Primordial Martian Atmosphere had Little Carbon Dioxide?

The CO2 level in Mars' primitive atmosphere 3.5 billion years ago was too low for sediments, such as those found by NASA's Curiosity exploration vehicle in areas like the Gale Crater on the planet's equator, to be deposited. This and other conclusions are drawn from a paper written with the participation of researchers from the Spanish National Research Council (CSIC) and published in the latest issue of the journal, Proceedings of the National Academy of Sciences (PNAS).

The area Curiosity has been analysing since 2012, as part of NASA's Mars Science Laboratory mission, is composed primarily of sedimentary sequences deposited at the bottom of a lake 3.5 billion years ago. These sediments contain various secondary minerals, such as clays or sulphates, which indicate that the primitive surface was in contact with liquid water.

The existence of liquid water requires a warm surface temperature brought about by a minimum content of CO2 in the atmosphere. Yet this was not the case with Mars in its beginnings. "This contradiction has two possible solutions. Either we have not yet developed climatic models which explain the environmental conditions on Mars at the beginning of its history, or the Gale sedimentary sequences really did form in a very cold climate. The second option is the most reasonable", explains CSIC researcher Alberto Fairén, who works at the Centre for Astrobiology near Madrid (a joint centre run by CSIC and Spain's National Institute of Aerospace Technology).

[...]

"However, the rover has not found carbonates, thereby confirming the results of studies by all previous probes: carbonates are very scarce on the surface of Mars and, therefore, the CO2 level in the atmosphere was very low", adds. Fairén.

link.

Veins of Minerals in Gale Crater on Mars Probably From Evaporating Lakes

Mineral veins found in Mars's Gale Crater were formed by the evaporation of ancient Martian lakes, a new study has shown.

The research, by Mars Science Laboratory Participating Scientists at The Open University and the University of Leicester, used the Mars Curiosity rover to explore Yellowknife Bay in Gale Crater on Mars, examining the mineralogy of veins that were paths for groundwater in mudstones.

The study suggests that the veins formed as the sediments from the ancient lake were buried, heated to about 50 degrees Celsius and corroded.

Professor John Bridges from the University of Leicester Department of Physics and Astronomy said: "The taste of this Martian groundwater would be rather unpleasant, with about 20 times the content of sulphate and sodium than bottled mineral water for instance!

"However as Dr Schwenzer from The Open University concludes, some microbes on Earth do like sulphur and iron rich fluids, because they can use those two elements to gain energy. Therefore, for the question of habitability at Gale Crater the taste of the water is very exciting news."

link.

The Black Dunes of Mars

Tridymite Discovered on Mars, Suggesting Acidic Conditions in Martian Gale Crater Waters

In detective stories, as the plot thickens, an unexpected clue often delivers more questions than answers. In this case, the scene is a mountain on Mars. The clue: the chemical compound silica. Lots of silica. The sleuths: a savvy band of Earthbound researchers whose agent on Mars is NASA's laser-flashing, one-armed mobile laboratory, Curiosity.

NASA's Curiosity rover has found much higher concentrations of silica at some sites it has investigated in the past seven months than anywhere else it has visited since landing on Mars 40 months ago. Silica makes up nine-tenths of the composition of some of the rocks. It is a rock-forming chemical combining the elements silicon and oxygen, commonly seen on Earth as quartz, but also in many other minerals.

"These high-silica compositions are a puzzle. You can boost the concentration of silica either by leaching away other ingredients while leaving the silica behind, or by bringing in silica from somewhere else," said Albert Yen, a Curiosity science team member at NASA's Jet Propulsion Laboratory, Pasadena, California. "Either of those processes involve water. If we can determine which happened, we'll learn more about other conditions in those ancient wet environments."

Water that is acidic would tend to carry other ingredients away and leave silica behind. Alkaline or neutral water could bring in dissolved silica that would be deposited from the solution. Apart from presenting a puzzle about the history of the region where Curiosity is working, the recent findings on Mount Sharp have intriguing threads linked to what an earlier NASA rover, Spirit, found halfway around Mars. There, signs of sulfuric acidity were observed, but Curiosity's science team is still considering both scenarios -- and others -- to explain the findings on Mount Sharp.

link.

A different take.

Curiosity Reaches Martian Sand Dunes

link.

