NASA Discovery Reveals Complex Water Systems on Early Mars - Jet Propulsion Laboratory

The Perseverance rover captured the data used in this panorama of the “Margin Unit,” a geologic area that hugs the inner edge of Jezero Crater’s rim, between Oct. 8 and Oct. 16, 2023.

NASA/JPL-Caltech/MSSS

When NASA’s Perseverance rover reached the inner edge of Mars’ Jezero Crater in September 2023, mission scientists were surprised by what they found. Called the “Margin Unit,” the geologic area stretches along the shoreline of an ancient Martian lake, so they expected sedimentary rocks, which would have formed as layers of sand piled on top of each other over millennia. Composed of clay and silt, sedimentary rocks on Earth are good at preserving past microbial life. The scientists were especially intrigued by strong signals of carbonate minerals detected by Mars orbiters. On Earth, carbonates frequently form in shallow ocean and lake environments capable of supporting life.  

Instead, the rover team found igneous rock, which can form deep underground from magma or from volcanic activity at the surface. Igneous rocks are excellent record-keepers, particularly because mineral crystals within them preserve details about the precise moment they formed. In this case, they preserved an astonishingly complex record of water activity on early Mars. In fact, these rocks showed signs of having interacted with water on at least three separate occasions, with each encounter further altering their chemistry and appearance. The findings were published Monday in the journal Communications Earth & Environment. 

The instrument behind the findings is SuperCam, which perches on the rover’s mast and determines the mineralogy of geologic features based on the light they reflect. When the science team spots an intriguing rock, they can send commands for SuperCam to fire its laser up to 21 feet (6.5 meters) away. The spectrum of the resulting plasma reveals the target’s chemistry. Perseverance has analyzed more than 185 bedrock targets across the unit this way. 

“Before we arrived at the Margin Unit, the main hypothesis — derived from orbital observations — was that the carbonate seen from orbit formed from interaction with the lake that existed in Jezero Crater,” said Candice Bedford, a research scientist at Purdue University in West Lafayette, Indiana, and the study’s lead author. “But now we know that this location became a sort of crossroads for aqueous systems. The Margin Unit findings are important because Jezero Crater sits inside one of the largest exposures of carbonate on Mars, so what we learn here reaches well beyond this crater.” 

Slow-cooling underground 

Perseverance explored the Margin Unit across approximately 870 feet (265 meters) of elevation. At higher elevations, it found rock that was coarse-grained and crystalline — hallmarks of the mineral olivine — with almost no sign that water had ever touched it. Made of magnesium and iron, the area’s olivine unit formed in a body of magma deep underground, cooling slowly enough for its grains to grow large, and reached the surface only after the ground above it eroded away. Lower in the unit, on the lakebed, the rock looks transformed, as the olivine grains were fractured with silica between them. 

Carbonate and silica minerals are an important signpost in the search for ancient life. When water interacts with olivine on Earth, the reaction can release hydrogen, which can be a food source for some microbes, and it leaves behind carbonate and silica, two minerals that lock in traces of the past existence of those microbes. 

Multiple episodes 

The Perseverance team can determine the sequence of the Margin Unit’s interactions with water, but not their age. On the first occasion water reached the rocks of the Margin Unit, carbon-dioxide-rich groundwater reacted with olivine, resulting in ridges of carbonate that run through the fractures in bedrock at low elevations. Today, these carbonate-filled fractures are left standing as the softer rock around them wears away.  

The second time water reached the rocks may have been related to the lake that once existed in the crater. 

“Some of the Margin Unit rocks also contain silica,” said Eleni Ravanis, a planetary scientist at the University of Hawaii at Manoa and a coauthor of the study. “Turning olivine into carbonate can leave silica behind, and we see more of that silica in rocks that sat below the water line.” 

Last came a water event that generated mineral veins at one location in the eastern part of the Margin Unit, about 10 inches (25 centimeters) thick, creating minerals like calcium sulfate and fluorite. Finding fluorite is an important clue because it typically forms when hot water circulates through volcanic rocks, revealing that this area experienced a later, heated underground-water event. 

“If there is one thing I have learned after 10 years working with Mars rovers, it is that Mars constantly throws surprises at you,” said Bedford. “It is very rare that things are as we expect them to be from orbital data. I hope this work helps reshape how scientists view the history of water in Jezero Crater and across Mars. Ultimately, I hope it helps planetary scientists reconstruct the changing climate and habitability of early Mars.” 

More about Perseverance 

A key objective of Perseverance’s mission on Mars is astrobiology, including the search for signs of ancient microbial life. The rover characterizes the planet’s geology and past climate and collects and stores Martian rock and regolith. 

Managed for NASA by Caltech, Jet Propulsion Laboratory in Southern California built and manages operations of the Perseverance rover on behalf of the agency’s Science Mission Directorate as part of NASA’s Mars Exploration Program portfolio. SuperCam is co-led by Purdue University in Indiana, Los Alamos National Laboratory in New Mexico, and IRAP (Research Institute in Astrophysics and Planetology) and CNES (Centre National d’Etudes Spatiales) in Toulouse, France. 

