Category: Astrobiology

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In March 2007, the Spirit rover found a patch of bright-colored soil rich in silica. Scientists proposed water must have been involved in creating the region, and not just water, but hot water. Now, data from retrieved from the Mars Reconnaissance Orbiter (MRO) suggest the discovery of another ancient hot springs region in Vernal Crater in Arabia Terra, an area in the northern hemisphere of Mars that is densely cratered and heavily eroded. The research team says the striking similarities between these features on Mars and hot springs found on Earth provide evidence of an ancient Martian hot-spring environment. On Earth these environments teem with microbial life.

If life forms have ever been present on Mars, hot spring deposits would be ideal locations to search for physical or chemical evidence of these organisms and could be target areas for future exploratory missions such as the Mars Science Labortory. Arabia Terra is currently on the list of possible landing sites for MSL.

In their research paper “A Case for Ancient Springs in Arabia Terra, Mars,” Carlton C. Allen and Dorothy Z. Oehler, from the Astromaterials Research and Exploration Science Directorate at the NASA Johnson Space Center, Houston, Texas, propose that new image data from the HiRISE (High Resolution Imaging Science Experiment) camera on MRO show structures in Vernal Crater that appear to be the product of ancient spring activity. The data suggest that the southern part of Vernal Crater has experienced episodes of water flow from underground to the surface and may be a site where Martian life could have developed.

Vernal Crater is a 55-km diameter crater located at 6°N, 355.5°E, in the southwestern part of Arabia Terra. From orbital images, the crater appears to have layered sediments, and potentially, remnants of activity from water.

One feature that is bright in both daytime and nighttime in THEMIS infrared images is prominent in the southern part of Vernal crater. In this image, marked A, the feature appears dark, as the THEMIS grayscale was inverted to resemble HiRISE images in the visible range. The feature is 3 km wide and is composed of alternating light-toned and dark-toned subunits, which the researchers interpret as cemented, resistant dunes,and water-laid deposits.

The research team compares this and other structures in the region with hot springs regions on Earth, using Google Earth. The similarities of the features on Mars and Earth, the researchers say, provides a strong case that the Vernal Crater structures are relics of ancient Martian springs.

The team says their results are consistent with the growing body of orbital and rover data that is suggestive of widespread hydrothermal activity and possible spring deposits elsewhere on Mars.

“If clays or chemical precipitates such as evaporates or silica comprise the terraced structures or tonal anomalies, signatures of that life may be preserved in those minerals,” write the research team in their paper. “The fact that several other potential spring deposits occur on-trend with Vernal structures suggests that this may have been a significant province of long-lasting spring activity.”

Source: Paper: “A Case for Ancient Springs in Arabia Terra, Mars,” by Carlton C. Allen and Dorothy Z. Oehler.

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Methane has been measured in large quantities in Mars atmosphere over several seasons, meaning Mars is active, either geologically or biologically. “We found methane,” said Dr. Geronimo Villanueva from the NASA Goddard Space Flight Center, one member of a team of scientists reporting on their research at a press conference today at NASA Headquarters. “We can measure not only the methane, but where it is coming from and when it is being released.” This is the first definitive detection of methane on Mars that includes maps identifying areas of active release. “Mars is active,” said Michael Meyers, lead NASA scientist for the Mars Program, “but we don’t know if it’s because of biology or geology or both.”

The methane on Mars was first detected in 1999, again in 2001 and 2003, which was widely reported, but not much was known about the origin or amount of the gas on Mars.

The research team found methane in the atmosphere of Mars by carefully observing the planet over several Mars years, and during all the Martian seasons with NASA’s Infrared Telescope Facility, run by the University of Hawaii, and the W. M. Keck telescope, both at Mauna Kea, Hawaii.

Measurements were made using spectroscopy by which light is split into its individual wavelengths, and then the “fingerprint” of individual molecules can be identified.

From Earth the aperture of the spectrometer is placed along the north-south direction of the planet, and during observations, the instrument can acquire between 30 and 50 individual spectra of Mars for every sixty seconds. Doing this they can build a map of the planet, as the planet rotates under the “slit” or aperture of the spectrometer.

The origin of methane could either be geologic where water reacts with hot rock and produces methane gas which escapes through pores in the planet’s surface in a process called serpentinization. Or it could be evidence of biology under the surface, where the methane generated by microbes could accumulate and then escape through the rocks.

Three regions of active release of methane were found and were seen over areas that show evidence of ancient ground ice or flowing water. The plumes of methane appeared over northern hemisphere regions such as east of Arabia Terra, the Nili Fossae region, and the south-east quadrant of Syrtis Major, an ancient volcano 1,200 kilometers (about 745 miles) across.

