More evidence that ancient Mars was Earth-like and habitable

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In a remarkable discovery, scientists have found higher-than-usual amounts of manganese in lakebed rocks within Gale Crater on Mars. The results suggest that the sediments were formed in a river, delta, or near the shoreline of an ancient, habitable lake on ancient Mars.

The research team, led by Patrick Gasda of Los Alamos National Laboratory's Space Science and Applications group (ISR-1), used the ChemCam instrument onboard NASA's Curiosity rover to make this intriguing finding.

"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 Gasda, expressing his surprise at the discovery.

"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," Gasda explained.

Mystery of manganese on Mars

The presence of manganese oxide on Mars is perplexing, as there is no evidence of life or a clear mechanism to produce oxygen in the planet's ancient atmosphere.

"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," Gasda added.

"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," he concluded.

Exploring sedimentary rocks from ancient Mars

The sedimentary rocks explored by the Curiosity rover are a mix of sands, silts, and muds. The research team investigated how manganese could have been enriched in the sandy rocks.

The confusion lies in the fact that they are more porous and allow for easier groundwater passage compared to the muds that make up most of the lakebed rocks in the Gale Crater.

They considered possibilities such as the 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.

ChemCam: Unveiling the elemental composition of Martian rocks

The ChemCam (Chemistry and Camera) instrument, referred to above, is a key scientific tool onboard NASA's Mars Science Laboratory mission's Curiosity rover.

It was developed through a collaboration between Los Alamos National Laboratory (LANL) in the United States and the French space agency, Centre National d'Études Spatiales (CNES).

ChemCam is designed to analyze the chemical composition of Martian rocks and soil using a technique called Laser-Induced Breakdown Spectroscopy (LIBS).

Here are some key features and facts about the ChemCam instrument:

• Laser-Induced Breakdown Spectroscopy (LIBS): ChemCam uses a powerful laser to vaporize small portions of Martian rocks or soil from a distance of up to 7 meters (23 feet). The laser creates a plasma, which emits light with wavelengths characteristic of the elements present in the target.

• Remote Micro-Imager (RMI): In addition to the LIBS system, ChemCam also includes a high-resolution camera called the Remote Micro-Imager. The RMI provides context images of the analyzed targets, allowing scientists to better understand the geological setting of the sampled area.

• Elemental analysis: ChemCam can detect and quantify the presence of various elements, including lighter elements like hydrogen, lithium, beryllium, and boron, which are difficult to detect with other techniques. It can also measure the abundances of heavier elements, such as carbon, oxygen, nitrogen, and sulfur.

• Rapid analysis: The instrument can analyze multiple points on a single rock or soil target within a matter of minutes, providing a quick and efficient means of gathering chemical data.

• Depth profiling: By firing multiple laser pulses at the same location, ChemCam can analyze the composition of rocks and soils at different depths, providing insights into the vertical distribution of elements.

• Discovering manganese: In 2016, ChemCam detected high levels of manganese oxides in Martian rocks, which was unexpected given the planet's current atmospheric conditions. This discovery led to new questions about the history of Mars' atmosphere and the potential for past habitable environments.

• Instrument specs: ChemCam's laser operates at a wavelength of 1067 nanometers and can fire at a rate of up to 10 Hz. The instrument weighs approximately 10 kilograms (22 pounds) and consumes about 14 watts of power during operation.

The data collected by ChemCam has greatly contributed to our understanding of the geological history and potential habitability of Mars, including its contribution to this recent study of Gale Crater.

Implications for life on ancient Mars

On Earth, manganese becomes enriched due to atmospheric oxygen, a process often accelerated by the presence of microbes. If life existed on ancient Mars, the increased amounts of manganese in these rocks along the lake shore would have been a helpful energy source for metabolism.

"The Gale lake environment, as revealed by these ancient rocks, gives us a window into a habitable environment that looks surprisingly similar to places on Earth today," remarked Nina Lanza, principal investigator for the ChemCam instrument.

"Manganese minerals are common in the shallow, toxic waters found on lake shores on Earth, and it's remarkable to find such recognizable features on ancient Mars," she explained.

Window into the past shows Earth/Mars similarities

In summary, the discovery of higher manganese levels in ancient lakebed rocks on Mars by NASA's Curiosity rover and the ChemCam instrument opens up exciting new possibilities for understanding the Red Planet's geological history and its potential for hosting life in the past.

As scientists continue to investigate these intriguing findings, they inch closer to unraveling the mysteries surrounding the Martian atmosphere, surface water, and the formation of manganese oxide deposits.

This intriguing research showcases the similarities between Earth and Mars and highlights the importance of ongoing exploration and scientific inquiry in our quest to comprehend the universe and our place within it.

The full study was published in the Journal of Geophysical Research Planets.

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