn't ensure that we’ll also do the same for future environmental problems, like global warming. It will almost certainly be harder to reduce our reliance on fossil fuels than it was to curtail our use of CFCs. (For one thing, Dupont developed easy substitutes to CFCs fairly quickly.) But the ozone case remains the best example of international cooperation to halt a slow-moving ecological disaster. And it worked.
We barely dodged a bullet with the ozone layer
It's worth reflecting on what a close call we had with the ozone layer. Scientists in Antarctica first began measuring stratospheric ozone levels in 1957, but it still took decades to realize how dire the situation actually was. Indeed, when researchers found signs of severe ozone depletion in the 1970s, they initially thought their instruments were faulty.
It wasn't until 1974 that chemists Mario Molina and Sherwood Rowland published a paper proposing that rising concentrations of CFCs in the atmosphere could deplete the ozone layer. These stable chemicals were widely used as refrigerants and cleaning solvents. But when CFCs wafted up into the stratosphere, they got ripped apart by UV rays, and the free chlorine atoms would catalytically destroy the ozone there.
This hypothesis was difficult to prove, and it was fiercely disputed by Dupont, the world's biggest manufacturer of CFCs, for many years. But evidence kept accumulating, and by the 1980s, scientists finally had incontrovertible proof that CFCs were to blame. That's also when the massive "hole" over Antarctica received widespread attention. (This hole is a severe thinning of the ozone column throughout the atmosphere during the spring and summer.)
We were lucky that the damage wasn't even greater by that point. Dupont had been using chlorine instead of bromine to create its refrigerants. The two elements were roughly interchangeable for this purpose; it just so happened that chlorine was cheaper. Yet, as Paul Crutzen later observed in his Nobel acceptance speech, bromine is 45 times more effective at destroying ozone. Had Dupont used bromine, the ozone layer might have been damaged beyond repair long before anyone even noticed.
Fortunately, that didn't happen. Under the Montreal Protocol of 1987, the world's nations agreed to phase out the use of CFCs in refrigerators, spray cans, insulation foam and fire suppression. By and large, countries complied. Atmospheric concentrations of chlorine have stabilized and have been declining slowly over time.
In their 2014 report, the UN panel noted that without that agreement, atmospheric levels of ozone-depleting substances might have increased tenfold by mid-century. The resulting ozone loss could have led to 2 million additional cases of skin cancer by 2030 — to say nothing of crop damage or other impacts.
Today, recovery is slow, since there's still chlorine lingering in the stratosphere. The Antarctic hole still appears every spring and summer, even reaching a record size in 2006. And it's not just Antarctica: An especially cold Arctic winter in 2011 led to an ozone hole up north, too.
But the broad picture is encouraging: The ozone layer is on track to bounce back to 1980 levels by around mid-century.
Unexpected side effects of the Montreal Protocol
Meanwhile, there have been a few unexpected side effects of this whole affair.
As a result of the Montreal Protocol, companies and countries stopped using CFCs and started using HFCs (hydrofluorocarbons), which have a much more benign effect on the ozone layer. That seemed like a satisfying solution — at least until global warming became a much more pressing concern.
Both CFCs and HFCs are potent greenhouse gases that help warm the planet. And, on net, swapping out CFCs for HFCs reduced the overall amount of greenhouse gases in the atmosphere (making the Montreal Protocol unintentionally one of the biggest steps we've ever taken to prevent climate change).
But now HFCs are becoming a big climate problem in their own right, especially as air-conditioning becomes more popular in fast-growing countries like China and India. HFCs are up to 10,000 times as effective as carbon-dioxide at trapping heat, and their use is soaring.
"Hydrofluorocarbons (HFCs) do not harm the ozone layer but many of them are potent greenhouse gases," the UN panel noted in 2014. "They currently contribute about 0.5 gigatonnes of CO2-equivalent emissions per year. These emissions are growing at a rate of about 7 percent per year. Left unabated, they can be expected to contribute very significantly to climate change in the next decades."
Many environmental groups have urged world nations to revisit the Montreal Protocol and phase out HFCs in favor of chemicals that — like HFO-1234YF — that are both harmless to the ozone layer and don't warm the planet significantly.
In June 2016, the United States and India reached a side agreement to amend the Montreal Protocol in this fashion. The hope is to get a new international agreement late this year. Many companies in the United States, such as Dupont, Coca-Cola, and Target, have already pledged to shift away from using HFCs as refrigerants and toward more benign alternatives.
