Table Of Contents Page, PNAS Volume 122, Number 2
Special Feature
The Scientific Value of Mars Sample Return
Mars Sample Return (MSR) has been the highest flagship mission priority in the last
two Planetary Decadal Surveys of the National Academies of Science, Engineering, and
Medicine (hereafter, “the National Academies”) and was the highest priority flagship
...
NASA’s Mars 2020 mission has initiated collection of samples from Mars’ Jezero Crater,
which has a wide range of ancient rocks and rock types from lavas to lacustrine sedimentary
rocks. The Mars Sample Return (MSR) Campaign, a joint effort between NASA ...
The search for evidence of past prebiotic or biotic activity on Mars will be enhanced
by the return of samples to Earth laboratories. While impressive analytical feats
have been accomplished by in situ missions on the red planet, accessing the ...
The radiogenic isotopic compositions of basaltic Martian meteorites (shergottites)
and clinopyroxene/olivine cumulate meteorites (nakhlite/chassignites) are used to
define the global evolution of Mars. However, the two main groups of meteorites ...
The elemental and isotopic abundances of major species in the Martian atmosphere have
been determined, but analyses often lack sufficient precision, and those of minor
and trace species are frequently not well known. Many important questions about the
...
One of the most surprising and important findings of the first human landings on the
Moon was the discovery of a very fine layer of lunar dust covering the entire surface
of Moon along with the negative impacts of this dust on the well-being and ...
Physical materials from planetary bodies are crucial for understanding fundamental
processes that constrain the evolution of the solar system, as samples can be analyzed
at high precision and accuracy in Earth-based laboratories. Mars is the only planet
...
The NASA Mars 2020 Perseverance Rover Mission has collected samples of rock, regolith,
and atmosphere within the Noachian-aged Jezero Crater, once the site of a delta-lake
system with a high potential for habitability and biosignature preservation. ...
Much has been learned about Mars through data returned from space missions and analyses
of martian meteorites. There are, however, many questions still outstanding which
cannot currently be answered—including the issue of whether there is, or was, life
on ...
The Red Planet is a magnetic planet. The Martian crust contains strong magnetization
from a core dynamo that likely was active during the Noachian period when the surface
may have been habitable. The evolution of the dynamo may have played a central role
...
This Week in PNAS
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Commentaries
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Letters
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Brief Reports
Below a critical temperature , superconductors transport electrical charge without dissipative energy losses. The
application of a magnetic field generally acts to suppress , up to some critical field strength at which 0 K. Here, we investigate magnetic ...
A P value is conventionally interpreted either as a) the probability by chance of obtaining
more extreme results than those observed or b) a tool for declaring significance at
a prespecified level. Both approaches carry difficulties: b) does not allow ...
Physical Sciences
Applied Physical Sciences
A central paradigm of nonequilibrium physics concerns the dynamics of heterogeneity
and disorder, impacting processes ranging from the behavior of glasses to the emergent
functionality of active matter. Understanding these complex mesoscopic systems ...
Biophysics and Computational Biology
The course of evolution is strongly shaped by interaction between mutations. Such
epistasis can yield rugged sequence–function maps and constrain the availability of
adaptive paths. While theoretical intuition is often built on global statistics of
large, ...
Chemotaxis enables marine bacteria to increase encounters with phytoplankton cells
by reducing their search times, provided that bacteria detect noisy chemical gradients
around phytoplankton. Gradient detection depends on bacterial phenotypes and ...
DNA methylation is a crucial epigenetic modification that orchestrates chromatin remodelers
that suppress transcription, and aberrations in DNA methylation result in a variety
of conditions such as cancers and developmental disorders. While it is ...
The bacterial type 6 secretion system (T6SS) is a toxin-injecting nanoweapon that
mediates competition in plant- and animal-associated microbial communities. Bacteria
can evolve de novo resistance against T6SS attacks, but resistance is far from universal
...
