NASA’s DART Mission Changed Orbit of Asteroid Didymos Around Sun - Jet Propulsion Laboratory

New research reveals that when NASA’s DART (Double Asteroid Redirection Test) spacecraft intentionally impacted the asteroid moonlet Dimorphos in September 2022, it didn’t just change the motion of Dimorphos around its larger companion, Didymos; the crash also shifted the orbit of both asteroids around the Sun. Linked together by gravity, Didymos and Dimorphos orbit each other around a shared center of mass in a configuration known as a binary system, so changes to one asteroid affect the other.

As detailed in a study published on Friday in the journal Science Advances, observations of the pair’s motion revealed that the 770-day orbital period around the Sun changed by a fraction of a second after the DART spacecraft’s impact on Dimorphos. That change marks the first time a human-made object has measurably altered the path of a celestial body around the Sun. 

The Hubble Space Telescope observed two tails of dust ejected from the Didymos-Dimorphos asteroid system several days after NASA’s DART spacecraft impacted the smaller asteroid.

NASA, ESA, Jian-Yang Li (PSI), Joe Depasquale (STScI)

“This is a tiny change to the orbit, but given enough time, even a tiny change can grow to a significant deflection,” said Thomas Statler, lead scientist for solar system small bodies at NASA Headquarters in Washington. “The team’s amazingly precise measurement again validates kinetic impact as a technique for defending Earth against asteroid hazards and shows how a binary asteroid might be deflected by impacting just one member of the pair.”

High impact

When DART struck Dimorphos, the impact blasted a huge cloud of rocky debris into space, altering the shape of the asteroid, which measures 560 feet (170 meters) wide. Because the debris carried its own momentum away from the asteroid, it gave Dimorphos an explosive thrust — what scientists call the momentum enhancement factor. More debris being kicked out means more oomph. According to the new research, the momentum enhancement factor for DART’s impact was about two, meaning that the debris loss doubled the punch created by the spacecraft alone.

Earlier research showed that the smaller asteroid’s 12-hour orbital period around the nearly half-mile-wide (805-meter-wide) Didymos shortened by 33 minutes. The new study shows the impact ejected so much material from the binary system that it also changed the binary’s orbital period around the Sun by 0.15 seconds.

“The change in the binary system’s orbital speed was about 11.7 microns per second, or 1.7 inches per hour,” said Rahil Makadia, the study’s lead author at the University of Illinois Urbana-Champaign. “Over time, such a small change in an asteroid’s motion can make the difference between a hazardous object hitting or missing our planet.”

Although Didymos was not on an impact trajectory with Earth and it was impossible for the DART mission to put it on one, that change in orbital speed underscores the role spacecraft — aka kinetic impactors in this context — could play if a potentially hazardous asteroid is found to be on a collision course in the future. The key is detecting near-Earth objects far enough in advance to send a kinetic impactor.

To that end, NASA is building the Near-Earth Object (NEO) Surveyor mission. Managed by NASA’s Jet Propulsion Laboratory in Southern California, this next-generation space survey telescope is the first to be built for planetary defense. The mission will seek out some of the hardest-to-find near-Earth objects, such as dark asteroids and comets that don’t reflect much visible light.

How they did it

To prove DART had a detectable influence on both asteroids — not just on the smaller Dimorphos — the researchers needed to measure Didymos’ orbit around the Sun to exquisite precision. So, in addition to making radar and other ground-based observations of the asteroid, they tracked stellar occultations, which occur when the asteroid passes exactly in front of a star, causing the pinpoint of light to blink out for a fraction of a second. This technique provides extremely precise measurements of the asteroid’s speed, shape, and position.

Measuring stellar occultations is challenging: Astronomers have to be in the right place at the right time with several observing stations, sometimes miles apart, to track the predicted path of the asteroid in front of a specific star. The team relied on volunteer astronomers around the globe who recorded 22 stellar occultations between October 2022 and March 2025.

“When combined with years of existing ground-based observations, these stellar occultation observations became key in helping us calculate how DART had changed Didymos’ orbit,” said study co-lead Steve Chesley, a senior research scientist at JPL. “This work is highly weather dependent and often requires travel to remote regions with no guarantee of success. This result would not have been possible without the dedication of dozens of volunteer occultation observers around the world.”

Studying changes in Didymos’ motion also helped the researchers calculate the densities of both asteroids. Dimorphos is slightly less dense than previously thought, supporting the theory that it formed from rocky debris shed by a rapidly spinning Didymos. This loose material eventually clumped together to form Dimorphos, a “rubble pile” asteroid.

