Science
Vesuvius Erupted, but When Exactly?
When Mount Vesuvius erupted in A.D. 79, fiery avalanches of ash and pumice assaulted Pompeii, displacing some 15,000 inhabitants and killing at least 1,500 more. Volcanic debris “poured across the land,” wrote the Roman lawyer Pliny the Younger, and blanketed the town in a darkness “like the black of closed and unlighted rooms.” Within two days Pompeii had vanished, leaving little more than a legend until 1748, when the chance discovery of a water line prompted the first deliberate excavation.
In his late-18th-century travelogue “Italian Journey,” Goethe observed that no calamity in history had given greater entertainment to posterity than the eruption that had buried Pompeii. For scholars and armchair archaeologists, that entertainment has involved wrangling over pretty much every facet of the disaster. They still can’t agree on the day Vesuvius blew its top, the height of the umbrella-shaped cloud or the length and the aggression of the blasts. Two new research projects add kindling to those embers.
A report published by the Archaeological Park of Pompeii resurrected the once widely accepted belief that the cataclysm began to unfold on Aug. 24, the date put forward by Pliny, who was 17 when he witnessed the event from a villa across the Bay of Naples. His letters to the historian Tacitus, written more than 25 years after the fact, are the only surviving firsthand account and the only documents that offer a precise date.
We no longer have the original letters, only translations and transcriptions of copies, the first of which was made in the fifth century A.D. “Many manuscripts of Pliny’s letters came down to us with differing dates,” said the classicist Daisy Dunn. Her 2019 biography of Pliny, “The Shadow of Vesuvius,” is the definitive guide to him and his uncle, the naturalist Pliny the Elder, who died during the eruption. “Aug. 24 was chosen as the most secure on textual grounds,” Dr. Dunn said.
In sticking by Pliny, the park walked back some of the recent enthusiasm for Oct. 24 as a possible start date for the eruption, a theory that had been fueled by the 2018 discovery of a scrap of graffiti on a wall of the site’s freshly excavated House of the Garden. The charcoal scrawl records a date that translates to Oct. 17 in the modern calendar, suggesting that the eruption might have occurred after this time. The find, which did not specify a year, seemed to corroborate other unearthed clues that pointed to cooler weather than is typical in August: remnants of unripe autumnal fruits such as chestnuts and pomegranates; heavy wool clothing found on bodies; wine in sealed jars, indicating that the grape harvest was over; and wood-burning braziers in homes.
Massimo Osanna, general director of the park at the time of the discovery, was convinced that the graffiti was idly doodled a week before the explosion. “This spectacular find finally allows us to date, with confidence, the disaster,” he said. Dr. Dunn found it improbable that Pliny would have forgotten such a momentous date; still, she said, “in my view, the traditional date of Aug. 24 is just too early in the year to be accurate.”
The dating game
The park’s recent about-face from October to August relied in part on a forensic analysis of Pliny’s letters by Pedar Foss, a classicist at DePauw University in Indiana. For his 2022 book, “Pliny and the Eruption of Vesuvius,” Dr. Foss examined 79 early hand-copied manuscripts of the letters and mapped out how textural errors had been compounded. He concluded that a simple scribal mistake, made in the 1420s, of switching a “u” for an “n” had resulted in an incorrect eruption date of Nov. 1. The error appeared in the second print edition of Pliny’s letters, in 1474, and gave rise to further misreadings, misunderstandings and misuses.
By the 20th century, seven different possibilities were in circulation — eight, counting Nov. 9, which Mark Twain casually proposed in “Innocents Abroad,” his 1869 travel narrative. “Those many options gave the appearance of doubt concerning what Pliny actually wrote but, upon examination, I was able to explain away each of the mistaken alternatives,” Dr. Foss said.
He also explained away each of the archaeological alternatives to Aug. 24, some of which he believes fail based on the evidence; some, on the basis of faulty reasoning. He argued that the pomegranate rinds were used for dyeing, not eating; that the Romans commonly used braziers for cooking, not just heating; that wool clothing was standard gear for Roman firefighters; and that Roman agricultural and storage practices allowed for the preservation of fruits beyond their natural harvest seasons.