“We observed and mapped multiple plumes of methane on Mars, one of which released about 19,000 metric tons of methane,” said Villanueva. “The plumes were emitted during the warmer seasons — spring and summer — perhaps because the permafrost blocking cracks and fissures vaporized, allowing methane to seep into the Martian air. Curiously, some plumes had water vapor while others did not,” said Villanueva. The rate of release is about 1 pound per second or .6 kg per second.

“Methane is quickly destroyed in the Martian atmosphere in a variety of ways, so our discovery of substantial plumes of methane in the northern hemisphere of Mars in 2003 indicates some ongoing process is releasing the gas,” said Dr. Michael Mumma of NASA’s Goddard Space Flight Center in Greenbelt, Md. “At northern mid-summer, methane is released at a rate comparable to that of the massive hydrocarbon seep at Coal Oil Point in Santa Barbara, Calif.”

Another team member, Lisa Pratt, professor of geological sciences, Indiana University in
Bloomington, elaborated on whether the process creating the methane could be geological or biological. “If there is an “A” line of evidence that makes me think we need to seriously consider biology, it’s the processes in the subsurface that would allow for methane generation that seems slightly more plausible for biology than geochemistry,” she said. “Serpentinization is a simple water/rock reaction and is a process we see only in a few special places on Earth, usually associated with major fracturing and faulting that allows mantle like materials to be exposed to sea water and groundwater. That’s a process that ‘plugs up the plumbing’ and isolates the reactive site, and we don’t see a lot of evidence for major active, deep faulting and uplift that would bring these reactive materials into contact with water.”

While the team reported on results from observations in 2003 and 2006, they said they were not at liberty to discuss findings from subsequent observations, as the work to decipher the findings is still being done. But they hinted that relatively soon, more information would be available. They are also developing a strategy for further studies with ground-based telescopes, current spacecraft orbiting Mars, and future spacecraft such as the Mar Science Laboratory, as well as re-looking at data already obtained to see if more clues can be found as to the origin of the methane on Mars.

Sources: NASA press conference, NASA

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For a geologist, looking inside a rock is essential to help determine the makeup and history of the rock sample. That’s why geologists have rock hammers, and also why the Mars Exploration Rovers, Spirit and Opportunity, have their Rock Abrasion Tool. For future missions to Mars, or even for a sample return mission, one of the main goals will be to look for signs of life, past or present, that might be hiding inside the rocks. Scientists are working on a new, simple technique for detecting biological and pre-biotic molecules that become trapped inside the minerals in rocks.

This new technique utilizes a laser-based optical and chemical imager or LOCI. A single laser shot vaporizes a small portion of the surface into individual ions. These pass through a mass spectrometer, which can identify each ion by how much mass and charge it has. The great thing about this technique is that the sample requires no preparation: just shoot and detect.

Previous techniques for required that the minerals be dissolved in a solution or mixed in with some other medium, which dilutes the sample and runs the risk of introducing contamination.

This procedure was tested on Earth using samples of the mineral jarosite. Jarosite is a yellowish-brown sulfate mineral containing iron, potassium and hydroxide. It is found in places around the world such as southern California beaches and volcanic fields in New Zealand. It forms only in the presence of highly acidic water.

In 2004, jarosite was discovered on Mars by the rover Opportunity. Scientists immediately recognized the find as clear evidence for past water on the red planet.

But there is something else about jarosite that makes it interesting. On Earth, for jarosite to form, oxidation of the rock must occur – usually the rock is pyrite (ferrous sulfide). And on Earth, the oxidation reaction is usually performed by certain “rock-eating” microorganisms.

Scientists say the rate of the jarosite formation would be extremely slow without microbes, as well as without the presence of water.

Whether jarosite can form without the assistance of these microbes is very difficult to say, since every corner of Earth is occupied by little bugs of some sort or another.

And yet, there remains the tantalizing possibility that jarosite on Mars exists because of some little, rock-eating microbes. If so, remnants of these organisms may be locked in the mineral. And there’s only one way to find out: look inside Mars rocks.

Right now, this method couldn’t be used on the next bigger Mars rover, the Mars Science Laboratory, which will hopefully launch in 2009. The LOCI instrument is just too big and too complex to use remotely, said David Beaty, chief scientist of the Mars Exploration Directorate at the Jet Propulsion Laboratory.

But it could be used on a sample return mission. But hopefully, scientists will be able to develop a smaller, simpler version to be used on future missions to look for signs of life in rocks on Mars.

Original News Source: Astrobiology Magazine