Further reading
— Roger Pielke Jr. once wrote a nice essay about why the Montreal Protocol isn’t a great template for efforts to tackle climate change. Relatedly, I wrote a piece here about how the success of the Montreal Protocol in the 1980s arguably led UN climate negotiators astray in trying to craft a similar treaty for global warming.
— Back in June, the US and India agreed to tackle HFCs, a little-known (but potent) climate problem
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We successfully reduced the ozone hole, is climate change next?
A new study discusses “the first fingerprints” of healing of the Antarctic ozone layer that protects life on Earth from dangerous ultraviolet radiation from the sun. It’s a success story but does it mean it’s possible to tackle a bigger problem like climate change?
A new study published today in the journal Science today discusses “the first fingerprints” of healing of the Antarctic ozone layer that protects life on Earth from dangerous ultraviolet radiation from the sun. It’s a success story of environmental policy, but does it mean it’s possible to tackle a bigger problem like climate change?
It’s easy to be cynical about the state of climate action, with rising sea levels, what seems like increasing incidents of extreme weather and decades of sluggish response or complete inaction from policymakers. But the ozone hole and other modern environmental disasters like acid rain once seemed to pose near existential threats of our own creation, and yet we managed to reverse them.
The problem with climate change, though, is a matter of scale. The increasing ozone hole could be traced to the use of chlorofluorocarbons, and phasing out their use was a significant but not overwhelming task to accomplish. Anthropogenic climate change is as much a problem of demographics and of scale as it is atmospheric chemistry. It is not a single group of chemicals contributing to global warming/weirding, but rather the exhaust of a civilization that is growing not only in population, but in consumption at unprecedented rates.
Growth, of course, is the presumed constant upon which the entire global economy and most of our lives is built upon. In a sense, fixing climate change is as simple as fixing ozone depletion by just reducing our dependence on CFCs — the catch is that what needs to be reduced in the case of climate change is growth itself, and that’s a bit of a tall order.
Then again, a cap-and-trade system for power plants led to a reversal of a growing acid rain problem in the 1990s. Emissions causing acid rain went down faster than expected and at far less cost than anticipated. It was a successful market-based approach that created a new commodities market in the process.
So perhaps there is hope; hope for a solution that can use our addiction to growth to solve our biggest problem; hope that technology can find ways that allow us to continue to grow but produce less exhaust in the process. We’ve fixed things before, and with far less knowledge and ability than we have now. Each new success, like the latest with the ozone layer, should be a reminder to stay vigilant against the constant temptation of cynicism.
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NOAA
No increase in methane emissions on North Slope, despite warming temperatures.
Three decades of atmospheric monitoring on Alaska's North Slope show no signs that a feared "methane bomb" capable of accelerating climate change is emerging from thawing permafrost.
Three decades of atmospheric monitoring on Alaska's North Slope show no signs that a feared "methane bomb" capable of accelerating climate change is emerging from thawing permafrost.
The results, detailed in a new study published in the American Geophysical Union's Geophysical Research Letters, provide some assurances that thawing permafrost in rapidly warming Alaska Arctic is not venting the powerful greenhouse gas that feeds into the warming cycle.
Atmospheric methane levels on the North Slope held steady over the three decades even as the region has warmed about 2.16 degrees each decade, said the study, by researchers at the University of Colorado's Cooperative Institute for Research in Environmental Sciences, the National Oceanic and Atmospheric Administration, NASA and other institutions.
"If we were starting to have large impacts, we would be starting to detect that. And we really don't see that," said lead author Colm Sweeney, a CIRES scientist working at NOAA's Earth System Research Laboratory in Boulder, Colorado.
The only noticeable upward trend has been a slight increase in methane levels in November and December in the years since 2010, a period when air temperatures have increased, according to the study.
The new methane study comes a few weeks after the release of a U.S. Geological Survey study downgraded the risks of carbon emissions from thawing Alaska permafrost and increased wildfires. According to that USGS research paper, which inventoried Alaska's carbon stores, expansion of vegetation, with its ability to lock up carbon, is expected to offset new atmospheric carbon releases through the end of the 21st century.
Methane is of special concern in global warming because it is an especially potent greenhouse gas. It has more than 25 times the heat-trapping power of carbon dioxide.
The methane levels used in the study were measured from 1986 to 2015 at NOAA's Barrow Atmospheric Baseline Observatory, part of the agency's Global Greenhouse Gas Reference Network
The year-round atmospheric monitoring at the site has detected seasonal methane increases from July to December as wind blows from the south over the landscape and toward the ocean, the study said. But there is no long-term trend, the study said.
Yet to be evaluated is the long-term Slope emissions trend for carbon dioxide, the most abundant greenhouse gas. That is next for the research group, Sweeney said.