As for the House of the Garden doodle, on Oct. 12, 2023, researchers commissioned by Dr. Osanna’s successor, Gabriel Zuchtriegel, left their own charcoal message on the same wall on which the graffito appeared. Ten months later — on Aug. 24, 2024 — the text was still perfectly legible. “The inscription could have been put on the wall during October of any number of previous years,” Dr. Foss said.
So much for dating the disaster with confidence.
Letting off steam
Claudio Scarpati, a volcanologist at the University of Naples Federico II, favors the traditional date. “In my mind, the eruption occurred in August, on a sunny day,” he said. Dr. Scarpati is the lead author of two recent studies of the catastrophe published in The Journal of the Geological Society. One offered an hour-by-hour reconstruction, extending the chronology from the previously estimated 19 hours to 32 hours. The other revealed a dynamic sequence with 17 distinct “pyroclastic density currents,” many of them previously undocumented.
Pyroclastic currents are hot, swift-moving mixtures of volcanic particles — ash, pumice lava fragments and gas — that flow according to their density in relation to the surroundings. Dr. Scarpati said that contrary to popular belief, Pompeians were neither entombed by molten lava nor poisoned by gas. “No lava reached Pompeii, and the gas was predominantly vaporized water and, to a lesser extent, carbon dioxide,” he said. “According to our studies, the victims died primarily from asphyxiation caused by inhaling ash.”
To measure the distribution and the volume of the ash and the pumice layers, the team measured the thickness of the single layers over a 775-square-mile area around Mount Vesuvius. The deposits recorded dramatic, increasingly violent pulses from the volcano.
At noon on Day 1, Vesuvius began to eject a plume of rocky volcanic fragments and gas into the air, known as an eruption column. The mushroom cloud that Pliny observed at 1 p.m. was typical of what is now known as a Plinian eruption, in tribute to his richly detailed testament.
Dr. Scarpati said that the first currents had flowed to the town of Herculaneum, west of Vesuvius, bringing intense heat that essentially roasted inhabitants and, in one documented case, turned human tissue into glass, a process known as vitrification. At Pompeii, south of the volcano, the currents were cooler, and only the final eight penetrated the town.
During the first 17 hours, Dr. Scarpati said, Pompeii was blanketed with pumice lapilli from the column, which fluctuated like a giant fountain through 12 distinct pulses. At 2 p.m., the volcano began to spew pumice mixed with gas. Over the next four hours, roofs began to cave in under the weight of the pumice lapilli, causing some supporting walls to crumble as well. After 17 hours, the debris in Pompeii was up to nine feet thick. Enough was ejected to bury Manhattan roughly 450 feet, or 45 building stories, deep.
The eruption peaked when the column reached its maximum height of 21 miles, at about 1 a.m. on Day 2. “The column rose as long as its density was lower than that of the air, like a balloon,” Dr. Scarpati said. At daybreak, enormous amounts of fine ash and pumice collapsed the eruptive column, forming pyroclastic currents.
During a brief lull, Pompeians presumably tried to flee the town. Then, just after 7 a.m., the 13th and most lethal current struck — a thick concoction of ash was disgorged for nine hours, spreading detritus 16 miles across the plain and into the Lattari Mountains. In Pompeii, many victims of the volcano were found in the streets encased in this layer.
Around 4 p.m., the magma in the volcano’s conduit interacted with groundwater, causing the magma to break up into fine ash. No human remains were found in any of the layers after the 13th, suggesting to Dr. Scarpati that the morning’s devastation left no survivors. The eruption ceased at 8 p.m.
Paul Cole, a volcanologist at the University of Plymouth in England who was not involved with the project, said, “The work places a finer timeline on the events of 2,000 years ago, and also provides fresh evidence for how the hazard from such large, explosive eruptions can change even during the event.”