For more about Perseverance: https://science.nasa.gov/mission/mars-2020-perseverance 

Source: NASA Discovery Reveals Complex Water Systems on Early Mars - NASA 

Scientists Find a New Layer of Alzheimer’s Hidden in the Genome

When people talk about the biology of Alzheimer’s disease, the conversation almost always centers on two culprits: amyloid-beta plaques and tau tangles. A new study from Carnegie Mellon University, the University of Pittsburgh School of Medicine, and the University of Washington suggests there’s a third, much less explored layer to the story, not in what genes a cell has, but in how those genes are physically folded and arranged inside the nucleus.

DNA Isn’t Just a String of Letters

DNA doesn’t sit inside a cell as a simple straight strand. It folds into an intricate three-dimensional structure, looping and packing itself into a compact shape that determines which genes are physically accessible to the cellular machinery that turns them on or off. That 3D organization is sometimes called the genome’s architecture, and it’s now emerging as its own layer of biology, one that can go wrong independently of the DNA sequence itself.

“Alzheimer’s disease cannot be understood one layer at a time,” said Jian Ma, the Ray and Stephanie Lane Professor of Computational Biology at CMU’s School of Computer Science, who led and supervised the study. “The genome’s 3D structure is a fundamental regulatory layer that helps to connect DNA sequence to gene activity. By integrating genome folding, cell state, and tissue context, we can move beyond cataloging disease-associated changes toward understanding how they fit together and which mechanisms to test next.”

Combining Three Layers of Data

To investigate this, the team examined postmortem prefrontal cortex tissue from people with and without Alzheimer’s disease who had taken part in a long-term dementia study and donated their brains for research afterward. They used a technique called GAGE-seq, which can measure both gene expression and 3D genome contacts within the very same individual cell, letting researchers see, cell by cell, how a gene’s activity relates to how its DNA is physically folded.

Those single-cell measurements were then layered with spatial transcriptomic maps, which preserve information about exactly where in the intact brain tissue different genes are active. Combining the two let the researchers connect genome architecture, gene regulation, and tissue-level context all at once, rather than studying each in isolation.

An AI Model Built to Test the Connection

The team also built a deep learning model called Hicformer, which combines raw DNA sequence information with broader patterns of genome folding and detailed maps of which DNA regions physically touch one another. Fed these inputs, Hicformer predicts gene activity across different brain cell types, effectively acting as a computational test bed for asking how a change in genome folding might translate into a change in gene activity, according to Xinyue Lu, a doctoral student in Computational Biology who co-led the research.

“Measuring gene activity and genome folding in the same cell allows us to directly connect chromosome structure with disease-related gene programs,” said Yang Zhang, a project scientist in the Computational Biology Department who co-led the research. “Across several kinds of brain cells, this paired view revealed a consistent signature of 3D genome reorganization in Alzheimer’s disease and helped us prioritize regulatory regions for future mechanistic and therapeutic investigation.”

When Genome Boundaries Blur

Large sections of the genome are normally sorted into fairly distinct “active” and “inactive” zones known as compartments. In brain cells from people with Alzheimer’s disease, those boundaries were noticeably less sharp, a pattern the researchers describe as increased compartment mingling. Several types of brain cells also showed fewer contacts between nearby DNA regions and more contacts between regions that are normally far apart, along with weaker connections between genes and the regulatory elements that help switch them on or off.

Notably, cells with more of this compartment mingling tended to have lower overall gene activity. These structural shifts were linked to reduced activity in gene programs involved in neurons and synapses, changes in metabolism and cellular stress responses, and, in microglia, the brain’s resident immune cells, links to senescence-related gene programs.

Adding to the Picture, Not Replacing It

“Our study represents a major advance in understanding what goes wrong in Alzheimer’s disease,” said Hansruedi Mathys, assistant professor of neurobiology at Pitt’s Department of Neurobiology, who directed the Pitt arm of the study. “We know the classic hallmarks of Alzheimer’s disease, accumulation of amyloid-beta plaques and tau tangles, but our results establish higher-order chromatin alterations as a component of the molecular pathology associated with the disease, which currently affects seven million Americans, a number that continues to grow.”

Importantly, this isn’t a competing explanation for Alzheimer’s, it’s an additional one. Chromatin, the material made of DNA and its associated proteins that packages the genome inside a cell, now joins amyloid and tau as part of the disease’s broader molecular landscape.

Where This Could Lead

When the researchers mapped these molecular changes across intact brain tissue, the genome reorganization was tied not just to altered gene activity, but to differences in how brain cells were physically arranged within the tissue itself. That gives the field a new, testable framework: future studies can now ask whether specific structural changes actively drive Alzheimer’s progression, and whether any of the newly flagged regulatory regions could eventually become targets for treatment.

The research, supported by grants from the National Institutes of Health, also included collaborators from the Broad Institute of MIT and Harvard, UCLA, and the Rush Alzheimer’s Disease Center. The study was published in Science.

Sources

·         Press release (Carnegie Mellon University, quoting Pitt’s Dr. Mathys who led the Pitt arm of the study): AI, Single-Cell Technology Reveal How 3D Genome Differs in People With Alzheimer’s Disease

·         Original paper: Zhang et al., “Single-cell multiomics connects 3D genome and transcriptome alterations in Alzheimer’s disease,” Science, 2026

Source: Scientists Find a New Layer of Alzheimer’s Hidden in the Genome