Other conditions are changing dramatically on the Slope and in the rest of the Arctic. The region is warming faster than the rest of the world, and the Slope is warming faster than most of the Arctic, Sweeney said.
Arctic permafrost is approaching thaw temperatures on the Slope and elsewhere, and in some places has passed that threshold. Thaw in Arctic lake-beds has created some much-documented bubbles of methane, and there are estimates of large amounts expected to vent from marine waters in eastern Siberia.
Even those methane releases, however, have yet to contribute to a noticeable increase in atmospheric methane, at least on the Slope, Sweeney said.
There have been big concerns about thawing permafrost and the carbon it will release to the atmosphere. The carbon currently locked in the Arctic's permafrost — remnants of old plant and animal matter — is believed to total 2½ times the amount of carbon that has been emitted since the start of the Industrial Revolution in the 18th Century, according to NOAA. Since atmospheric carbon traps the Earth's heat, the gas released from thawed permafrost is expected to feed into a self-perpetuating warming cycle.
But carbon from permafrost is not necessarily destined to vent into the atmosphere, Sweeney said. There are instead four possible fates for it, he said.
Under some circumstances, generally in wet conditions where bacteria thrive, the bacterial consumption of thawed carbon will release methane, he said. In generally dry conditions, thawed permafrost will release carbon dioxide into the atmosphere, he said.
Carbon from thawed permafrost might also be swept into the river systems, as appears to be happening in Canada's Mackenzie River. And the thawed permafrost might release carbon that feeds new plant growth, Sweeney said. That last effect seems to be more prevalent in Alaska in the boreal areas south of the Brooks Range, where permafrost is patchy rather than continuous and where forest ecosystems are changing fast, he said.
About a fifth of the world's atmospheric methane comes from wetlands, Sweeney said. Warm regions, where there is much more bacterial activity, dominate global wetlands' methane emissions, he said.
"The amount of methane coming out of the Arctic is actually relatively small compared to the tropics," he said.
Other sources of global methane emissions include agricultural operations, oil and gas operations, coal mining and landfills, according to the U.S. Environmental Protection Agency.
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Dennis Burger/flickr
The surprising importance of stratospheric life.
The science of bacteria in the atmosphere is getting its moment in the sun.
The science of bacteria in the atmosphere is getting its moment in the sun.
BY CHELSEA WALD
ILLUSTRATION BY TIANHUA MAO
JUNE 2, 2016
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Rippling like a jellyfish, a helium balloon big enough to envelop the Empire State Building lofted over the New Mexico desert. Its passengers, suspended below in a boxy white gondola, were hardy specimens: millions of cells of a remarkably resilient bacterium known as Bacillus pumilus SAFR-032. NASA scientists had first collected the strain more than a decade ago in the Mars Odyssey assembly facility, where the bacteria had survived sterilization. Before sending the pill-shaped cells into the sky last October, researchers starved them until they morphed into endospores, an armored dormant state.
Higher and higher the wee wayfarers rose: to 17,000 feet, the maximum altitude at which trees grow; to 24,000 feet, the upper limit of the highest-flying migratory bird, the bar-headed goose; to 60,000 feet, where atmospheric pressure is so low that water in bodily tissues would boil away. At last, at 100,000 feet, the balloon reached its destination. Here in the stratosphere, above the troposphere and most of Earth’s protective ozone layer, conditions are extreme: cold as an Antarctic winter, drier than the driest desert, and flooded in ultraviolet rays. “Mostly, it’s eventual death,” says Cindy Morris, a microbial ecologist at the French National Institute for Agriculture Research.
A GIANT LEAP FOR LIFE: A NASA research balloon that took a ride to the stratosphere to collect bacteria in October 2015. NASA / David J. Smith
Yet scientists are finding that a rich variety of life—archaea, bacteria, and single-celled eukaryotes—can thrive at high altitudes. In the troposphere, where day-to-day weather happens, each cubic meter of cloud contains on average tens of thousands of microbial cells. Even above the clouds in near space—as high as 250,000 feet, according to a 1978 Soviet study—rocket and balloon missions have collected hearty voyagers. “We’re not just finding corpses that are blown up there and preserved,” says Brent Christner, a microbiologist at the University of Florida. “Some fraction of these organisms is still alive.”
