University of Bern simulations and ESA Hera observations point to one non-destructive asteroid impact as the source of Deimos’ southern depression and dusty surface.
The post A Single Asteroid Impact May Have Shaped Mars’ Moon Deimos appeared first on Curiosmos.
Dr. Stephen Kane from the University of California, Riverside and colleagues offer a tidy explanation for one of the Solar System’s enduring puzzles: why Venus, so similar to Earth in size and mass, has no moon at all.
The post New Study Explains Why Venus Has No Moon appeared first on Sci.News: Breaking Science News.
In April, the world watched as four humans circled the Moon for the first time in over 50 years with NASA’s Artemis II mission. On Saturday, Sept. 19, the public is invited to look up again with NASA events across the country, including the International Observe the Moon Night celebration held at NASA’s Goddard Space Flight Center Visitor Center in Greenbelt, Maryland.
International Observe the Moon Night is an annual celebration that brings people together to learn about the Moon and explore our connection to Earth’s nearest celestial neighbor. Since the program began in 2010, people around the world have participated through lunar observations, hands-on activities, artwork, music, and more.
At NASA Goddard, this year’s celebration will highlight the agency’s ongoing exploration of the Moon, including the historic Artemis II mission. Visitors can peer behind the scenes to learn more about what it took to make Artemis II’s journey around the Moon a success and discover how Goddard scientists and engineers are helping advance our understanding of the Moon, solar system, and beyond.
The event will run from 6 p.m. to 9 p.m. EDT.
Throughout the event at NASA Goddard, visitors can take part in interactive hands-on activities, create artwork and crafts, and capture selfies at a photo kiosk. Telescopes will also be set up outside (depending on weather), giving attendees an opportunity to observe the Moon and other astronomical objects up close. Inside the Visitor Center, guests can even see a real Apollo 14 Moon rock on display.
The event will also offer a chance to learn more about the groundbreaking research happening at NASA Goddard as scientists work to unlock the secrets of the Moon with missions like the Lunar Reconnaissance Orbiter (LRO) and explore our solar system and the universe beyond.
International Observe the Moon Night at Goddard is free and family friendly. Registration is not required, although registering in advance will help the Visitor Center team plan for the event. The event will take place rain or shine, and free parking is available at the Visitor Center.
Additional event details, including registration, accessibility and other logistics: https://www.nasa.gov/goddard/visitor-center/events-and-programs/.
For people who cannot travel to Greenbelt, there are opportunities to participate in International Observe the Moon Night from all around the planet. Join lunar observers around the world by observing the Moon with friends and family, attending a virtual event or finding an event in your area. Learn more and register your participation at go.nasa.gov/ObserveTheMoon.
International Observe the Moon Night is sponsored by NASA’s LRO mission and the Solar System Exploration Division of NASA’s Goddard Space Flight Center, with support from many partners. The celebration is a way for people to pause and look up at our future destination, as NASA prepares for deep space missions to the Moon and beyond.
To learn about NASA’s Artemis program, visit:
https://www.nasa.gov/artemis
To learn about LRO, visit:
https://www.nasa.gov/lro
The Moon may have emerged largely intact within hours of the colossal impact that shaped its birth. Earth has an unusually large moon for a planet of its size and position in the solar system, yet scientists still do not fully understand how that companion came to exist. Now, researchers from the Southwest Research Institute [...]
The Solar System’s smallest planet has contracted by nearly 19 km (12 miles) across, as crater debris masked telltale wrinkles on its surface, according to new research led by the German Aerospace Center’s Institute of Space Research.
The post Mercury Has Shrunk Even More than Planetary Scientists Thought appeared first on Sci.News: Breaking Science News.
Mercury has been slowly shrinking for billions of years. But scientists studying the smallest planet in the solar system may have overlooked just how dramatic that transformation has been because some of the evidence has literally been buried.
A new study suggests Mercury’s battered, crater-covered surface has concealed a significant fraction of the faults created as the planet cooled and contracted. After accounting for those hidden geological structures, researchers estimate Mercury may have shrunk by as much as 7.2 miles (11.6 kilometers) in radius—up to 30% more than previous estimates based on the same tectonic record.
The findings could alter models of how Mercury’s interior evolved and raise an interesting possibility beyond the planet itself. For instance, scientists may also be underestimating how much other rocky worlds, particularly the Moon, have contracted.
“Combined with the contractional strain map from Broquet and Andrews-Hanna (2026a), we show that radial contraction may have been underestimated by 10%–30%,” researchers write. “Our radial contraction correction should be considered as a lower bound.”