Chemistry
A signaling molecule from intratumor bacteria promotes trastuzumab resistance in breast cancer cells
Emerging evidence indicates that intratumor bacteria exist as an active and specific
tumor component in many tumor types beyond digestive and respiratory tumors. However,
the biological impact and responsible molecules of such local bacteria–tumor direct
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Molecular catalysts with a single metal center are reported to reduce CO2 to a wide range of valuable single-carbon products like CO, HCOOH, CH3OH, etc. However, these catalysts cannot reduce CO2 to two carbon products like ethane or ethylene and the ...
Combining Deep-UV second harmonic generation spectroscopy with molecular simulations,
we confirm and quantify the specific adsorption of guanidinium cations to the air–water
interface. Using a Langmuir analysis of measurements at multiple concentrations, ...
Despite the broad catalytic relevance of metal–support interfaces, controlling their
chemical nature, the interfacial contact perimeter (exposed to reactants), and consequently,
their contributions to overall catalytic reactivity, remains challenging, as ...
Computer Sciences
Systematic reviews (SR) synthesize evidence-based medical literature, but they involve
labor-intensive manual article screening. Large language models (LLMs) can select
relevant literature, but their quality and efficacy are still being determined ...
Earth, Atmospheric, and Planetary Sciences
Turbulence in the tropical stratosphere, equatorial Kelvin waves, and the quasi-biennial oscillation
The tropical stratosphere is the gateway to the global stratosphere and a commonly
proposed location for solar geoengineering. The dynamics of this remote and difficult
to observe region are poorly understood, particularly at turbulent length scales.
...
Concomitant formation of protocells and prebiotic compounds under a plausible early Earth atmosphere
Revealing the origin of life and unambiguously detecting fossil remains of the earliest
organisms are closely related aspects of the same scientific research. The synthesis
of prebiotic molecular building blocks of life and the first compartmentalization
...
Crystallization of the lunar magma ocean yielded a chemically unique liquid residuum
named KREEP. This component is expressed as a large patch on the near side of the
Moon and a possible smaller patch in the northwest portion of the Moon’s South Pole-...
The origin of complex life and the evolution of terrestrial ecosystems are fundamental
aspects of the natural history on Earth. Here, we present evidence for a protracted
stabilization of the Earth’s ozone layer. The destruction of atmospheric ozone today
...
Induced earthquakes are manifestations of highly heterogeneous distributions of effective
stress changes imparted by anthropogenic activities such as hydraulic fracturing and
wastewater injection. It is critical to disentangle the mechanisms behind these ...
The organic carbon content of ancient rocks provides a fundamental record of the biosphere
on early Earth. For over 50 y, the high organic content of Archean (>2.5 Ga) mudrocks
has puzzled geologists and evolutionary biologists, because high biological ...
Engineering
High degree of fluorination for ether electrolytes has resulted in improved cycling
stability of lithium metal batteries due to stable solid electrolyte interphase (SEI)
formation and good oxidative stability. However, the sluggish ion transport and ...
The strength−ductility trade-off exists ubiquitously, especially in brittle intermetallic-containing
multiple principal element alloys (MPEAs), where the intermetallic phases often induce
premature failure leading to severe ductility reduction. ...
Physics
Human perception systems are highly refined, relying on an adaptive, plastic, and
event-driven network of sensory neurons. Drawing inspiration from Nature, neuromorphic
perception systems hold tremendous potential for efficient multisensory signal ...
Social Sciences
Social Sciences
Socioeconomic status (SES) is a critical factor in determining health outcomes and
is influenced by genetic and environmental factors. However, our understanding of
the genetic structure of SES remains incomplete. Here, we conducted a large-scale
exome ...
Sustainability Science
Many climate policies adopt improving equity as a key objective. A key challenge is
that policies often conceive of equity in terms of individuals but introduce strategies
that focus on spatially coarse administrative areas. For example, the Justice40 ...
Biological Sciences
Agricultural Sciences
The harlequin ladybird, Harmonia axyridis, is a predatory beetle used globally to control pests such as aphids and scale insects.