Curiosity Headed to Active Sand Dunes on Mars

On its way to higher layers of the mountain where it is investigating how Mars' environment changed billions of years ago, NASA's Curiosity Mars rover will take advantage of a chance to study some modern Martian activity at mobile sand dunes.

n the next few days, the rover will get its first close-up look at these dark dunes, called the "Bagnold Dunes," which skirt the northwestern flank of Mount Sharp. No Mars rover has previously visited a sand dune, as opposed to smaller sand ripples or drifts. One dune Curiosity will investigate is as tall as a two-story building and as broad as a football field. The Bagnold Dunes are active: Images from orbit indicate some of them are migrating as much as about 3 feet (1 meter) per Earth year. No active dunes have been visited anywhere in the solar system besides Earth.

link.

Some Pebbles in the Gale Crater on Mars may Have Been Transported for tens of Miles

While new evidence suggests that Mars may harbor a tiny amount of liquid water, it exists today as a largely cold and arid planet. Three billion years ago, however, the situation may have been much different.

In 2012 the Mars Curiosity rover beamed images back to Earth containing some of the most concrete evidence that water once flowed in abundance on the planet. Small, remarkably round and smooth pebbles suggested that an ancient riverbed had once carried these rocks and abraded them as they traveled.

To Douglas Jerolmack, a geophysicist at the University of Pennsylvania, and his collaborator Gábor Domokos, a mathematician at Budapest University of Technology and Economics, Curiosity's findings raised a fundamental geological question: Can we use shape alone to interpret the transport history of river pebbles -- on Mars, Earth or any planet?

"Thousands of years ago, Aristotle pondered the question of pebbles on the beach and how they become rounded," Jerolmack said. "But until recently, descriptions of pebble shape have been qualitative, and we lacked a basic understanding of the rounding process."

Now that has changed. In a new report in Nature Communications, Jerolmack, Domokos and colleagues report the first-ever method to quantitatively estimate the transport distance of river pebbles from their shape alone. The researchers' estimate that the Martian pebbles traveled roughly 30 miles from their source, providing additional evidence for the idea that Mars once had an extensive river system, conditions that could support life.

link.

Gale Crater was Long Term Lakebed 3.3 to 3.8 Billion Years ago From Late Noachian Into Hesperian

We have heard the Mars exploration mantra for more than a decade: follow the water. In a new paper published October 9, 2015, in the journal Science, the Mars Science Laboratory (MSL) team presents recent results of its quest to not just follow the water but to understand where it came from, and how long it lasted on the surface of Mars so long ago.

The story that has unfolded is a wet one: Mars appears to have had a more massive atmosphere billions of years ago than it does today, with an active hydrosphere capable of storing water in long-lived lakes. The MSL team has concluded that this water helped to fill Gale Crater, the MSL rover Curiosity's landing site, with sediment deposited as layers that formed the foundation for the mountain found in the middle of the crater today.

Curiosity has been exploring Gale Crater, which is estimated to be between 3.8 billion and 3.6 billion years old, since August 2012. In mid-September 2014, the rover reached the foothills of Aeolis Mons, a three-mile-high layered mountain nicknamed "Mount Sharp" in honor of the late Caltech geologist Robert Sharp. Curiosity has been exploring the base of the mountain since then.

"Observations from the rover suggest that a series of long-lived streams and lakes existed at some point between 3.8 billion to 3.3 billion years ago, delivering sediment that slowly built up the lower layers of Mount Sharp," says Ashwin Vasavada (PhD '98), MSL project scientist. "However, this series of long-lived lakes is not predicted by existing models of the ancient climate of Mars, which struggle to get temperatures above freezing," he says.

This mismatch between the predictions of Mars's ancient climate that arise from models developed by paleoclimatologists and indications of the planet's watery past, as interpreted by geologists, bears similarities to a century-old scientific conundrum--in this case, about Earth's ancient past.

link.

paper link.

Keep in mind that is the equivalent of the entirety of the Phanerozoic (ie all the time system the beginning of the Cambrian Explosion).

Mars Recon Orbiter Spots Curiosity Rover on Mount Sharp

Mars Took Longer to Lose its Atmosphere, Water Than Originally Thought

The imprint of atmospheric evolution in the D/H of Hesperian clay minerals on Mars

Authors:

Mahaffy et al

Abstract:

The deuterium-to-hydrogen (D/H) ratio in strongly bound water or hydroxyl groups in ancient martian clays retains the imprint of the water of formation of these minerals. Curiosity’s Sample Analysis at Mars (SAM) experiment measured thermally evolved water and hydrogen gas released between 550° and 950°C from samples of Hesperian-era Gale crater smectite to determine this isotope ratio. The D/H value is 3.0 (±0.2) times the ratio in standard mean ocean water. The D/H ratio in this ~3-billion-year-old mudstone, which is half that of the present martian atmosphere but substantially higher than that expected in very early Mars, indicates an extended history of hydrogen escape and desiccation of the planet.