In the study published in Geophysical Research Letters, researchers led by Dr. Gaku Nishiyama of the German Aerospace Center (DLR) examined a longstanding mystery in Mercury’s geology.
As a rocky planet loses heat, its interior contracts. Much like the skin of a drying fruit, the planet’s rigid exterior must accommodate a shrinking interior, producing faults and enormous cliff-like features known as lobate scarps, along with wrinkle ridges and other shortening structures.
Scientists therefore use the crustal shortening recorded by these structures as a geological ruler to determine how much Mercury has contracted.
The problem is that those structures aren’t distributed across Mercury the way scientists might expect.
If cooling caused the entire planet to contract, the resulting deformation should be comparatively widespread. Instead, previous mapping has revealed regions filled with large scarps alongside enormous areas where surprisingly few contractional structures have been identified.
Dr. Nishiyama and his colleagues investigated whether at least part of that discrepancy could be an illusion created by Mercury’s extraordinarily battered surface.
The researchers constructed a global map of Mercury’s surface roughness using topographic measurements acquired from NASA’s MESSENGER mission and a global digital terrain model produced from spacecraft imagery.
They then compared that roughness with previously cataloged tectonic structures.
Findings showed that fault scarps and other shortening structures were preferentially identified in smoother terrain, while rougher regions contained substantially fewer detectable structures. The relationship remained apparent across geographic scales extending to roughly 93 miles or about 150 kilometers.
That is counterintuitive because tectonic ridges themselves create topographic roughness. If roughness and plate movements were unrelated, areas with scarps might be expected to be slightly rougher than the surrounding terrain.
Instead, the researchers found the opposite.
One explanation is evident around relatively young impact craters such as Rachmaninoff. Large impacts blasted enormous quantities of debris across the surrounding landscape, producing thick blankets of material and secondary craters. In some locations, long tectonic structures appear to lose relief as they approach these deposits—consistent with the older structures being progressively hidden under impact material.
Other faults may still exist but become difficult to recognize against heavily cratered terrain. Once the surrounding topography becomes rough enough, a weathered ridge only a little higher than the background landscape can effectively disappear into the geological noise.
There is also a third possibility.
Heavily cratered regions may contain thick, porous layers of broken rock called regolith. During planetary contraction, some deformation could be absorbed as pores collapse rather than producing large faults visible from orbit. Alternatively, deformation could create faults too small for current observations to resolve. The researchers say available evidence cannot yet rule out that possibility.
Whatever mechanism is responsible, Dr. Nishiyama and his colleagues argue the relationship creates a systematic bias, where scientists see more evidence of contraction where Mercury’s surface makes that evidence easier to preserve and identify.
The team developed a correction using comparatively smooth regions, where tectonic structures appear less affected by this bias.
Applied to an earlier global estimate of 5.2 miles (8.3 kilometers) of radial contraction, the correction increased Mercury’s estimated shrinkage to roughly 7.2 miles or about 11.6 kilometers.
Depending on which tectonic structures are included, the researchers estimate surface roughness could have caused previous calculations to underestimate Mercury’s contraction by roughly 10% to 30%. They also caution that their corrected figure may itself represent a lower limit.
Ultimately, Mercury’s shrinking surface effectively records what has happened deep inside the planet.
The amount of contraction constrains how quickly Mercury lost heat, the thickness of its insulating regolith, the abundance of heat-producing elements, and even the composition and freezing history of its enormous metallic core. The revised estimate, for example, favors models involving a thinner regolith and lower sulfur content in Mercury’s core than some previous estimates.
Scientists may soon get a much sharper look.
The ESA-JAXA BepiColombo mission’s laser altimeter will eventually measure Mercury’s topography at scales as small as about 330 feet or 100 meters, possibly revealing geological relationships that MESSENGER could not resolve.
And Mercury may not be the only world whose geological record has been hiding in plain sight.
The Moon’s highlands are even rougher than Mercury’s cratered plains—by roughly 40% at the little-over 6-mile (10-kilometer) scale examined by the researchers. Yet evidence suggests the Moon contracted less than some thermal models estimate. If rough terrain similarly hides lunar faults, part of that difference might reflect structures scientists haven’t been able to see.
In other words, Mercury’s missing wrinkles may expose a wider problem in planetary geoscience. The more battered an ancient world becomes, the more effectively its later surface can erase the visible record of what happened before it.
“Investigating roughness alongside tectonic landforms may therefore refine our understanding of the lunar thermal evolution as well,” researchers conclude. “Mars could also be subject to this roughness effect, while topographic smoothing due to fluvial and aeolian processes may introduce more complex correlation between surface roughness and shortening structures.”