Originating from East Asia, this species has become highly invasive since its introduction
in the late 19th century to Europe ...
Biophysics and Computational Biology
DNA methylation is a crucial epigenetic modification that orchestrates chromatin remodelers
that suppress transcription, and aberrations in DNA methylation result in a variety
of conditions such as cancers and developmental disorders. While it is ...
Cell Biology
Ataxia–telangiectasia (A-T) is a pleiotropic genome instability syndrome resulting
from the loss of the homeostatic protein kinase ATM. The complex phenotype of A-T
includes progressive cerebellar degeneration, immunodeficiency, gonadal atrophy, ...
To achieve replicative immortality, cancer cells must activate telomere maintenance
mechanisms. In 10 to 15% of cancers, this is enabled by recombination-based alternative
lengthening of telomeres pathways (ALT). ALT cells display several hallmarks ...
Developmental Biology
Understanding the role of metabolic processes during inner ear development is essential
for identifying targets for hair cell (HC) regeneration, as metabolic choices play
a crucial role in cell proliferation and differentiation. Among the metabolic ...
Female mosquitoes require a vertebrate blood meal to activate reproduction, transmitting
numerous devastating human diseases. Vitellogenesis is a central event of female reproduction
that involves the massive production of vitellogenin (Vg) in the fat ...
Ecology
The unsustainable use of wildlife is a primary driver of global biodiversity loss.
No comprehensive global dataset exists on what species are in trade, their geographic
origins, and trade’s ultimate impacts, which limits our ability to sustainably manage
...
The boreal forest biome is warming four times faster than the global average. Changes
so far are moderate, but time lags in responses may transiently maintain forest states
which are no longer supported by current environmental conditions. Here, we ...
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Environmental Sciences
Pesticide application is essential for stabilizing agricultural production. However,
the effects of increasing pesticide diversity on soil microbial functions remain unclear,
particularly under varying nitrogen (N) fertilizer management practices. In this ...
Climate-driven changes in high-elevation forest distribution and reductions in snow
and ice cover have major implications for ecosystems and global water security. In
the Greater Yellowstone Ecosystem of the Rocky Mountains (United States), recent melting
...
Evolution
The course of evolution is strongly shaped by interaction between mutations. Such
epistasis can yield rugged sequence–function maps and constrain the availability of
adaptive paths. While theoretical intuition is often built on global statistics of
large, ...
The bacterial type 6 secretion system (T6SS) is a toxin-injecting nanoweapon that
mediates competition in plant- and animal-associated microbial communities. Bacteria
can evolve de novo resistance against T6SS attacks, but resistance is far from universal
...
Climate warming is expected to shift the distributions of mosquitoes and mosquito-borne
diseases, promoting expansions at cool range edges and contractions at warm range
edges. However, whether mosquito populations could maintain their warm edges through
...
Genetics
Socioeconomic status (SES) is a critical factor in determining health outcomes and
is influenced by genetic and environmental factors. However, our understanding of
the genetic structure of SES remains incomplete. Here, we conducted a large-scale
exome ...
CAG/CTG repeats are prone to expansion, causing several inherited human diseases.
The initiating sources of DNA damage which lead to inaccurate repair of the repeat
tract to cause expansions are not fully understood. Expansion-prone CAG/CTG repeats
are ...
From RNA interference to chromatin silencing, diverse genome defense pathways silence
selfish genetic elements to safeguard genome integrity. Despite their diversity, different
defense pathways share a modular organization, where numerous specificity ...
During meiosis, each pair of homologous chromosomes becomes connected by at least
one crossover, as required for accurate segregation, and adjacent crossovers are widely
separated thereby limiting total numbers. In coarsening models, this crossover ...
Immunology and Inflammation
Class I major histocompatibility complex (MHC-I) proteins play a pivotal role in adaptive
immunity by displaying epitopic peptides to CD8+ T cells. The chaperones tapasin and
TAPBPR promote the selection of immunogenic antigens from a large pool of ...
