Analysis of Martian seismic data recorded by the InSight mission in combination with first-principles simulations of the seismic properties of liquid metal alloys have revealed that Mars’s liquid iron core is surrounded by a 150-km thick molten silicate layer, as a consequence of which its core is smaller than previously proposed. The decrease in core radius implies a higher density than estimated earlier and is compatible with a metal core consisting of 9–15 wt% of light elements, chiefly S, C, O, and H. Credit: Thibaut Roger, NCCR PlanetS, ETH Zurich
Mars is the second smallest planet in our solar system and the fourth planet from the sun. It is a dusty, cold, desert world with a very thin atmosphere. Iron oxide is prevalent in Mars' surface resulting in its reddish color and its nickname "The Red Planet." Mars' name comes from the Roman god of war.
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>Mars’s liquid iron core is smaller and denser than previously thought. Not only is it smaller, but it is also surrounded by a layer of molten rock. This is what ETH Zurich researchers conclude on the basis of seismic data from the InSight lander.
One year after the <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
NASA
Established in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. Its vision is "To discover and expand knowledge for the benefit of humanity." Its core values are "safety, integrity, teamwork, excellence, and inclusion." NASA conducts research, develops technology and launches missions to explore and study Earth, the solar system, and the universe beyond. It also works to advance the state of knowledge in a wide range of scientific fields, including Earth and space science, planetary science, astrophysics, and heliophysics, and it collaborates with private companies and international partners to achieve its goals.
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>NASA InSight Mission ended, the analysis of the recorded marsquakes, combines with computer simulations, is still yielding new findings.
An analysis of the initially observed marsquakes shows that the average density of the Martian core had to be significantly lower than that of pure liquid iron.
The new observations show that the radius of the Martian core has decreased from the initially determined range of 1,800–1,850 kilometers to somewhere in the range of 1,650– 1,700 kilometers.
Discovering Mars’ Interior: Insights from NASA’s InSight Lander
For four years, NASA’s InSight lander recorded tremors on Mars with its seismometer. Researchers at ETH Zurich collected and analyzed the data transmitted to Earth to determine the planet’s internal structure. “Although the mission ended in December 2022, we’ve now discovered something very interesting,” says Amir Khan, a Senior Scientist in the Department of Earth Sciences at ETH Zurich.
Mars’ Unique Silicate Layer
An analysis of recorded marsquakes, combined with computer simulations, paint a new picture of the planet’s interior. Sandwiched between Mars’s liquid iron <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
alloy
A mixture of two metallic elements typically used to give greater strength or higher resistance to corrosion.
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>alloy core and its solid silicate mantle lies a layer of liquid silicate (magma) about 150 kilometers thick. “Earth doesn’t have a completely molten silicate layer like that,” Khan says.
This finding, now published in the scientific journal Nature alongside a study led by Henri Samuel, Institut de Physique de Globe de Paris, that reaches a similar conclusion using complementary methods, also provides new information on the size and composition of Mars’ core, resolving a mystery that researchers have until now been unable to explain.
Mars’ Core Composition
An analysis of the initially observed marsquakes had shown that the average density of the Martian core had to be significantly lower than that of pure liquid iron. The Earth’s core, for example, consists of about 90 percent iron by weight. Light elements such as sulfur, carbon, oxygen, and hydrogen make up a combined total of around 10 percent by weight.
Initial estimates of the density of the Martian core showed that it is comprised of a much larger share of light elements – around 20 percent by weight. “This represents a very large complement of light elements, bordering on the impossible. We have been wondering about this result ever since,” says Dongyang Huang, a postdoctoral researcher in the Department of Earth Sciences at ETH Zurich.
The new observations show that the radius of the Martian core has decreased from the initially determined range of 1,800–1,850 kilometers to somewhere in the range of 1,650– 1,700 kilometers, which is about 50 percent of the radius of Mars. If the Martian core is smaller than previously thought but has the same mass, it follows that its density is greater and that it, therefore, contains fewer light elements. According to the new calculations, the proportion of light elements dropped to between 9 and 14 percent by weight.
