An environmental threat of very real proportions concerns celestial objects such as asteroids that hit the Earth—as everyone knows, one did in the dinosaurs. The same applies in a less dangerous but more frequent manner to unwanted “de-orbiting” of artificial satellites, and to the careless discarding of the boosters used to get them aloft.
As to the first, debris left over from the formation of the solar system pummels our planet on a constant basis—we call these asteroid or comet fragments meteors when they burn up in the atmosphere and meteorites if they hit the ground. As to human-made space debris that can fall to our planet’s surface, “More than 1,000 rocket bodies are estimated to have uncontrollably re-entered the atmosphere in the past 30 years,” according to New Scientist.
Last April, a piece of such artificial space debris, reportedly from a Chinese Long March rocket, hit near a village in India. Two years earlier a part of another Chinese rocket landed in a village in Ivory Coast. No one was harmed in either incident. And readers of a certain age will remember Skylab, the first space station, which fell from orbit in 1979, scattering debris over Western Australia and the Indian Ocean.
Skylab weighed 100 tons and would have caused real damage if it had landed in a populated area. The last few weeks of its existence were met with a worldwide response finding humor in the event—painting rooftop targets, for instance—as technicians desperately succeeded in using the huge satellite’s fuel reserves to wrest it to a safe demise.
But in fact had Skylab landed in Mombasa or Mumbai or Quito, the death toll would have been unimaginable. Because most satellites orbit near the equator and not high up, their debris when atmospheric drag forces them down can land on the largely poor countries of the tropical zone, raising a real environmental justice issue.
So far there have been no casualties from falling artificial space objects, but there are bound to be. Rocket launches have, well, skyrocketed, escalating to well over one hundred per year, and many loft multiple satellites. Scientists at University of British Columbia, New Scientist reports, calculate that the odds are one in ten of “casualties being caused by falling debris over the next decade.”
How can at-risk societies fight back? According to Ram Jakhu of McGill University in Montreal, the United Nations Liability Convention of 1972 comes into play here. The convention has only been used once in this manner, when Ottawa won $2.3 million from the Soviet Union after one of its satellites crashed in Canada in 1978. “I have no doubt there is going to be another serious incident,” according to Jakhu. “There’s a strong probability of hurting somebody or damage to property.”
There is a solution: an international agreement or arrangement such that rocket boosters and satellites contain sufficient surplus fuel—a rounding error in their total mission costs—so they can be brought down safely or be put into a benign orbit. These sort of “best practices” would be easy to put into place on a voluntary basis or by making the liability convention’s provisions dissuade slackers—sort of an astronomic Superfund. It’s not rocket science.
Chances are you won’t have a satellite fall on your head. But humans have in fact been injured by pieces of meteors entering Earth’s atmosphere or by the flash and shock waves they produce. There was the 2013 event in Siberia, mirroring a much more destructive meteorite that hit an uninhabited region in that wilderness in 1908. The recent event did hospitalize people and cause property damage. And it was caught on video by numerous observers.
According to an account on Space.com, the “meteor was a small asteroid—about the size of a six-story building—that broke up over the city of Chelyabinsk, Russia. . . . The blast was stronger than a nuclear explosion. . . . The shock wave it generated shattered glass and injured about 1,200 people.” But, as the Daily Beast reports, “Perhaps the most disconcerting thing about it aside from the damage and injuries it caused to the city was that it went largely undetected by astronomers and asteroid surveyors on the ground.”
In 2002 a small asteroid large enough to cause mass casualties should it hit Earth was given “about a 1 in 9,300 chance of an impact in 2049,” Wikipedia relates. Compare such a risk estimate, in which large swaths of humanity are seemingly at stake, with the response we give to the excess cancers expected at Superfund sites. The asteroid was later found to be benign, but it was a wakeup call to events that are low probability but high impact.
Three years later, Congress mandated that NASA monitor all Near Earth Objects of a dangerous size. In 2016, the Daily Beast notes, “NASA launched the Planetary Defense Coordination Office to identify and respond to any potential comet or asteroid impact endangering Earth.” But, “The task remains undone.”