Rumpus involving Vesuvius may go on endlessly, but unlike Pliny’s letters, the geological history of the eruption seems to have been written in stone.
WASHINGTON — NASA recaptured the world’s attention with Artemis II, which took astronauts to the moon and back for the first time in half a century. But the agency’s scientific projects could again be under threat as the Trump administration makes a renewed push to drastically cut their funding — including at the Jet Propulsion Laboratory.
The cuts, proposed in the Trump administration’s 2027 budget request to Congress, would pose further challenges to the already weakened Caltech-managed lab and could be broadly damaging to American efforts to bring back new discoveries from space. They echo last year’s attempt by the administration to slash NASA funding, which Congress rejected.
Though the Artemis project is billed as laying a foundation for a crewed NASA mission to Mars, exploration of the Red Planet is among the endeavors that could be slashed. The rover currently exploring Mars’ ancient river delta and a mission to orbit Venus are among projects with JPL involvement targeted for spending cuts, according to an analysis of the NASA budget proposal by the nonprofit Planetary Society.
“This isn’t [because] they’re not producing good science anymore. There’s no rhyme or reason to it,” said Casey Dreier, chief of space policy at the Planetary Society, which led opposition to the administration’s similar effort to cut NASA funding last year.
Storm clouds hang over the Jet Propulsion Laboratory on Feb. 7, 2024.
(David McNew / Getty Images)
This time, the administration is asking Congress to cut NASA funding by 23% — including a 46% cut to its science programs, which are responsible for developing spacecraft, sending them into outer space to observe and analyzing the data they send back.
The proposal would cancel 53 science missions and reduce funding for others, according to the Planetary Society analysis. The effort to pare down NASA Science comes amid the Trump administration’s broader effort to cut scientific research across federal agencies.
The plan swiftly drew bipartisan criticism from members of Congress, who rejected the administration’s similar 2026 proposal in January. Republican Sen. Jerry Moran of Kansas, who chairs the Senate appropriations subcommittee that oversees NASA, indicated last week that he would work to fund NASA similarly for 2027, saying it would be “a mistake” not to fund science missions.
Moran plans to hold a hearing with NASA Administrator Jared Isaacman before the end of April to review the budget request, a spokesperson for his office said. The president’s budget request is an ask to Congress, which ultimately holds the power to allocate funding.
But until Congress creates its own budget, NASA will use the plan as its road map, which could slow grants and contracts. The proposal “still creates enormous chaos and uncertainty in the meantime for critical missions, the scientific workforce, and long-term research planning,” said Rep. Judy Chu (D-Monterey Park), whose district includes JPL.
A NASA spokesperson declined to comment Friday. In the budget request, Isaacman wrote that NASA was “pursuing a focused and right-sized portfolio” for its space science missions in order to align with Trump’s federal cost-cutting goals.
The budget “reinforces U.S. leadership in space science through groundbreaking missions, completed research, and next-generation observatories,” Isaacman wrote.
Jared Isaacman testifies during his confirmation hearing to be the NASA administrator in the Russell Senate Office Building on Capitol Hill on Dec. 3, 2025.
(Anna Moneymaker / Getty Images)
At JPL — which has for decades led innovation in space science and technology from its La Cañada Flintridge campus — questions had already swirled about the lab’s role in the future of NASA work.
Multiple rounds of layoffs over the last two years, the defunding of its embattled Mars Sample Return mission and a shift by the Trump administration toward lunar exploration and away from the type of scientific work that JPL executes had pushed the lab into a challenging stretch.
It has had a steady stream of employee departures in recent months, and those left have been scrambling to court outside funding from private investors, sell JPL technology to companies and increase productivity in hopes of keeping the lab afloat, according to two former staffers, who requested anonymity to describe the mood inside the lab.
“If we’re not doing science, then what are we doing?” asked one former employee, who recently left JPL after more than a decade there.
A spokesperson for the lab declined to comment, referring The Times to the budget proposal.