“This means that the average density of the Martian core is still somewhat low, but no longer inexplicable in the context of typical planet formation scenarios,” says Paolo Sossi, Assistant Professor in the Department of Earth Sciences at ETH Zurich and member of the National Centres of Competence in Research (NCCRs) PlanetS.
The fact that the Martian core contains a significant amount of light elements indicates that it must have formed very early, possibly when the Sun was still surrounded by the nebula gas from which light elements could have accumulated in the Martian core.
Utilizing Distant Marsquakes
The initial calculations were based on tremors that had occurred in close proximity to the InSight lander. However, in August and September 2021, the seismometer registered two quakes on the opposite side of Mars. One of them was caused by a meteorite impact.
“These quakes produced seismic waves that traversed the core,” explains Cecilia Duran, a doctoral student in the Department of Earth Sciences at ETH Zurich. “This allowed us to illuminate the core.”
In the case of the earlier marsquakes, by contrast, the waves were reflected at the core-mantle boundary, providing no information about the deepest interior of the Red Planet. As a result of these new observations, the researchers have now been able to determine the density and seismic wave speed of the fluid core up to a depth of about 1,000 kilometers.
Quantum-Mechanical Supercomputer Simulations
To infer the composition of the material from such profiles, researchers usually compare the data with that of synthetic iron alloys containing different proportions of light elements (S, C, O, and H). In the lab, these alloys are exposed to high temperatures and pressures equivalent to those found in Mars’s interior, allowing researchers to measure density and seismic wave speed directly.
At the moment, however, most experiments are conducted at conditions prevailing in the Earth’s interior and are, therefore, not immediately applicable to Mars. Consequently, the ETH Zurich researchers resorted to a different method. They computed the properties of a wide variety of alloys using quantum-mechanical calculations, which they carried out at the Swiss National Supercomputing Centre (CSCS) in Lugano, Switzerland.
When the researchers compared the calculated profiles with their measurements based on the InSight seismic data, they encountered a problem. It turned out that no iron-light element alloys simultaneously matched the data at both the top and center of the Martian core. At the core-mantle boundary, for example, the iron alloy would have had to contain much more carbon than in the core’s interior.
“It took us a while to realize that the region we had previously considered to be the outer liquid iron core wasn’t the core after all, but the deepest part of the mantle,” explains Huang. In support of this, the researchers also found that the density and seismic wave speed measured and computed in the outermost 150 kilometers of the core were consistent with those of liquid silicates – the same material, in solid form, of which the Martian mantle is composed.
Further analysis of earlier marsquakes and additional computer simulations confirmed this result. It is only regrettable that dusty solar panels and the resulting lack of power made it impossible for the InSight lander to provide additional data that could have shed more light on the composition and structure of Mars’s interior. “Yet, InSight was a very successful mission that provided us with a lot of new data and insights that will be analyzed for years to come,” Khan says.
“Evidence for a liquid silicate layer atop the Martian core” by A. Khan, D. Huang, C. Durán, P. A. Sossi, D. Giardini and M. Murakami, 25 October 2023, Nature. DOI: 10.1038/s41586-023-06586-4
“Geophysical evidence for an enriched molten silicate layer above Mars’s core” by Henri Samuel, Mélanie Drilleau, Attilio Rivoldini, Zongbo Xu, Quancheng Huang, Raphaël F. Garcia, Vedran Lekić, Jessica C. E. Irving, James Badro, Philippe H. Lognonné, James A. D. Connolly, Taichi Kawamura, Tamara Gudkova and William B. Banerdt, 25 October 2023, Nature. DOI: 10.1038/s41586-023-06601-8
The NASA Mars InSight Mission
The Jet Propulsion Laboratory (<span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
JPL
The Jet Propulsion Laboratory (JPL) is a federally funded research and development center that was established in 1936. It is owned by NASA and managed by the California Institute of Technology (Caltech). The laboratory's primary function is the construction and operation of planetary robotic spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA's Deep Space Network. JPL implements programs in planetary exploration, Earth science, space-based astronomy and technology development, while applying its capabilities to technical and scientific problems of national significance.
