Proceedings of the National Academy of Sciences
Articles in this Issue
A synapse-specific refractory period for plasticity at individual dendritic spines
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 plastic...
Funding rules that promote equity in climate adaptation outcomes
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 coar...
The magnitude of legal wildlife trade and implications for species survival
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 i...
Individualized temporal patterns drive human sleep spindle timing
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 syn...
Reconciling Archean organic-rich mudrocks with low primary productivity before the Great Oxygenation Event
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 geologis...
Human and primate categorical understanding of color
The value of returning a sample of the Martian atmosphere
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...
Characterizing progenitor cells in developing and injured spinal cord: Insights from single-nucleus transcriptomics and lineage tracing
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 rema...
Mars Sample Return: From collection to curation of samples from a habitable world
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 Sampl...
A tale of two planets: Disparate evolutionary models for Mars inferred from radiogenic isotope compositions of Martian meteorites
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...
What we can learn about Mars from the magnetism of returned samples
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...
Constraining the history of water and climate on Mars through light element stable isotope analysis of volatiles in returned martian samples
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—i...
Evolution of the iodine cycle and the late stabilization of the Earth’s ozone layer
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...
Sampling Mars: Geologic context and preliminary characterization of samples collected by the NASA Mars 2020 Perseverance Rover Mission
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...
Transforming literature screening: The emerging role of large language models in systematic reviews
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...
Pore pressure inhibits clustering of induced earthquakes in Western Canada
Induced earthquakes are manifestations of highly heterogeneous distributions of effective stress changes imparted by anthropogenic activities such as hydraulic fracturing and wastewater injection. It...
Completion of lunar magma ocean solidification at 4.43 Ga
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...
Le Chatelier’s concrete conundrum
Fundamental constraints and questions from the study of Martian meteorites and the need for returned samples
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...
Perspectives on Mars Sample Return: A critical resource for planetary science and exploration
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 Natio...
The scientific value of Mars Sample Return
Distinct and interdependent functions of three RING proteins regulate recombination during mammalian meiosis
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 tot...
Organic matter and biomarkers: Why are samples required?
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 sit...
Utilizing Martian samples for future planetary exploration—Characterizing hazards and resources
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 negati...