Transient Methane Plumes Detected by Curiosity in Gale Crater on Mars

Mars methane detection and variability at Gale crater

Authors:

Webster et al

Abstract:

Reports of plumes or patches of methane in the martian atmosphere that vary over monthly time scales have defied explanation to date. From in situ measurements made over a 20-month period by the tunable laser spectrometer of the Sample Analysis at Mars instrument suite on Curiosity at Gale crater, we report detection of background levels of atmospheric methane of mean value 0.69 ± 0.25 parts per billion by volume (ppbv) at the 95% confidence interval (CI). This abundance is lower than model estimates of ultraviolet degradation of accreted interplanetary dust particles or carbonaceous chondrite material. Additionally, in four sequential measurements spanning a 60-sol period (where 1 sol is a martian day), we observed elevated levels of methane of 7.2 ± 2.1 ppbv (95% CI), implying that Mars is episodically producing methane from an additional unknown source.

Curiosity Spots Metal Meteorite on Mars

link.

Mars Curiosity Panorama

Mars Panorama - Curiosity rover: Martian solar day 530 in The World

Perchlorates May be Universal Across the Martian Surface

The quest for evidence of life on Mars could be more difficult than scientists previously thought.

A scientific paper published today details the investigation of a chemical in the Martian soil that interferes with the techniques used by the Curiosity rover to test for traces of life. The chemical causes the evidence to burn away during the tests.

In search of clues to life's presence on Mars – now or in the past – Curiosity checks Martian soil and rocks for molecules known as organic carbon compounds that are the hallmark of living organisms on Earth.

While trekking around the Rocknest sand dune in November 2012, the rover found evidence of perchlorate—a salt comprised of chlorine and oxygen. When Curiosity heats a scoop of Martian soil to test it for organic carbon, perchlorates can cause a chemical reaction that destroys organic carbon. Daniel Glavin, an astrobiologist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and first author on the new paper, said he now believes the troublesome perchlorates are likely prevalent throughout the Martian surface.

link.

Curiosity Finds Martian Regolith is 2% Water

The first scoop of soil analyzed by the analytical suite in the belly of NASA's Curiosity rover reveals that fine materials on the surface of the planet contain several percent water by weight. The results were published today in Science as one article in a five-paper special section on the Curiosity mission. Rensselaer Polytechnic Institute Dean of Science Laurie Leshin is the study's lead author.

"One of the most exciting results from this very first solid sample ingested by Curiosity is the high percentage of water in the soil," said Leshin. "About 2 percent of the soil on the surface of Mars is made up of water, which is a great resource, and interesting scientifically." The sample also released significant carbon dioxide, oxygen, and sulfur compounds when heated.

link.

NASA's Curiosity Finds no Methane on Mars

Data from NASA's Curiosity rover has revealed the martian environment lacks methane. This is a surprise to researchers because previous data reported by U.S. and international scientists indicated positive detections.

The roving laboratory performed extensive tests to search for traces of martian methane. Whether the martian atmosphere contains traces of the gas has been a question of high interest for years because methane could be a potential sign of life, although it also can be produced without biology.

"This important result will help direct our efforts to examine the possibility of life on Mars," said Michael Meyer, NASA's lead scientist for Mars exploration. "It reduces the probability of current methane-producing martian microbes, but this addresses only one type of microbial metabolism. As we know, there are many types of terrestrial microbes that don't generate methane."

Curiosity analyzed samples of the martian atmosphere for methane six times from October 2012 through June and detected none. Given the sensitivity of the instrument used, the Tunable Laser Spectrometer, and not detecting the gas, scientists calculate the amount of methane in the martian atmosphere today must be no more than 1.3 parts per billion. That is about one-sixth as much as some earlier estimates. Details of the findings appear in the Thursday edition of Science Express.

"It would have been exciting to find methane, but we have high confidence in our measurements, and the progress in expanding knowledge is what's really important," said the report's lead author, Chris Webster of NASA's Jet Propulsion Laboratory in Pasadena, Calif. "We measured repeatedly from martian spring to late summer, but with no detection of methane."

link.

Visual Traces of Curiosity

Stunning Interpolated Video of Curiosity's Landing