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>JPL) managed InSight for NASA’s Science Mission Directorate. InSight is part of NASA’s Discovery Program, managed by the agency’s Marshall Space Flight Center. Lockheed Martin Space built the InSight spacecraft, including its cruise stage and lander, and supported spacecraft operations for the mission.
A number of European partners, including France’s Centre National d’Études Spatiales (CNES) and the German Aerospace Center (DLR), are supporting the InSight mission. CNES provided the Seismic Experiment for Interior Structure (SEIS) instrument to NASA, with the principal investigator at IPGP (Institut de Physique du Globe de Paris). Significant contributions for SEIS came from IPGP; the Max Planck Institute for Solar System Research (MPS) in Germany; the Swiss Federal Institute of Technology (ETH Zurich) in Switzerland; <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
Imperial College London
Established on July 8, 1907, by Royal Charter, Imperial College London is a public research university in London with a focus on science, engineering, medicine, and business. Its main campus is located in South Kensington, and it has an innovation campus in White City, a research field station at Silwood Park, and teaching hospitals throughout London. Its full legal name is the Imperial College of Science, Technology and Medicine.
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>Imperial College London and Oxford University in the United Kingdom; and JPL. The Marsquake Service is headed by ETH Zurich, with significant contributions from IPGP; the <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
University of Bristol
The University of Bristol, a red brick research university in Bristol, England, received its royal charter in 1909. However, it can trace its history back to 1876 (as University College, Bristol) and 1595 (as Merchant Venturers School). It is organized into six academic faculties composed of multiple schools and departments running over 200 undergraduate courses.
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>University of Bristol; Imperial College; ISAE (Institut Supérieur de l’Aéronautique et de l’Espace); MPS; and JPL. DLR provided the Heat Flow and Physical Properties Package (HP3) instrument, with significant contributions from the Space Research Center (CBK) of the Polish Academy of Sciences and Astronika in Poland. Spain’s Centro de Astrobiología (CAB) supplied the temperature and wind sensors.
NAIROBI, Kenya (AP) — The body of Ugandan Olympic athlete Rebecca Cheptegei — who died after being set on fire by her partner in Kenya — was received Friday by family and anti-femicide crusaders, ahead of her burial a day later.
Cheptegei’s family met with dozens of activists Friday who had marched to the Moi Teaching and Referral Hospital’s morgue in the western city of Eldoret while chanting anti-femicide slogans.
She is the fourth female athlete to have been killed by her partner in Kenya in yet another case of gender-based violence in recent years.
Viola Cheptoo, the founder of Tirop Angels – an organization that was formed in honor of athlete Agnes Tirop, who was stabbed to death in 2021, said stakeholders need to ensure this is the last death of an athlete due to gender-based violence.
“We are here to say that enough is enough, we are tired of burying our sisters due to GBV,” she said.
It was a somber mood at the morgue as athletes and family members viewed Cheptegei’s body which sustained 80% of burns after she was doused with gasoline by her partner Dickson Ndiema. Ndiema sustained 30% burns on his body and later succumbed.
Ndiema and Cheptegei were said to have quarreled over a piece of land that the athlete bought in Kenya, according to a report filed by the local chief.
Cheptegei competed in the women’s marathon at the Paris Olympics less than a month before the attack. She finished in 44th place.
Cheptegei’s father, Joseph, said that the body will make a brief stop at their home in the Endebess area before proceeding to Bukwo in eastern Uganda for a night vigil and burial on Saturday.
“We are in the final part of giving my daughter the last respect,” a visibly distraught Joseph said.
He told reporters last week that Ndiema was stalking and threatening Cheptegei and the family had informed police.
Four in 10 women or an estimated 41% of dating or married Kenyan women have experienced physical or sexual violence perpetrated by their current or most recent partner, according to the Kenya Demographic and Health Survey 2022.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