The NASA programs marked for cancellation or cutbacks support thousands of jobs at JPL and other centers, said Chu, who has led a push for increased funding for NASA Science. After last year’s layoffs, JPL “cannot afford to lose more of this expertise,” she said in a statement.
Among the JPL projects that appear to be slated for cancellation are two involving Venus, Dreier said. One, Veritas, is early in development and would give work to the lab for the next several years, he said.
The project would be the first U.S. mission to Venus in more than 30 years, Dreier said, and aims to make a high-resolution mapping of the planet’s surface and observe its atmosphere.
The Perseverance rover, which is on Mars collecting rock and soil samples, could face spending reductions. The budget request proposes pulling some funding from Perseverance to fund other planetary science missions and reducing “the pace of operations” for the rover.
Though how the Mars samples might get back to Earth is uncertain, the rover is still being used to explore the planet and search for evidence of whether it could have ever been habitable to life.
Researchers hope the tubes of Martian rock, soil and sediment can eventually be brought back to Earth for study. The team has about a half a dozen more sample tubes to fill and the rover is in good shape, said Jim Bell, a planetary scientist and Arizona State University professor who leads the camera team on Perseverance, which works daily with JPL.
He said NASA’s spending proposal put forth “no plan” for the future of the agency’s work.
“Are people just supposed to walk away from their consoles,” Bell asked, “and let these orbiters around other planets or rovers on other worlds — just let them die?”
The NASA document did not clearly show which programs were targeted for cuts and did not list which projects were targeted for cancellation. The Planetary Society and the American Astronomical Society each analyzed the proposal and found that dozens of projects appeared to be canceled without being named in the document.
Across NASA, other projects slated for cancellation according to the Planetary Society’s analysis include New Horizons, a spacecraft exploring the outer edge of the solar system; the Atmosphere Observing System, a planned project to collect weather, air quality and climate data; and Juno, a spacecraft studying Jupiter.
The administration’s plan also doesn’t prioritize new scientific projects, Bell said, which further jeopardizes long-term job stability and space discovery at centers like JPL.
“We’re going through this long stretch now with very few opportunities to build these spacecrafts,” Bell said. “All of the NASA centers are suffering from the lack of opportunities.”
Last year, the Trump administration proposed to slash NASA’s 2026 funding by nearly half. Instead, Congress approved funding in January that provided $24.4 billion for the agency — a cut of about 29% rather than the proposed 46%. The 2027 budget request asks for $18.8 billion.
Congress kept funding for science missions nearly steady, allocating $7.25 billion for science missions, about a 1% decrease from 2025. The administration had proposed cutting the science investment down to $3.91 billion. This time, the budget requests $3.89 billion.
Under the Trump administration, NASA has put an emphasis on moon exploration, including this month’s successful Artemis II mission. Isaacman, who defended the proposed cuts on CNN last week, touted the agency’s lunar plans, including a project to build a base on the moon.
The agency has indicated commitment to some existing science missions, including the James Webb Space Telescope, the to-be-launched Nancy Grace Roman Space Telescope, the Dragonfly spacecraft set to launch for Saturn’s moon in 2028, and other projects.
“NASA doesn’t have a topline problem, we just need to focus on executing and delivering world-changing outcomes,” Isaacman said on CNN.
Scientists have urged the government not to choose between funding science and exploration but to keep up investment in both.
“It’s ultimately kind of confusing, especially on the heels of the Artemis II mission,” said Roohi Dalal, deputy director for public policy at the American Astronomical Society. “The scientific community … is providing critical services to ensure that the astronauts are able to carry out their mission safely, and yet at the same time, they’re facing this significant cut.”
After years of heated debates among fire officials, scientists and local advocates, California’s Board of Forestry and Fire Protection released new proposed landscaping rules for fire-prone areas Friday that outline what residents can and can’t do within the first 5 feet of their homes.
Many of these proposed rules — designed to reduce the risk of a home burning down amid a wildfire — have wide support (or at least acceptance); however, the most contentious by far has been whether the state would allow healthy plants in the zone.