The effects of T cell differentiation arising from immune checkpoint inhibition targeting
cytotoxic T lymphocyte–associated antigen 4 (CTLA-4) and programmed cell death protein
1 (PD-1) on the immunological memory response remain unclear. Our ...
Innate immunity relies on Toll-like receptors (TLRs) to detect pathogen-associated
molecular patterns. The TIR (Toll/interleukin-1 receptor) domain-containing TLR adaptors
TRIF (TIR domain–containing adaptor-inducing interferon-β) and TRAM (TRIF-related
...
Medical Sciences
A signaling molecule from intratumor bacteria promotes trastuzumab resistance in breast cancer cells
Emerging evidence indicates that intratumor bacteria exist as an active and specific
tumor component in many tumor types beyond digestive and respiratory tumors. However,
the biological impact and responsible molecules of such local bacteria–tumor direct
...
Deep brain stimulation is an efficacious treatment for dystonia. While the internal
pallidum serves as the primary target, recently, stimulation of the subthalamic nucleus
(STN) has been investigated. However, optimal targeting within this structure and
...
Microbiology
Chemotaxis enables marine bacteria to increase encounters with phytoplankton cells
by reducing their search times, provided that bacteria detect noisy chemical gradients
around phytoplankton. Gradient detection depends on bacterial phenotypes and ...
Among new antimalarials discovered over the past decade are multiple chemical scaffolds
that target Plasmodium falciparum P-type ATPase (PfATP4). This essential protein is a Na+ pump responsible for the maintenance of Na+ homeostasis. PfATP4 belongs to ...
Sialic acids derived from colonic mucin glycans are crucial nutrients for enteric
bacterial pathogens like Salmonella. The uptake and utilization of sialic acid in Salmonella depend on coordinated regulons, each activated by specific metabolites at the ...
Neuroscience
Various mature tissue-resident cells exhibit progenitor characteristics following
injury. However, the existence of endogenous stem cells with multiple lineage potentials
in the adult spinal cord remains a compelling area of research. In this study, we
...
How newly formed memories are preserved while brain plasticity is ongoing has been
a source of debate. One idea is that synapses which experienced recent plasticity
become resistant to further plasticity, a type of metaplasticity often referred to
as ...
While traditionally studied for their proapoptotic functions in activating the caspase,
research suggests BH3-only proteins also have other roles such as mitochondrial dynamics
regulation. Here, we find that EGL-1, the BH3-only protein in Caenorhabditis ...
BK channels can control neuronal function, but their functional relevance in activity-dependent
changes of synaptic function remains elusive. Here, we report that repetitive low-frequency
stimulation activates BK channels through 12(S)HPETE, an ...
Sleep spindles are cortical electrical oscillations considered critical for memory
consolidation and sleep stability. The timing and pattern of sleep spindles are likely
to be important in driving synaptic plasticity during sleep as well as preventing
...
Physiology
Loss-of-function sequence variants in KCNA1, which encodes the voltage-gated potassium channel Kv1.1, cause Episodic Ataxia Type
1 (EA1) and epilepsy. Due to a paucity of drugs that directly rescue mutant Kv1.1
channel function, current therapeutic ...
Sustainability Science
The unsustainable use of wildlife is a primary driver of global biodiversity loss.
No comprehensive global dataset exists on what species are in trade, their geographic
origins, and trade’s ultimate impacts, which limits our ability to sustainably manage
...
Corrections
SI Correction
Cover image: Pictured is NASA’s Perseverance rover on Mars with a sample tube in the foreground. A collection of articles in The Scientific Value of Mars Sample Return Special Feature explores the critical scientific questions that could be answered by returning Martian samples collected by Perseverance to Earth. Together, the articles outline how returned Martian samples could provide insight into the evolution of Mars, including the planet’s past or present habitability, inform future missions, and represent a scientific resource for decades to come. See the Introduction to the Special Feature, e2415280121. Image credit: NASA/Jet Propulsion Laboratory (JPL)-California Institute of Technology (Caltech)/Malin Space Science Systems.
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