Study: Nishiyama, G., Broquet, A., Tosi, N., Preusker, F., Stark, A., Hussmann, H., & Hauber, E. “Underestimation of Planetary Contraction Due to Obscuration by Surface Roughness: The Case of Mercury.” Geophysical Research Letters 53, (2026).
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com
A new study using data from a space mission suggests that most of Mercury’s crustal magnetic fields can be explained by iron and other magnetized rocks in the crust responding to the planet’s weak present-day core magnetic field, rather than from an ancient field, as had been inferred previously. Mercury is the only solar-system planet other than Earth to possess both a global magnetic field arising from its core and a crustal magnetic field resulting from rocks that were magnetized in either the present-day or an ancient core field. Present-day (induced) magnetization reveals the location and amount of iron in the crust, whereas ancient (remanent) magnetization records the planet’s dynamo history.
NASA’s MErcury, Surface, Space ENvironment, GEochemistry and Ranging (MESSENGER) mission observed the planet in 2011–2015. Data from the mission are allowing scientists to explore the strength and distribution of Mercury’s magnetic field. During the mission, a last-minute decision was made “to reduce the orbit altitude thereby allowing crustal fields to be detected” explains Lon Hood at the Lunar and Planetary Laboratory at the University of Arizona. He has worked extensively on Mercury’s crustal magnetism using the MESSENGER data but was not involved in the new study.
Crustal magnetism was expected to be “partly due to remanent magnetization dating from the time when the crustal sources formed in the planetary magnetic field,” Hood says. This interpretation is drawn from earlier analyses of the mission data. But a key challenge in understanding the crustal magnetic field remained – how to delineate the contributions of induced and remanent magnetization. Separating the relative contributions of ancient and present-day induced magnetization on the crustal magnetic field can reveal new ways of understanding the spatial abundance of magnetic rocks, variations of magnetic properties of crustal minerals, and the dynamo history of Mercury.
The new study, led by Catherine Johnson at the University of British Columbia in Vancouver, uses field observations of Mercury’s crustal magnetic fields from MESSENGER to develop a magnetization model of the planet and identify sources of its magnetization. The researchers calculated the expected induced magnetization strength using the low-altitude observations with assumptions on the crustal thickness, magnetic mineralogy, iron content, and the present-day core field.
In line with previous studies, the researchers found that the largest magnetization strengths occur in the Caloris region, along with localized signals elsewhere. The spatial pattern of magnetization strength, however, does not consistently match the variation in near-surface iron content seen in MESSENGER spectroscopic data. Instead, magnetization strength correlates with crustal thickness, up to about 30 km, suggesting the magnetized rocks are concentrated within the upper part of the crust.
The researchers found that induced magnetization is relatively small, given the low iron content of the planet’s crust and its weak core field – about a hundred times weaker than Earth’s. Even so, they estimate that induced magnetization can fully account for the calculated magnetization strength across more than 85% of the area north of 38 °N. This assumes it extends through the crustal column to a depth of about 30 km, which means that no remanent magnetization is required to explain the observed crustal field over that majority of the mapped region. Areas where induced magnetization does not explain the observed crustal fields may be the result of iron delivered by ancient asteroid impacts, which would locally increase the induced magnetization. Elsewhere, a contribution from remanent magnetization may be required to explain the observed fields.
On Earth, the robust separation of induced and remanent magnetizations requires laboratory measurements of rock samples. For Mercury no such samples exist, so the magnetic properties of its crust must be inferred from satellite observations constrained by assumptions about the composition and magnetic behaviour of its rocks. The delineation in the new study depends on “assumptions about magnetic mineralogy that cannot be verified due to the lack of returned samples”, says Hood.
Better characterization of the crust’s low-field magnetic susceptibility – currently inferred from a limited number of laboratory measurements on meteorites and minerals believed to resemble Mercury’s crust – can advance our understanding of Mercury’s crustal fields. Better core-field models and higher-resolution iron maps from the European–Japanese BepiColombo mission could help. This mission comprises two spacecraft that launched in 2018 and is expected to run until 2029.
However, Hood says “there are no current plans for either spacecraft to approach near enough to the planet to detect or map more of the crustal magnetic field”. Although the spacecraft will eventually descend below 100 kilometres, giving us a first look at the southern hemisphere. Indeed, we may have a long wait before we have the complete picture because Hoods says, ” there are no plans to obtain samples of Mercury’s crustal rocks, which are needed to definitively determine the origin of the crustal magnetization”.
The researchers report their findings in PNAS.
The post Mercury may not need an ancient dynamo to explain its magnetic crust appeared first on Physics World.
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