Many fire officials and safety advocates have essentially argued anything that can burn, will burn and have supported removing virtually anything capable of combustion from this zone within 5 feet of houses, dubbed “Zone Zero.” They point to the string of devastating urban wildfires in recent years as reason to move quickly.
Yet, researchers who study the array of benefits shade and extra foliage can bring to neighborhoods — and local advocates who are worried about the money and labor needed to comply with the regulations — have argued that this approach goes beyond what current science shows is effective. They have, instead, generally been in favor of allowing green, healthy plants within the zone.
The new draft regulations attempt to bridge the gap. They outline more stringent requirements to remove all plants in a new “Safety Zone” within a foot of the house and within a bigger buffer around potential vulnerabilities in a home’s wildfire armor, including windows that can shatter in extreme heat and wooden decks that can easily burst into flames. Everywhere else, the rules would allow residents to maintain some plants, although still with significant restrictions.
The rules generally do not require the removal of healthy trees — instead, they require giving these trees routine haircuts.
Once the state adopts a final version of the rules, homeowners would have three years to get their landscaping in order and up to five years for the bigger asks, including removing all vegetation from the Safety Zone and updating combustible fencing and sheds within 5 feet of the home. New constructions would have to comply immediately.
The rules only apply to areas with notable fire hazard, including urban areas that Cal Fire has determined have “very high” fire hazard and rural wildlands.
Officials with the Board will meet in Calabasas on Thursday from 1 p.m. to 7 p.m. to discuss the new proposal and hear from residents.
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Some L.A. residents are championing a proposed fire-safety rule, referred to as “Zone Zero,” requiring the clearance of flammable material within the first five feet of homes. Others are skeptical of its value.
Where is the Safety Zone?
The proposed Safety Zone with stricter requirements to remove all vegetation would extend 1 foot from the exterior walls of a house.
In a few areas with heightened vulnerabilities to wildfires, it extends further.
The Safety Zone covers any land under the overhang of roofs. If the overhang extends 3 feet, so does the Safety Zone in that area. It also extends 2 feet out from any windows, doors and vents, as well as 5 feet out from attached decks.
What plants would be allowed in the Safety Zone?
Generally, nothing that can burn can sit in the Safety Zone. This includes mulch, green grass, bushes and flowers.
What plants would be allowed in the rest of Zone Zero?
Homeowners can keep grasses (and other ground-covers, like moss) in this area, as long as it’s trimmed down to no taller than 3 inches.
The rules also allow small plants — from begonias to succulents — up to 18 inches tall as long as they are spaced out in groups. Residents can also keep spaced-out potted plants under this height, as long as they’re easily movable.
What about fences, trees and gates?
Any sheds or other outbuildings would need noncombustible exterior walls and roofs in Zone Zero — Safety Zone or not.
Residents would have to replace the first five feet of any combustible fencing or gates attached to their house with something made out of a noncombustible material, such as metal.
Trees generally would be allowed in Zone Zero. Homeowners would need to keep any branches one foot away from the walls, five feet above the roof and 10 feet from chimneys.
Residents would also have to remove any branches from the lower third of the tree (or up to 6 feet, whichever is shorter) to prevent fires on the ground from climbing into the canopy.
Some trees with trunks directly up against a house in this 1-foot buffer or under the roof’s overhang might need to go — since keeping branches away from the home could prove difficult (or impossible).
However, the board stressed it wants to avoid the removal of trees whenever feasible and encouraged homeowners to work with their local fire department’s inspectors to find case-by-case solutions.
What’s new and what’s not
Some of the rules discussed in Zone Zero are not new — they’ve been on the books for years, classified as requirements for Zone One, extending 30 feet from the home with generally less strict rules, and Zone Two, extending 100 feet from the house with the least strict rules.
For example, homeowners are already required to remove any dead or dying grasses, plants and trees. They also have to remove leaves, twigs and needles from gutters, and they already cannot keep exposed firewood in piles next to their house.
Residents are also already required to keep grasses shorter than 4 inches; Zone Zero lowers this by an inch.
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