Just in case, in September NASA impacted a refrigerator-size satellite into an asteroid as big as the Great Pyramid at Giza in an attempt to alter its path. “The target was Dimorphos, a rock orbiting another, much larger asteroid called Didymos,” according to the Washington Post. Scientists picked such a pair because it would be easy to evaluate the effect on the smaller space rock’s trajectory. And Dimorphos was not in danger of hitting Earth, nor could the collision produce a dangerous orbit.
—Stephen R. Dujack
A longstanding problem for solar farms has a surprisingly cute solution. “Sheep are the solar industry’s lawn mowers of choice,” writes Amrith Ramkumar in the Wall Street Journal. Farmers maintaining thousands of acres of panels need to contend with tall grasses, which, unabated, can obstruct sunlight. Enter the star of nursery rhymes and an unexpected hero of renewables. Hard-working flocks are now generating millions of dollars in annual revenue by helping to chomp on pesky weeds.
Many grazing animals were initially considered for the role. But some, like cows and horses, were too tall to tidy up grass underneath low-hanging panels. Others, like goats, strayed from the assignment—“chewing on wiring and climbing on equipment,” Ramkumar writes. “Sheep—docile, ravenous, and just the right height—easily smoked the field.”
The recent boom in solar has unexpectedly shot up demand for shepherds, “centuries after [their] breakout roles in the Bible,” Ramkumar writes. He reports that in just four short years, an estimated five thousand acres of solar fields employing sheep in the United States has now grown to tens of thousands, though there doesn’t appear to be an official head count yet.
Finding enough sheep has posed challenges. The Journal notes that while some advanced courses for solar grazing are offered through North Carolina State University and Cornell University, entry-level classes are scarce. Meanwhile, shepherds are already taking out loans to buy more sheep. One shepherd interviewed by Ramkumar spent $500,000 to purchase additional ewes to secure a contract with an energy farm.
The American Solar Grazing Association, a society that this editor is delighted to find exists, touts many other perks for the practice beyond clearing grass. “Solar grazing contributes dairy, meat, and wool to regional markets,” the group’s website notes. “Farm incomes are down, and solar grazing allows farmers to increase and diversify revenues without taking land out of food production.”
The sheep reap benefits too. “The vegetation at solar sites becomes a source of nutrition and a pasture” for these “resourceful foragers,” who “enjoy the shade of the solar panels on hot days, napping and grazing where humans would struggle to reach,” the association notes. “Some of the animals like being petted while they graze,” notes the Journal—adding up to a seemingly ideal workday for these high-in-demand flocks.
The phenomenon brings full circle the use of once arable farmland now occupied by solar panels. From up above, grazing sheep look like fluffy white clouds slowly moving under huge, sleek mirrors. Just like old times, shepherds use dogs to fend off predators and herd the sheep when necessary. They haul in food, pump water, and even set up enclosures for the sheep to sleep in. For those in the business of renewable energy and sheep, “It’s changing all of our lives,” says farmer Ely Valdez.
Notice & Comment is the editors’ column and represents each writer’s views.
Greenhouse Carbon Dioxide Now Legally an “Air Pollutant”
When the Supreme Court restricted the ability of the Environmental Protection Agency to fight climate change this year, the reason it gave was that Congress had never granted the agency the broad authority to shift America away from burning fossil fuels.
Now it has.
Throughout the landmark climate law, passed this month [August], is language written specifically to address the Supreme Court’s justification for reining in the EPA, a ruling that was one of the court’s most consequential of the term. The new law amends the Clean Air Act, the country’s bedrock air-quality legislation, to define the carbon dioxide produced by the burning of fossil fuels as an “air pollutant.”
That language, according to legal experts as well as the Democrats who worked it into the legislation, explicitly gives the EPA the authority to regulate greenhouse gases and to use its power to push the adoption of wind, solar, and other renewable energy sources.
—New York Times
In 2020 and 2021 alone, the world added 464 gigawatts of wind and solar power-generation capacity, which is more power than can be generated by all the nuclear plants operating in the world today.
—Farhad Manjoo in
the New York Times
Dodging Falling Rockets and Errant Minor Asteroids.