More about DART

The DART spacecraft was designed, built, and operated by the Johns Hopkins Applied Physics Laboratory in Laurel, Maryland, for NASA’s Planetary Defense Coordination Office, which oversees the agency’s ongoing efforts in planetary defense. It was humanity’s first mission to intentionally move a celestial object.

For more information about the DART mission visit: https://science.nasa.gov/mission/dart/ 

Source: NASA’s DART Mission Changed Orbit of Asteroid Didymos Around Sun - NASA

A race against time to save Alpine ice cores that record medieval mining, fires, and volcanoes - Earth - Earth Sciences - Environment

Researchers of the Ca' Foscari University of Venice and the Austrian Academy of Science drill an ice core at Weißseespitze, Ötztal Alps, in 2018. Credit: Prof Andrea Fischer

Ice cores taken from glaciers reveal the air pollution of the past, using atmospheric particles incorporated in snow that fell on the glacier and became ice. Now, scientists have extracted a record of thousands of years' worth of air pollution from 9.5 meters of ice at the Weißseespitze glacier, close to the border between Austria and Italy. But this ice is under threat from global warming, and scientists warn that it is now a race against time to capture critical climate information locked in these glaciers before it's gone forever.

"These remarkable climate archives function much like a history book: past atmospheric conditions and environmental changes are recorded in their layers," said Dr. Azzurra Spagnesi of the University Ca' Foscari of Venice, lead author of the article in Frontiers in Earth Science.

"Alpine glaciers offer a unique opportunity to investigate the critical transition between pre-industrial and industrial times, because of their proximity to human settlements."

Frozen in time

In 2019, the team visited Weißseespitze and drilled down to the bedrock to take an ice core nearly 10 meters long. They used argon isotope data to estimate the age of its layers, showing that the surface of the glacier formed between 1552 and 1708 CE, while the deepest layer dated back to 349 BCE and 420 CE.

Then they analyzed the core for traces of 18 different elements, microcharcoal, levoglucosan—a chemical compound that forms when wood burns—and carboxylic and dicarboxylic acids.

The summit of Weißseespitze in 2023. The dark surface shows significant melting. Credit: Prof Andrea Fischer

"Between 700 and 1200 CE, lead and other metals showed very low concentrations, reflecting the regional background of a mostly unpolluted pre-industrial environment," explained Spagnesi. "From roughly 950 CE onward, peaks in arsenic, lead, copper, and silver appear, corresponding to periods of intensified medieval mining and smelting in the Alps and other European regions."

"Some of the strongest metal peaks also coincide with major volcanic eruptions, as well as periods of dry climate and increased dust transport," Spagnesi added. "This suggests that both natural events and human activities contributed to the chemical signals preserved in the ice."

The scientists found a striking peak in chemical pollution between approximately 902 and 1280 CE. They compared this to the levels of microcharcoal found in cores of peat taken from nearby swampy areas and found matching peaks, which confirms that fires were more common and more intense in this region during this period.

"The elevated fire signal we observe during the roughly century-long drought between about 950 and 1040 CE is likely the result of several interacting factors," said Spagnesi.

"Such dry conditions can promote cycles of vegetation growth followed by desiccation, creating highly flammable landscapes that are more prone to burning.

"At the same time, human activity in Alpine regions appears to have intensified. Historical and paleoenvironmental evidence points to increased grassland management, agricultural expansion, and land clearing, all of which commonly involved fire. Periods of conflict may have contributed locally, either through deliberate burning or accidental ignitions."

"However, although the age–depth scale was substantially improved by adding 39Ar dating to the radiocarbon constraints previously used, the remaining uncertainties are still relatively large," cautioned Spagnesi. "This makes it more challenging to link individual chemical peaks to specific events."

Melting away

At Weißseespitze, local mining and other human activities drove peaks in pollution, while natural factors like volcanoes amplified them. But anthropogenic emissions can only account for about 7% of the air pollution recorded in the ice core.

Emissions caused by humans appear as peaks against a comparatively stable, natural background—which is sadly not the case today.

The scientists have continued to return to Weißseespitze for research. But alarmingly, a visit to the drilling site in 2025 showed that the ice was now only 5.5 meters deep. Unless we act now to sample these disappearing glaciers, the information they carry will be lost.

"Glaciers in the Ötztal Alps are projected to disappear within the coming decades," said Spagnesi.

"If glaciers disappear, the chemical and physical information they contain will be lost forever, leaving gaps in our understanding of past climate variability. In this sense, preserving glaciers is not just about protecting ice. It is about safeguarding the memory of Earth's climate." 

Provided by Frontiers 

by Frontiers

edited by Sadie Harley, reviewed by Robert Egan 

Source: A race against time to save Alpine ice cores that record medieval mining, fires, and volcanoes