Lacking wings or pressure suits, these Lilliputian aeronauts have devised ways to protect themselves from irradiation, desiccation, and severe cellular stress, and find food in the bleakest of food deserts. Their unique set of survival skills has allowed them to soar the skies, dispersing to some of the harshest environments on Earth. And perhaps beyond: If B. pumilus cells can live through a balloon ride to the stratosphere, what’s stopping them from hitching a lift to Mars? “If organisms are blowing around in the stratosphere, and we took them and we put them on the Mars surface,” Christner says, “they wouldn’t even know the difference.”
Of course, microbes don’t need balloons to fly. Some fungal spores catapult from cannon-like structures in their parent. Wind or sea spray can similarly launch cells into the air. But most simply levitate, Mary Poppins style, in a passing updraft. “There’s always upward movement of air because the Earth is always heating the atmosphere,” Morris says. “It’s impossible for a particle that small to not get incorporated in these currents.”
Once airborne, the tiny drifters ride a complex and ever-shifting network of “highways in the sky,” says David Schmale, an aerobiologist at Virginia Tech. With engineer Shane Ross, he is developing ways to predict these turbulent routes. By pairing fluid dynamics modeling with data from air-sampling drones, the team has identified atmospheric features as large as countries, called Lagrangian coherent structures (LCSs), that behave “like waves moving through the atmosphere,” Schmale says. As an LCS moves over the landscape, it morphs much like an ocean swell, shuffling microbes along various air masses, like plankton along eddies.
What would happen if hardy microbes stowed away in a dark crevice on a lander?
Depending on their size and aerodynamics, microbes can stay aloft in the atmosphere for days to weeks—long enough to jump a continent, or an ocean, in one go. Analyses of meteorological data, for instance, suggest that transatlantic winds carried fungal spores from West Africa to the Americas, spreading sugarcane and coffee leaf rusts to New World plantations in the 1970s. Bacteria kicked up by dust storms in Africa’s drought-plagued Sahel appear to be making a similar leap to the Caribbean, where they are killing coral reefs. And in China, at the start of every growing season, spores causing wheat yellow rust migrate hundreds to thousands of miles from plants in the western provinces of Sichuan and Gansu to recolonize the country’s main wheat belt farther north.
Most of this globetrotting happens in the troposphere because the air there rarely mixes with air in the stratosphere above. But there are ways to catch a lift to loftier locales, including transport via thunderstorms, volcanic eruptions, and deep tropical convection. Microbes that make it to the stratosphere get swept along in its steady horizontal currents, allowing them to sail swiftly over vast distances, Christner says. “It’s a ticket to anywhere on the planet.”
BACTERIA TRAP: The gondola of the NASA research balloon seen in the photo above. If bacteria can live in this extreme environment, they may be able to survive similar conditions on Mars.NASA / David J. Smith
No known organism can survive high altitudes indefinitely. Scientists estimate that even the fittest microbes probably last no longer than a week in the stratosphere, and around a couple of weeks in the troposphere. Eventually they “get fried by radiation,” says David J. Smith, a NASA microbiologist who led the October balloon mission testing the stamina of B. pumilus cells. As a result, some high-flying species may have evolved a method to get down fast: hijacking the weather.
Microbial matter typically falls from the sky in rain or snow. To precipitate, clouds must grow ice crystals big enough to outweigh air, but pure water vapor won’t normally freeze above -36 degrees Fahrenheit—unless it gets help from an “ice nucleator.” Most often, airborne particles such as salts or mineral dust provide this service. By supplying a seed around which water molecules can arrange themselves, a nucleator enables ice to form at temperatures up to 5 degrees. Some microorganisms produce proteins that catalyze the process in even warmer conditions, up to 28 degrees in a laboratory. Scientists have yet to prove this happens in real clouds. But if it does, it’s a handy trick: Not only have these microbes found a way to encase themselves in an icy escape capsule, but they may be able to make it drop from the sky when it otherwise wouldn’t.
According to one model, possessing these icemaking powers could help shorten a microbe’s time in the sky to about a twentieth of what it would be if it couldn’t nucleate ice at all. “The ones that are not ice-nucleation active have a little more trouble getting out,” Morris says. From a microbe’s perspective, she explains, the atmosphere is like a subway system. “There are people there all the time, but the metro is not a place to live—it’s a place to move.”
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By Michael Segal
Chiara Mingarelli has a pretty sweet gig. As the Marie Curie Fellow at Caltech, Mingarelli gets to hunt for gravity waves down the hall from some of the luminaries in the field. She was there when the recent, historic detection...READ MORE
If Earth’s atmosphere is a microbial metro, it’s an especially brutal one, and commuters have evolved various means to survive the trip. Some, like the B. pumilus cells in the NASA balloon, form endospores. “Sporulation is like hibernation for bacteria,” Smith says. “They shrivel down, dehydrate all of their innards, and wrap their DNA. They remain in that state until water and nutrients arrive, and then they flip the switch and germinate, and go on living.”
