Earth-like environment likely on ancient Mars

A research team using the ChemCam instrument onboard NASA's Curiosity rover discovered higher-than-usual amounts of manganese in lakebed rocks within Gale Crater on Mars, which indicates that the sediments were formed in a river, delta, or near the shoreline of an ancient lake. The results were published today in Journal of Geophysical Research: Planets.

"It is difficult for manganese oxide to form on the surface of Mars, so we didn't expect to find it in such high concentrations in a shoreline deposit," said Patrick Gasda, of Los Alamos National Laboratory's Space Science and Applications group and lead author on the study. "On Earth, these types of deposits happen all the time because of the high oxygen in our atmosphere produced by photosynthetic life, and from microbes that help catalyze those manganese oxidation reactions.

"On Mars, we don't have evidence for life, and the mechanism to produce oxygen in Mars's ancient atmosphere is unclear, so how the manganese oxide was formed and concentrated here is really puzzling. These findings point to larger processes occurring in the Martian atmosphere or surface water and shows that more work needs to be done to understand oxidation on Mars," Gasda added.

ChemCam, which was developed at Los Alamos and CNES (the French space agency), uses a laser to form a plasma on the surface of a rock, and collects that light in order to quantify elemental composition in rocks.

The sedimentary rocks explored by the rover are a mix of sands, silts, and muds. The sandy rocks are more porous, and groundwater can more easily pass through sands compared to the muds that make up most of the lakebed rocks in the Gale Crater. The research team looked at how manganese could have been enriched in these sands -- for example, by percolation of groundwater through the sands on the shore of a lake or mouth of a delta -- and what oxidant could be responsible for the precipitation of manganese in the rocks.

On Earth, manganese becomes enriched because of oxygen in the atmosphere, and this process is often sped up by the presence of microbes. Microbes on Earth can use the many oxidation states of manganese as energy for metabolism; if life was present on ancient Mars, the increased amounts of manganese in these rocks along the lake shore would have been a helpful energy source for life.

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Biomolecules from formaldehyde on ancient Mars

Organic materials discovered on Mars may have originated from atmospheric formaldehyde, according to new research, marking a step forward in our understanding of the possibility of past life on the Red Planet.

Scientists from Tohoku University have investigated whether the early atmospheric conditions on Mars had the potential to foster the formation of biomolecules -- organic compounds essential for biological processes.

Their findings, published in Scientific Reports, offer intriguing insights into the plausibility of Mars harboring life in its distant past.

Today, Mars presents a harsh environment characterized by dryness and extreme cold, but geological evidence hints at a more hospitable past.

About 3.8-3.6 billion years ago, the planet probably had a temperate climate, sustained by the warming properties of gases like hydrogen.

In such an environment, Mars may have had liquid water, a key ingredient for life as we know it.

The researchers investigated whether formaldehyde could have formed in the early Martian environment.

Formaldehyde is a simple organic compound that plays a crucial role as a precursor for the formation of vital biomolecules through purely chemical or physical processes.

These biomolecules, like amino acids and sugars, serve as the fundamental building blocks for proteins and RNA, essential components of life.

Using an advanced computer model, the team simulated the potential atmospheric composition of early Mars to explore the potential for formaldehyde production.

The model was built with the assumption that the atmosphere was rich in carbon dioxide, hydrogen, and carbon monoxide.

Their simulations suggest that the ancient Martian atmosphere could have provided a continuous supply of formaldehyde which would have potentially led to the creation of various organic compounds.

This raises the intriguing possibility that the organic materials detected on the Martian surface could have originated from atmospheric sources, particularly during the planet's two earliest geological periods.

"Our research provides crucial insights into the chemical processes that may have occurred on ancient Mars, offering valuable clues to the possibility of past life on the planet," says Shungo Koyama, lead author of the study.

By revealing that there were conditions favorable for the formation of bio molecules, the research broadens our understanding of the planet's ancient capacity to sustain life.

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Little groundwater recharge in ancient Mars aquifer, according to new models

Mars was once a wet world. The geological record of the Red Planet shows evidence for water flowing on the surface -- from river deltas to valleys carved by massive flash floods.

But a new study shows that no matter how much rainfall fell on the surface of ancient Mars, very little of it seeped into an aquifer in the planet's southern highlands.

A graduate student at The University of Texas at Austin made the discovery by modeling groundwater recharge dynamics for the aquifer using a range of methods -- from computer models to simple back-of-the-envelope calculations.

No matter the degree of complexity, the results converged on the same answer -- a miniscule .03 millimeters of groundwater recharge per year on average.

That means that wherever rain fell in the model, only an average of .03 millimeters per year could have entered the aquifer and still produced the landforms remaining on the planet today.

For comparison, the annual rate of groundwater recharge for the Trinity and Edwards-Trinity Plateau aquifers that provide water to San Antonio generally ranges from 2.5 to 50 millimeters per year, or about 80 to 1,600 times the Martian aquifer recharge rate calculated by the researchers.

There are a variety of potential reasons for such low groundwater flow rates, said lead author Eric Hiatt, a doctoral student at the Jackson School of Geosciences.

When it rained, the water may have mostly washed across the Martian landscape as runoff.

Or it may have just not rained very much at all.

These findings can help scientists constrain the climatic conditions capable of producing rainfall on early Mars.

They also suggest a very different water regime on the Red Planet than what exists on Earth today.

"The fact that the groundwater isn't as big of a process could mean that other things are," Hiatt said.

"It might magnify the importance of runoff, or it could mean that it just didn't rain as much on Mars. But it's just fundamentally different from how we think about [water] on Earth."

The results were published in the journal Icarus. The paper's co-authors are Mohammad Afzal Shadab, a doctoral student at the Jackson School and faculty members Sean Gulick, Timothy Goudge and Marc Hesse.

The models used in the study work by simulating groundwater flow in a "steady state" environment where inflow and outflow of water into the aquifer is balanced.

Scientists then changed the parameters affecting the flow -- for example, where rain falls or the average porosity of the rock -- and observed what other variables would have to change to maintain the steady state and how plausible those charges are.

While other researchers have simulated groundwater flow on Mars using similar techniques, this model is the first to incorporate the influence of the oceans that existed on the surface of Mars more than three billion years ago in the Hellas, Argyre, and Borealis basins.

The study also incorporates modern topographical data collected by satellites.

The modern landscape, Hiatt said, still preserves one of the planet's oldest and most influential topographical features -- an extreme difference in elevation between the northern hemisphere -- the lowlands -- and the southern hemisphere -- the highlands -- known as the "great dichotomy." The dichotomy preserves signs of past groundwater upwelling in which groundwater rose up from the aquifer to the surface.

The researchers used geological markers of these past upwelling events to evaluate different model outputs.

Across different models, the researchers found the mean groundwater recharge rate of .03 millimeters per year to match most closely with what's known about the geologic record.

The research isn't just about understanding the Red Planet's past.

It has implications for future Mars exploration too. Understanding groundwater flow can help inform where to find water today, Hiatt said.

Whether you're looking for signs of ancient life, trying to sustain human explorers, or making rocket fuel to get back home to Earth, it's essential to know where the water would most likely be.

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