Other longest-distance travelers sequester themselves in protective dust plumes. Researchers have collected deposits of African dust from all over the world, and “they’re just loaded with microbes,” Schmale says. Shade from dust can cut UV radiation by half. And as the plumes cross water bodies, they pick up particulates such as pieces of algae or phytoplankton, which “can provide wetting, moist environments for microbial populations to sustain viability as they trek across the ocean.”
Microbes can also make a temporary home in clouds. Atop the 5,000-foot peak of Puy de Dôme, in central France, microbial ecologist Pierre Amato sucks up cloud water with a droplet impactor—“a vacuum cleaner, basically,” he says. He then takes the samples back to his lab at the National Center for Scientific Research, in Aubière, where he extracts living bacteria and cultures them in flasks. Some specimens can subsist on formaldehyde and other organic compounds commonly found in cloud water, suggesting they can metabolize, and perhaps even reproduce, in clouds. “They eat some very strange things,” he says.
The most successful cloud-squatters, Amato has found, are bacteria that spend their terrestrial lives on plants—no surprise, he says, considering that these species are well-adapted to life on the surface of a leaf, where light, temperature, and humidity change rapidly, as they do in a cloud. Many of these organisms have also evolved protections against UV radiation: pigments that act as sunscreens, for instance, or the ability to rapidly repair their own DNA.
Where these widespread adaptations first arose is an open question. Did microbes hone their survival skills on the ground and then use them to take to the skies? Or vice versa? Smith, for one, argues that the arduous conditions of the upper atmosphere likely provided a selective pressure that drove terrestrial life to be as robust as it is. “Think about trillions upon trillions of tiny cells continuously passing through the Earth’s deadly upper atmosphere for billions of years,” he says. “In that framework, evolved resistance to environmental extremes seems almost inevitable.”
Take Antarctica’s ice sheets. Some of the most hostile places on Earth, they were once thought to be devoid of life. Yet in the past decade, scientists have discovered microbial species living on and in the ice, and in lakes buried below. “These microbes might not be growing actively—they might just be frozen in suspended animation—but as the climate changes and as these places melt, and as surface water starts to form, you may well see them metabolizing and reproducing,” says David Pearce, a microbiologist at Northumbria University in the United Kingdom who is part of an international collaboration to survey microbial diversity over Antarctica. Many ice dwellers, Pearce suspects, probably arrived on the winds: When he and his colleagues analyzed microbial DNA from air samples over a remote research station, they found that almost half of the airborne explorers not associated with human activity had likely originated from soils and other terrestrial sources on other continents. (Incredibly, some of these strains have also been found in spacecraft assembly rooms.)
“The upper atmosphere acts like a pre-selection filter,” Pearce says—it ensures that only the hardiest individuals disperse to colonize Earth’s remotest and most barren outposts.
The same might be said for other worlds. If the rigors of air travel can prepare microbes to thrive in Antarctica, why not the atmosphere of Venus, where relatively mild temperatures and pressures may be able to sustain Earthly life? Or the surface of Mars, where conditions aren’t so different from Earth’s upper atmosphere? If microbes like B. pumilus can survive the stratosphere, Smith says, they may be able to persevere long enough on the Martian surface to establish themselves in a more hospitable spot, such as underground, “where it might be warmer and wetter.” His team is still analyzing results from the balloon mission, but he says they seem “consistent” with what’s already known about these super-survivors, which have endured stratospheric simulation chambers and once lived for 18 months outside the International Space Station while shaded from UV light.
How Earth life might get to other planets is a matter of much debate. Airborne cells can’t reach escape velocities great enough to break free of Earth’s gravitational pull. Nor have scientists come up with a convincing explanation of how they would survive the long transport times and lethal radiation levels in deep space. But that hasn’t stopped astrobiologists from musing about panspermia, the hypothesis that life spreads throughout the universe via meteors and other cosmic vehicles—like, say, spacecraft.
For NASA, this is a very real, and troubling, possibility. The agency has identified hundreds of bacterial strains like B. pumilus that have outlived spacecraft sterilization procedures such as peroxide baths, heat shock, and UV radiation. What would happen if these or other hardy microbes stowed away in a dark crevice on a lander, or latched on as it passed through Earth’s atmosphere?
“These organisms are really very robust,” Morris says, “and they are going places.” All they need is a lift.
Chelsea Wald is a science writer in Vienna, Austria, who writes often for Nautilus.
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